Atmospheric Environment (v.120, #C)
Editorial board (i).
A CFD study on the effectiveness of trees to disperse road traffic emissions at a city scale by A.P.R. Jeanjean; G. Hinchliffe; W.A. McMullan; P.S. Monks; R.J. Leigh (1-14).
This paper focuses on the effectiveness of trees at dispersing road traffic emissions on a city scale. CFD simulations of air-pollutant concentrations were performed using the OpenFOAM software platform using the k-ε model. Results were validated against the CODASC wind tunnel database before being applied to a LIDAR database of buildings and trees representing the City of Leicester (UK). Most other CFD models in the literature typically use idealised buildings to model wind flow and pollution dispersion. However, the methodology used in this study uses real buildings and trees data from LIDAR to reconstruct a 3D representation of Leicester City Centre. It focuses on a 2 × 2 km area which is on a scale larger than those usually used in other CFD studies. Furthermore, the primary focus of this study is on the interaction of trees with wind flow dynamics. It was found that in effect, trees have a regionally beneficial impact on road traffic emissions by increasing turbulence and reducing ambient concentrations of road traffic emissions by 7% at pedestrian height on average. This was an important result given that previous studies generally concluded that trees trapped pollution by obstructing wind flow in street canyons. Therefore, this study is novel both in its methodology and subsequent results, highlighting the importance of combining local and regional scale models for assessing the impact of trees in urban planning.
Keywords: Computational Fluid Dynamics (CFD); Road side; Dispersion modeling; OpenFOAM;
Particulate and gaseous emissions from the combustion of different biofuels in a pellet stove by E.D. Vicente; M.A. Duarte; L.A.C. Tarelho; T.F. Nunes; F. Amato; X. Querol; C. Colombi; V. Gianelle; C.A. Alves (15-27).
Seven fuels (four types of wood pellets and three agro-fuels) were tested in an automatic pellet stove (9.5 kWth) in order to determine emission factors (EFs) of gaseous compounds, such as carbon monoxide (CO), methane (CH4), formaldehyde (HCHO), and total organic carbon (TOC). Particulate matter (PM10) EFs and the corresponding chemical compositions for each fuel were also obtained. Samples were analysed for organic carbon (OC) and elemental carbon (EC), anhydrosugars and 57 chemical elements. The fuel type clearly affected the gaseous and particulate emissions. The CO EFs ranged from 90.9 ± 19.3 (pellets type IV) to 1480 ± 125 mg MJ−1 (olive pit). Wood pellets presented the lowest TOC emission factor among all fuels. HCHO and CH4 EFs ranged from 1.01 ± 0.11 to 36.9 ± 6.3 mg MJ−1 and from 0.23 ± 0.03 to 28.7 ± 5.7 mg MJ−1, respectively. Olive pit was the fuel with highest emissions of these volatile organic compounds. The PM10 EFs ranged from 26.6 ± 3.14 to 169 ± 23.6 mg MJ−1. The lowest PM10 emission factor was found for wood pellets type I (fuel with low ash content), whist the highest was observed during the combustion of an agricultural fuel (olive pit). The OC content of PM10 ranged from 8 wt.% (pellets type III) to 29 wt.% (olive pit). Variable EC particle mass fractions, ranging from 3 wt.% (olive pit) to 47 wt.% (shell of pine nuts), were also observed. The carbonaceous content of particulate matter was lower than that reported previously during the combustion of several wood fuels in traditional woodstoves and fireplaces. Levoglucosan was the most abundant anhydrosugar, comprising 0.02–3.03 wt.% of the particle mass. Mannosan and galactosan were not detected in almost all samples. Elements represented 11–32 wt.% of the PM10 mass emitted, showing great variability depending on the type of biofuel used.
Keywords: Pellet stove; PM10; OC/EC; Anhydrosugars; Inorganic species;
Re-examination of C1–C5 alkyl nitrates in Hong Kong using an observation-based model by X.P. Lyu; Z.H. Ling; H. Guo; S.M. Saunders; S.H.M. Lam; N. Wang; Y. Wang; M. Liu; T. Wang (28-37).
The photochemical formation of alkyl nitrates (RONO2) and their impact on ozone (O3) formation were investigated using a Photochemical Box Model incorporating the Master Chemical Mechanism (PBM-MCM). The model was constrained with field measurement data collected on selected O3 episode days at Tai O, a rural-coastal site in southwestern Hong Kong, from August 2001–December 2002. The in-situ observations showed that the sum of C1–C5 RONO2 varied from 30.7 ± 14.8 pptv in spring to 120.7 ± 10.4 pptv in autumn, of which 2-butyl nitrate dominated with the highest average concentration of 30.8 ± 2.6 pptv. Model simulations indicated that the pathway of CH3O reacting with NO2, proposed in our previous study, made minor contributions (11.3 ± 0.7%) to methyl nitrate formation. Indeed, 51.8 ± 3.1% and 36.5 ± 6.3% of the methyl nitrate was attributed to the reaction of CH3O2+NO and to oceanic emissions/biomass burning, respectively. For the C2–C5 alkyl nitrates, the contribution of photochemical formation increased with increasing carbon number, ranging from 64.4 ± 4.0% for ethyl nitrate (EtONO2) to 72.6 ± 4.2% for 2-pentyl nitrate (2-PenONO2), while the contribution of oceanic emissions/biomass burning decreased from 35.1 ± 6.5% for EtONO2 to 26.8 ± 6.8% for 2-PenONO2. Model simulations of photochemical O3 levels influenced by RONO2 chemistry showed that the formation of methyl-, ethyl-, i-propyl-, n-propyl-, 2-butyl-, 2-pentyl-, and 3-pentyl-nitrates led to O3 reduction of 0.05 ± 0.03, 0.05 ± 0.03, 0.06 ± 0.02, 0.02 ± 0.02, 0.18 ± 0.04, 0.09 ± 0.02 and 0.06 ± 0.02 ppbv, respectively, with an average reduction rate of 11.0 ± 3.2 ppbv O3 per 1 ppbv RONO2 formation. The C1–C5 RONO2 constituted 18.6 ± 1.9% of the entire RONO2, and had a nitrogen reserve of 4.1 ± 0.2%, implying their potential influence on O3 production in downwind areas.
Keywords: Alkyl nitrate; Photochemical formation; O3 production; PBM-MCM model; Field observation;
Estimate of biogenic VOC emissions in Japan and their effects on photochemical formation of ambient ozone and secondary organic aerosol by Satoru Chatani; Sou N. Matsunaga; Seiji Nakatsuka (38-50).
A new gridded database has been developed to estimate the amount of isoprene, monoterpene, and sesquiterpene emitted from all the broadleaf and coniferous trees in Japan with the Model of Emissions of Gases and Aerosols from Nature (MEGAN). This database reflects the vegetation specific to Japan more accurately than existing ones. It estimates much lower isoprene emitted from other vegetation than trees, and higher sesquiterpene emissions mainly emitted from Cryptomeria japonica, which is the most abundant plant type in Japan. Changes in biogenic emissions result in the decrease in ambient ozone and increase in organic aerosol simulated by the air quality simulation over the Tokyo Metropolitan Area in Japan. Although newly estimated biogenic emissions contribute to a better model performance on overestimated ozone and underestimated organic aerosol, they are not a single solution to solve problems associated with the air quality simulation.
Keywords: Biogenic volatile organic compound; Emission inventory; Air quality simulation; Tropospheric ozone; Secondary organic aerosol;
Characteristics of the east Mediterranean dust variability on small spatial and temporal scales by Yuval; Meytar Sorek–Hamer; Amnon Stupp; Pinhas Alpert; David M. Broday (51-60).
The presence of naturally–occurring dust is a conspicuous meteorological phenomenon characterised by very high load of relatively coarse airborne particulate matter (PM), which may contain also various deleterious chemical and biological materials. Much work has been carried out to study the phenomenon by modelling the generation and transport of dust plumes, and assessment of their temporal characteristics on a large (>1000 km) spatial scale. This work studies in high spatial and temporal resolution the characteristics of dust presence on the mesoscale (>100 km). The small scale variability is important both for better understanding the physical characteristics of the dust phenomenon and for PM exposure specification in epidemiological studies. Unsupervised clustering–based method, using PM10 records and their derived attributes, was developed and applied to detect the impact of dust at the observation locations of a PM10 monitoring array. It was found that dust may cover the whole study area but very often the coverage is partial. On average, the larger the spatial extent of a dust event, the higher and more homogeneous are the associated PM10 concentrations. Dust event lengths however, are only weakly associated with the PM concentrations (Pearson correlation below 0.44). The large PM concentration variability during spatially small events and the fact that their occurrence is strongly correlated with the elevation above sea level of the reporting stations (Pearson correlation 0.87, p–value < 10−5) points to small scale spatiotemporal dynamics of dust plumes.
Keywords: Cluster analysis; Dust presence detection; Mesoscale character of dust plumes;
Passive methods for improving air quality in the built environment: A review of porous and solid barriers by John Gallagher; Richard Baldauf; Christina H. Fuller; Prashant Kumar; Laurence W. Gill; Aonghus McNabola (61-70).
Protecting the health of growing urban populations from air pollution remains a challenge for planners and requires detailed understanding of air flow and pollutant transport in the built environment. In recent years, the work undertaken on passive methods of reducing air pollution has been examined to address the question: “how can the built environment work to alter natural dispersion patterns to improve air quality for nearby populations?” This review brings together a collective of methods that have demonstrated an ability to influence air flow patterns to reduce personal exposure in the built environment. A number of passive methods exists but, in the context of this paper, are split into two distinct categories: porous and solid barriers. These methods include trees and vegetation (porous) as well as noise barriers, low boundary walls and parked cars (solid); all of which have gained different levels of research momentum over the past decade. Experimental and modelling studies have provided an understanding of the potential for these barriers to improve air quality under varying urban geometrical and meteorological conditions. However, differences in results between these studies and real-world measurements demonstrate the challenges and complexities of simulating pollutant transport in urban areas. These methods provide additional benefits to improving air quality through altering dispersion patterns; avenue trees and vegetation are aesthetically pleasing and provides cooling and shade from direct sunlight. Additionally, real-world case studies are considered an important direction for further verification of these methods in the built environment. Developing design guidelines is an important next stage in promoting passive methods for reducing air pollution and ensuring their integration into future urban planning strategies. In addition, developing channels of communication with urban planners will enhance the development and uptake of design guidelines to improve air quality in the built environment.
Keywords: Passive methods; Pollutant dispersion; Barriers; Air quality; Urban planning; Policy;
Transboundary secondary organic aerosol in western Japan: An observed limitation of the f 44 oxidation indicator by Satoshi Irei; Akinori Takami; Yasuhiro Sadanaga; Takao Miyoshi; Takemitsu Arakaki; Kei Sato; Naoki Kaneyasu; Hiroshi Bandow; Shiro Hatakeyama (71-75).
To obtain evidence for secondary organic aerosol formation during the long-range transport of air masses over the East China Sea, we conducted field measurements in March 2012 at the Fukue atmospheric monitoring station, Nagasaki, in western Japan. The relative abundance of m/z 44 in fine organic aerosol (f 44) was measured by an Aerodyne aerosol chemical speciation monitor. The stable carbon isotope ratio (δ13C) of low-volatile water-soluble organic carbon (LV-WSOC) in the daily filter samples of total suspended particulate matter was also analyzed using an elemental-analyzer coupled with an isotope ratio mass spectrometer. Additionally, in situ measurements of NOx and NOy were performed using NOx and NOy analyzers. The measurements showed that, unlike the systematic trends observed in a previous field study, a scatter plot for δ13C of LV-WSOC versus f 44 indicated a random variation. Comparison of f 44 with the estimated photochemical age by the NOx/NOy ratio revealed that the random distribution of f 44 values near 0.2 is likely an indication of saturation already. Such f 44 values were significantly lower than the observed f 44 (∼0.3) at Hedo in the previous study. These findings imply that the saturation point of f 44, and the use of f 44 as an oxidation indicator, is case dependent.Display Omitted
Keywords: SOA isotope; Transboundary pollution; HULIS; WSOC; Photochemical age;
Probing the severe haze pollution in three typical regions of China: Characteristics, sources and regional impacts by Qiongzhen Wang; Guoshun Zhuang; Kan Huang; Tingna Liu; Congrui Deng; Jian Xu; Yanfen Lin; Zhigang Guo; Ying Chen; Qingyan Fu; Joshua S. Fu; Jiakuan Chen (76-88).
PM2.5 with its major chemical components were measured and analyzed during a concurrent haze in Jan. 1–19, 2013 at three sites (Shanghai, Beijing, and Huaniao, a remote isle over the East China Sea) to probe the sources and formation process of such a severe haze over three typical regions in China. The mean PM2.5 concentrations during the severely polluted days reached 180.8 μg m−3, 299.2 μg m−3, and 131.1 μg m−3 in Shanghai, Beijing, and the Huaniao Isle, respectively. The mass ratio of the sum of SO 4 2 − , NO 3 − , and NH 4 + to PM2.5 were over 1/3 during the polluted days at all the three sites. Promoted gas-to-particle transformations from acidic SO2 and NOx to SO 4 2 − and NO 3 − under high relative humidity conditions played a major role in the formation of this severe haze. Significant contribution of traffic emissions to the haze formation over China was suggested to be one of the major sources in triggering the heavy haze over China. Specifically, there was a more contribution from traffic in Shanghai than in Beijing as indicated by the higher NO 3 − / SO 4 2− ratio in Shanghai. In Beijing, the enhanced coal combustion for winter heating along with the traffic emission was suggested to be the major two sources of this haze episode. Typical pollution elements such as As, Cd, and Pb as well as Cl− and K+ were substantially enhanced in the severely polluted days. Although the Huaniao Isle is located in the remote oceanic area as a background site, pollution elements, secondary ions, and K+ all increased substantially during the polluted days. As visualized by the backward air mass trajectories associated with the potential source region identification technique, air masses that passed over Northern China and Yangtze River Delta evidently invaded the offshore areas of Eastern China. The ratios of As, Cd, Cu, Zn, and K+ to Al at the Huaniao Isle were closer to those of Beijing rather than Shanghai, indicating that the marine aerosol over the East China Sea had been significantly polluted via the long-range transport of anthropogenic pollutants originating from Northern China.
Keywords: Haze; Sources; Formation process; Regional transport;
Sources of air pollution in a region of oil and gas exploration downwind of a large city by Andrew P. Rutter; Robert J. Griffin; Basak Karakurt Cevik; Kabindra M. Shakya; Longwen Gong; Saewung Kim; James H. Flynn; Barry L. Lefer (89-99).
The air quality in the outflow from Fort Worth, TX was studied in June 2011 at a location surrounded by oil and gas development in the Barnett Shale. The objectives of this study were to understand the major sources of volatile organic compounds (VOCs) and organic aerosols and explore the potential influence each VOC source had on ozone and secondary organic aerosol formation. Measurements of VOCs were apportioned between six factors using Positive Matrix Factorization (PMF): Natural Gas (25 ± 2%; ±99% CL); Fugitive Emissions (15 ± 2%); Internal Combustion Engines (15 ± 2%); Biogenic Emissions (7 ± 1%); Industrial Emissions/Oxidation 1(8 ± 1%); and Oxidation 2 (18 ± 2%). Reactivity calculations suggest the Biogenic and Oxidation 2 factors were the most likely VOC sources to influence local ozone. However, enough OH reactivity was calculated for factors related to the oil and gas development that they could incrementally increase O3. Three organic aerosol (OA) types were identified with PMF applied to high-resolution time-of-flight aerosol mass spectrometry measurements: hydrocarbon-like OA (HOA; 11% of mass) and two classes of oxidized OA (semi- and less-volatile OOA, SV and LV; 45% and 44%, respectively). The HOA correlated with the Internal Combustion Engine VOC factor indicating that a large fraction of the HOA was emitted by gasoline and diesel motors. The SV-OOA correlated with the oxidized VOC factors during most of the study, whereas a correlation between LV-OOA and the oxidized VOC factors was only observed during part of the study. It is hypothesized that SV-OOA and the oxidized VOC factors correlated reasonably well because these factors likely were separated by at most only a few oxidation generations on the oxidation pathway of organic compounds.
Keywords: Barnett shale; Hydraulic fracturing; Organic aerosols; PMF; VOCs; Photochemical reactivity;
A tale of two cities: Comparison of impacts on CO2 emissions, the indoor environment and health of home energy efficiency strategies in London and Milton Keynes by C. Shrubsole; P. Das; J. Milner; I.G. Hamilton; J.V. Spadaro; E. Oikonomou; M. Davies; P. Wilkinson (100-108).
Dwellings are a substantial source of global CO2 emissions. The energy used in homes for heating, cooking and running electrical appliances is responsible for a quarter of current total UK emissions and is a key target of government policies for greenhouse gas abatement. Policymakers need to understand the potential impact that such decarbonization policies have on the indoor environment and health for a full assessment of costs and benefits. We investigated these impacts in two contrasting settings of the UK: London, a predominantly older city and Milton Keynes, a growing new town. We employed SCRIBE, a building physics-based health impact model of the UK housing stock linked to the English Housing Survey, to examine changes, 2010–2050, in end-use energy demand, CO2 emissions, winter indoor temperatures, airborne pollutant concentrations and associated health impacts. For each location we modelled the existing (2010) housing stock and three future scenarios with different levels of energy efficiency interventions combined with either a business-as-usual, or accelerated decarbonization of the electricity grid approach. The potential for CO2 savings was appreciably greater in London than Milton Keynes except when substantial decarbonization of the electricity grid was assumed, largely because of the lower level of current energy efficiency in London and differences in the type and form of the housing stock. The average net impact on health per thousand population was greater in magnitude under all scenarios in London compared to Milton Keynes and more beneficial when it was assumed that purpose-provided ventilation (PPV) would be part of energy efficiency interventions, but more detrimental when interventions were assumed not to include PPV. These findings illustrate the importance of considering ventilation measures for health protection and the potential variation in the impact of home energy efficiency strategies, suggesting the need for tailored policy approaches in different locations, rather than adopting a universally rolled out strategy.
Keywords: Built environment; Housing; Energy efficiency; CO2 reduction; Indoor air quality; Health impacts;
Main components and human health risks assessment of PM10, PM2.5, and PM1 in two areas influenced by cement plants by Francisco Sánchez-Soberón; Joaquim Rovira; Montse Mari; Jordi Sierra; Martí Nadal; José L. Domingo; Marta Schuhmacher (109-116).
Particulate matter (PM) is widely recorded as a source of diseases, being more harmful those particles with smaller size. PM is released to the environment as a consequence of different activities, being one of them cement production. The objective of this pilot study was to characterize PM of different sizes around cement facilities to have a preliminary approach of their origin, and evaluate their potential health risks. For that purpose, three fractions of PM (10, 2.5, and 1) were collected in the nearby area of two cement plants with different backgrounds (urban and rural) in different seasons. Subsequently, main components, outdoor and indoor concentrations, exposure, and human health risks were assessed. Greatest levels of PM1, organic matter, and metals were found in urban location, especially in winter. Consequently, environmental exposure and human health risks registered their highest values in the urban plant during wintertime. Exposure was higher for indoor activities, expressing some metals their peak values in the PM1 fraction. Non-carcinogenic risks were below the safety threshold (HQ < 1). Carcinogenic risks for most of the metals were below the limit of 10−5, except for Cr (VI), which exceeded it in both locations, but being in the range considered as assumable (10−6–10−4).
Keywords: Cement; Particulate matter fractions; Indoor/outdoor exposure; Human risk assessment;
Volatile organic compound emission profiles of four common arctic plants by Ida Vedel-Petersen; Michelle Schollert; Josephine Nymand; Riikka Rinnan (117-126).
The biogenic volatile organic compound (BVOC) emissions from plants impact atmosphere and climate. The species-specific emissions, and thereby the atmospheric impact, of many plant species are still unknown. Knowledge of BVOC emission from arctic plants is particularly limited. The vast area and relatively high leaf temperature give the Arctic potential for emissions that cannot be neglected. This field study aimed to elucidate the BVOC emission profiles for four common arctic plant species in their natural environment during the growing season. BVOCs were sampled from aboveground parts of Empetrum hermaphroditum, Salix glauca, Salix arctophila and Betula nana using the dynamic enclosure technique and collection of volatiles in adsorbent cartridges, analyzed by gas chromatography-mass spectrometry. Sampling occurred three times: in late June/early July, in mid-July and in early August. E. hermaphroditum emitted the least BVOCs, dominated by sesquiterpenes (SQTs) and non-isoprenoid BVOCs. The Salix spp. emitted the most, dominated by isoprene. The emissions of B. nana were composed of about two-thirds non-isoprenoid BVOCs, with moderate amounts of monoterpenes (MTs) and SQTs. The total B. nana emissions and the MT and SQT emissions standardized to 30 °C were highest in the first measurement in early July, while the other species had the highest emissions in the last measurement in early August. As climate change is expected to increase plant biomass and change vegetation composition in the Arctic, the BVOC emissions from arctic ecosystems will also change. Our results suggest that if the abundance of deciduous shrubs like Betula and Salix spp. increases at the expense of slower growing evergreens like E. hermaphroditum, there is the potential for increased emissions of isoprene, MTs and non-isoprenoid BVOCs in the Arctic.Display Omitted
Keywords: BVOC; Isoprene; Monoterpene; Sesquiterpene; Betula nana; Empetrum hermaphroditum; Salix;
Semi-empirical process-based models for ammonia emissions from beef, swine, and poultry operations in the United States by Alyssa M. McQuilling; Peter J. Adams (127-136).
Farm-level ammonia emissions factors in the literature vary by an order of magnitude due to variations in manure management practices and meteorology, and it is essential to capture this variability in emission inventories used for atmospheric modeling. Loss of ammonia to the atmosphere is modeled here through a nitrogen mass balance with losses controlled by mass transfer resistance parameters, which vary with meteorological conditions and are tuned to match literature-reported emissions factors. Variations due to management practices are captured by having tuned parameters that are specific to each set of management practices. The resulting farm emissions models (FEMs) explain between 20% and 70% of the variability in published emissions factors and typically estimate emission factors within a factor of 2. The r2 values are: 0.53 for swine housing (0.67 for shallow-pit houses); 0.48 for swine storage; 0.29 for broiler chickens; 0.70 for layer chickens; and 0.21 for beef feedlots (0.36 for beef feedlots with more farm-specific input data). Mean fractional error was found to be 22–44% for beef feedlots, swine housing, and layer housing; fractional errors were greater for swine lagoons (90%) and broiler housing (69%). Unexplained variability and errors result from model limitations, measurement errors in reported emissions factors, and a lack of information about measurement conditions.
Keywords: Ammonia emissions; Process-based model; Livestock production; Manure management;
Mineral dust and major ion concentrations in snowpit samples from the NEEM site, Greenland by Jung-Ho Kang; Heejin Hwang; Sang Bum Hong; Soon Do Hur; Sung-Deuk Choi; Jeonghoon Lee; Sungmin Hong (137-143).
Polar ice sheets conserve atmospheric aerosols at the time of snowfall, which can be used to reconstruct past climate and environmental conditions. We investigated mineral dust and major ion records in snowpit samples obtained from the northwestern Greenland ice sheet near the North Greenland Eemian Ice Drilling (NEEM) camp in June 2009. We analyzed the samples for mineral dust concentrations as well as stable water isotopes (δ18O, δD, and deuterium excess) and major ions (Cl−, SO 4 2 - , methanesulfonic acid (MSA), Na+, and Ca2+). Seasonal δ18O and δD cycles indicate that the snowpit samples covered a six-year period from spring 2003 to early summer 2009. Concentrations of mineral dust, nss-Ca2+, and nss- SO 4 2 - showed seasonal deposition events with maxima in the winter–spring layers. On the other hand, the Cl−/Na+ ratio and the concentrations of MSA exhibited maxima in the summer layers, making them useful indicators for the summer season. Moreover, an anomalous atmospheric mineral dust event was recorded at a depth of 165–170 cm corresponding to late winter 2005 to spring 2006. A back trajectory analysis suggests that a major contributor to the Greenland aerosol was an air mass passing over the Canadian Arctic and North America. Several trajectories point to Asian regions as a dust source. The mineral dust deposited at NEEM was strongly influenced by long-range atmospheric transport and dust input from arid source areas in northern China and Mongolia.
Keywords: Atmospheric mineral dust; Major ions; Seasonal variation; Greenland;
Atmospheric behaviors of polycyclic aromatic hydrocarbons at a Japanese remote background site, Noto peninsula, from 2004 to 2014 by Ning Tang; Mariko Hakamata; Kousuke Sato; Yumi Okada; Xiaoyang Yang; Michiya Tatematsu; Akira Toriba; Takayuki Kameda; Kazuichi Hayakawa (144-151).
Total suspended particulates were collected at a Japanese remote background site (Noto Air Monitoring Station; NAMS) on the Noto Peninsula from September 2004 to June 2014. Nine polycyclic aromatic hydrocarbons (PAHs) in the particulates (fluoranthene, pyrene, benz[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[ghi]perylene and indeno[1,2,3-cd]pyrene) were determined by HPLC with fluorescence detection. The mean total concentrations of the nine PAHs in the cold season (November to May for the years 2004–2014) was 670 pg m−3 (range 37–4100 pg m−3). The mean total concentration in the warm season (June to October for the same period) was 170 pg m−3 (range 31–960 pg m−3). The atmospheric PAH level at NAMS decreased in recent years, although no significant change was found in the warm season. An analysis of meteorological conditions showed that the atmospheric PAHs at NAMS were long range transported from Northeast China in the cold seasons and were contributed to by Japanese domestic sources in the warm seasons. Lower concentration ratios of reactive PAHs to their isomers at NAMS also supported these results. Activities associated with the Beijing Olympic and Paralympic Games in 2008 and reconstruction after the 2007 Noto Hanto earthquake may have contributed to the yearly variations of atmospheric PAH levels at NAMS during the period 2007–2009. Source control measures implemented by the Chinese and Japanese governments appear to have been effective in decreasing the atmospheric PAH levels at NAMS in recent years.Display Omitted
Keywords: PAH; Long-range transportation; Air pollution; Northeast Asia;
Exposure to volatile organic compounds and associated health risks in windsor, Canada by Aziz Khanchi; Christopher A. Hebbern; Jiping Zhu; Sabit Cakmak (152-159).
We examined relationships among measurements of volatile organic compounds (VOCs) and performed cancer and non-cancer risk assessments to determine potential adverse health effects.Personal, indoor and outdoor concentrations of VOCs were measured for 50 non-smoking adults in Windsor, Ontario during winter and summer 2005. The potential excess cancer cases associated with personal concentration were estimated by the Inhalation Unit Risk (USEPA IRIS) and Tumorigenic Concentration (Health Canada). Inhalation Reference Concentration (RfC) was used to evaluate non-cancer adverse effects. Indoor and personal concentrations were statistically compared. Correlations of personal concentrations were estimated to investigate the associations among VOCs.Estimated median lifetime excess cancer risks (95th percentile upper-bound) of benzene and 1,3-butadiene were 8.09 and 4.77 per 1 million. Acetaldehyde presented the highest non-cancer risk. For some VOCs, the personal and indoor geometric means were similar, but arithmetic personal means were higher than the arithmetic indoor means (p < 0.05). Negative correlations among personal VOC concentrations were not sizable.Evaluation of potential cancer and non-cancer risks from VOCs at the personal level should not rely merely on ambient (indoor and outdoor) VOC concentrations. Our analysis showed that personal risk had a complicated pattern that needs further investigation. Our results can be used to prioritize mitigation strategies to protect human health.
Keywords: Volatile organic compound; Personal exposure; Excess cancer risk; Inhalation unit risk; Tumorigenic dose;
Role of clay minerals in the formation of atmospheric aggregates of Saharan dust by Javier Cuadros; José L. Diaz-Hernandez; Antonio Sanchez-Navas; Antonio Garcia-Casco (160-172).
Saharan dust can travel long distances in different directions across the Atlantic and Europe, sometimes in episodes of high dust concentration. In recent years it has been discovered that Saharan dust aerosols can aggregate into large, approximately spherical particles of up to 100 μm generated within raindrops that then evaporate, so that the aggregate deposition takes place most times in dry conditions. These aerosol aggregates are an interesting phenomenon resulting from the interaction of mineral aerosols and atmospheric conditions. They have been termed “iberulites” due to their discovery and description from aerosol deposits in the Iberian Peninsula. Here, these aggregates are further investigated, in particular the role of the clay minerals in the aggregation process of aerosol particles. Iberulites, and common aerosol particles for reference, were studied from the following periods or single dust events and locations: June 1998 in Tenerife, Canary Islands; June 2001 to August 2002, Granada, Spain; 13–20 August 2012, Granada; and 1–6 June 2014, Granada. Their mineralogy, chemistry and texture were analysed using X-ray diffraction, electron microprobe analysis, SEM and TEM. The mineral composition and structure of the iberulites consists of quartz, carbonate and feldspar grains surrounded by a matrix of clay minerals (illite, smectite and kaolinite) that also surrounds the entire aggregate. Minor phases, also distributed homogenously within the iberulites, are sulfates and Fe oxides. Clays are apparently more abundant in the iberulites than in the total aerosol deposit, suggesting that iberulite formation concentrates clays. Details of the structure and composition of iberulites differ from descriptions of previous samples, which indicates dependence on dust sources and atmospheric conditions, possibly including anthropic activity. Iberulites are formed by coalescence of aerosol mineral particles captured by precursor water droplets. The concentration of clays in the iberulites is suggested to be the result of higher efficiency for clay capture than for the capture of larger mineral grains. The high hygroscopicity of clay minerals probably causes retention of water in the evaporation stage and some secondary minerals (mainly gypsum) are associated with clays.
Keywords: Clay; Iberulite; Mineral aerosol;
Does urban forestry have a quantitative effect on ambient air quality in an urban environment? by P.J. Irga; M.D. Burchett; F.R. Torpy (173-181).
Increasing urban greenspace has been proposed as a means of reducing airborne pollutant concentrations; however limited studies provide experimental data, as opposed to model estimates, of its ability to do so. The current project examined whether higher concentrations of urban forestry might be associated with quantifiable effects on ambient air pollutant levels, whilst accounting for the predominant source of localized spatial variations in pollutant concentrations, namely vehicular traffic. Monthly air samples for one year were taken from eleven sites in central Sydney, Australia. The sample sites exhibited a range of different traffic density, population usage, and greenspace/urban forest density conditions. Carbon dioxide (CO2), carbon monoxide (CO), total volatile organic compounds (TVOCs), nitric oxide (NO), nitrogen dioxide (NO2), sulfur dioxide (SO2), total suspended particulate matter (TSP), suspended particles <10 μm in diameter (PM10) and particulate matter <2.5 μm (PM2.5), were recorded, using portable devices. It was found that air samples taken from sites with less greenspace frequently had high concentrations of all fractions of aerosolized particulates than other sites, whilst sites with high proximal greenspace had lower particulates, even when vehicular traffic was taken into account. No observable trends in concentrations of NO, TVOC and SO2 were observed, as recorded levels were generally very low across all sampled areas. The findings indicate, first, that within the urban areas of a city, localized differences in air pollutant loads occur. Secondly, we conclude that urban areas with proportionally higher concentrations of urban forestry may experience better air quality with regards to reduced ambient particulate matter; however conclusions about other air pollutants are yet to be elucidated.
Keywords: PM10; PM2.5; Vehicular traffic; Air pollution; Particulate matter; Urban vegetation;
Metrics of ozone risk assessment for Southern European forests: Canopy moisture content as a potential plant response indicator by A. De Marco; P. Sicard; M. Vitale; G. Carriero; C. Renou; E. Paoletti (182-190).
Present standards for protecting ecosystems from ozone (O3), such as AOT40, use atmospheric concentrations. A stomatal flux-based approach (Phytotoxic O3 Dose, PODY) has been suggested. We compared the spatial and temporal distribution of AOT40 and PODY – with and without a hourly threshold of uptake (POD1 and POD0) – for Pinus halepensis and Fagus sylvatica in South-eastern France and North-western Italy. Ozone uptake was simulated by including limitation due to soil water content, as this is an important parameter in water-limited environments. Both AOT40 and POD1 exceeded the critical levels suggested for forests. AOT40 suggested a larger O3 risk relative to PODY. No significant spatial and temporal difference occurred between POD1 and POD0. The use of POD0 in the assessment of ambient O3 risk for vegetation is thus recommended, because it is more biologically-meaningful than AOT40 and easier to be calculated than POD1. Canopy Moisture Content (CMC), a proxy of foliar water content, was modelled and tested as a potential plant O3 response indicator. CMC response to O3 was species-specific, and thus cannot be recommended in the epidemiology of O3 injury to forests.Display Omitted
Keywords: AOT40; Canopy moisture content; Ground-level ozone; Phytotoxic ozone dose; Random forest analysis; Stomatal ozone flux;
Indoor emission, dispersion and exposure of total particle-bound polycyclic aromatic hydrocarbons during cooking by Jun Gao; Yating Jian; Changsheng Cao; Lei Chen; Xu Zhang (191-199).
Cooking processes highly contribute to indoor polycyclic aromatic hydrocarbon (PAH) pollution. High molecular weight and potentially carcinogenic PAHs are generally found attached to small particles, i.e., particulate phase PAHs (PPAHs). Due to the fact that indoor particle dynamics have been clear, describing the indoor dynamics of cooking-generated PPAHs within a specific time span is possible. This paper attempted to quantify the dynamic emission rate, simultaneous spatial dispersion and individual exposure of PPAHs using a cooking source. Experiments were conducted in a real-scale kitchen chamber to elucidate the time-resolved emission and effect of edible oil temperature and mass. Numerical simulations based on indoor particle dynamics were performed to obtain the spatial dispersion and individual inhalation intake of PPAHs under different emission and ventilation conditions. The present work examined the preheating cooking stage, at which edible oil is heated up to beyond its smoke point. The dynamic emission rate peak point occurred much earlier than the oil heating temperature. The total PPAH emission ranged from 2258 to 6578 ng upon heating 40–85 g of edible oil. The overall intake fraction by an individual within a period of 10 min, including 3 min for heating and 7 min for natural cooling, was generally ∼1/10,000. An important outcome of this work was that the overall intake fraction could be represented by multiplying the range hood escape efficiency by the inhalation-to-ventilation rate ratio, which would be no greater than the same ratio. The methodology and results of this work were extendible for the number-based assessment of PPAHs. This work is expected to help us understand the health risks due to inhalation exposure to cooking-generated PPAHs in the kitchen.
Keywords: PAH; Cooking; Exposure; Emission rate; CFD; Ventilation;
Stability of polycyclic aromatic compounds in polyurethane foam-type passive air samplers upon O3 exposure by Narumol Jariyasopit; Yongchun Liu; John Liggio; Tom Harner (200-204).
Stability of polycyclic aromatic compounds (PACs) in polyurethane foam (PUF) disks upon O3 exposure was studied in a flow tube. A wide range of PACs was evaluated by spiking PUF disks with PACs and exposing to O3 at concentrations that were equivalent to two months exposure, a typical deployment period for these passive air samplers. Ambient concentrations of O3 (∼50 ppb) at 0% and 50% relative humidity (RH) were applied. At 0% RH, 23 of 68 PACs yielded more than 50% loss after exposure. The mean percent loss was 30% with perylene and 9,10-dimethylanthracene the most reactive polycyclic aromatic hydrocarbons (PAHs) and alkylated PAHs, respectively. At 50% RH, 77% of the studied PACs was stable upon O3 exposure (PACexposed/PACunexposed > 0.7). The mean percent loss was 17% and only 7 of 68 PACs yielded greater than 50% loss. In general, the reactivity of most of the PACs decreased at higher RH, except for the reactive PAHs (acenaphthylene, 2,3-dimethylanthracene, 9,10-dimethylanthracene, dibenzothiophene, and 2-methyldibenzothiophene) which demonstrated lower RH dependence. The experimental conditions in this study represent a worst case scenario for the stability of PACs sorbed to PUF. In reality, the sampling of PACs in ambient air represents an ‘aged’ component of PACs where the most reactive species have already partially been removed. Also, PACs in ambient air will be associated with the particle phase to varying extents that will help to enhance their stability. Therefore, under regular operating conditions, over a 2-month exposure, we expect a minimal error in the measurement of total concentration of PACs in air using the PUF disk passive sampler.
Keywords: Passive air sampling; PUF disk; PACs; Alkylated PACs; Ozone exposure; Flow tube chamber;
Influence of the El Niño southern oscillation on the total ozone column and clear-sky ultraviolet radiation over China by Jiankai Zhang; Wenshou Tian; Fei Xie; Yuanpu Li; Feiyang Wang; Jinlong Huang; Hongying Tian (205-216).
The influence of the El Niño Southern Oscillation (ENSO) on the total ozone column (TOC) and clear-sky ultraviolet (UV) radiation over China is analysed using various datasets and a chemistry-climate model. Higher TOC values than normal are found over most parts of China during El Niño events. La Niña events have almost the opposite effect on TOC anomalies over China. It is particularly noticeable that the maximum response of the TOC to ENSO shifts northward from southern China in winter to northern China in summer. The seasonal shift of the centre of TOC anomalies is related to the seasonal shift of the location of the East Asia westerly jet, accompanied by tropopause height changes and anomalous circulations induced by Rossby wave trains along the jet. The differences in the TOC between El Niño and La Niña events can cause up to 6–10% clear-sky erythemal UV changes over the middle and lower reaches of the Yangtze River in winter and the northwestern Tibetan Plateau during spring, which may have public health consequences.
Keywords: Total ozone column; ENSO; Ultraviolet radiation;
Forest-atmosphere BVOC exchange in diverse and structurally complex canopies: 1-D modeling of a mid-successional forest in northern Michigan by Alexander M. Bryan; Susan J. Cheng; Kirsti Ashworth; Alex B. Guenther; Brady S. Hardiman; Gil Bohrer; Allison L. Steiner (217-226).
Foliar emissions of biogenic volatile organic compounds (BVOC)—important precursors of tropospheric ozone and secondary organic aerosols—vary widely by vegetation type. Modeling studies to date typically represent the canopy as a single dominant tree type or a blend of tree types, yet many forests are diverse with trees of varying height. To assess the sensitivity of biogenic emissions to tree height variation, we compare two 1-D canopy model simulations in which BVOC emission potentials are homogeneous or heterogeneous with canopy depth. The heterogeneous canopy emulates the mid-successional forest at the University of Michigan Biological Station (UMBS). In this case, high-isoprene-emitting foliage (e.g., aspen and oak) is constrained to the upper canopy, where higher sunlight availability increases the light-dependent isoprene emission, leading to 34% more isoprene and its oxidation products as compared to the homogeneous simulation. Isoprene declines from aspen mortality are 10% larger when heterogeneity is considered. Overall, our results highlight the importance of adequately representing complexities of forest canopy structure when simulating light-dependent BVOC emissions and chemistry.
Keywords: Biogenic volatile organic compounds; Canopy modeling; Mixed forests; Forest succession; Tropospheric chemistry;
Effect of selective catalytic reduction (SCR) on fine particle emission from two coal-fired power plants in China by Zhen Li; Jingkun Jiang; Zizhen Ma; Shuxiao Wang; Lei Duan (227-233).
Nitrogen oxides (NOx) emission abatement of coal-fired power plants (CFPPs) requires large-scaled installation of selective catalytic reduction (SCR), which would reduce secondary fine particulate matter (PM2.5) (by reducing nitrate aerosol) in the atmosphere. However, our field measurement of two CFPPs equipped with SCR indicates a significant increase of SO4 2− and NH4 + emission in primary PM2.5, due to catalytic enhancement of SO2 oxidation to SO3 and introducing of NH3 as reducing agent. The subsequent formation of (NH4)2SO4 or NH4HSO4 aerosol is commonly concentrated in sub-micrometer particulate matter (PM1) with a bimodal pattern. The measurement at the inlet of stack also showed doubled primary PM2.5 emission by SCR operation. This effect should therefore be considered when updating emission inventory of CFPPs. By rough estimation, the enhanced primary PM2.5 emission from CFPPs by SCR operation would offset 12% of the ambient PM2.5 concentration reduction in cities as the benefit of national NOx emission abatement, which should draw attention of policy-makers for air pollution control.By rough estimation, the enhanced primary PM2.5 emission from coal-fired power plants due to SCR installation would offset 12% of the ambient PM2.5 concentration reduction in cities as the benefit of national NOx emission abatement.Display Omitted
Keywords: PM2.5; Emission factor; Coal-fired power plant; Selective catalytic reduction (SCR); Water-soluble inorganic ion; Ammonium sulfate;
Assessing the air quality impact of nitrogen oxides and benzene from road traffic and domestic heating and the associated cancer risk in an urban area of Verona (Italy) by Marco Schiavon; Martina Redivo; Gianluca Antonacci; Elena Cristina Rada; Marco Ragazzi; Dino Zardi; Lorenzo Giovannini (234-243).
Simulations of emission and dispersion of nitrogen oxides (NOx) are performed in an urban area of Verona (Italy), characterized by street canyons and typical sources of urban pollutants. Two dominant source categories are considered: road traffic and, as an element of novelty, domestic heaters. Also, to assess the impact of urban air pollution on human health and, in particular, the cancer risk, simulations of emission and dispersion of benzene are carried out. Emissions from road traffic are estimated by the COPERT 4 algorithm, whilst NOx emission factors from domestic heaters are retrieved by means of criteria provided in the technical literature. Then maps of the annual mean concentrations of NOx and benzene are calculated using the AUSTAL2000 dispersion model, considering both scenarios representing the current situation, and scenarios simulating the introduction of environmental strategies for air pollution mitigation. The simulations highlight potentially critical situations of human exposure that may not be detected by the conventional network of air quality monitoring stations. The proposed methodology provides a support for air quality policies, such as planning targeted measurement campaigns, re-locating monitoring stations and adopting measures in favour of better air quality in urban planning. In particular, the estimation of the induced cancer risk is an important starting point to conduct zoning analyses and to detect the areas where population is more directly exposed to potential risks for health.
Keywords: AUSTAL2000; NOx; COPERT 4; Street canyon; Human exposure; Dispersion modelling;
Evolution of biomass burning smoke particles in the dark by Chunlin Li; Zhen Ma; Jianmin Chen; Xinming Wang; Xingnan Ye; Lin Wang; Xin Yang; Haidong Kan; D.J. Donaldson; Abdelwahid Mellouki (244-252).
The evolution in the dark of physiochemical properties and chemical composition of smoke particles emitted from wheat straw burning, as well as the effect of relative humidity (RH) on these properties, was investigated in an aerosol chamber. The smoke particles are composed primarily of carbonaceous materials and a considerable amount of inorganic salts (∼25 wt.%). During aging, the fraction of inorganic salts in smoke PM1.0 increases, mainly due to the formation of more sulfate and nitrate at the expense of chloride; this heterogeneous conversion is facilitated at high RH. The hygroscopicity parameter κ H of fresh smoke particles is 0.27 and this is estimated to decrease by 0.01 after 4 h dark aging. Both aging and high RH lead to increases of particle size and density. The effective densities of smoke PM2.5 and PM1.0 deduced from concurrent mass and volume concentration measurements gradually increase from about 1.18 to 1.44 g/m3 within 4 h aging at 45%–55% RH, in line with the results obtained both from size-resolved particle density analysis using an aerosol particle mass analyzer (APM) and from estimation using composition-weighted bulk densities. The density of smoke particle is size-, RH-, and aging extent-dependent; the size effect becomes less pronounced with aging.
Keywords: Smoke particle; Aerosol chamber; Dark aging; RH effect; Effective density; Hygroscopicity;
Spatial and seasonal atmospheric PAH deposition patterns and sources in Rhode Island by Laura A. Schifman; Thomas B. Boving (253-261).
Polycyclic aromatic hydrocarbons (PAH) enter the environment through various combustion processes and can travel long distances via atmospheric transport. Here, atmospheric PAH deposition was measured in six locations throughout Rhode Island using passive atmospheric bulk-deposition samplers for three years. The measurements were evaluated using two source-specific PAH isomer signatures, a multivariate receptor model, and an innovative contamination index that is weighted based on PAH contamination, number of detected compounds, and toxicity. Urban areas had significantly higher deposition rates (up to 2261 μg m−2 yr−1 ∑PAH) compared to peri-urban, coastal, and rural areas (as low as 73.6 μg m−2 yr−1 ∑PAH). In fall and winter, PAH deposition was up to 10 times higher compared to summer/spring. On an annual basis a total of 3.64 t yr−1 ∑PAH (2256.9 μg yr−1 m−2 ∑PAH) are estimated to be deposited atmospherically onto Rhode Island. Both, the analysis using isomer ratios and the statistical analysis using positive matrix factorization agreed on source identification. Overall gasoline, petrodiesel, and oil combustion sources were identified in all samples year-round while wood combustion associated PAH deposition was only detected during the cold season.Display Omitted
Keywords: Passive bulk sampling; Diffuse pollution; Polycyclic aromatic hydrocarbons; PMF analysis; Source attribution; Contaminant index;
Air quality and climate responses to anthropogenic black carbon emission changes from East Asia, North America and Europe by Makliyar Sadiq; Wei Tao; Junfeng Liu; Shu Tao (262-276).
East Asia, North America and Europe are the world largest emitters of anthropogenic black carbon (BC). In this study, the role of each region's anthropogenic BC emissions on domestic air quality and climate is investigated. A ten-year six-member parallel simulation (i.e., with anthropogenic emissions in each region reduced by 0%, 50% or 100%, or increased by 200%, 500% or 1000%) is conducted based on the state-of-the-art Community Earth System Model (CESM). Linearity of the emission-response relationship is examined for a variety of air quality and climate indicators. Generally, a change in BC emissions tend to linearly influence BC concentrations over both source and nearby downwind regions even taking into account the effect of BC-induced climate perturbations. Aerosol optical depth (AOD) and the net radiative flux perturbation at top of atmosphere (TOA) tend to preserve a similar linear relationship to local BC emission changes, with a robust signal confined only to the source areas. However, the response of temperature in most places is inconsistent to BC emission changes. Though the presence of BC in the atmosphere absorbs solar and terrestrial radiation which has a tendency to warm the atmosphere, the perturbed atmospheric circulation induces substantial meridional exchanges of warm and cold air masses, which overpasses the warming tendency of BC exerted on the atmosphere. This indicates that reducing/increasing regional BC emissions immediately ameliorate/deteriorate local air quality proportionally, but the associated effects on climate perturbation may lack a clear trend within the initial 10-year time span.
Keywords: Black carbon; East Asia; Europe; North America; Climate response; Radiation budget;
Biomass burning in the Amazon region: Aerosol source apportionment and associated health risk assessment by Nilmara de Oliveira Alves; Joel Brito; Sofia Caumo; Andrea Arana; Sandra de Souza Hacon; Paulo Artaxo; Risto Hillamo; Kimmo Teinilä; Silvia Regina Batistuzzo de Medeiros; Pérola de Castro Vasconcellos (277-285).
The Brazilian Amazon represents about 40% of the world's remaining tropical rainforest. However, human activities have become important drivers of disturbance in that region. The majority of forest fire hotspots in the Amazon arc due to deforestation are impacting the health of the local population of over 10 million inhabitants. In this study we characterize western Amazonia biomass burning emissions through the quantification of 14 Polycyclic Aromatic Hydrocarbons (PAHs), Organic Carbon, Elemental Carbon and unique tracers of biomass burning such as levoglucosan. From the PAHs dataset a toxic equivalence factor is calculated estimating the carcinogenic and mutagenic potential of biomass burning emissions during the studied period. Peak concentration of PM10 during the dry seasons was observed to reach 60 μg m−3 on the 24 h average. Conversely, PM10 was relatively constant throughout the wet season indicating an overall stable balance between aerosol sources and sinks within the filter sampling resolution. Similar behavior is identified for OC and EC components. Levoglucosan was found in significant concentrations (up to 4 μg m−3) during the dry season. Correspondingly, the estimated lung cancer risk calculated during the dry seasons largely exceeded the WHO health-based guideline. A source apportionment study was carried out through the use of Absolute Principal Factor Analysis (APFA), identifying a three-factor solution. The biomass burning factor is found to be the dominating aerosol source, having 75.4% of PM10 loading. The second factor depicts an important contribution of several PAHs without a single source class and therefore was considered as mixed sources factor, contributing to 6.3% of PM10. The third factor was mainly associated with fossil fuel combustion emissions, contributing to 18.4% of PM10. This work enhances the knowledge of aerosol sources and its impact on climate variability and local population, on a site representative of the deforestation which occupies a significant fraction of the Amazon basin.
Keywords: Biomass burning; Amazon region; PM10; PAHs and lung cancer risk;
Impact of primary and secondary organic sources on the oxidative potential of quasi-ultrafine particles (PM0.25) at three contrasting locations in the Los Angeles Basin by Arian Saffari; Sina Hasheminassab; Dongbin Wang; Martin M. Shafer; James J. Schauer; Constantinos Sioutas (286-296).
To investigate the changing contribution of primary and secondary sources on the oxidative potential of particulate matter (PM) in a real-world urban atmosphere, 7 sets of quasi-ultrafine particles (PM0.25) were collected at three contrasting locations in the Los Angeles Basin, California, USA. Samples were collected in the coastal area of Long Beach during the morning rush hour period, representing fresh primary emissions from nearby freeways and the LA port; in central Los Angeles during midday, representing a mixture of fresh primary emissions and early products of photochemical secondary organic aerosol (SOA) formation; and at a downwind site (Upland) during afternoon, when the impacts of photochemically aged secondary PM are significant. Chemical composition showed distinctive trends, with the lowest fraction of water soluble organic carbon (WSOC) and other organic tracers of SOA formation (e.g. organic acids) at Long Beach, and the lowest abundance of organic tracers of primary vehicular emissions (such as polycyclic aromatic hydrocarbons and hopanes) at Upland. A molecular marker-based chemical mass balance (MM-CMB) model indicated that 72% of the total organic carbon at Long Beach was comprised of primary vehicular sources (combined heavy duty and light duty vehicles), while the vehicular fraction was found to be 50% and 39% at Los Angeles and Upland, respectively. Regression analysis suggested that at Long Beach, the variation in oxidative potential of PM0.25 (quantified using a macrophage-based reactive oxygen species (ROS) assay) was mainly driven by mobile vehicular emissions and the water-insoluble fraction of the organic carbon. In contrast, at Upland, where photochemical processing and secondary aerosol formation was the highest, WSOC and secondary organics were the major drivers of the oxidative potential variation. The multivariate regression analysis also indicated that as much as 58% of the overall spatial and temporal variation in the oxidative potential of PM0.25 at these three locations can be explained by mobile emissions and SOA.
Keywords: Particulate matter; Ultrafine; Oxidative potential; CMB; Photochemical aging;
Characterization of aerosol composition, concentrations, and sources at Baengnyeong Island, Korea using an aerosol mass spectrometer by Taehyoung Lee; Jinsoo Choi; Gangwoong Lee; Junyoung Ahn; Jin Soo Park; Samuel A. Atwood; Misha Schurman; Yongjoo Choi; Yoomi Chung; Jeffrey L. Collett (297-306).
To improve understanding of the sources and chemical properties of particulate pollutants on the western side of the Korean Peninsula, an Aerodyne High Resolution Time of Flight Aerosol Mass Spectrometer (HR-ToF-AMS) measured non-refractory fine (PM1) particles from May to November, 2011 at Baengnyeong Island, South Korea. Organic matter and sulfate were generally the most abundant species and exhibited maximum concentrations of 36 μg/m3 and 39 μg/m3, respectively. Nitrate concentrations peaked at 32 μg/m3 but were typically much lower than sulfate and organic matter concentrations. May, September, October, and November featured the highest monthly average concentrations, with lower concentrations typically observed from June through August. Potential source contribution function (PSCF) analysis and individual case studies revealed that transport from eastern China, an area with high SO2 emissions, was associated with high particulate sulfate concentrations at the measurement site. Observed sulfate aerosol sometimes was fully neutralized by ammonium but often was acidic; the average ammonium to sulfate molar ratio was 1.49. Measured species size distributions revealed a range of sulfate particle size distributions with modes between 100 and 600 nm. Organic aerosol source regions were widespread, including contributions from eastern China and South Korea. Positive matrix factorization (PMF) analysis indicated three “factors,” or types of organic aerosol, comprising one primary, hydrocarbon-like organic aerosol (HOA) and two oxidized organic aerosol (OOA) components, including a more oxidized (MO-OOA) and a less oxidized (LO-OOA) oxidized organic aerosol. On average, HOA and OOA contributed 21% and 79% of the organic mass (OM), respectively, with the MO-OOA fraction nearly three times as abundant as the LO-OOA fraction. Biomass burning contributions to observed OM were low during the late spring/early summer agricultural burning season in eastern China, since airflow into eastern China during the Asian Monsoon generally prevents transport of emissions eastward to the Korean Peninsula. Concentrations of the m/z 60 AMS biomass burning marker were more abundant in autumn, when transport patterns appeared to bring some smoke from fires in northern Asia to the island.
Keywords: HR-ToF-AMS; Baengnyeong island; Long-range transport; Biomass burning; Potential source contribution;
Characterization of submicron aerosols and effect on visibility during a severe haze-fog episode in Yangtze River Delta, China by X.J. Shen; J.Y. Sun; X.Y. Zhang; Y.M. Zhang; L. Zhang; H.C. Che; Q.L. Ma; X.M. Yu; Y. Yue; Y.W. Zhang (307-316).
Particle size, composition and optical properties were measured at a regional atmosphere background station in the Yangtze River Delta (YRD) to understand the formation and evolution of haze-fog episodes in Jan. 2013. The peak of particle number size distribution was in the size range of 80–100 nm during the measurements. PM1 mass concentration contributed 84% to the total particle mass (PM10). Based on visibility and ambient relative humidity, three types of weather conditions (i.e., clear, haze and fog) were classified in this study. The extinction coefficients of PM1 and PM10 under dry conditions were simulated by the Mie model. Under dry conditions, PM1 was found to contribute approximately 91% to the light extinction coefficient of PM10. However, the PM1 with the assumption of dry state was found to contribute approximately 85% to the ambient extinction coefficient of PM10 during clear conditions, 58% during haze conditions and approximately 41% during fog conditions. The variation of the dry PM1 contribution was related to the water uptake of particles under different relative humidity conditions.A severe haze-fog event on Jan. 14–17 was discussed in more detail as a case study. Two episodes were chosen to show that nitrate and organics dominated the aerosol component during the severe haze-fog episode and were related to secondary aerosol formation and air mass origin. Nitrate played a more dominant role than sulfate in heavy haze formation in the YRD region, which was different from the North China Plain region.
Keywords: Particle number size distribution; Light extinction of submicron aerosol; Secondary aerosol formation; Severe haze-fog; Air mass origin;
Variation and co-variation of PM10, particle number concentration, NOx and NO2 in the urban air – Relationships with wind speed, vertical temperature gradient and weather type by M. Grundström; C. Hak; D. Chen; M. Hallquist; H. Pleijel (317-327).
Atmospheric ultrafine particles (UFP; diameter < 0.1 μm) represent a growing global health concern in urban environments and has a strong link to traffic related emissions. UFP is usually the dominating fraction of atmospheric particle number concentrations (PNC) despite being a minor part of total particle mass. The aim of this study was to empirically investigate the relationship between PNC and other air pollutants (NOX, NO2 and PM10) in the urban environment and their dependence on meteorology and weather type, using the Lamb Weather Type (LWT) classification scheme. The study was carried out in Gothenburg, Sweden, at an urban background site during April 2007–May 2008. It was found that daily average [PNC] correlated very well with [NOx] (R2 = 0.73) during inversion days, to a lesser extent with [NO2] (R2 = 0.58) and poorly with [PM10] (R2 = 0.07). Both PNC and NOx had similar response patterns to wind speed and to the strength of temperature inversions. PNC displayed two regimes, one strongly correlated to NOx and a second poorly correlated to NOx which was characterised by high wind speed. For concentration averages based on LWTs, the PNC-[NOx] relationship remained strong (R2 = 0.70) where the windy LWT W deviated noticeably. Exclusion of observations with wind speed >5 ms−1 or ΔT < 0 °C from LWTs produced more uniform and stronger relationships (R2 = 0.90; R2 = 0.93). Low wind speeds and positive vertical temperature gradients were most common during LWTs A, NW, N and NE. These weather types were also associated with the highest daily means of NOx (∼30 ppb) and PNC (∼10 000 # cm−3). A conclusion from this study is that NOx (but not PM10) is a good proxy for PNC especially during calm and stable conditions and that LWTs A, NW, N and NE are high risk weather types for elevated NOx and PNC.
Keywords: Urban air pollution; NOx; NO2; PM10; Proxy; PNC; Wind; Atmospheric stability; Lamb weather types;
Diurnal and seasonal variation of the PM2.5 apparent particle density in Beijing, China by Zirui Liu; Bo Hu; Dongsheng Ji; Yonghong Wang; Mingxing Wang; Yuesi Wang (328-338).
To characterize the features of particle apparent density and its correlation with chemical composition and meteorological conditions, continuous measurements of particle number size distributions and particle mass concentrations were conducted in the winter and summer periods in Beijing using a Scanning Mobility Particle Sizer and a Tapered Element Oscillating Microbalance with a Filter Dynamic Measurement System. The apparent density, as determined by the particle mass to volume ratios, showed strong seasonal and diurnal variations, with higher values were observed during the warm season (1.60 ± 0.43 g cm−3, July to September 2014) compared to the cold season (1.41 ± 0.40 g cm−3, November 2013 to January 2014). A minimum in the morning and afternoon rush hours was observed in both seasons, representing fresh primary aerosol emissions, which were related to soot particles with low density due to their agglomerate structure, especially observed in the late afternoon hours of the cold season (approximately 1.3 g cm−3) when traffic emissions combined with the coal combustion for heating supply. The highest values were found during midday (approximately 1.8 g cm−3) in the warm season, likely due to increased secondary particle production and the presence of more aged particles with a build-up of the convectively mixed boundary layer. The apparent particle density has the potential to serve as a crude tracer for chemical composition and atmospheric processing and might play an important role when considering the associations between health effects and ambient particles.
Keywords: Fine particles; Apparent density; Material density; Morphology;
Spatial-temporal analysis and projection of extreme particulate matter (PM10 and PM2.5) levels using association rules: A case study of the Jing-Jin-Ji region, China by Shanshan Qin; Feng Liu; Chen Wang; Yiliao Song; Jiansheng Qu (339-350).
The Jing-Jin-Ji region of Northern China has experienced serious extreme PM concentrations, which could exert considerable negative impacts on human health. However, only small studies have focused on extreme PM concentrations. Therefore, joint regional PM research and air pollution control has become an urgent issue in this region. To characterize PM pollution, PM10 and PM2.5 hourly samples were collected from 13 cities in Jing-Jin-Ji region for one year. This study initially analyzed extreme PM data using the Apriori algorithm to mine quantitative association rules in PM spatial and temporal variations and intercity influences. The results indicate that 1) the association rules of intercity PM are distinctive, and do not completely rely on their spatial distributions; 2) extreme PM concentrations frequently occur in southern cities, presenting stronger spatial and temporal associations than in northern cities; 3) the strength of the spatial and temporal associations of intercity PM2.5 are more substantial than those of intercity PM10.
Keywords: Extreme particulate matter; Spatial-temporal; Analysis and projection; Association rules;
Fractionating ambient humic-like substances (HULIS) for their reactive oxygen species activity – Assessing the importance of quinones and atmospheric aging by Vishal Verma; Ying Wang; Rawan El-Afifi; Ting Fang; Janessa Rowland; Armistead G. Russell; Rodney J. Weber (351-359).
In this paper, we present a technique to identify the redox-active components of fine organic aerosols by fractionating humic-like substances (HULIS). We applied this technique to a dithiothreitol (DTT) assay – a measure of the capability of PM to generate reactive oxygen species (ROS), and assessed the contribution of quinones to the DTT activity of ambient water-soluble PM. Filter samples from the Southeastern Center for Air Pollution & Epidemiology (SCAPE) were extracted in water and then passed-through a C-18 column to isolate the HULIS fraction by retention on the column. The HULIS was then eluted with a sequence of solvents of increasing polarity, i.e., hexane, dichloromethane (DCM) and then methanol. Each of these eluted fractions was analyzed for DTT activity. The methanol fraction was found to possess most of the DTT activity (>70%), while the hexane fraction had the least activity (<5%), suggesting that the ROS-active compounds of ambient water-soluble PM2.5 HULIS are mostly polar in nature. A number of quinones thought to contribute to ambient PM DTT activity were also tested. 1,4 Naphthoquinone (1,4 NQ), 1,2 Naphthoquinone (1,2 NQ), 9,10 Phenanthrenequinone (PQ), and 5-hydroxy-1,4 NQ were analyzed by the same protocol. The hexane fraction of two quinones (PQ, and 1,4 NQ) was the most-DTT active, while methanol was the least, confirming that PQ, 1,4 NQ, and 1,2 NQ (which could not be recovered from the column) do not contribute significantly to the water-soluble DTT activity of ambient PM2.5. However, an oxygenated derivative of 1,4 NQ, (5-hydroxy-1,4 NQ), which is also intrinsically more DTT-active than 1,4 NQ, was mostly (>60%) eluted in methanol. The results demonstrate the importance of atmospheric aging (oxidation) of organic aerosols in enhancing the ROS activity of ambient PM.Display Omitted
Keywords: Quinones; Dithiothreitol (DTT assay); Reactive oxygen species (ROS); Humic-like substances (HULIS); Atmospheric aging;
Association between air pollution and daily mortality and hospital admission due to ischaemic heart diseases in Hong Kong by Wilson Wai San Tam; Tze Wai Wong; Andromeda H.S. Wong (360-368).
Ischaemic heart disease (IHD) is one of the leading causes of death worldwide. The effects of air pollution on IHD mortalities have been widely reported. Fewer studies focus on IHD morbidities and PM2.5, especially in Asia. To explore the associations between short-term exposure to air pollution and morbidities and mortalities from IHD, we conducted a time series study using a generalized additive model that regressed the daily numbers of IHD mortalities and hospital admissions on daily mean concentrations of the following air pollutants: nitrogen dioxide (NO2), particulate matter with an aerodynamic diameter less than 10 μm (PM10), particulate matter with an aerodynamic diameter less than 2.5 μm (PM2.5), ozone (O3), and sulfur dioxide (SO2). The relative risks (RR) of IHD deaths and hospital admissions per 10 μg/m3 increase in the concentration of each air pollutant were derived in single pollutant models. Multipollutant models were also constructed to estimate their RRs controlling for other pollutants. Significant RRs were observed for all five air pollutants, ranging from 1.008 to 1.032 per 10 μg/m3 increase in air pollutant concentrations for IHD mortality and from 1.006 to 1.021 per 10 μg/m3 for hospital admissions for IHD. In the multipollutant model, only NO2 remained significant for IHD mortality while SO2 and PM2.5 was significantly associated with hospital admissions. This study provides additional evidence that mortalities and hospital admissions for IHD are significantly associated with air pollution. However, we cannot attribute these health effects to a specific air pollutant, owing to high collinearity between some air pollutants.
Keywords: Ischaemic heart disease; Air pollution; PM10; PM2.5; Hospital admissions; Mortality;
Geochemical evidence for seasonal variations in potential loess sources of the western Chinese Loess Plateau by Xunming Wang; Lili Lang; Hui Li; Ting Hua; Guangtao Wang; Na Zhou; Linlin Jiao (369-375).
This paper aims to characterize seasonal variations in the potential sources of loess deposited on the western Chinese Loess Plateau (CLP). Fallout was sampled every five days between March 2013 and August 2014 at Jiuzhoutai, the site with the largest loess deposits in northwest China. A total of 45 macro and trace elements, as well as rare earth elements, were analyzed in the samples. The results show that, at present, the potential sources of loess are mixed with pollutants. After exclusion of the pollutants, principal component analysis (PCA) showed significant seasonal variations in the potential loess sources on the western CLP. During the spring, summer–autumn, and winter periods, there are possibly six, four, and two potential loess sources, respectively, with crustal provenance at Jiuzhoutai. No significant differences in fallout amounts were found on the western CLP during periods with and without dust events, which suggests that the frequency of dust events may not be an effective index for deposition rates in areas of loess formation. The relatively high proportion of coarser material (>50 μm in diameter) in the fallout indicates that at least part of the loess in the fallout samples originated from adjacent deserts and associated systems, and that both dry and wet deposition contributed equally to the fallout. Based on the significant seasonal and spatial variations in the loess sources, combined with variations in the link between the different particle size classes and the geochemical characteristics of potential components of the loess on the western CLP, the use of the geochemical characteristics of loess stratigraphic sequences as a proxy for regional paleoclimatic and environmental reconstructions should be carefully appraised.
Keywords: Loess; Source; Principal components analysis; Chinese Loess Plateau;
Fuel regulation in inland navigation: Reduced soil black carbon deposition in river valleys in Germany by M. Bläsing; Y. Shao; E. Lehndorff (376-384).
Inland navigation is of increasing economic and ecological interest, however its contribution to environmental quality is hardly known. We hypothesized that i) inland navigation emits considerable amounts of soot-Black Carbon (BC) as a product of incomplete combustion of diesel fuel, which is then deposited on soils along river valleys, that ii) improvement of fuel quality by sulfur reduction in 2011 decreased BC inputs to soil, and that iii) this provides a tracer for the spatial impact of inland navigation emissions. The spatial and temporal patterns of soil BC deposits from inland navigation were investigated yearly (2010–2013) working within transects perpendicular to the rivers Rhine, Moselle and Ahr, Germany (the Ahr Valley is free of shipping and served as a reference). In rural areas at inland waterways navigation likely represented the dominant BC emitter. Topsoils (0–10 cm depth) were sampled in vineyards. Their BC content and composition was determined via oxidation of bulk soil organic matter to benzene polycarboxylic acids (BPCAs). The highly trafficked Rhine Valley yielded only little more BC (64.7 ± 12 g BC kg−1 soil organic carbon (SOC) compared to 51.7 ± 9 at the Moselle, and 53.6 ± 6 at the reference Ahr Valley). At both inland waterways soil BC increased towards the river, following the simulated dispersal of ship-derived BC using a Lagrangian model. In the course of ship fuel regulation, soil BC deposits at the Rhine and Moselle waterways decreased significantly from 70.2 ± 3.2 to 47.9 ± 1.1 and 57.6 ± 1.3 to 41.7 ± 0.9 g BC kg−1 SOC within 3 years. Even more pronounced was the change in BC composition, i.e., the ratio of pentacarboxylated to mellitic acid increased from 0.75 to 1.3 (Rhine) and 1 to 1.4 (Moselle) during this time span. From this we calculated that ∼30% less BC was deposited by inland navigation likely due to reduced BC emissions after sulfur regulation in ship diesel.Display Omitted
Keywords: Soil black carbon; Diesel; Biomass burning; Inland navigation; Dispersion simulation;
Future trends of global atmospheric antimony emissions from anthropogenic activities until 2050 by Junrui Zhou; Hezhong Tian; Chuanyong Zhu; Jiming Hao; Jiajia Gao; Yong Wang; Yifeng Xue; Shenbin Hua; Kun Wang (385-392).
This paper presents the scenario forecast of global atmospheric antimony (Sb) emissions from anthropogenic activities till 2050. The projection scenarios are built based on the comprehensive global antimony emission inventory for the period 1995–2010 which is reported in our previous study. Three scenarios are set up to investigate the future changes of global antimony emissions as well as their source and region contribution characteristics. Trends of activity levels specified as 5 primary source categories are projected by combining the historical trend extrapolation with EIA International energy outlook 2013, while the source-specific dynamic emission factors are determined by applying transformed normal distribution functions. If no major changes in the efficiency of emission control are introduced and keep current air quality legislations (Current Legislation scenario), global antimony emissions will increase by a factor of 2 between 2010 and 2050. The largest increase in Sb emissions is projected from Asia due to large volume of nonferrous metals production and waste incineration. In case of enforcing the pollutant emission standards (Strengthened Control scenario), global antimony emissions in 2050 will stabilize with that of 2010. Moreover, we can anticipate further declines in Sb emissions for all continents with the best emission control performances (Maximum Feasible Technological Reduction scenario). Future antimony emissions from the top 10 largest emitting countries have also been calculated and source category contributions of increasing emissions of these countries present significant diversity. Furthermore, global emission projections in 2050 are distributed within a 1° × 1°latitude/longitude grid. East Asia, Western Europe and North America present remarkable differences in emission intensity under the three scenarios, which implies that source-and-country specific control measures are necessary to be implemented for abating Sb emissions from varied continents and countries in the future.
Keywords: Global emission inventory; Antimony; Scenario analysis; Geospatial distribution characteristics; Fuel combustion; Waste incineration;
Real-world emissions and fuel consumption of diesel buses and trucks in Macao: From on-road measurement to policy implications by Xiaomeng Wu; Shaojun Zhang; Ye Wu; Zhenhua Li; Yu Zhou; Lixin Fu; Jiming Hao (393-403).
A total of 13 diesel buses and 12 diesel trucks in Macao were tested using portable emission measurement systems (PEMS) including a SEMTECH-DS for gaseous emissions and a SEMTECH-PPMD for PM2.5. The average emission rates of gaseous pollutants and CO2 are developed with the operating mode defined by the instantaneous vehicle specific power (VSP) and vehicle speed. Both distance-based and fuel mass-based emission factors for gaseous pollutants (e.g., CO, THC and NOX) are further estimated under typical driving conditions. The average distance-based NOX emission of heavy-duty buses (HDBs) is higher than 13 g km−1. Considering the unfavorable conditions for selective reductions catalyst (SCR) systems, such as low-speed driving conditions, more effective technology options (e.g., dedicated natural gas buses and electric buses) should be considered by policy makers in Macao. We identified strong effects of the vehicle size, engine displacement and driving conditions on real-world CO2 emission factors and fuel consumption for diesel vehicles. Therefore, detailed profiles regarding vehicle specifications can reduce the uncertainty in their fleet-average on-road fuel consumption. In addition, strong correlations between relative emission factors and driving conditions indicated by the average speed of generated micro-trips are identified based on a micro-trip method. For example, distance-based emission factors of HDBs will increase by 39% for CO, 29% for THC, 43% for NOX and 26% for CO2 when the average speed decreases from 30 km h−1 to 20 km h−1. The mitigation of on-road emissions from diesel buses and trucks by improving traffic conditions through effective traffic and economic management measures is therefore required. This study demonstrates the important role of PEMS in understanding vehicle emissions and mitigation strategies from science to policy perspectives.
Keywords: Vehicle; Diesel; Emissions; Fuel consumption; Macao; PEMS;
Modeling the uncertainty of several VOC and its impact on simulated VOC and ozone in Houston, Texas by Shuai Pan; Yunsoo Choi; Anirban Roy; Xiangshang Li; Wonbae Jeon; Amir Hossein Souri (404-416).
A WRF-SMOKE-CMAQ modeling system was used to study Volatile Organic Compound (VOC) emissions and their impact on surface VOC and ozone concentrations in southeast Texas during September 2013. The model was evaluated against the ground-level Automated Gas Chromatograph (Auto-GC) measurement data from the Texas Commission on Environmental Quality (TCEQ). The comparisons indicated that the model over-predicted benzene, ethylene, toluene and xylene, while under-predicting isoprene and ethane. The mean biases between simulated and observed values of each VOC species showed clear daytime, nighttime, weekday and weekend variations. Adjusting the VOC emissions using simulated/observed ratios improved model performance of each VOC species, especially mitigating the mean bias substantially. Simulated monthly mean ozone showed a minor change: a 0.4 ppb or 1.2% increase; while a change of more than 5 ppb was seen in hourly ozone data on high ozone days, this change moved model predictions closer to observations. The CMAQ model run with the adjusted emissions better reproduced the variability in the National Aeronautics and Space Administration (NASA)'s Ozone Monitoring Instrument (OMI) formaldehyde (HCHO) columns. The adjusted model scenario also slightly better reproduced the aircraft HCHO concentrations from NASA's DISCOVER-AQ campaign conducted during the simulation episode period; Correlation, Mean Bias and RMSE improved from 0.34, 1.38 ppb and 2.15 ppb to 0.38, 1.33 ppb and 2.08 ppb respectively. A process analysis conducted for both industrial/urban and rural areas suggested that chemistry was the main process contributing to ozone production in both areas, while the impact of chemistry was smaller in rural areas than in industrial and urban areas. For both areas, the positive chemistry contribution increased in the sensitivity simulation largely due to the increase in emissions. Nudging VOC emissions to match the observed concentrations shifted the ozone hotspots outside the industrial/urban region and enhanced the peaked ozone in the outflow region with consistent southerly/southeasterly winds during the afternoon time (1–5 pm). This study helps in the understanding of these processes which are critical to constrain high peak ozone values in the outflow regions. The results indicate that formation of ozone in the outflow could complicate attainment status in neighboring counties.
Keywords: VOC; Emission; Modeling; Ozone; Process analysis; OMI HCHO; Houston;
Real-time indoor and outdoor measurements of black carbon at primary schools by C. Reche; I. Rivas; M. Pandolfi; M. Viana; L. Bouso; M. Àlvarez-Pedrerol; A. Alastuey; J. Sunyer; X. Querol (417-426).
Epidemiological and toxicological studies have demonstrated the association between Black Carbon in indoor and outdoor air and the occurrence of health risks. Data on air quality in schools is of special interest, as children are more vulnerable to health hazards. In this context, indoor and outdoor measurements of real-time Equivalent Black Carbon (EBC) were collected at 39 primary schools located in Barcelona (Spain), with classrooms naturally ventilated under warm weather conditions. A main contribution of road traffic emissions to indoor and outdoor EBC levels was evidenced through different approaches. Simultaneous measurements of EBC levels at schools under different traffic conditions revealed concentrations by 30–35% higher at schools exposed to higher vehicles intensities. Moreover, a significant correlation was obtained between average outdoor EBC levels at different districts of the city and the percentage of surface area in each district used for the road network (R2 = 0.61). Higher indoor than outdoor levels were recorded at some instances when the indoor sampling location was relatively closer to road traffic, even under low outdoor temperatures. Indeed, the average indoor/outdoor EBC ratios for each school correlate moderately between campaigns in spite of significant differences in temperature between sampling periods. These two facts highlight the strong dependency of the EBC levels on the distance to traffic. The peaks of exposure inside the classrooms seemed to be determined by outdoor concentrations, as shown by the parallelism between indoor and outdoor mean EBC daily cycles and the similar contribution of traffic rush hours to indoor and outdoor daily mean levels. The airtightness of the classroom was suggested as the responsible for the indoor/outdoor ratios of EBC higher than 1 recorded at nights.
Keywords: Children's exposure; Traffic rush-hour; Infiltration; Airtightness;
Day and night variation in chemical composition and toxicological responses of size segregated urban air PM samples in a high air pollution situation by P.I. Jalava; Q. Wang; K. Kuuspalo; J. Ruusunen; L. Hao; D. Fang; O. Väisänen; A. Ruuskanen; O. Sippula; M.S. Happo; O. Uski; S. Kasurinen; T. Torvela; H. Koponen; K.E.J. Lehtinen; M. Komppula; C. Gu; J. Jokiniemi; M.-R. Hirvonen (427-437).
Urban air particulate pollution is a known cause for adverse human health effects worldwide. China has encountered air quality problems in recent years due to rapid industrialization. Toxicological effects induced by particulate air pollution vary with particle sizes and season. However, it is not known how distinctively different photochemical activity and different emission sources during the day and the night affect the chemical composition of the PM size ranges and subsequently how it is reflected to the toxicological properties of the PM exposures. The particulate matter (PM) samples were collected in four different size ranges (PM10-2.5; PM2.5-1; PM1-0.2 and PM0.2) with a high volume cascade impactor. The PM samples were extracted with methanol, dried and thereafter used in the chemical and toxicological analyses. RAW264.7 macrophages were exposed to the particulate samples in four different doses for 24 h. Cytotoxicity, inflammatory parameters, cell cycle and genotoxicity were measured after exposure of the cells to particulate samples. Particles were characterized for their chemical composition, including ions, element and PAH compounds, and transmission electron microscopy (TEM) was used to take images of the PM samples. Chemical composition and the induced toxicological responses of the size segregated PM samples showed considerable size dependent differences as well as day to night variation. The PM10-2.5 and the PM0.2 samples had the highest inflammatory potency among the size ranges. Instead, almost all the PM samples were equally cytotoxic and only minor differences were seen in genotoxicity and cell cycle effects. Overall, the PM0.2 samples had the highest toxic potential among the different size ranges in many parameters. PAH compounds in the samples and were generally more abundant during the night than the day, indicating possible photo-oxidation of the PAH compounds due to solar radiation. This was reflected to different toxicity in the PM samples. Some of the day to night difference may have been caused also by differing wind directions transporting air masses from different emission sources during the day and the night. The present findings indicate the important role of the local particle sources and atmospheric processes on the health related toxicological properties of the PM. The varying toxicological responses evoked by the PM samples showed the importance of examining various particle sizes. Especially the detected considerable toxicological activity by PM0.2 size range suggests they're attributable to combustion sources, new particle formation and atmospheric processes.
Keywords: Particulate matter; Air quality; Toxicology; In vitro; Inflammation; Cytotoxicity;
Stable isotopes of lead and strontium as tracers of sources of airborne particulate matter in Kyrgyzstan by Nitika Dewan; Brian J. Majestic; Michael E. Ketterer; Justin P. Miller-Schulze; Martin M. Shafer; James J. Schauer; Paul A. Solomon; Maria Artamonova; Boris B. Chen; Sanjar A. Imashev; Greg R. Carmichael (438-446).
Central Asia is dominated by an arid climate and desert-like conditions, leading to the potential for long-range transport of desert dust within and out of the region. Of particular interest is the Aral Sea, which has receded in size largely due to water diversion. As a result, newly exposed sediments are resuspended by wind and thus, may be a potential new source of particulate matter within the region. Here, strontium and lead stable isotope ratios are employed along with detailed elemental composition, to explore the contribution of long-range transport of Aral Sea sediments, as well as other potential sources of dust, within Central Asia. Ambient PM10 samples were collected during dust and non-dust events from mid-2008 to mid-2009 at two sites in Kyrgyzstan located ∼1200 and 1500 km ESE of the Aral Sea. Aral Sea sediments and local Kyrgyzstan soils were resuspended and sized to PM10. The Aral Sea sediments have an average 87Sr/86Sr ratio of 0.70992. In contrast, the Sr isotope ratio in local soils exhibits an average ratio of 0.71579. Ambient PM10 collected in Kyrgyzstan has an average 87Sr/86Sr ratio of 0.71177, falling between the values of these two potential sources and indicating a complex mixture of contributing sources. At both sites, airborne Sr isotope ratios measured during dust events were similar, suggesting that Aral Sea sediments only minimally affect air quality in Kyrgyzstan. Elemental analysis and Pb isotope ratios supported this finding. While the Pb isotopes and elemental data both indicate an anthropogenic source, long-range dust transport from other deserts inside and outside the region cannot be ruled out as sources of PM10 in Central Asia.
Keywords: Air pollution; Soils; PM10; Sediments; Dust; Long-range transport; Strontium (Sr) isotopes; Lead (Pb) isotopes; Aral Sea; Central Asia;
Marine and urban influences on summertime PM2.5 aerosol in the Po basin using mobile measurements by R. Wolf; I. El Haddad; M. Crippa; S. Decesari; J.G. Slowik; L. Poulain; S. Gilardoni; M. Rinaldi; S. Carbone; F. Canonaco; R.-J. Huang; U. Baltensperger; A.S.H. Prévôt (447-454).
We report ambient measurements using a high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) on a mobile platform in the southeast Po Valley (Italy) in summer 2012. During the PEGASOS southbound campaign measurements of non-refractory aerosol were performed in urban and rural environments as well as near the coast of the Adriatic Sea. Organic source apportionment analysis of the aerosol mass spectrometer data was carried out using positive matrix factorization and multilinear engine (ME-2) receptor modelling. Five major organic aerosol components were identified: hydrocarbon-like organic aerosol (HOA), semi-volatile oxygenated organic aerosol (SVOOA), low volatility oxygenated organic aerosol (LVOOA), cooking organic aerosol (COA) and a regionally influenced highly oxygenated organic aerosol (HOOA). Essential changes in both aerosol composition and concentration were induced by the ventilation and recirculation of air masses in the East-West direction of the valley (land/sea breeze system) and via the Apennine mountain range (mountain/valley wind system). An urban increment of the non-refractory aerosol mass concentration in Bologna of about 1.6–2.3 μg/m3 compared to the surrounding regions was quantified which can be explained by the sum of local contributions from cooking activities and from hydrocarbon-like aerosol related to traffic emissions.
Keywords: Aerosol mass spectrometry; Source apportionment; Mobile measurements;
Refueling emissions from cars in Japan: Compositions, temperature dependence and effect of vapor liquefied collection system by Hiroyuki Yamada; Satoshi Inomata; Hiroshi Tanimoto (455-462).
Refueling emissions from cars available on the Japanese market, which were not equipped with specific controlling devices, were investigated. For the composition analysis, a proton transfer reaction plus switchable reagent ion mass spectrometry (PTR + SRI-MS), which is capable of real-time measurement, was used. In addition, the performance of a vapor liquefied collection system (VLCS), which is a recently developed controlling device, was evaluated and compared with an onboard refueling vapor recovery (ORVR) system. The refueling emission factor of uncontrolled vehicles at 20 °C was 1.02 ± 0.40 g/L in the case dispensing 20 L of fuel. The results of composition analysis indicated that the maximum incremental reactivity (MIR) of refueling emissions in Japan was 3.49 ± 0.83. The emissions consist of 80% alkanes and 20% alkenes, and aromatics and di-enes were negligible. C4 alkene had the highest impact on the MIR of refueling emissions. The amounts of refueling emissions were well reproduced by a function developed by MOVE2010 in the temperature range of 5–35 °C. The compositions of the refueling emissions varied in this temperature range, but the change in MIR was negligible. The trapping efficiency of VLCS was the same level as that of the ORVR (over 95%). The MIRs of refueling and evaporative emissions were strongly affected by that of the test fuel. This study and our previous study indicated that MIR breakthrough ≈ MIR refueling ≈ MIR fuel + 0.5 and MIR permeation ≈ MIR fuel . The real-world estimated average MIR fuel in Japan was about 3.0.Display Omitted
Keywords: Refueling emissions; Vapor liquefied collection system; ORVR; PTR+SRI-MS; Ozone formation potential;
Particulate matter, carbon emissions and elemental compositions from a diesel engine exhaust fuelled with diesel–biodiesel blends by A.M. Ashraful; H.H. Masjuki; M.A. Kalam (463-474).
A comparative morphological analysis was performed on the exhaust particles emitted from a CI engine using different blending ratios of palm biodiesel at several operating conditions. It was observed from this experiment; peak particle concentration for PB10 at 1200 rpm is 1.85E + 02 and at 1500 rpm is 2.12E + 02. A slightly smaller amount of volatile material has found from the biodiesel samples compared to the diesel fuel sample. Thermogravimetric analysis (TGA) showed that the amount of volatile material in the soot from biodiesel fuels was slightly lower than that of diesel fuel. PB20 biodiesel blends reduced maximum 11.26% of volatile matter from the engine exhaust, while PB10 biodiesel blend reduced minimum 5.53% of volatile matter. On the other hand, the amount of fixed carbon from the biodiesel samples was slightly higher than diesel fuel. Analysis of carbon emissions, palm biodiesel (PB10) reduced elemental carbon (EC) was varies 0.75%–18%, respectively. Similarly, the emission reduction rate for PB20 was varies 11.36%–23.46% respectively. While, organic carbon (OC) emission rates reduced for PB20 was varied 13.7–49% respectively. Among the biodiesel blends, PB20 exhibited highest oxygen (O), sulfur (S) concentration and lowest silicon (Si) and iron (Fe) concentration. Scanning electron microscope (SEM) images for PB20 showed granular structure particulates with bigger grain sizes compared to diesel. Particle diameter increased under the 2100–2400 rpm speed condition and it was 8.70% higher compared to the low speed conditions. Finally, the results indicated that the composition and degree of unsaturation of the methyl ester present in biodiesel, play an important role in the chemical composition of particulate matter emissions.
Keywords: Biodiesel; Particulate matter; Carbon; Thermogravimetric analysis; Energy dispersive X-ray analysis;
Contributions to cities' ambient particulate matter (PM): A systematic review of local source contributions at global level by Federico Karagulian; Claudio A. Belis; Carlos Francisco C. Dora; Annette M. Prüss-Ustün; Sophie Bonjour; Heather Adair-Rohani; Markus Amann (475-483).
For reducing health impacts from air pollution, it is important to know the sources contributing to human exposure. This study systematically reviewed and analysed available source apportionment studies on particulate matter (of diameter of 10 and 2.5 microns, PM10 and PM2.5) performed in cities to estimate typical shares of the sources of pollution by country and by region. A database with city source apportionment records, estimated with the use of receptor models, was also developed and available at the website of the World Health Organization.Systematic Scopus and Google searches were performed to retrieve city studies of source apportionment for particulate matter. Six source categories were defined. Country and regional averages of source apportionment were estimated based on city population weighting.A total of 419 source apportionment records from studies conducted in cities of 51 countries were used to calculate regional averages of sources of ambient particulate matter. Based on the available information, globally 25% of urban ambient air pollution from PM2.5 is contributed by traffic, 15% by industrial activities, 20% by domestic fuel burning, 22% from unspecified sources of human origin, and 18% from natural dust and salt. The available source apportionment records exhibit, however, important heterogeneities in assessed source categories and incompleteness in certain countries/regions.Traffic is one important contributor to ambient PM in cities. To reduce air pollution in cities and the substantial disease burden it causes, solutions to sustainably reduce ambient PM from traffic, industrial activities and biomass burning should urgently be sought. However, further efforts are required to improve data availability and evaluation, and possibly to combine with other types of information in view of increasing usefulness for policy making.Display Omitted
Keywords: Particulate matter; Urban ambient PM; PM2.5; PM10; Source apportionment; Receptor models;
Study of aerosol hygroscopic events over the Cabauw experimental site for atmospheric research (CESAR) using the multi-wavelength Raman lidar Caeli by A.J. Fernández; A. Apituley; I. Veselovskii; A. Suvorina; J. Henzing; M. Pujadas; B. Artíñano (484-498).
This article presents a study of aerosol optical and microphysical properties under different relative humidity (RH) but well mixed layer conditions using optical and microphysical aerosol properties from multi-wavelength (MW) Raman lidar and in-situ aerosol observations collected at the Cabauw Experimental Site for Atmospheric Research (CESAR). Two hygroscopic events are described through 3 backscatter (β) and 2 extinction (α) coefficients which in turn provide intensive parameters such as the backscatter-related Ångström exponent (å β ) and the lidar ratio (LR). Along with it, profiles of RH were inferred from Raman lidar observations and therefore, as a result of varying humidity conditions, a shift on the aerosol optical properties can be described. Thus, it is observed that as RH increases, aerosols uptake water vapour, augment their size and consequently the å β diminishes whereas the LR increases. The enhancement factor based on the backscatter coefficient at 532 nm, which characterizes the aerosol from hygroscopic standpoint, is also estimated. Finally, microphysical properties that are necessary for aerosol radiative forcing estimates – such as volume, effective radii, refractive index and size distribution, all vertically resolved – are retrieved using the inversion with regularization. Using this method, two hygroscopic events are described in detail.
Keywords: Lidar; Aerosol; Hygroscopicity; Optical properties; Microphysical properties;