Atmospheric Environment (v.106, #C)
Editorial board (i).
Two-week NO2 maps for the City of Zurich, Switzerland, derived by statistical modelling utilizing data from a routine passive diffusion sampler network by M.D. Mueller; M. Wagner; I. Barmpadimos; Ch. Hueglin (1-10).
We developed a method to generate two-week NO2 concentration maps with a high spatial resolution (10 m by 10 m) for the city of Zurich, Switzerland, based on statistical modelling. Our models utilize data from a dense passive diffusion sampler network consisting of 49 sites that measured 14-day mean NO2 concentrations in the year 2008. The regression analysis is based on Generalized Additive Models (GAMs) and a stepwise forward selection algorithm that leads to models relying on a small number of explanatory variables (2–3). The explanatory variables included in the regression analysis are spatially resolved information on traffic and heating systems related NOX and NO2 emissions, respectively, sky view factors, and topography (elevation). Deviance explained of the 26 models ranges from 0.66 to 0.79. 81% of the modelled and 77% of the predicted NO2 concentrations, respectively, deviate less than 25% from the observations.The modelling approach outlined in this paper augments the value of point measurements obtained from urban routine passive diffusion sampler networks by providing spatially resolved concentration fields. The derived maps allow a detailed assessment of NO2 levels in cities and can be used in applications such as public health protection.
Keywords: Statistical modelling; Generalized Additive Models; Nitrogen dioxide; Geoinformation; Air quality assessment; Urban environment;
Global impacts of surface ozone changes on crop yields and land use by Clifford Chuwah; Twan van Noije; Detlef P. van Vuuren; Elke Stehfest; Wilco Hazeleger (11-23).
Exposure to surface ozone has detrimental impacts on vegetation and crop yields. In this study, we estimate ozone impacts on crop production and subsequent impacts on land use in the 2005–2050 period using results of the TM5 atmospheric chemistry and IMAGE integrated assessment model. For the crops represented in IMAGE, we compute relative yield losses based on published exposure-response functions. We examine scenarios with either constant or declining emission factors in a weak climate policy future (radiative forcing target of 6.0 W/m2 at the end of the century), as well as co-benefits of stringent climate policy (targeted at 2.6 W/m2). Without a large decrease in air pollutant emissions, higher ozone concentrations could lead to an increase in crop damage of up to 20% locally in 2050 compared to the situation in which the changes in ozone are not accounted for. This may lead to a 2.5% global increase in crop area, and a regional increase of 8.9% in Asia. Implementation of air pollution policies could limit crop yield losses due to ozone to maximally 10% in 2050 in the most affected regions. Similar effects can be obtained as a result of co-benefits from climate policy (reducing ozone precursor emissions). We also evaluated the impact of the corresponding land-use changes on the carbon cycle. Under the worst-case scenario analysed in this study, future ozone increases are estimated to increase the cumulative net CO2 emissions between 2005 and 2050 by about 3.7 Pg C, which corresponds to about 10% of baseline land use emissions over the same period.
Keywords: Ozone crop damage; Land use change; Emission scenarios; Air pollution control; Climate change mitigation;
Simultaneous evaluation of polycyclic aromatic hydrocarbons and carbonyl compounds in the atmosphere of Niterói City, RJ, Brazil by Caroline Fernandes Jaegger Franco; Soraya de Mendonça Ochs; Lucas de Oliveira Grotz; Leonardo de Almeida Furtado; Annibal Duarte Pereira Netto (24-33).
Atmospheric particulate matter (total suspended particulate – TSP – and inhalable particles – PM10) and gas-phase samples were collected in three periods of seven to nine consecutive days in June and December 2011, and May 2012, in the central area of Niterói City, Rio de Janeiro State, Brazil. TSP (48.8–214 μg m−3) showed higher concentrations than PM10 (nd – 82.6 μg m−3). Sixteen polycyclic aromatic hydrocarbons (PAH) and thirty-one carbonyl compounds (CC) were evaluated. Concentrations of individual PAH ranged from <LOQ to 2.25 ng m−3 in TSP and <LOQ to 3.42 ng m−3 in PM10; five- and six-ringed PAH predominated. The concentrations of benzo[a]pyrene (BaP) were below the air quality standard established by the European Union (1.00 ng m−3). The human health risks evaluated by BaPeq and total carcinogenic risk associated with exposure to PM were low. The mean total concentration of CC in PM10 and TSP were 86.0 and 3.9 ng m−3, respectively, whereas in the gaseous phase it was 29.5 μg m−3 and corresponded to around 99.7% of total CC concentration. The total concentrations of CC associated with PM10 showed a discrete seasonal variation according to Principal Component Analysis.Display Omitted
Keywords: PAH; Carbonyl compounds; TSP; PM10; Atmosphere;
Combined field/modelling approaches to represent the air-vegetation distribution of benzo[a]pyrene using different vegetation species by Nuno Ratola; Pedro Jiménez-Guerrero (34-42).
A strategy designed to combine the features of field-based experiments and modelling approaches is presented in this work to assess air-vegetation distribution of benzo(a)pyrene (BaP) in the Iberian Peninsula (IP). Given the lack of simultaneous data in both environmental matrices, a methodology with two main steps was employed. First, evaluating the simulations with the chemistry transport model (CTM) WRF (Weather Research and Forecasting) + CHIMERE data against the European Monitoring and Evaluation Programme (EMEP) network, to test the aptitude of the CTM to replicate the respective atmospheric levels. Then, using modelled concentrations and a method to estimate air levels of BaP from biomonitoring data to compare the performance of different pine species (Pinus pinea, Pinus pinaster, Pinus nigra and Pinus halepensis) to describe the atmospheric evidences. The comparison of modelling vs. biomonitoring has a higher dependence on the location of the sampling points, rather than on the pine species, as some tend to overestimate and others to underestimate BaP concentrations, in most cases regardless of the season. The climatology of the canopy levels of BaP was successfully validated with the concentrations in pine needles (most biases below 26%), however, the model was unable to distinguish between species. This should be taken into consideration in future studies, as biases can rise up to 48%, especially in summer and autumn, the. The comparison with biomonitoring data showed a similar pattern, but with the best results in the warmer months.
Keywords: Benzo(a)pyrene; Pine needles; Biomonitoring; Air sampling; WRF+CHIMERE;
Long-term measurements of submicrometer aerosol chemistry at the Southern Great Plains (SGP) using an Aerosol Chemical Speciation Monitor (ACSM) by Caroline Parworth; Jerome Fast; Fan Mei; Tim Shippert; Chitra Sivaraman; Alison Tilp; Thomas Watson; Qi Zhang (43-55).
In this study the long-term trends of non-refractory submicrometer aerosol (NR-PM1) composition and mass concentration measured by an Aerosol Chemical Speciation Monitor (ACSM) at the Atmospheric Radiation Measurement (ARM) program's Southern Great Plains (SGP) site are discussed. NR-PM1 data was recorded at ∼30 min intervals over a period of 19 months between November 2010 and June 2012. Positive Matrix Factorization (PMF) was performed on the measured organic mass spectral matrix using a rolling window technique to derive factors associated with distinct sources, evolution processes, and physiochemical properties. The rolling window approach also allows us to capture the dynamic variations of the chemical properties in the organic aerosol (OA) factors over time. Three OA factors were obtained including two oxygenated OA (OOA) factors, differing in degrees of oxidation, and a biomass burning OA (BBOA) factor. Back trajectory analyses were performed to investigate possible sources of major NR-PM1 species at the SGP site. Organics dominated NR-PM1 mass concentration for the majority of the study with the exception of winter, when ammonium nitrate increases due to transport of precursor species from surrounding urban and agricultural areas and also due to cooler temperatures. Sulfate mass concentrations have little seasonal variation with mixed regional and local sources. In the spring BBOA emissions increase and are mainly associated with local fires. Isoprene and carbon monoxide emission rates were obtained by the Model of Emissions of Gases and Aerosols from Nature (MEGAN) and the 2011 U.S. National Emissions Inventory to represent the spatial distribution of biogenic and anthropogenic sources, respectively. The combined spatial distribution of isoprene emissions and air mass trajectories suggest that biogenic emissions from the southeast contribute to SOA formation at the SGP site during the summer.
Keywords: Aerodyne aerosol mass spectrometer (AMS); Rural; Organic aerosols; Back-trajectory analysis; Biomass burning;
PM2.5 source apportionment in Lombardy (Italy): Comparison of receptor and chemistry-transport modelling results by G. Pirovano; C. Colombi; A. Balzarini; G.M. Riva; V. Gianelle; G. Lonati (56-70).
This work discusses the source apportionment results produced by receptor and chemistry-transport modelling for PM2.5 in Northern Italy, selected as case study due to its very critical conditions. Receptor modelling was performed using the Chemical Mass Balance model, while source oriented analysis by means of the CAMx chemistry transport model. Models shared the same source profiles, mostly based on local data. CMB showed a better reconstruction of the mass closure, while CAMx systematically underestimated cold season concentrations. Nevertheless both models provided the same source ranking at several receptors. According to CMB results, the most relevant contributions during the cold season, ranging around 10 μg m−3, were yielded by road transport, domestic heating and ammonium nitrate. CAMx provided similar results for the secondary sources, while systematically underestimated road transport and domestic heating. A similar behaviour was observed during the summer season. The main discrepancies between the models were: the questionable results from CMB at some receptors, missing the road transport contribution, clearly pointed out by CAMx/PSAT; the ability of CAMx/PSAT to apportion the contribution of sources sharing similar profiles and strongly correlated such as CI and SI vehicles, altogether recognized as traffic source by CMB; the ability of CAMx/PSAT to identify the contribution of secondary PM deriving from complex chemical transformation, such as anthropogenic and biogenic SOA. Finally, the comparison of specific source contribution pointed out that CAMx missed the reconstruction of the road transport contribution to the OC, mostly as a consequence of deficiencies in the emission inventories concerning the primary OC in the cold season and the concurrent underestimation of emissions and secondary OC formation in the warm season.
Keywords: Source apportionment; Chemistry transport models; Receptor models; Po valley; CMB8.2; CAMx/PSAT;
Spatio-temporal distribution of VOC emissions in urban area based on receptor modeling by A. Stojić; S. Stanišić Stojić; Z. Mijić; A. Šoštarić; S. Rajšić (71-79).
In the present study, the concentrations of VOC were measured using Proton Transfer Reaction Mass Spectrometer, together with NOx, NO2, NO, SO2, CO, and PM10 during winter 2014 in Belgrade, Serbia. For the purpose of source apportionment, receptor models Positive Matrix Factorization and Unmix were applied to the obtained dataset, both resolving six profiles. The reliable identification of pollutant sources, description of their characteristics, and estimation of their spatio-temporal distribution are presented through comprehensive analysis and comparison of receptor model solutions, with respect to meteorological data, planetary boundary layer height, and regional and long-range transport. For emissions from petrochemical industry and oil refinery a significant contribution of transport is observed, and hybrid receptor models were applied for identification of potential non-local source regions.
Keywords: VOC; PTR-MS; PMF; Unmix; Transport;
Analysis of the effectiveness of the NEC Directive on the tropospheric ozone levels in Portugal by N. Barros; T. Fontes; M.P. Silva; M.C. Manso; A.C. Carvalho (80-91).
The National Emission Ceilings Directive 2001/81/CE (NEC Directive) was adopted in the European Community in 2001 and went through a revision process in 2005. One of its main objectives is to improve the protection of the environment and human health against the risks of adverse effects from ground-level ozone, moving towards the long-term objective of not exceeding critical levels proved to effectively protect the populations and ecosystems. Considering such objectives, national emission ceilings were established imposing the years 2010 and 2020 as benchmarks. Ten years later, what was the effectiveness of this Directive concerning the control of tropospheric ozone levels in Portugal? In order to answer the previous question, annual ozone precursors' emissions (NOx, NMVOC) and annual atmospheric concentrations (NOx and O3) were analyzed between 1990 and 2011. The background concentrations were assessed in each environment type of air quality station (urban, suburban and rural) through their annual mean ozone concentration and the hourly information threshold exceedances (episodic peak levels). To evaluate the statistical differences in the inter-annual episodic peak levels, a Peak Ozone Index (POIx) was defined and calculated. The results show that, despite the achievement on the emissions NEC Directive goals, associated to the reduction of ozone precursors' emissions, and the decrease of ozone episodic peak levels, the mean tropospheric ozone concentrations significantly increased between 2003 and 2007 (p < 0.05) although the number of exceedances to the information threshold (180 μg m−3) has decreased. During the period of 1990–2000, before the implementation of the NEC Directive, the mean ozone values were 25% lower in rural stations, 26% in urban stations and 12% in suburban stations, demonstrating that the NEC policy based on NOx and NMVOCs emissions reduction does not lead to an effective overall reduction of ozone concentrations considering the reduction on these pollutants independently. Indeed, the mesoscale ozone production and/or the long range advection may play also an important role as the analysis of Mace Head ozone concentrations suggests. Above all, and due to its non-linear interactions in the ozone chemical balance, the NEC directive should impose emissions' reduction respecting the NOx/NMVOC ratio instead of consider it as a mere guideline value. The mesoscale photochemical ozone production should be carefully analyzed under the new policies, namely in coastal countries like Portugal where the mesoscale circulations play a crucial role in this type of phenomena.
Keywords: NEC Directive; Tropospheric ozone; Nitrogen oxides; Emissions; Air quality management;
Airborne pollen assemblages and weather regime in the central-eastern Loess Plateau, China by Yuecong Li; Yawen Ge; Qinghai Xu; Jane M. Bunting; Suqing Lv; Junting Wang; Zetao Li (92-99).
This paper presents the results of pollen trapping studies designed to quantify the pollen assemblages carried in the winds of the Loess Plateau in Luochuan and Hunyuan. The one-year-collection samples analysis results show that pollen assemblages can be more sensitive to the change of climate than the vegetation composition, because of the change of pollen production. The analysis results of pollen traps in different weather regimes indicate that the pollen influx coming from dust weather contribute more to the total pollen influx than that coming from non-dust weather. The wind speed is the most important influenced factor to pollen assemblages, then the mean temperature and the mean relative humidity, the wind direction also contributes some. Strong wind coming from dust direction can make the percent and influx of Artemisia and Chenopodiaceae increase obviously with averagely higher than over 2.7 times in dust weather than in non-dust samples. The influences of wind speed and wind direction are not serious to some arboreal pollen such as Rosaceae, Quercus, Betula, Pinus and Ostryopsis, which are mainly influenced by temperature or the relative humidity such as Salix, Hippophae, Carpinus, Brassicaceae, Cupressaceae, Fabaceae.
Keywords: Loess Plateau; Airborne pollen; Dust weather; Non-dust weather; Redundancy analysis;
Nitrous acid (HONO) in a polluted subtropical atmosphere: Seasonal variability, direct vehicle emissions and heterogeneous production at ground surface by Zheng Xu; Tao Wang; Jueqi Wu; Likun Xue; James Chan; Qiaozhi Zha; Shengzhen Zhou; Peter K.K. Louie; Connie W.Y. Luk (100-109).
Although nitrous acid (HONO) plays an important role in the chemistry of polluted atmospheres, its atmospheric abundances and sources are still not well understood. This paper reports ambient measurements of HONO taken over four select months in different seasons at a suburban site in Hong Kong. The data were analyzed to elucidate the seasonal characteristics, emission ratios and rates of heterogeneous production. The monthly averaged HONO concentrations ranged from 0.35 ± 0.30 ppbv in late spring (May) to 0.93 ± 0.67 ppbv in late autumn (November). The similar variation patterns of HONO, NOx, and traffic flow from midnight to rush hours suggest that the HONO concentration was strongly influenced by vehicle emissions. The emission ratios (HONO/NOx) were derived from an analysis of 21 fresh plumes (NO/NOx > 0.80), with the range of 0.5–1.6%. The large variability in the emission ratios is attributed to the reaction of NO2 on black carbon (BC) emitted from vehicles, based on a strong correlation between the HONO/NOx and concurrently measured BC. The mean conversion rate of NO2 to HONO on ground surface during nighttime estimated on nine select days was 0.52 × 10−2 h−1, which is relatively low compared with other reported values. This paper highlights a large variability in vehicle emission ratios and heterogeneous conversions of NO2 at ground surface. Photochemical models must consider this variability to better simulate the primary sources of HONO and subsequent photochemistry in the lower part of the troposphere.
Keywords: Nitrous acid; Seasonal variation; Vehicle emission; Black carbon; Heterogeneous reaction;
Numerical study of natural sea salt aerosol and its radiative effects on climate and sea surface temperature over East Asia by Jun Guo; Yan Yin; Jian Wu; Deming Zhao (110-119).
A regional climate model, RIEMS-POM, was used to study the direct radiative forcing (DRF) of sea salt on precipitation, sea surface temperature (SST) and summer circulation over East Asia with aerosol dataset from GOCART. The simulations predicted negative DRFs of −0.87 W m−2 at the surface and −1.40 W m−2 at the top of the atmosphere by sea salt. Results from the simulations suggest the forcing of sea salt produces a slight positive temperature anomaly and a reduction in precipitation over Southern China, accompanied by an opposite trend north of 40°N in Northern and Northeastern China. The tendency of wetting in North and drying in South by sea salt was mainly determined by the wind field, the vertical motion, as well as the local evaporation anomalies. The impacts of sea salt on SST suggest that the net surface shortwave radiative flux and the changes in convective cloud are important in forming the decreased SST throughout the year, while the northward oceanic heat transport anomaly and the other heat flux anomalies contribute relatively smaller. The feature by sea salt on SST imposes an extra force from the atmosphere to the ocean. The sea salt could also diminish the land-sea temperature contrast (LSTC) in summer and therefore the climatological summer circulation over East Asia, leading to reduced precipitation in Southern China. All these climatic feedbacks, such as LSTC and precipitation anomaly, will be attenuated when the SST is fixed.
Keywords: Sea salt aerosol; Radiative forcing; Precipitation; East Asia; Sea surface temperature;
Quantifying regional, seasonal and interannual contributions of environmental factors on isoprene and monoterpene emissions estimates over eastern Texas by Ling Huang; Gary McGaughey; Elena McDonald-Buller; Yosuke Kimura; David T. Allen (120-128).
Recent years have brought renewed attention to the effects of drought on emissions of biogenic volatile organic compounds. Variability in environmental inputs that influence isoprene and monoterpene emissions within eastern Texas was quantified by examining seasonal and interannual changes in activity factors intrinsic to the Model of Emissions of Gases and Aerosols from Nature (MEGAN) during years that included average-to-wet conditions (2007) and extreme drought and heat (2006 and 2011). Activity factors are used in MEGAN to multiplicatively adjust emissions rates from an assumed set of standard conditions for temperature, light, leaf area index (LAI), and soil moisture. Temperature was found to be the primary driver of seasonal and interannual variations of isoprene and monoterpene emissions; during drought years, reductions in LAI were dominated by predicted emissions increases caused by much warmer temperatures. The response of biogenic emissions to soil water stress is a major source of uncertainty. Dependent on the specific soil moisture database employed, predicted reductions in isoprene emissions ranged from minimal to −70% during the summer of 2011, a period characterized by all-time record drought in the South Central U.S.
Keywords: Biogenic emissions; Drought; MEGAN; Soil moisture; Isoprene;
Outdoor infiltration and indoor contribution of UFP and BC, OC, secondary inorganic ions and metals in PM2.5 in schools by I. Rivas; M. Viana; T. Moreno; L. Bouso; M. Pandolfi; M. Alvarez-Pedrerol; J. Forns; A. Alastuey; J. Sunyer; X. Querol (129-138).
Infiltration of outdoor-sourced particles into indoor environments in 39 schools in Barcelona was assessed during school hours. Tracers of road traffic emissions (NO2, Equivalent Black Carbon (EBC), Ultrafine Particles (UFP), Sb), secondary inorganic aerosols (SO4 2−, NO3 −, NH4 +) and a number of PM2.5 trace elements showed median indoor/outdoor (I/O) ratios ≤ 1, indicating that outdoor sources importantly contributed to indoor concentrations. Conversely, OC and mineral components had I/O ratios>1. Different infiltration factors were found for traffic and secondary components (0.31–0.75 and 0.50–0.92, cold and warm season respectively), with maxima corresponding to EBC and Cd. Higher concentrations of indoor-generated particles were observed when closed windows hindered dispersion (cold season). Building age was not a major determinant of indoor levels. Neither were the window's material, except for NO2 (with an increase of 8 μg m−3 for wood framed windows) and the mineral components (also dependent on the presence of sand in a distance <20 m) that reach the indoor environment via soil adhering to footwear with their dispersion being more barred by Aluminium/PVC framed windows than the wooden ones. Enlarged indoor concentrations of some trace elements suggest the presence of indoor sources that should be further investigated in order to achieve a healthier school indoor environment.Display Omitted
Keywords: Particulate matter; Black carbon; Ultrafine particles; Road traffic; Indoor air quality;
Field and wind tunnel modeling of an idealized street canyon flow by K. Blackman; L. Perret; E. Savory; T. Piquet (139-153).
The present work examines the flow field in a simple street canyon that has been modeled at full-scale and at 1:200 scale in a wind tunnel. It relies on the detailed analysis of statistics of both flows including two-point correlation coefficients, an approach not commonly done for canyon flows. Comparison between the field and wind tunnel study has demonstrated good agreement for the mean velocity and turbulence statistics, which are typically within 20%. However, significant differences in the along-canyon mean and turbulent components have been observed and are shown to be a result of the changing of the ambient wind direction and low frequency motion present in the field. As the wind direction changes over time the result is a channeling of flow along the canyon axis. This phenomenon cannot be accurately reproduced by the wind tunnel model, which produces nominally 2D flow. The turbulence dynamics were investigated through two-point spatial correlation of the streamwise, spanwise and vertical components, which show agreement to within 15–30% between the field and wind tunnel results. From estimation of boundary layer log-law parameters it has been shown that using a single point reference velocity measurement at 10 m height to estimate the boundary layer log-law parameters is unreliable in the present case.
Keywords: Boundary layer; Street canyon; Field experiment; Particle image velocimetry; Wind tunnel;
A comparative analysis of potential impact area of common sugar cane burning methods by A.L. Hiscox; S. Flecher; J.J. Wang; H.P. Viator (154-164).
The negative effects of agricultural burning are well-known, although the actual impact area of different activities has not previously been quantified. An elastic backscatter lidar system was used to examine the impact-area size and dispersion of smoke generated from different types of sugarcane burning activities; pre-harvest (standing) burning and post-harvest (ground) burning. Experiments were conducted in the sugarcane harvest season of 2010 and 2011 at two locations in Louisiana, USA. Current dispersion theory would suggest that the primary difference between burn types would be primarily in the initial plume rise, but that the overall plume shape would remain the same. However, remotely sensed lidar data with the capability to measure plume dispersion and the short time dynamics of plume location showed pre-harvest (standing) burning produced a larger plume with greater rise and more spread within the 300 m of the plume, but a decrease in dispersion, but not concentration further downwind. Post-harvest (ground) burning produced a more traditional plume shape, but still exceeded impact area predictions near the source. Moreover, large changes in plume size can occur with small increases in wind speed. These are the first instrumented measurements of the meteorological effects of the different types of sugarcane burning. These results indicate that ground burning is preferable, but should be avoided in lower wind speed conditions.
Keywords: Lidar; Agricultural air quality; Smoke; Dispersion; Sugarcane;
Development of land-use regression models for metals associated with airborne particulate matter in a North American city by Joyce J.Y. Zhang; Liu Sun; Olesya Barrett; Stefania Bertazzon; Fox E. Underwood; Markey Johnson (165-177).
Airborne particulate matter has been associated with cardiovascular and respiratory morbidity and mortality, and there is evidence that metals may contribute to these adverse health effects. However, there are few tools for assessing exposure to airborne metals. Land-use regression modeling has been widely used to estimate exposure to gaseous pollutants. This study developed seasonal land-use regression (LUR) models to characterize the spatial distribution of trace metals and other elements associated with airborne particulate matter in Calgary, Alberta.Two-week integrated measurements of particulate matter with <1.0 μm in aerodynamic diameter (PM1.0) were collected in the City of Calgary at 25 sites in August 2010 and 29 sites in January 2011. PM1.0 filters were analyzed using inductively-coupled plasma mass spectrometry. Industrial sources were obtained through the National Pollutant Release Inventory and their locations verified using Google Maps. Traffic volume data were obtained from the City of Calgary and zoning data were obtained from Desktop Mapping Technologies Incorporated. Seasonal wind direction was incorporated using wind rose shapes produced by Wind Rose PRO3, and predictor variables were generated using ArcMap-10.1. Summer and winter LUR models for 30 PM1.0 components were developed using SAS 9.2.We observed significant intra-urban gradients for metals associated with airborne particulate matter in Calgary, Alberta. LUR models explained a high proportion of the spatial variability in those PM1.0 components. Summer models performed slightly better than winter models. However, 24 of the 30 PM1.0 related elements had models that were either good (R2 > 0.70) or acceptable (R2 > 0.50) in both seasons. Industrial point-sources were the most influential predictor for the majority of PM1.0 components. Industrial and commercial zoning were also significant predictors, while traffic indicators and population density had a modest but significant contribution for most elements. Variables incorporating wind direction were also significant predictors. These findings contrast with LUR models for PM and gaseous pollutants in which traffic indicators are typically the most important predictors of ambient concentrations.These results suggest that airborne PM components vary spatially with the distribution of local industrial sources and that LUR modeling can be used to predict local concentrations of these airborne elements. These models will support future health studies examining the impact of PM components including metals.
Keywords: Air pollution; Land-use regression modeling; Spatial air quality modeling; Airborne metals; Particulate matter; PM-Related metals;
Seasonal effect and source apportionment of polycyclic aromatic hydrocarbons in PM2.5 by Md Firoz Khan; Mohd Talib Latif; Chee Hou Lim; Norhaniza Amil; Shoffian Amin Jaafar; Doreena Dominick; Mohd Shahrul Mohd Nadzir; Mazrura Sahani; Norhayati Mohd Tahir (178-190).
This study aims to investigate distribution and sources of 16 polycyclic aromatic hydrocarbons (PAHs) bound to fine particulate matter (PM2.5) captured in a semi-urban area in Malaysia during different seasons, and to assess their health risks. PM2.5 samples were collected using a high volume air sampler on quartz filter paper at a flow rate of 1 m3 min−1 for 24 h. PAHs on the filter paper were extracted with dichloromethane (DCM) using an ultrasonic centrifuge solid-phase extraction method and measured by gas chromatography–mass spectroscopy. The results showed that the range of PAHs concentrations in the study period was between 0.21 and 12.08 ng m−3. The concentrations of PAHs were higher during the south-west monsoon (0.21–12.08 ng m−3) compared to the north-east monsoon (0.68–3.80 ng m−3). The high molecular weight (HMW) PAHs (≥5 ring) are significantly prominent (>70%) compared to the low molecular weight (LMW) PAHs (≤4 ring) in PM2.5. The Spearman correlation indicates that the LMW and HMW PAHs correlate strongly among themselves. The diagnostic ratios (DRs) of I[c]P/I[c]P + BgP and B[a]P/B[g]P suggest that the HMW PAHs originated from fuel combustion sources. The source apportionment analysis of PAHs was resolved using DRs-positive matrix factorization (PMF)-multiple linear regression (MLR). The main sources identified were (a) gasoline combustion (65%), (b) diesel and heavy oil combustion (19%) and (c) natural gas and coal burning (15%). The health risk evaluation, by means of the lifetime lung cancer risk (LLCR), showed no potential carcinogenic risk from the airborne BaPeq (which represents total PAHs at the present study area in Malaysia). The seasonal LLCR showed that the carcinogenic risk of total PAHs were two fold higher during south-westerly monsoon compared to north-easterly monsoon.Display Omitted
Keywords: Monsoon effect; PAH diagnostic ratio; Positive matrix factorization; Health risk;
Isotopic composition of nitrate in sequential Hurricane Irene precipitation samples: Implications for changing NOx sources by J. David Felix; Emily M. Elliott; G. Brooks Avery; Robert J. Kieber; Ralph N. Mead; Joan D. Willey; Katherine M. Mullaugh (191-195).
Previous studies have concentrated on adverse ecosystem effects resulting from nitrogen (N) loading from runoff and increased N2O emissions due to hurricane activity but little focus has been placed on N inputs delivered by hurricane precipitation. Understanding these N inputs during extreme rain events is increasingly important since global climate change may alter hurricane activity. In this study, ten sequential Hurricane Irene rain samples were analyzed for isotopic composition of nitrate ( NO 3 − ) to investigate NOx (=NO + NO2) sources contributing to NO 3 − deposited by a hurricane. The samples were divided into three groups (I, II, II) by k-means clustering using rain event back trajectories, δ15N– NO 3 − values, and NO 3 − concentrations. Chemical, physical and isotopic analyses, including δ15N- and δ18O– NO 3 − , anions, cations, H+, H2O2, DOC, acetaldehyde, ethanol and rainfall intensity, were then used to explore similarities in geographic origins and potential relationships with NOx and other emission sources. While it is possible that all samples had contributions from various NOx sources, group I samples had marine back trajectories and a mean δ15N– NO 3 − value (−0.7 ± 1.9‰) suggesting primarily lightning-sourced NOx contributions to NO 3 − deposition. As the hurricane made landfall, Group II samples transitioned to reflect more of a terrestrial signature with a higher mean δ15N– NO 3 − value (+11.0 ± 0.5‰) indicating NOx emission contributions from vehicles and power plants sources. As the hurricane continued to move inland, Group III δ15N– NO 3 − values (−5.5 and −5.7‰) reflect the potential mixing of biogenic soil NOx emissions with vehicle and power plant sources. Higher concentrations of ethanol, acetaldehyde, NH4 +, and carbohydrates in Group III samples support the influence of biogenic sources. The isotopic composition of NO 3 − in hurricane rain can aid in discerning varying NOx sources contributing to nitrate concentrations in extreme rain events. This knowledge can in turn further our understanding of how forthcoming hurricane events may alter the N cycle of an ecosystem.
Keywords: Nitrate; NOx; Isotope; Hurricane; Emissions; Wet deposition;
A comparative study of daytime-based methane emission from two wetlands of Nepal Himalaya by Dan Zhu; Ning Wu; Nabin Bhattarai; Krishna Prasad Oli; Kuenzang Tsering; Gopal Singh Rawat; Huai Chen; Gang Yang; Yinxin He; Srijana Joshi; Pradyumna Rana; Muhammad Ismail (196-203).
Natural wetlands constitute one of the major sources of methane emission to the atmosphere. Data on methane emission from wetlands on southern slopes of the Himalaya (SSH) have not been reported so far. Such data are very valuable for filling the gap and generating the whole emission patterns at regional or even global scale. We selected two wetlands at different altitudinal locations in Nepal, i.e. Beeshazar Lake (286 m a.s.l.) and Dhaap Lake (2089 m a.s.l.), to monitor the daytime methane emissions in monsoon season and dry season separately. Daytime methane emission varied between monsoon and dry seasons and also across different plant communities. The daytime methane emission variations were stronger in dry season than in monsoon season. The source/sink strengths of the two selected plant communities in each wetland were significantly different, presenting the strong spatial variation of methane emission within wetland. The methane emissions recorded in monsoon season were significantly higher (7.74 ± 6.49 mg CH4 m−2 h−1 and 1.00 ± 1.23 mg CH4 m−2 h−1 in low and high altitude wetlands, respectively) than those in dry season (1.84 ± 4.57 mg CH4 m−2 h−1 and 0.27 ± 0.71 mg CH4 m−2 h−1 in low and high altitude wetlands, respectively). Methane emissions from the low altitude wetland were significantly higher than those from the high altitude wetland in both of the seasons. Plant community height, standing water depth and soil temperature correlated to the methane emission from wetlands in this region.
Keywords: Daytime pattern; Himalayan wetlands; Methane emission; Plant growth; Soil temperature; Standing water depth;
WRF/Chem modeling of the impacts of urban expansion on regional climate and air pollutants in Yangtze River Delta, China by Jingbiao Liao; Tijian Wang; Ziqiang Jiang; Bingliang Zhuang; Min Xie; Changqin Yin; Xuemei Wang; Jialei Zhu; Yu Fu; Ying Zhang (204-214).
The Yangtze River Delta (YRD) region has experienced a rapid urbanization process accompanied with economic development during last decades. To investigate impacts of urbanization on regional climate and air quality, two-month (January and July 2010) simulations with two different land-use scenarios (USGS and MODIS land-use types) are conducted using the Advanced Weather Research and Forecasting/Chemistry (WRF/Chem) modeling system in this study. Results show that the conversion of vegetated and irrigated cropland into urban type significantly changes 2-m temperature and 10-m wind speed, which are obtained from differences of two simulations based on significance t-test at 95% confidence level. Changes of land-use cause an increase in 2-m temperature with maximum (minimum) value of 2.3 °C (0.9 °C) over urbanized area, a decrease in 10-m wind speed with magnitude of 0.6–1.2 m s−1 for both the two months. Planetary boundary layer height (PBLH) differences show a maximum increase of 425 m during daytime in July, and the increases are about 100 m during nighttime for both January and July. Urbanization reduces near-surface PM10 concentration due to increase of PBLH, with maximum decrease of 57.6 μg m−3 during nighttime in July. The biggest increase of O3 is around 6.8 ppb during daytime in July and the difference is about 1.7–2.3 ppb in January. Vertical profiles show that PM10 concentrations decrease due to increase of mixing height during both daytime and nighttime. While for O3 concentration, urbanization causes an increase during daytime due to higher air temperature and decrease of wind speed and leads to a decrease during nighttime. Overall, influences of urbanization on climate and air quality are important and significant over YRD region, which must be considered in any climate and air quality assessment.
Keywords: Urban expansion; Climate; Air pollutants; WRF/Chem; YRD;
Skyscraper rooftop tracer concentration observations in Manhattan and comparisons with urban dispersion models by Steven Hanna; Joseph Chang (215-222).
This paper focuses on the observed and model-predicted rooftop concentrations on very tall buildings at distances less than a few hundred meters downwind of near-surface releases in built-up urban centers. These results are important when public health must be protected in populated urban areas with deliberate or accidental releases of toxic chemicals, or with significant traffic emissions. Observations of tracer concentrations taken at seven samplers on skyscraper rooftops (113 m < z < 197 m) during the Manhattan Midtown 2005 (MID05) field experiment are analyzed, with emphasis on the near-field (x < 100 m). To calculate the ratio of rooftop to surface concentrations, we pair each rooftop sampler with the closest street level sampler. Six tracer gases (SF6 and five perfluorocarbon tracers (PFTs)) were released near street level from several locations. In the near-field, the median ratio of observed rooftop to surface concentration is about 0.02, even very close to the source, although there is much scatter. The large recirculating eddies adjacent to the tall buildings may cause the relatively large vertical spread. It is noted that, at distances greater than a few hundred meters, the ratio approaches unity (although there is still significant scatter). The observed normalized rooftop and surface concentrations and rooftop to surface ratios are compared to the predicted concentrations and ratios by three urban dispersion options (Urban Dispersion Model (UDM), Urban Canopy (UC), and MicroSwiftSpray (MSS)) in the HPAC/SCIPUFF model. There is a general tendency towards an underprediction of the rooftop concentrations and a slightly smaller underprediction of the surface concentrations. The median ratio of rooftop to surface concentrations is underpredicted by most of the meteorology-urban module options, with much scatter for all options. These results underline the need to better parameterize the dispersion of plumes in the street canyons and recirculating eddies around tall buildings.
Keywords: Urban dispersion; Midtown 2005 (MID05) Manhattan field experiment; Rooftop concentrations; Vertical mixing;
Seasonal variation of urban carbonaceous aerosols in a typical city Nanjing in Yangtze River Delta, China by Bing Li; Jie Zhang; Yu Zhao; Siyu Yuan; Qiuyue Zhao; Guofeng Shen; Haisuo Wu (223-231).
The Yangtze River Delta (YRD) is one of the regions with the most dynamic economy and severe atmospheric pollution in China. In order to characterize the particle features, especially the carbonaceous component in the YRD, particulate matter smaller than 2.5 μm (PM2.5) and 10 μm (PM10) samples in each season were collected in urban Nanjing, a typical city that locates in the west part of the YRD. The organic carbon (OC) and elemental carbon (EC) was differentiated using the thermal optical reflectance method. The average concentrations of PM2.5, OC and EC during the study periods were observed to be 117.6, 13.8, and 5.3 μg/m3 respectively, with all the highest levels in winter. The mass fraction of the Total carbonaceous aerosol (TCA) in PM2.5 was estimated at 23% on average, lower than those reported for other cities in the YRD. The OC and EC correlated well in all the seasons, especially in spring and winter, implying that OC and EC were attributed to common emission sources. Good correlation was observed between OC and estimated K+ from biomass burning in the harvest season in autumn and summer, indicating biomass burning a significant source of carbonaceous aerosols. This could also be confirmed by the lower fraction of OC3 + OC4 in OC during autumn and summer. The secondary organic carbon (SOC) estimated by EC-tracer method was the highest in winter (7.3 μg/m3) followed by autumn (6.7 μg/m3), summer (3.7 μg/m3) and spring (2.0 μg/m3). However, the SOC/OC in winter was not as high as that in summer and autumn, implying the high concentration of OC in winter was probably due to the stable weather but not mainly caused by SOC formation. The high SOC/OC ratio in summer was attributed to stronger oxidation, which could be suggested by higher sulfur oxidation ratio (SOR).
Keywords: Particles; OC; EC; SOC; Carbon fractions; YRD;
Seasonal behavior and long-term trends of tropospheric ozone, its precursors and chemical conditions over Iran: A view from space by Yunsoo Choi; Amir Hossein Souri (232-240).
To identify spatial and temporal variations over the Iranian region, this study analyzed tropospheric formaldehyde (HCHO) and nitrogen dioxide (NO2) columns from Ozone Monitoring Instrument (OMI), carbon monoxide (CO) columns from the Measurement of Pollution in the Troposphere (MOPITT), and tropospheric column O3 (TCO) from OMI/MLS (Microwave Limb Sounder) satellites from 2005 to 2012. The study discovered high levels of HCHO (∼12 × 1015 molec./cm2) from plant isoprene emissions in the air above parts of the northern forest of Iran during the summer and from the oxidation of HCHO precursors emitted from petrochemical industrial facilities and biomass burning in South West Iran. This study showed that maximum NO2 levels (∼18 × 1015 molec./cm2) were concentrated in urban cities, indicating the predominance of anthropogenic sources. The results indicate that maximum concentrations were found in the winter, mainly because of weaker local winds and higher heating fuel consumption, in addition to lower hydroxyl radicals (OH). The high CO concentrations (∼2 × 1018 molec./cm2) in the early spring were inferred to mainly originate from a strong continental air mass from anthropogenic CO “hotspots” including regions around Caspian Sea, Europe, and North America, although the external sources of CO were partly suppressed by the Arabian anticyclone and topographic barriers. Variations in the TCO were seen to peak during the summer (∼40 DU), due to intensive solar radiation and stratospheric sources. This study also examined long-term trends in TCO and its precursors over a period of eight years in five urban cities in Iran. To perform the analysis, we estimated seasonal changes and inter-seasonal variations using least-squares harmonic estimation (LS-HE), which reduced uncertainty in the trend by 5–15%. The results showed significant increases in the levels of HCHO (∼0.08 ± 0.06 × 1015 molec./cm2 yr−1), NO2 (∼0.08 ± 0.02 × 1015 molec./cm2 yr−1), and peak annual TCO (∼0.59 ± 0.56 DU yr−1) but decreases in minimum annual TCO (∼−0.42 ± 0.60 DU yr−1) caused by an increase in NO2 species and annual CO (∼−0.95 ± 0.41 × 1016 molec./cm2 yr−1) partly resulting from the transport of reduced CO. The time series of the HCHO/NO2 column ratio (a proxy for the chemical conditions) indicated that during the last decade, the cities of Tehran, Ahvaz, and Isfahan exhibited steady chemical conditions while Tabriz and Mashhad exhibited a change from NOx-saturated/mixed to more NOx-sensitive chemical conditions.
Keywords: Tropospheric ozone; Ozone precursors; Chemical condition; Long-term trends; Remote sensing;
Source term estimation using air concentration measurements and a Lagrangian dispersion model – Experiments with pseudo and real cesium-137 observations from the Fukushima nuclear accident by Tianfeng Chai; Roland Draxler; Ariel Stein (241-251).
A transfer coefficient matrix (TCM) was created in a previous study using a Lagrangian dispersion model to provide plume predictions under different emission scenarios. The TCM estimates the contribution of each emission period to all sampling locations and can be used to estimate source terms by adjusting emission rates to match the model prediction with the measurements. In this paper, the TCM is used to formulate a cost functional that measures the differences between the model predictions and the actual air concentration measurements. The cost functional also includes a background term which adds the differences between a first guess and the updated emission estimates. Uncertainties of the measurements, as well as those for the first guess of source terms are both considered in the cost functional. In addition, a penalty term is added to create a smooth temporal change in the release rate. The method is first tested with pseudo observations generated using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model at the same location and time as the actual observations. The inverse estimation system is able to accurately recover the release rates and performs better than a direct solution using singular value decomposition (SVD). It is found that computing ln(c) differences between model and observations is better than using the original concentration c differences in the cost functional. The inverse estimation results are not sensitive to artificially introduced observational errors or different first guesses. To further test the method, daily average cesium-137 air concentration measurements around the globe from the Fukushima nuclear accident are used to estimate the release of the radionuclide. Compared with the latest estimates by Katata et al. (2014), the recovered release rates successfully capture the main temporal variations. When using subsets of the measured data, the inverse estimation method still manages to identify most of the major events in the temporal profile of the release.
Keywords: Lagrangian dispersion model; Fukushima nuclear accident; Cost functional; Source term estimation; Air concentration; Pseudo observations; Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model; Transfer coefficient matrix (TCM); Cesium-137;
Characteristics of water-soluble organic nitrogen in fine particulate matter in the continental area of China by K.F. Ho; Steven Sai Hang Ho; Ru-Jin Huang; S.X. Liu; Jun-Ji Cao; T. Zhang; Hsiao-Chi Chuang; C.S. Chan; Di Hu; Linwei Tian (252-261).
In recent years growing evidence has shown that organic nitrogen (ON) constitutes a significant fraction of the nitrogen budget in particulate matter (PM). However, the composition and sources of ON in Chinese PM are not clear to date due to the lack of field measurements and receptor modeling interpretations. In this study, water-soluble ON (WSON), free amino acids (FAAs) and primary amines, together with water-soluble ionic species and carbonaceous components, were quantified in PM2.5 collected in Xi'an, China from 2008 to 2009. The yearly average WSON concentration (300 nmol N m−3, ranging from 29 to 1250 nmol N m−3) was one order of magnitude higher than that reported in other urban and rural regions in U.S. A total of 24 organic nitrogen species were determined, with an average total concentration of 2180 pmol m−3, which account for 1.2% of the WSON in PM2.5. Glycine, β-alanine and methylamine were the most abundant protein type amino acid, non-protein type amino acid and primary amine, respectively, contributing to 21.1%, 5.2% and 20.6% of the total quantified organic nitrogen species (TONS). Strong linear correlations (Pearson's correlation) (r = .72, p < 0.001) between WSON and one of biomass burning tracer (K+) potentially indicate the contribution from biomass burning (especially in spring and fall) and the correlation (r = .76–.87, p < 0.001) between WSON and secondary species ( NH 4 + , NO 3 − , and SO 4 2 − ) also suggests the important contribution to WSON from secondary formation processes. Moreover, both protein type amino acids and primary amines revealed good correlations with water-soluble ions in spring, which indicates that seasonal variability occurred in primary sources and secondary formation pathway of the organic nitrogen species were found in Xi'an.
Keywords: Water-soluble organic nitrogen; Amino acids; Amines; PM2.5; Xi'an;
Satellite observations of tropospheric ammonia and carbon monoxide: Global distributions, regional correlations and comparisons to model simulations by Ming Luo; Mark W. Shephard; Karen E. Cady-Pereira; Daven K. Henze; Liye Zhu; Jesse O. Bash; Robert W. Pinder; Shannon L. Capps; John T. Walker; Matthew R. Jones (262-277).
Ammonia (NH3) and carbon monoxide (CO) are primary pollutants emitted to the Earth's atmosphere from common as well as distinct sources associated with anthropogenic and natural activities. The seasonal and global distributions and correlations of NH3 and CO from the Tropospheric Emission Spectrometer (TES) satellite observations and GEOS-Chem model simulations for 2007 are investigated to evaluate how well the global and seasonal pollutant sources are prescribed in the model. Although the GEOS-Chem simulations of NH3 and CO atmospheric mixing ratio values are lower than the TES satellite observations, the global distribution patterns from the model reasonably agree with the observations, indicating that the model represents the general location of the source regions and the seasonal enhancements of NH3 and CO globally over large regional scales. In regions and seasons where biomass burning is the dominant source of both NH3 and CO emissions into the atmosphere, there are strong NH3:CO correlations, which is consistent with the relationship demonstrated by surface measurements over fires. In regions where the enhanced NH3 and CO are known to be produced by different sources, the NH3:CO correlations from TES observations and model simulations are weak or non-existent. For biomass burning regions the NH3:CO ratios are 0.015 (TES) and 0.013 (GEOS-Chem). In regions of high-population density, known heavy traffic, and limited biomass burning sources, such as the rapidly developing areas of South Asia and northern China, which include mixtures of megacities, industrial, and agricultural areas, the two species show weaker but still positive correlations and NH3:CO ratios of 0.051 (TES) and 0.036 (GEOS-Chem). These enhancement ratios of NH3 relative to CO are useful in constraining NH3 emission inventories when CO emission inventories are better known for some events or regions (i.e. biomass burning).
Keywords: Satellite observations of carbon monoxide and ammonia; GEOS-Chem model simulations;
Global analysis of peroxy radicals and peroxy radical-water complexation using the STOCHEM-CRI global chemistry and transport model by M.A.H. Khan; M.C. Cooke; S.R. Utembe; A.T. Archibald; R.G. Derwent; M.E. Jenkin; W.C. Morris; N. South; J.C. Hansen; J.S. Francisco; C.J. Percival; D.E. Shallcross (278-287).
The importance of peroxy radical (RO2) chemistry in the troposphere is investigated using the STOCHEM-CRI global chemistry and transport model. The oxidation of VOCs leads to the formation of RO2 radicals which are dominated by CH3O2 (83%), RCO3 (5%), isoprene derived peroxy radicals (6%), and terpene derived peroxy radicals (1%). A good correlation between model and field measurements for total RO2 for most of the selected stations suggests that they are appropriate background sites as the atmospheric processes occurring at these stations are representative of the chemistry taking place within the entire model grid square in which they are located. The seasonality exhibited by RO2 has been studied, with well-defined cycles (highest in summer and lowest in winter) seen in both hemispheres. Peroxy radical-water complexes, whilst not represented using Chemical Transport Models (CTMs) previously, are postulated to perturb RO2 chemistry. The significance of water clusters (RO2.H2O) is investigated using the STOCHEM-CRI model and reveals that at 300 K the proportion of RO2 participating in complexation with water is approximately 12% in the tropics. Isoprene derived radicals are the most strongly bound of RO2 species investigated and their degree of complexation at approx. 300 K far surpasses that of the generic peroxy radicals by 3–5%. At higher altitudes (approx. 8 km) characterized by sub-ambient temperatures, the fraction of RO2.H2O complex that can exist is approximately 17% in the upper troposphere above Mace Head (Northern Hemisphere), 14% above Cape Grim (Southern Hemisphere), and 8% above Mauna Loa (Tropics).
Keywords: Peroxy radical; Peroxy radical-water complexation; STOCHEM-CRI; Global sources; Global sinks;
Assessment of air quality benefits from the national pollution control policy of thermal power plants in China: A numerical simulation by Zhanshan Wang; Libo Pan; Yunting Li; Dawei Zhang; Jin Ma; Feng Sun; Wenshuai Xu; Xingrun Wang (288-304).
In 2010, an emission inventory of air pollutants in China was created using the Chinese Bulletin of the Environment, the INTEX-B program, the First National Pollution Source Census, the National Generator Set Manual, and domestic and international research studies. Two emission scenarios, the standard failed emission scenario (S1) and the standard successful emission scenario (S2), were constructed based upon the Instructions for the Preparation of Emission Standards for Air Pollutants from Thermal Power Plants (second draft). The Fifth-Generation NCAR/Penn State Mesoscale Model (MM5) and the U.S. EPA Models-3 Community Multiscale Air Quality (CMAQ) model were applied to China to study the air quality benefits from Emission Standards for Air Pollutants from Thermal Power Plants GB13223-2011. The performance of MM5 and CMAQ was evaluated with meteorological data from Global Surface Data from the National Climatic Data Center (NCDC) and the daily Air Pollution Index (API) reported by Chinese local governments. The results showed that the implementation of the new standards could reduce the concentration of air pollutants and acid deposition in China by varying degrees. The new standards could reduce NO2 pollution in China. By 2020, for the scenario S2, the area with an NO2 concentration higher than the second-level emission standard, and the average NO2 concentration in 31 selected provinces would be reduced by 55.2% and 24.3%, respectively. The new standards could further reduce the concentration of declining SO2 in China. By 2020, for S2, the area with an SO2 concentration higher than the second-level emission standard and the average SO2 concentration in the 31 selected provinces would be reduced by 40.0% and 31.6%, respectively. The new standards could also reduce PM2.5 pollution in China. By 2020, for S2, the area with a PM2.5 concentration higher than the second-level emission standard and the average concentration of PM2.5 in the 31 selected provinces would be reduced by 17.2% and 14.7%, respectively. The new standard could reduce nitrogen deposition pollution in China. By 2020, for S2, the area with a nitrogen deposition concentration >2.0 tons·km−2 and the total nitrogen deposition in China would be reduced by 28.6% and 16.8%, respectively. The new standards could reduce sulfur deposition pollution in China. By 2020, for S2, the area with a sulfur deposition >1.5 tons·km−2 and the total sulfur deposition in China would be reduced by 55.3% and 21.0%, respectively.
Keywords: Thermal power plant; Emission standards; China; Models-3/CMAQ; PM2.5; Sulfur deposition; Nitrogen deposition;
A comprehensive ammonia emission inventory with high-resolution and its evaluation in the Beijing–Tianjin–Hebei (BTH) region, China by Ying Zhou; Shuiyuan Cheng; Jianlei Lang; Dongsheng Chen; Beibei Zhao; Chao Liu; Ran Xu; Tingting Li (305-317).
A comprehensive ammonia (NH3) emission inventory for the Beijing–Tianjin–Hebei (BTH) region was developed based on the updated source-specific emission factors (EFs) and the county-level activity data obtained from a full-coverage investigation launched in the BTH region for the first time. The NH3 emission inventory within 1 km × 1 km grid was generated using source-based spatial surrogates with geographical information system (GIS) technology. The total NH3 emission was 1573.7 Gg for the year 2010. The contributions from livestock, farmland, human, biomass burning, chemical industry, fuel combustion, waste disposal and on-road mobile source were approximately 56.6%, 28.6%, 7.2%, 3.4%, 1.1%, 1.3%, 1.0% and 0.8%, respectively. Among different cities, Shijiazhang, Handan, Xingtai, Tangshan and Cangzhou had higher NH3 emissions. Statistical analysis aiming at county-level emission of 180 counties in BTH indicated that the NH3 emission in most of the counties were less than 16 Gg. The maximum value of the county level emission was approximately 25.5 Gg. Higher NH3 emission was concentrated in the areas with more rural and agricultural activity. Monthly, higher NH3 emission occurred during the period from April to September, which could be attributed to the temperature and timing of planting practice. The validity of the estimated emissions were further evaluated from multiple perspectives covering (1) uncertainty analysis based on Monte Carlo simulation, (2) comparison with other studies, (3) quantitative analysis of improvement in spatial resolution of activity data, and (4) verification based on a comparison of the simulated and observed surface concentrations of ammonium. The detailed and validated ammonia emission inventory could provide valuable information for understanding air pollution formation mechanisms and help guide decision-making with respect to control strategies.
Keywords: Ammonia (NH3) emission; High resolution; Ammonium concentration observation; Evaluation; Beijing–Tianjin–Hebei (BTH);
Improvement of PM10 prediction in East Asia using inverse modeling by Youn-Seo Koo; Dae-Ryun Choi; Hi-Yong Kwon; Young-Kee Jang; Jin-Seok Han (318-328).
Aerosols from anthropogenic emissions in industrialized region in China as well as dust emissions from southern Mongolia and northern China that transport along prevailing northwestern wind have a large influence on the air quality in Korea. The emission inventory in the East Asia region is an important factor in chemical transport modeling (CTM) for PM10 (particulate matters less than 10 ㎛ in aerodynamic diameter) forecasts and air quality management in Korea. Most previous studies showed that predictions of PM10 mass concentration by the CTM were underestimated when comparing with observational data. In order to fill the gap in discrepancies between observations and CTM predictions, the inverse Bayesian approach with Comprehensive Air-quality Model with extension (CAMx) forward model was applied to obtain optimized a posteriori PM10 emissions in East Asia. The predicted PM10 concentrations with a priori emission were first compared with observations at monitoring sites in China and Korea for January and August 2008. The comparison showed that PM10 concentrations with a priori PM10 emissions for anthropogenic and dust sources were generally under-predicted. The result from the inverse modeling indicated that anthropogenic PM10 emissions in the industrialized and urbanized areas in China were underestimated while dust emissions from desert and barren soil in southern Mongolia and northern China were overestimated. A priori PM10 emissions from northeastern China regions including Shenyang, Changchun, and Harbin were underestimated by about 300% (i.e., the ratio of a posteriori to a priori PM10 emission was a factor of about 3). The predictions of PM10 concentrations with a posteriori emission showed better agreement with the observations, implying that the inverse modeling minimized the discrepancies in the model predictions by improving PM10 emissions in East Asia.
Keywords: PM10; Emissions inventory; CTM; Inverse modeling; East Asia;
Surface area as a dose metric for carbon black nanoparticles: A study of oxidative stress, DNA single-strand breakage and inflammation in rats by Hsiao-Chi Chuang; Li-Chen Chen; Yu-Chen Lei; Kuen-Yuh Wu; Po-Hao Feng; Tsun-Jen Cheng (329-334).
Combustion-derived nanoparticles are characterised by a high surface area (SA) per mass. SA is proposed to regulate the bioreactivity of nanoparticles; however, the dose metric for carbon black remains controversial. To determine the relationships between bioreactivity and SA, male spontaneously hypertensive rats were exposed to carbon black (CB) nanoparticles (15, 51 and 95 nm) via intratracheal instillation for 24 h. Pulmonary exposure to CB resulted in a significant increase in systemic 8-hydroxy-2′-deoxyguanosine (8-OHdG), DNA single-strand breakages in peripheral blood cells and pulmonary cell infiltration in rats. The oxidative potential and particularly the corresponding SA of CB were correlated with the level of 8-OHdG, DNA single-strand breakages and pulmonary cell infiltration in rats. We conclude that SA is an important dose metric for CB that can regulate oxidative stress and DNA damage in rats. Furthermore, this observation was more significant for smaller sized CB.
Keywords: 8-Hydroxy-2′-deoxyguanosine; Carbon black; Surface area; DNA single-strand breakage; Nanoparticle;
Projections of summertime ozone concentration over East Asia under multiple IPCC SRES emission scenarios by Jae-Bum Lee; Jun-Seok Cha; Sung-Chul Hong; Jin-Young Choi; Ji-Su Myoung; Rokjin J. Park; Jung-Hun Woo; Changhoi Ho; Jin-Seok Han; Chang-Keun Song (335-346).
We have developed the Integrated Climate and Air Quality Modeling System (ICAMS) through the one-way nesting of global–regional models to examine the changes in the surface ozone concentrations over East Asia under future climate scenarios. Model simulations have been conducted for the present period of 1996–2005 to evaluate the performance of ICAMS. The simulated surface ozone concentrations reproduced the observed monthly mean concentrations at sites in East Asia with high R2 values (0.4–0.9), indicating a successful simulation to capture both spatial and temporal variability. We then performed several model simulations with the six IPCC SRES scenarios (A2, A1B, A1FI, A1T, B1, and B2) for the next three periods, 2016–2025 (the 2020s), 2046–2055 (the 2050s), and 2091–2100 (the 2090s). The model results show that the projected changes of the annual daily mean maximum eight-hour (DM8H) surface ozone concentrations in summertime for East Asia are in the range of 2–8 ppb, −3 to 8 ppb, and −7 to 9 ppb for the 2020s, the 2050s, and the 2090s, respectively, and are primarily determined based on the emission changes of NOx and NMVOC. The maximum increases in the annual DM8H surface ozone and high-ozone events occur in the 2020s for all scenarios except for A2, implying that the air quality over East Asia is likely to get worse in the near future period (the 2020s) than in the far future periods (the 2050s and the 2090s). The changes in the future environment based on IPCC SRES scenarios would also influence the change in the occurrences of high-concentrations events more greatly than that of the annual DM8H surface ozone concentrations. Sensitivity simulations show that the emissions increase is the key factor in determining future regional surface ozone concentrations in the case of a developing country, China, whereas a developed country, Japan would be influenced more greatly by effects of the regional climate change than the increase in emissions.
Keywords: Air quality; Ozone; East Asia; Climate change; ICAMS;
Long-term trend of NO2 in major urban areas of Korea and possible consequences for health by Hang Thi Nguyen; Ki-Hyun Kim; Chuljin Park (347-357).
Long-term trend of the atmospheric NO2 was analyzed using ambient monitoring data collected from seven major cities in Korea over two decades (1989–2010). In light of the notable environmental policies initiated since June 2000, these NO2 data were also evaluated after dividing the entire study period into period I (1989–1999) and period II (2000–2010). Accordingly, the mean concentrations of NO2 in five out of seven cities in period II were higher by 1–26% than period I. This recognizable increase in period II is likely to reflect the effect of increasing consumption rates in primary energy (e.g., petroleum and LNG). An examination of the seasonal trend of NO2 consistently indicates the highest concentrations occurred during winter because of the combined effects of the anthropogenic emission and meteorological conditions. A health risk assessment of our data indicated that the NO2 exposure (to adults, children, and infants) increased from period I to period II. Also, the long-term trends of NO2 were analyzed based on the seasonal Mann–Kendall test and the Sen's slopes. It revealed that NO2 levels of most cities had the linearly increasing trends during period I. However, decreasing trends appeared during period II to reflect the direct effect of implementation of administrative efforts including the fuel switching control policy.
Keywords: Nitrogen oxides; Long-term; Urban; Health risk; Korea;
A trans-Pacific Asian dust episode and its impacts to air quality in the east coast of U.S. by Yonghua Wu; Zaw Han; Chowdhury Nazmi; Barry Gross; Fred Moshary (358-368).
The transport of an intense trans-Pacific Asian dust episode to the Northeast United States (U.S.) is studied using a synergistic suite of observations and models including a ground-based lidar, AERONET-sunphotometer, satellite measurements and global aerosol transport model for New York City (40.821°N, 73.949°W). During the dust intrusion on March 17–19, 2010, the multi-wavelength lidar observations indicate dense dust plumes (∼80% of total column AOD) located between 3 and 9 km altitudes with the lower layer mixing toward the planetary boundary layer (PBL). The column AOD shows a significant increase from 0.08 to 0.38 at 532-nm while the Angstrom exponent indicates a decrease from 1.3 to 0.7. The linear particle depolarization ratio is estimated to be 0.1–0.15 and the single-scattering-albedo shows the dust-like spectral dependence with the value of 0.9–0.95 at 440-nm. The NOAA-NCEP reanalysis and HYSPLIT model indicate that this long-range transport is driven by the strong western jets and travels for 6 days to arrive the U.S. east coast versus the western and northern U.S. Both the NAAPS aerosol transport model and satellite CALIPSO observations for multiple orbits clearly illustrate the dust-dominated aerosol along the transport path. In addition, coincident increase of both particulate matter (PM) and fine soil concentrations indicate the potential impact of transported dust on the air quality that is found to be associated with a large area of sinking air along the U.S. east coast.
Keywords: Asian dust; Transport; Lidar; Particulate matter; Air quality;
New directions: Mineral dust and ozone – Heterogeneous chemistry by S. Ramachandran (369-370).
A roadmap for OH reactivity research by Jonathan Williams; William Brune (371-372).
How ambiguous are climate metrics? And are we prepared to assess and compare the climate impact of new air traffic technologies? by Volker Grewe; Katrin Dahlmann (373-374).
Indoor air: Contemporary sources, exposures and global implications by Lidia Morawska; Tunga Salthammer (375).
Improving the indoor air quality by using a surface emissions trap by Pawel Markowicz; Lennart Larsson (376-381).
The surface emissions trap, an adsorption cloth developed for reducing emissions of volatile organic compounds and particulate matter from surfaces while allowing evaporation of moisture, was used to improve the indoor air quality of a school building with elevated air concentrations of 2-ethyl-1-hexanol. An improvement of the perceived air quality was noticed a few days after the device had been attached on the PVC flooring. In parallel, decreased air concentrations of 2-ethyl-1-hexanol were found as well as a linear increase of the amounts of the same compound adsorbed on the installed cloth as observed up to 13 months after installation. Laboratory studies revealed that the performance of the device is not affected by differences in RH (35–85%), temperature (30–40 °C) or by accelerated aging simulating up to 10 years product lifetime, and, from a blinded exposure test, that the device efficiently blocks chemical odors. This study suggests that the device may represent a fast and efficient means of restoring the indoor air quality in a building e.g. after water damage leading to irritating and potentially harmful emissions from building material surfaces indoors.
Keywords: Indoor air purification; Volatile organic compounds; Building dampness; Formaldehyde; School environment;
Volatile organic compound conversion by ozone, hydroxyl radicals, and nitrate radicals in residential indoor air: Magnitudes and impacts of oxidant sources by Michael S. Waring; J. Raymond Wells (382-391).
Indoor chemistry may be initiated by reactions of ozone (O3), the hydroxyl radical (OH), or the nitrate radical (NO3) with volatile organic compounds (VOC). The principal indoor source of O3 is air exchange, while OH and NO3 formation are considered as primarily from O3 reactions with alkenes and nitrogen dioxide (NO2), respectively. Herein, we used time-averaged models for residences to predict O3, OH, and NO3 concentrations and their impacts on conversion of typical residential VOC profiles, within a Monte Carlo framework that varied inputs probabilistically. We accounted for established oxidant sources, as well as explored the importance of two newly realized indoor sources: (i) the photolysis of nitrous acid (HONO) indoors to generate OH and (ii) the reaction of stabilized Criegee intermediates (SCI) with NO2 to generate NO3. We found total VOC conversion to be dominated by reactions both with O3, which almost solely reacted with d-limonene, and also with OH, which reacted with d-limonene, other terpenes, alcohols, aldehydes, and aromatics. VOC oxidation rates increased with air exchange, outdoor O3, NO2 and d-limonene sources, and indoor photolysis rates; and they decreased with O3 deposition and nitric oxide (NO) sources. Photolysis was a strong OH formation mechanism for high NO, NO2, and HONO settings, but SCI/NO2 reactions weakly generated NO3 except for only a few cases.
Keywords: Indoor chemistry; VOC oxidation; Monte Carlo modeling; Photolysis; Terpenes;
Partitioning of trace elements and metals between quasi-ultrafine, accumulation and coarse aerosols in indoor and outdoor air in schools by M. Viana; I. Rivas; X. Querol; A. Alastuey; M. Álvarez-Pedrerol; L. Bouso; C. Sioutas; J. Sunyer (392-401).
Particle size distribution patterns of trace elements and metals across three size fractions (<0.25 μm, quasi-ultrafine particles, q-UF; 0.25–2.5 μm, accumulation particles; 2.5–10 μm, coarse particles) were analysed in indoor and outdoor air at 39 primary schools across Barcelona (Spain). Special attention was paid to emission sources in each particle size range. Results evidenced the presence in q-UF particles of high proportions of elements typically found in coarse PM (Ca, Al, Fe, Mn or Na), as well as several potentially health-hazardous metals (Mn, Cu, Sn, V, Pb). Modal shifts (e.g., from accumulation to coarse or q-UF particles) were detected when particles infiltrated indoors, mainly for secondary inorganic aerosols. Our results indicate that the location of schools in heavily trafficked areas increases the abundance of q-UF particles, which infiltrate indoors quite effectively, and thus may impact children exposure to these health-hazardous particles.
Keywords: Infiltration; Sources; Metals and elements; Ultrafine particles; UFP; PM0.25;
Indoor aerosol modeling for assessment of exposure and respiratory tract deposited dose by Tareq Hussein; Aneta Wierzbicka; Jakob Löndahl; Mihalis Lazaridis; Otto Hänninen (402-411).
Air pollution is one of the major environmental problems that influence people's health. Exposure to harmful particulate matter (PM) occurs both outdoors and indoors, but while people spend most of their time indoors, the indoor exposures tend to dominate. Moreover, higher PM concentrations due to indoor sources and tightness of indoor environments may substantially add to the outdoor originating exposures. Empirical and real-time assessment of human exposure is often impossible; therefore, indoor aerosol modeling (IAM) can be used as a superior method in exposure and health effects studies. This paper presents a simple approach in combining available aerosol-based modeling techniques to evaluate the real-time exposure and respiratory tract deposited dose based on particle size. Our simple approach consists of outdoor aerosol data base, IAM simulations, time-activity pattern data-base, physical–chemical properties of inhaled aerosols, and semi-empirical deposition fraction of aerosols in the respiratory tract. These modeling techniques allow the characterization of regional deposited dose in any metric: particle mass, particle number, and surface area. The first part of this presentation reviews recent advances in simple mass-balance based modeling methods that are needed in analyzing the health relevance of indoor exposures. The second part illustrates the use of IAM in the calculations of exposure and deposited dose. Contrary to previous methods, the approach presented is a real-time approach and it goes beyond the exposure assessment to provide the required information for the health risk assessment, which is the respiratory tract deposited dose. This simplified approach is foreseen to support epidemiological studies focusing on exposures originating from both indoor and outdoor sources.
Keywords: Particulate matter; Particle number; Health risk; Air exchange; Penetration; Deposition; Infiltration; Sources;
Airborne culturable fungi in naturally ventilated primary school environments in a subtropical climate by Heidi Salonen; Caroline Duchaine; Mandana Mazaheri; Sam Clifford; Lidia Morawska (412-418).
There is currently a lack of reference values for indoor air fungal concentrations to allow for the interpretation of measurement results in subtropical school settings. Analysis of the results of this work established that, in the majority of properly maintained subtropical school buildings, without any major affecting events such as floods or visible mould or moisture contamination, indoor culturable fungi levels were driven by outdoor concentration. The results also allowed us to benchmark the “baseline range” concentrations for total culturable fungi, Penicillium spp., Cladosporium spp. and Aspergillus spp. in such school settings. The measured concentration of total culturable fungi and three individual fungal genera were estimated using Bayesian hierarchical modelling. Pooling of these estimates provided a predictive distribution for concentrations at an unobserved school. The results indicated that “baseline” indoor concentration levels for indoor total fungi, Penicillium spp., Cladosporium spp. and Aspergillus spp. in such school settings were generally ≤1450, ≤680, ≤480 and ≤90 cfu/m3, respectively, and elevated levels would indicate mould damage in building structures. The indoor/outdoor ratio for most classrooms had 95% credible intervals containing 1, indicating that fungi concentrations are generally the same indoors and outdoors at each school. Bayesian fixed effects regression modelling showed that increasing both temperature and humidity resulted in higher levels of fungi concentration.Display Omitted
Keywords: Culturable fungi; School environment; Subtropical area; Concentration; Fungal flora;
Quantification of differences between occupancy and total monitoring periods for better assessment of exposure to particles in indoor environments by A. Wierzbicka; M. Bohgard; J.H. Pagels; A. Dahl; J. Löndahl; T. Hussein; E. Swietlicki; A. Gudmundsson (419-428).
For the assessment of personal exposure, information about the concentration of pollutants when people are in given indoor environments (occupancy time) are of prime importance. However this kind of data frequently is not reported. The aim of this study was to assess differences in particle characteristics between occupancy time and the total monitoring period, with the latter being the most frequently used averaging time in the published data. Seven indoor environments were selected in Sweden and Finland: an apartment, two houses, two schools, a supermarket, and a restaurant. They were assessed for particle number and mass concentrations and number size distributions. The measurements using a Scanning Mobility Particle Sizer and two photometers were conducted for seven consecutive days during winter in each location. Particle concentrations in residences and schools were, as expected, the highest during occupancy time. In the apartment average and median PM2.5 mass concentrations during the occupancy time were 29% and 17% higher, respectively compared to total monitoring period. In both schools, the average and medium values of the PM2.5 mass concentrations were on average higher during teaching hours compared to the total monitoring period by 16% and 32%, respectively. When it comes to particle number concentrations (PNC), in the apartment during occupancy, the average and median values were 33% and 58% higher, respectively than during the total monitoring period. In both houses and schools the average and median PNC were similar for the occupancy and total monitoring periods. General conclusions on the basis of measurements in the limited number of indoor environments cannot be drawn. However the results confirm a strong dependence on type and frequency of indoor activities that generate particles and site specificity. The results also indicate that the exclusion of data series during non-occupancy periods can improve the estimates of particle concentrations and characteristics suitable for exposure assessment, which is crucial for estimating health effects in epidemiological and toxicological studies.
Keywords: Particles; Indoor environment; Source strength;
Waterpipes and e-cigarettes: Impact of alternative smoking techniques on indoor air quality and health by Hermann Fromme; Wolfgang Schober (429-441).
Waterpipe (WP) smoking is growing as an alternative to cigarette smoking, especially in younger age groups. E-cigarette use has also increased in recent years. A majority of smokers mistakenly believe that WP smoking is a social entertainment practice that leads to more social behavior and relaxation and that this type of smoking is safe or less harmful and less addictive than cigarette smoking. In reality, WP smokers are exposed to hundreds of toxic substances that include known carcinogens. High exposures to carbon monoxide and nicotine are major health threats. Persons exposed to secondhand WP smoke are also at risk. There is growing evidence that WP smoke causes adverse effects on the pulmonary and cardiovascular systems and is responsible for cancer.E-cigarettes are marketed as a smokeless and safe way to inhale nicotine without being exposed to the many toxic components of tobacco cigarettes, and as an aid to smoking cessation. In fact, consumers (vapers) and secondhand vapers can be exposed to substantial amounts of VOC, PAH or other potentially harmful substances. Of major health concern is the inhalation of fine and ultrafine particles formed from supersaturated 1,2-propanediol vapor. Such particles can be deposited in the deeper parts of the lung and may harm the respiratory system or increase the risk of acquiring asthma. More research on the safety of e-cigarettes needs to be conducted to ensure a high level of public health protection in the long-term.
Keywords: Waterpipe; Shisha; E-cigarette; Vaping; Indoor air; Human biomonitoring; Health;
On the interaction between radon progeny and particles generated by electronic and traditional cigarettes by C. Vargas Trassierra; F. Cardellini; G. Buonanno; P. De Felice (442-450).
During their entire lives, people are exposed to the pollutants present in indoor air. Recently, Electronic Nicotine Delivery Systems, mainly known as electronic cigarettes, have been widely commercialized: they deliver particles into the lungs of the users but a “second-hand smoke” has yet to be associated to this indoor source. On the other hand, the naturally-occurring radioactive gas, i.e. radon, represents a significant risk for lung cancer, and the cumulative action of these two agents could be worse than the agents separately would. In order to deepen the interaction between radon progeny and second-hand aerosol from different types of cigarettes, a designed experimental study was carried out by generating aerosol from e-cigarette vaping as well as from second-hand traditional smoke inside a walk-in radon chamber at the National Institute of Ionizing Radiation Metrology (INMRI) of Italy. In this chamber, the radon present in air comes naturally from the floor and ambient conditions are controlled. To characterize the sidestream smoke emitted by cigarettes, condensation particle counters and scanning mobility particle sizer were used. Radon concentration in the air was measured through an Alphaguard ionization chamber, whereas the measurement of radon decay product in the air was performed with the Tracelab BWLM Plus-2S Radon daughter Monitor. It was found an increase of the Potential Alpha-Energy Concentration (PAEC) due to the radon decay products attached to aerosol for higher particle number concentrations. This varied from 7.47 ± 0.34 MeV L−1 to 12.6 ± 0.26 MeV L−1 (69%) for the e-cigarette. In the case of traditional cigarette and at the same radon concentration, the increase was from 14.1 ± 0.43 MeV L−1 to 18.6 ± 0.19 MeV L−1 (31%). The equilibrium factor increases, varying from 23.4% ± 1.11% to 29.5% ± 0.26% and from 30.9% ± 1.0% to 38.1 ± 0.88 for the e-cigarette and traditional cigarette, respectively. These growths still continue for long time after the combustion, by increasing the exposure risk.
Keywords: Indoor air quality; Electronic cigarette; Radon; Exposure risk; Equilibrium factor; Potential Alpha Energy Concentration;
WHO indoor air quality guidelines on household fuel combustion: Strategy implications of new evidence on interventions and exposure–risk functions by Nigel Bruce; Dan Pope; Eva Rehfuess; Kalpana Balakrishnan; Heather Adair-Rohani; Carlos Dora (451-457).
Background: 2.8 billion people use solid fuels as their primary cooking fuel; the resulting high levels of household air pollution (HAP) were estimated to cause more than 4 million premature deaths in 2012. The people most affected are among the world's poorest, and past experience has shown that securing adoption and sustained use of effective, low-emission stove technologies and fuels in such populations is not easy. Among the questions raised by these challenges are (i) to what levels does HAP exposure need to be reduced in order to ensure that substantial health benefits are achieved, and (ii) what intervention technologies and fuels can achieve the required levels of HAP in practice? New WHO air quality guidelines are being developed to address these issues. Aims: To address the above questions drawing on evidence from new evidence reviews conducted for the WHO guidelines. Methods: Discussion of key findings from reviews covering (i) systematic reviews of health risks from HAP exposure, (ii) newly developed exposure–response functions which combine combustion pollution risk evidence from ambient air pollution, second-hand smoke, HAP and active smoking, and (iii) a systematic review of the impacts of solid fuel and clean fuel interventions on kitchen levels of, and personal exposure to, PM2.5 and carbon monoxide (CO). Findings: Evidence on health risks from HAP suggest that controlling this exposure could reduce the risk of multiple child and adult health outcomes by 20–50%. The new integrated exposure–response functions (IERs) indicate that in order to secure these benefits, HAP levels require to be reduced to the WHO IT-1 annual average level (35 μg/m3 PM2.5), or below. The second review found that, in practice, solid fuel ‘improved stoves’ led to large percentage and absolute reductions, but post-intervention kitchen levels were still very high, at several hundreds of μg/m3 of PM2.5, although most solid fuel stove types met the WHO 24-hr average guideline for CO of 7 mg/m3. Clean fuel user studies were few, but also did not meet IT-1 for PM2.5, likely due to a combination of continuing multiple stove and fuel use, other sources in the home (e.g. kerosene lamps), and pollution from neighbours and other outdoor sources. Conclusions: Together, this evidence implies there needs to be a strategic shift towards more rapid and widespread promotion of clean fuels, along with efforts to encourage more exclusive use and control other sources in and around the home. For households continuing to rely on solid fuels, the best possible low-emission solid fuel stoves should be promoted, backed up by testing and in-field evaluation.
Keywords: WHO guidelines; Household air pollution; Exposure–response; Clean fuels; Testing and standards;
Contribution of indoor-generated particles to residential exposure by C. Isaxon; A. Gudmundsson; E.Z. Nordin; L. Lönnblad; A. Dahl; G. Wieslander; M. Bohgard; A. Wierzbicka (458-466).
The majority of airborne particles in residences, when expressed as number concentrations, are generated by the residents themselves, through combustion/thermal related activities. These particles have a considerably smaller diameter than 2.5 μm and, due to the combination of their small size, chemical composition (e.g. soot) and intermittently very high concentrations, should be regarded as having potential to cause adverse health effects.In this study, time resolved airborne particle measurements were conducted for seven consecutive days in 22 randomly selected homes in the urban area of Lund in southern Sweden. The main purpose of the study was to analyze the influence of human activities on the concentration of particles in indoor air. Focus was on number concentrations of particles with diameters <300 nm generated by indoor activities, and how these contribute to the integrated daily residential exposure. Correlations between these particles and soot mass concentration in total dust were also investigated.It was found that candle burning and activities related to cooking (using a frying pan, oven, toaster, and their combinations) were the major particle sources.The frequency of occurrence of a given concentration indoors and outdoors was compared for ultrafine particles. Indoor data was sorted into non-occupancy and occupancy time, and the occupancy time was further divided into non-activity and activity influenced time. It was found that high levels (above 104 cm−3) indoors mainly occur during active periods of occupancy, while the concentration during non-activity influenced time differs very little from non-occupancy time.Total integrated daily residential exposure of ultrafine particles was calculated for 22 homes, the contribution from known activities was 66%, from unknown activities 20%, and from background/non-activity 14%.The collected data also allowed for estimates of particle source strengths for specific activities, and for some activities it was possible to estimate correlations between the number concentration of ultrafine particles and the mass concentration of soot in total dust in 10 homes. Particle source strengths (for 7 specific activities) ranged from 1.6·1012 to 4.5·1012 min−1.The correlation between ultrafine particles and mass concentration of soot in total dust varied between 0.37 and 0.85, with an average of 0.56 (Pearson correlation coefficient).This study clearly shows that due to the importance of indoor sources, residential exposure to ultrafine particles cannot be characterized by ambient measurements alone.
Keywords: Ultrafine particles; Indoor sources; Exposure; Indoor measurements; Soot; Source strength;
Application of the Junge- and Pankow-equation for estimating indoor gas/particle distribution and exposure to SVOCs by Tunga Salthammer; Tobias Schripp (467-476).
In the indoor environment, distribution and dynamics of an organic compound between gas phase, particle phase and settled dust must be known for estimating human exposure. This, however, requires a detailed understanding of the environmentally important compound parameters, their interrelation and of the algorithms for calculating partitioning coefficients. The parameters of major concern are: (I) saturation vapor pressure (P S) (of the subcooled liquid); (II) Henry's law constant (H); (III) octanol/water partition coefficient (K OW); (IV) octanol/air partition coefficient (K OA); (V) air/water partition coefficient (K AW) and (VI) settled dust properties like density and organic content. For most of the relevant compounds reliable experimental data are not available and calculated gas/particle distributions can widely differ due to the uncertainty in predicted P s and K OA values. This is not a big problem if the target compound is of low (<10−6 Pa) or high (>10−2 Pa) volatility, but in the intermediate region even small changes in P s or K OA will have a strong impact on the result. Moreover, the related physical processes might bear large uncertainties. The K OA value can only be used for particle absorption from the gas phase if the organic portion of the particle or dust is high. The Junge- and Pankow-equation for calculating the gas/particle distribution coefficient K P do not consider the physical and chemical properties of the particle surface area. It is demonstrated by error propagation theory and Monte-Carlo simulations that parameter uncertainties from estimation methods for molecular properties and variations of indoor conditions might strongly influence the calculated distribution behavior of compounds in the indoor environment.Display Omitted
Keywords: SVOCs; Airborne particles; Settled house dust; Vapor pressure; Partition coefficient;
Desorption of a methamphetamine surrogate from wallboard under remediation conditions by Dustin Poppendieck; Glenn Morrison; Richard Corsi (477-484).
Thousands of homes in the United States are found to be contaminated with methamphetamine each year. Buildings used to produce illicit methamphetamine are typically remediated by removing soft furnishings and stained materials, cleaning and sometimes encapsulating surfaces using paint. Methamphetamine that has penetrated into paint films, wood and other permanent materials can be slowly released back into the building air over time, exposing future occupants and re-contaminating furnishings. The objective of this study was to determine the efficacy of two wallboard remediation techniques for homes contaminated with methamphetamine: 1) enhancing desorption by elevating temperature and relative humidity while ventilating the interior space, and 2) painting over affected wallboard to seal the methamphetamine in place. The emission of a methamphetamine surrogate, N-isopropylbenzylamine (NIBA), from pre-dosed wallboard chambers over 20 days at 32 °C and two values of relative humidity were studied. Emission rates from wallboard after 15 days at 32 °C ranged from 35 to 1400 μg h−1 m−2. Less than 22% of the NIBA was removed from the chambers over three weeks. Results indicate that elevating temperatures during remediation and latex painting of impacted wallboard will not significantly reduce freebase methamphetamine emissions from wallboard. Raising the relative humidity from 27% to 49% increased the emission rates by a factor of 1.4. A steady-state model of a typical home using the emission rates from this study and typical residential building parameters and conditions shows that adult inhalation reference doses for methamphetamine will be reached when approximately 1 g of methamphetamine is present in the wallboard of a house.Display Omitted
Keywords: Methamphetamine; Wallboard; Desorption; Remediation;
Volatile Organic Compounds: Characteristics, distribution and sources in urban schools by Nitika Mishra; Jennifer Bartsch; Godwin A. Ayoko; Tunga Salthammer; Lidia Morawska (485-491).
Long term exposure to organic pollutants, both inside and outside school buildings may affect children's health and influence their learning performance. Since children spend significant amount of time in school, air quality, especially in classrooms plays a key role in determining the health risks associated with exposure at schools. Within this context, the present study investigated the ambient concentrations of Volatile Organic Compounds (VOCs) in 25 primary schools in Brisbane with the aim to quantify the indoor and outdoor VOCs concentrations, identify VOCs sources and their contribution, and based on these; propose mitigation measures to reduce VOCs exposure in schools. One of the most important findings is the occurrence of indoor sources, indicated by the I/O ratio >1 in 19 schools. Principal Component Analysis with Varimax rotation was used to identify common sources of VOCs and source contribution was calculated using an Absolute Principal Component Scores technique. The result showed that outdoor 47% of VOCs were contributed by petrol vehicle exhaust but the overall cleaning products had the highest contribution of 41% indoors followed by air fresheners and art and craft activities. These findings point to the need for a range of basic precautions during the selection, use and storage of cleaning products and materials to reduce the risk from these sources.
Keywords: Volatile Organic Compounds; Ambient concentrations; Personal exposure; Schools; Children;
Impact of room fragrance products on indoor air quality by Erik Uhde; Nicole Schulz (492-502).
Everyday life can no longer be imagined without fragrances and scented products. For the consumer, countless products exists which are solely or partly intended to give off a certain scent in sufficient concentrations to odorize a complete room. Sprays, diffusers and evaporators, scented candles and automatic devices for the distribution of fragrance liquids are typical examples of such products. If the consumer uses such products, his consent to the release of certain chemicals in his home can be implied, however, he may not know what kind of fragrance substances and solvents will be present in which concentrations.In this study, we determined the volatile emissions of a number of fragrance products in detail. Measurements were carried out under controlled conditions in test chambers. The products were tested in a passive (unused) and an active state, wherever applicable. Following a defined test protocol, the release of volatile organic compounds, ultrafine particles and NO x was monitored for each product. The potential for forming secondary organic aerosols under the influence of ozone was studied, and for a selection of products the long-term emission behavior was assessed. A remarkable variety of fragrance substances was found and more than 100 relevant compounds were identified and quantified. While it is the intended function of such products to release fragrance substances, also considerable amounts of non-odorous solvents and by-products were found to be released from several air fresheners. Emissions rates exceeding 2 mg/(unit*h) were measured for the five most common solvents.
Keywords: Fragrance product; Room spray; Candle; Emission; Solvent;
Exposure to airborne engineered nanoparticles in the indoor environment by Marina E. Vance; Linsey C. Marr (503-509).
This literature review assesses the current state of knowledge about inhalation exposure to airborne, engineered nanoparticles in the indoor environment. We present principal exposure scenarios in indoor environments, complemented by analysis of the published literature and of an inventory of nanotechnology-enhanced consumer products. Of all products listed in the inventory, 10.8% (194 products) present the potential for aerosolization of nanomaterials and subsequent inhalation exposure during use or misuse. Among those, silver-containing products are the most prevalent (68 products). Roughly 50% of products would release wet aerosols and 50% would potentially release dry aerosols. Approximately 14% are cleaning products that can be broadly used in public indoor environments, where building occupants may be exposed. While a variety of nanomaterial compositions have been investigated in the limited number of published release and exposure studies, we identified a need for studies investigating nanofibers (beyond carbon nanotubes), nanofilms, nanoplatelets, and other emerging nanomaterials such as ceria and their nanocomposites. Finally, we provide recommendations for future research to advance the understanding of exposure to airborne nanomaterials indoors, such as studies into indoor chemistry of nanomaterials, better nanomaterial reporting and labeling in consumer products, and safer design of nanomaterial-containing consumer products.
Keywords: Aerosols; Exposure; Inhalation; Indoor air; Nanomaterials; Ultrafine aerosols;