Atmospheric Environment (v.134, #C)
Editorial board (i).
Estimation of the local and long-range contributions to particulate matter levels using continuous measurements in a single urban background site by Marianna Diamantopoulou; Ksakousti Skyllakou; Spyros N. Pandis (1-9).
The Particulate Matter Source Apportionment Technology (PSAT) algorithm is used together with PMCAMx, a regional chemical transport model, to develop a simple observation-based method (OBM) for the estimation of local and regional contributions of sources of primary and secondary pollutants in urban areas. We test the hypothesis that the minimum of the diurnal average concentration profile of the pollutant is a good estimate of the average contribution of long range transport levels. We use PMCAMx to generate “pseudo-observations” for four different European cities (Paris, London, Milan, and Dusseldorf) and PSAT to estimate the corresponding “true” local and regional contributions. The predictions of the proposed OBM are compared to the “true” values for different definitions of the source area.During winter, the estimates by the OBM for the local contributions to the concentrations of total PM2.5, primary pollutants, and sulfate are within 25% of the “true” contributions of the urban area sources. For secondary organic aerosol the OBM overestimates the importance of the local sources and it actually estimates the contributions of sources within 200 km from the receptor.During summer for primary pollutants and cities with low nearby emissions (ratio of emissions in an area extending 100 km from the city over local emissions lower than 10) the OBM estimates correspond to the city emissions within 25% or so. For cities with relatively high nearby emissions the OBM estimates correspond to emissions within 100 km from the receptor. For secondary PM2.5 components like sulfate and secondary organic aerosol the OBM's estimates correspond to sources within 200 km from the receptor. Finally, for total PM2.5 the OBM provides approximately the contribution of city emissions during the winter and the contribution of sources within 100 km from the receptor during the summer.
Keywords: PM2.5; Particle source apportionment; Continuous measurements;
Non-exhaust PM emissions from electric vehicles by Victor R.J.H. Timmers; Peter A.J. Achten (10-17).
Particulate matter (PM) exposure has been linked to adverse health effects by numerous studies. Therefore, governments have been heavily incentivising the market to switch to electric passenger cars in order to reduce air pollution. However, this literature review suggests that electric vehicles may not reduce levels of PM as much as expected, because of their relatively high weight. By analysing the existing literature on non-exhaust emissions of different vehicle categories, this review found that there is a positive relationship between weight and non-exhaust PM emission factors. In addition, electric vehicles (EVs) were found to be 24% heavier than equivalent internal combustion engine vehicles (ICEVs). As a result, total PM10 emissions from EVs were found to be equal to those of modern ICEVs. PM2.5 emissions were only 1–3% lower for EVs compared to modern ICEVs. Therefore, it could be concluded that the increased popularity of electric vehicles will likely not have a great effect on PM levels. Non-exhaust emissions already account for over 90% of PM10 and 85% of PM2.5 emissions from traffic. These proportions will continue to increase as exhaust standards improve and average vehicle weight increases. Future policy should consequently focus on setting standards for non-exhaust emissions and encouraging weight reduction of all vehicles to significantly reduce PM emissions from traffic.
Keywords: Electric vehicle; Particulate matter; Non-exhaust; PM10;
Development of an automated sampling-analysis system for simultaneous measurement of reactive oxygen species (ROS) in gas and particle phases: GAC-ROS by Wei Huang; Yuanxun Zhang; Yang Zhang; Limin Zeng; Huabin Dong; Peng Huo; Dongqing Fang; James J. Schauer (18-26).
A novel online system, GAC-ROS, for simultaneous measurement of reactive oxygen species (ROS) in both gas and particle phases was developed based on 2′,7′-dichlorofluorescin (DCFH) assay to provide fast sampling and analysis of atmospheric ROS. The GAC-ROS, composed of a Gas and Aerosol Collector (GAC), a series of reaction and transportation systems, and a fluorescence detector, was tested for instrumental performance in laboratory. Results showed good performance with a favorable R2 value for the calibration curve (above 0.998), high penetration efficiencies of ROS (above 99.5%), and low detection limits (gas-phase ROS: 0.16 nmol H2O2 m−3; particle-phase ROS: 0.12 nmol H2O2 m−3). Laboratorial comparison between online and offline methods for particle-bound ROS showed significant loss of ROS due to the relatively long time off-line treatment. Field observations in Beijing found that concentrations of ROS in winter time were significantly higher than those observed in spring. Only a few weak positive correlations were found between ROS and some air pollutants, which reflects the complexities of ROS generation and transformation in atmosphere. This study was the first to simultaneously obtain concentrations of gas and particle-phase ROS using an online method. Consequently, it provides a powerful tool to characterize the oxidizing capacity of the atmosphere and the sources of the oxidizing capacity.
Keywords: Reactive oxygen species; Online measurement; Sampling-analysis system; 2′,7′-dichlorofluorescin; Filed observation;
First field-based atmospheric observation of the reduction of reactive mercury driven by sunlight by Benjamin de Foy; Yindong Tong; Xiufeng Yin; Wei Zhang; Shichang Kang; Qianggong Zhang; Guoshuai Zhang; Xuejun Wang; James J. Schauer (27-39).
Hourly speciated measurements of atmospheric mercury made in a remote, high-altitude site in the Tibetan Plateau revealed the first field observations of the reduction of reactive mercury in the presence of sunlight in the atmosphere. Measurements were collected over four winter months on the shore of Nam Co Lake in the inland Tibetan Plateau. The data was analyzed to identify sources and atmospheric transformations of the speciated mercury compounds. The absence of local anthropogenic sources provided a unique opportunity to examine chemical transformations of mercury. An optimization algorithm was used to determine the parameters of a chemical box model that would match the measured reactive mercury concentrations. This required the presence of a photolytic reduction reaction previously observed in laboratory studies and in power plant plumes. In addition, the model estimated the role of vertical mixing in diluting reactive gaseous mercury during the day, and the role of bromine chemistry in oxidizing gaseous elemental mercury to produce reactive gaseous mercury. This work provides further evidence of the need to add the photolytic reduction reaction of oxidized mercury into atmospheric transport models in order to better simulate mercury deposition.Display Omitted
Keywords: Atmospheric mercury; Mercury chemistry; Photolytic reduction; Chemical box model; Tibetan plateau;
Measurement of ammonia emissions from temperate and sub-polar seabird colonies by S.N. Riddick; T.D. Blackall; U. Dragosits; F. Daunt; M. Newell; C.F. Braban; Y.S. Tang; J. Schmale; P.W. Hill; S. Wanless; P. Trathan; M.A. Sutton (40-50).
The chemical breakdown of marine derived reactive nitrogen transported to the land as seabird guano represents a significant source of ammonia (NH3) in areas far from other NH3 sources. Measurements made at tropical and temperate seabird colonies indicate substantial NH3 emissions, with emission rates larger than many anthropogenic point sources. However, several studies indicate that thermodynamic processes limit the amount of NH3 emitted from guano, suggesting that the percentage of guano volatilizing as NH3 may be considerably lower in colder climates. This study undertook high resolution temporal ammonia measurements in the field and coupled results with modelling to estimate NH3 emissions at a temperate puffin colony and two sub-polar penguin colonies (Signy Island, South Orkney Islands and Bird Island, South Georgia) during the breeding season. These emission rates are then compared with NH3 volatilization rates from other climates. Ammonia emissions were calculated using a Lagrangian atmospheric dispersion model, resulting in mean emissions of 5 μg m−2 s−1 at the Isle of May, 12 μg m−2 s−1 at Signy Island and 9 μg m−2 s−1 at Bird Island. The estimated percentage of total guano nitrogen volatilized was 5% on the Isle of May, 3% on Signy and 2% on Bird Island. These values are much smaller than the percentage of guano nitrogen volatilized in tropical contexts (31–65%). The study confirmed temperature, wind speed and water availability have a significant influence on the magnitude of NH3 emissions, which has implications for reactive nitrogen in both modern remote regions and pre-industrial atmospheric composition and ecosystem interactions.
Keywords: Coastal nitrogen; Seabirds; Penguins; Temperate; Sub-polar; NH3 emissions; Atmospheric dispersion; Inverse modelling;
Application of plume analysis to build land use regression models from mobile sampling to improve model transferability by Yi Tan; Timothy R. Dallmann; Allen L. Robinson; Albert A. Presto (51-60).
Mobile monitoring of traffic-related air pollutants was conducted in Pittsburgh, PA. The data show substantial spatial variability of particle-bound polycyclic aromatic hydrocarbons (PB-PAH) and black carbon (BC). This variability is driven in large part by pollutant plumes from high emitting vehicles (HEVs). These plumes contribute a disproportionately large fraction of the near-road exposures of PB-PAH and BC. We developed novel statistical models to describe the spatial patterns of PB-PAH and BC exposures. The models consist of two layers: a plume layer to describe the contributions of high emitting vehicles using a near-roadway kernel, and an urban-background layer that predicts the spatial pattern of other sources using land use regression. This approach leverages unique information content of highly time resolved mobile monitoring data and provides insight into source contributions. The two-layer model describes 76% of observed PB-PAH variation and 61% of BC variation. On average, HEVs contribute at least 32% of outdoor PB-PAH and 14% of BC. The transferability of the models was examined using measurements from 36 hold-out validation sites. The plume layer performed well at validation sites, but the background layer showed little transferability due to the large difference in land use between the city and outer suburbs.Display Omitted
Keywords: Air pollution; Black carbon; Exposure assessment; Geographic information systems; Land use regression;
Effects of design parameters and puff topography on heating coil temperature and mainstream aerosols in electronic cigarettes by Tongke Zhao; Shi Shu; Qiuju Guo; Yifang Zhu (61-69).
Emissions from electronic cigarettes (ECs) may contribute to both indoor and outdoor air pollution and the number of users is increasing rapidly. ECs operate based on the evaporation of e-liquid by a high-temperature heating coil. Both puff topography and design parameters can affect this evaporation process. In this study, both mainstream aerosols and heating coil temperature were measured concurrently to study the effects of design parameters and puff topography. The heating coil temperatures and mainstream aerosols varied over a wide range across different brands and within same brand. The peak heating coil temperature and the count median diameter (CMD) of EC aerosols increased with a longer puff duration and a lower puff flow rate. The particle number concentration was positively associated with the puff duration and puff flow rate. These results provide a better understanding of how EC emissions are affected by design parameters and puff topography and emphasize the urgent need to better regulate EC products.Display Omitted
Keywords: Electronic cigarette; Ultrafine particles; Heating coil temperature; Particle number concentration; Particle size;
Indian emissions of technology-linked NMVOCs with chemical speciation: An evaluation of the SAPRC99 mechanism with WRF-CAMx simulations by M. Sarkar; C. Venkataraman; S. Guttikunda; P. Sadavarte (70-83).
Non-methane volatile organic compounds (NMVOCs) are important precursors to reactions producing tropospheric ozone and secondary organic aerosols. The present work uses a detailed technology-linked NMVOC emission database for India, along with a standard mapping method to measured NMVOC profiles, to develop speciated NMVOC emissions, which are aggregated into multiple chemical mechanisms used in chemical transport models. The fully speciated NMVOC emissions inventory with 423 constituent species, was regrouped into model-ready reactivity classes of the RADM2, SAPRC99 and CB-IV chemical mechanisms, and spatially distributed at 25 × 25 km2 resolution, using source-specific spatial proxies. Emissions were considered from four major sectors, i.e. industry, transport, agriculture and residential and from non-combustion activities (use of solvents and paints). It was found that residential cooking with biomass fuels, followed by agricultural residue burning in fields and on-road transport, were largest contributors to the highest reactivity group of NMVOC emissions from India. The emissions were evaluated using WRF-CAMx simulations, using the SAPRC99 photochemical mechanism, over India for contrasting months of April, July and October 2010. Modelled columnar abundance of NO2, CO and O3 agreed well with satellite observations both in magnitude and spatial distribution, in the three contrasting months. Evaluation of monthly and spatial differences between model predictions and observations indicates the need for further refinement of the spatial distribution of NOX emissions, spatio-temporal distribution of agricultural residue burning emissions.
Keywords: RADM2; SAPRC99; CB-IV; Residential biomass cooking; Agricultural field burning; On-road transport;
On the source contribution to Beijing PM2.5 concentrations by Naděžda Zíková; Yungang Wang; Fumo Yang; Xinghua Li; Mi Tian; Philip K. Hopke (84-95).
Beijing is a city with some of the world's worst particulate air pollution. Although there have been various control strategies implemented since 1998, there are still episodes of PM2.5 concentrations of hundreds of micrograms per cubic meter. In this study, samples were collected over a year in Beijing, chemically characterized, and the resulting data analyzed for source apportionment. The new error analysis capabilities built into EPA PMF V5.0 have been employed to better evaluate the profiles and assign them to source types. Secondary sulfate, local coal combustion and secondary nitrate were the major contributors to the PM2.5 mass. However, in this study, traffic was found to be more important as a PM compared to prior studies. It was actually the largest PM2.5 source in autumn and winter although local coal combustion is also a large source of PM in the winter months. These results demonstrate the value of using the displacement method to assess the variability in source profiles to improve our interpretation of PMF results. They also suggest more attention needs to be paid to traffic emissions in Beijing.
Keywords: Beijing; Positive matrix factorization; PM2.5; Traffic; Coal combustion;
Modelling road dust emission abatement measures using the NORTRIP model: Vehicle speed and studded tyre reduction by M. Norman; I. Sundvor; B.R. Denby; C. Johansson; M. Gustafsson; G. Blomqvist; S. Janhäll (96-108).
Road dust emissions in Nordic countries still remain a significant contributor to PM10 concentrations mainly due to the use of studded tyres. A number of measures have been introduced in these countries in order to reduce road dust emissions. These include speed reductions, reductions in studded tyre use, dust binding and road cleaning. Implementation of such measures can be costly and some confidence in the impact of the measures is required to weigh the costs against the benefits. Modelling tools are thus required that can predict the impact of these measures. In this paper the NORTRIP road dust emission model is used to simulate real world abatement measures that have been carried out in Oslo and Stockholm. In Oslo both vehicle speed and studded tyre share reductions occurred over a period from 2004 to 2006 on a major arterial road, RV4. In Stockholm a studded tyre ban on Hornsgatan in 2010 saw a significant reduction in studded tyre share together with a reduction in traffic volume. The model is found to correctly simulate the impact of these measures on the PM10 concentrations when compared to available kerbside measurement data. Importantly meteorology can have a significant impact on the concentrations through both surface and dispersion conditions. The first year after the implementation of the speed reduction on RV4 was much drier than the previous year, resulting in higher mean concentrations than expected. The following year was much wetter with significant rain and snow fall leading to wet or frozen road surfaces for 83% of the four month study period. This significantly reduced the net PM10 concentrations, by 58%, compared to the expected values if meteorological conditions had been similar to the previous years. In the years following the studded tyre ban on Hornsgatan road wear production through studded tyres decreased by 72%, due to a combination of reduced traffic volume and reduced studded tyre share. However, after accounting for exhaust contributions and the impact of meteorological conditions in the model calculations then the net mean reduction in PM10 concentrations was only ∼50%, in agreement with observations. The NORTRIP model is shown to be able to reproduce the impacts of both traffic measures and meteorology on traffic induced PM10 concentrations, making it a unique and valuable tool for predicting the impact of measures for air quality management applications.
Keywords: Air quality; Non-exhaust emission; Road dust; Suspension; Emission modelling; Abatement measures;
Characterisation of diesel particulate emission from engines using commercial diesel and biofuels by T. Ajtai; M. Pintér; N. Utry; G. Kiss-Albert; G. Gulyás; P. Pusztai; R. Puskás; Á. Bereczky; Gy. Szabados; G. Szabó; Z. Kónya; Z. Bozóki (109-120).
In this paper, the number concentration and the size distribution of diluted diesel exhaust particulate matter were measured at three different engine operating points in the speed-load range of the engine as follows: 1600 rpm; 50% load, 1900 rpm; 25% load, 1900 rpm; 75% load, adopted from the UN ECE Vehicle Regulation no. 49 (Revision 2) test protocol using pure diesel and biodiesel fuels, as well as their controlled blends. The emitted particulate assembly had lognormal size distribution in the accumulation mode regardless of the engine operational condition and the type of fuel. The total number and volume concentration emitted by the diesel engine decreased with increasing revolution per minute and rated torque in case of all the fuel types. The mixing ratio of the fuels did not linearly affect the total emission but had a minimum at 75% biodiesel content. We also studied the thermal evolution of the emitted particulates using a specially designed thermodenuder (TD) heated at specific temperatures (50 °C, 120 °C, and 250 °C). The first transition, when the temperature was increased from 50 °C to 120 °C resulted in lower number concentrations with small relative shifts of the peak position. However, in case of the second transition, when the temperature reached 250 °C the individual volatile particulates adsorbed onto the surface of soot particles were completely or partly vaporised resulting in lower total number concentrations with a substantial shift in peak position.
Keywords: Diesel particulate; Biodiesel; Size distribution; Volatile particle; Thermodenuder;
Atmospheric carbon removal capacity of a mangrove ecosystem in a micro-tidal basin estuary in Sri Lanka by K.A.R.S. Perera; M.D. Amarasinghe (121-128).
Characterization of the micro-tidal mangrove forests in Negombo estuary, located on the west coast of Sri Lanka, with respect to its capacity to remove atmospheric carbon and sequestration in above and below ground plant components is the objective of this study. These mangroves constitute both natural stands (e.g. Kadolkele) and woodlots planted, protected and managed by fishermen (e.g. Wedikanda) to extract twigs and branches to construct “brush parks”, a traditional method of fishing in this estuary. Both types of mangrove stands support high species richness and structural diversity, indicating planted mangrove areas have reached a semi-natural state. Allometric relationships were used to calculate biomass increment. Differences in litterfall, above and below ground biomass increment and net primary productivity (NPP) of the two types of mangrove areas were statistically insignificant, thus indicating that they are structurally and functionally comparable. Average rate of mangrove litterfall in Negombo estuary was 802 ± 25 g m−2y−1. The average above ground biomass increment was 1213 ± 95 gm−2y−1 and below ground increment was 267 ± 18 gm−2y−1, thus the average NPP of these mangroves was 2282 ± 125 g m−2y−1. NPP showed a decreasing trend from water towards land, in line with plant density and leaf area index. A statistically significant relationship was found between vegetation structure (represented by complexity index), NPP and rate of organic carbon accumulation in mangroves. Potential carbon accumulation capacity of mangroves of Negombo estuary was estimated to be approximately 12 t ha−1y−1, which is equivalent to the amount of carbon emitted as CO2 through combustion of 19,357 L of diesel or 22,212 L of gasoline in motor vehicles. Potential atmospheric carbon removal capacity of Negombo estuarine mangroves (350 ha in extent) therefore was estimated to be 4143 t y−1, which is equivalent to removal of CO2 emitted through combustion of 6,779,000 L of diesel or 7,779,000 L of gasoline within a year.
Keywords: Micro-tidal estuaries; Mangroves net primary productivity; CO2 removal capacity;
Regionalized life cycle impact assessment of air pollution on the global scale: Damage to human health and vegetation by Rosalie van Zelm; Philipp Preiss; Thomas van Goethem; Rita Van Dingenen; Mark Huijbregts (129-137).
We developed regionalized characterization factors (CFs) for human health damage from particulate matter (PM2.5) and ozone, and for damage to vegetation from ozone, at the global scale. These factors can be used in the impact assessment phase of an environmental life cycle assessment. CFs express the overall damage of a certain pollutant per unit of emission of a precursor, i.e. primary PM2.5, nitrogen oxides (NOx), ammonia (NH3), sulfur dioxide (SO2) and non-methane volatile organic compounds (NMVOCs). The global chemical transport model TM5 was used to calculate intake fractions of PM2.5 and ozone for 56 world regions covering the whole globe. Furthermore, region-specific effect and damage factors were derived, using mortality rates, background concentrations and years of life lost. The emission-weighted world average CF for primary PM2.5 emissions is 629 yr kton−1, varying up to 3 orders of magnitude over the regions. Larger CFs were obtained for emissions in central Asia and Europe, and smaller factors in Australia and South America. The world average CFs for PM2.5 from secondary aerosols, i.e. NOx, NH3, and SO2, is 67.2 to 183.4 yr kton−1. We found that the CFs for ozone human health damage are 2–4 orders of magnitude lower compared to the CFs for damage due to primary PM2.5 and PM2.5 precursor emissions. Human health damage due to the priority air pollutants considered in this study was 1.7·10−2 yr capita−1 worldwide in year 2010, with primary PM2.5 emissions as the main contributor (62%). The emission-weighted world average CF for ecosystem damage due to ozone was 2.5 km2 yr kton−1 for NMVOCs and 8.7 m2 yr kg−1 for NOx emissions, varying 2–3 orders of magnitude over the regions. Ecosystem damage due to the priority air pollutants considered in this study was 1.6·10−4 km2 capita−1 worldwide in 2010, with NOx as the main contributor (72%). The spatial range in CFs stresses the importance of including spatial variation in life cycle impact assessment of priority air pollutants.Display Omitted
Keywords: Mortality; Characterization factor; Intake fraction; Damage factor; Photochemical ozone; PM2.5;
The effects of air mass transport, seasonality, and meteorology on pollutant levels at the Iskrba regional background station (1996–2014) by Matevž Poberžnik; Erik Štrumbelj (138-146).
Our main goal was to estimate the effects of long-range air transport on pollutant concentrations measured at the Iskrba regional background station (Slovenia). We cluster back-trajectories into categories and simultaneously model the effects of meteorology, seasonality, trends, and air mass trajectory clusters using a Bayesian statistical approach. This simplifies the interpretation of results and allows us to better identify the effects of individual variables, which is important, because pollutant concentrations, meteorology, and trajectories are seasonal and correlated. Similar to related work from other European sites, we find that slow and faster moving trajectories from eastern Europe and the northern part of the Balkan peninsula are associated with higher pollutant levels, while fast-moving trajectories from the Atlantic are associated with lower pollutant concentration. Overall, pollutant concentrations have decreased in the studied period.
Keywords: Climatology; Long-range transport; Backward trajectory; Clustering; Air pollutants; PM10; PM2.5; Slovenia; Bayesian statistics;
Towards a quantitative understanding of total OH reactivity: A review by Yudong Yang; Min Shao; Xuemei Wang; Anke C. Nölscher; Stephan Kessel; Alex Guenther; Jonathan Williams (147-161).
Over the past fifty years, considerable efforts have been devoted to measuring the concentration and chemical speciation of volatile organic compounds (VOCs) in ambient air and emissions. Recently, it has become possible to directly determine the overall effect of atmospheric trace gases on the oxidant hydroxyl radicals (OH), by measuring OH reactivity (OH loss frequency). Quantifying total OH reactivity is one way to characterize the roles of VOCs in formation of ground-level ozone and secondary organic aerosols (SOA). Approaches for measuring total OH reactivity in both emissions and ambient air have been progressing and have been applied in a wide range of studies. Here we evaluate the main techniques used to measure OH reactivity, including two methods directly measuring OH decay and one comparative reactivity method (CRM), and summarize the existing experimental and modeling studies. Total OH reactivity varies significantly on spatial, diurnal, seasonal and vertical bases. Comparison with individually detected OH sinks often reveals a significant missing reactivity, ranging from 20% to over 80% in some environments. Missing reactivity has also been determined in most source emission studies. These source measurements, as well as numerical models, have indicated that both undetected primary emissions and unmeasured secondary products could contribute to missing reactivity. A quantitative understanding of total OH reactivity of various sources and ambient environments will enhance our understanding of the suite of compounds found in emissions as well as chemical processes, and will also provide an opportunity for the improvement of atmospheric chemical mechanisms.
Keywords: OH reactivity; VOCs; Missing reactivity;
Spatial statistics of atmospheric particulate matter in China by Shenghui Gao; Yangjun Wang; Yongxiang Huang; Quan Zhou; Zhiming Lu; Xiang Shi; Yulu Liu (162-167).
In this paper, the spatial dynamics of the atmospheric particulate matters (resp. PM10 and PM2.5) are studied using turbulence methodologies. It is found experimentally that the spatial correlation function ρ(r) shows a log-law on the mesoscale range, i.e., 50 ≤ r ≤ 500 km, with an experimental scaling exponent β = 0.45. The spatial structure function shows a power-law behavior on the mesoscale range 90 ≤ r ≤ 500 km. The experimental scaling exponent ζ ( q ) is convex, showing that the intermittent correction is relevant in characterizing the spatial dynamic of particulate matter. The measured singularity spectrum f(α) also shows its multifractal nature. Experimentally, the particulate matter is more intermittent than the passive scalar, which could be partially due to the mesoscale movements of the atmosphere, and also due to local sources, such as local industry activities.
Keywords: Particulate matter; Logarithm spatial correlation; Multifractality;
A novel hybrid decomposition-and-ensemble model based on CEEMD and GWO for short-term PM2.5 concentration forecasting by Mingfei Niu; Yufang Wang; Shaolong Sun; Yongwu Li (168-180).
To enhance prediction reliability and accuracy, a hybrid model based on the promising principle of “decomposition and ensemble” and a recently proposed meta-heuristic called grey wolf optimizer (GWO) is introduced for daily PM2.5 concentration forecasting. Compared with existing PM2.5 forecasting methods, this proposed model has improved the prediction accuracy and hit rates of directional prediction. The proposed model involves three main steps, i.e., decomposing the original PM2.5 series into several intrinsic mode functions (IMFs) via complementary ensemble empirical mode decomposition (CEEMD) for simplifying the complex data; individually predicting each IMF with support vector regression (SVR) optimized by GWO; integrating all predicted IMFs for the ensemble result as the final prediction by another SVR optimized by GWO. Seven benchmark models, including single artificial intelligence (AI) models, other decomposition-ensemble models with different decomposition methods and models with the same decomposition-ensemble method but optimized by different algorithms, are considered to verify the superiority of the proposed hybrid model. The empirical study indicates that the proposed hybrid decomposition-ensemble model is remarkably superior to all considered benchmark models for its higher prediction accuracy and hit rates of directional prediction.Display Omitted
Keywords: Complementary ensemble empirical mode decomposition; Grey wolf optimizer; Support vector regression; Hybrid decomposition-ensemble model; PM2.5 concentration forecasting;
Chemical characterization of freshly emitted particulate matter from aircraft exhaust using single particle mass spectrometry by Manuel Abegglen; B.T. Brem; M. Ellenrieder; L. Durdina; T. Rindlisbacher; J. Wang; U. Lohmann; B. Sierau (181-197).
Non-volatile aircraft engine emissions are an important anthropogenic source of soot particles in the upper troposphere and in the vicinity of airports. They influence climate and contribute to global warming. In addition, they impact air quality and thus human health and the environment. The chemical composition of non-volatile particulate matter emission from aircraft engines was investigated using single particle time-of-flight mass spectrometry. The exhaust from three different aircraft engines was sampled and analyzed. The soot particulate matter was sampled directly behind the turbine in a test cell at Zurich Airport. Single particle analyses will focus on metallic compounds. The particles analyzed herein represent a subset of the emissions composed of the largest particles with a mobility diameter >100 nm due to instrumental restrictions. A vast majority of the analyzed particles was shown to contain elemental carbon, and depending on the engine and the applied thrust the elemental carbon to total carbon ratio ranged from 83% to 99%. The detected metallic compounds were all internally mixed with the soot particles. The most abundant metals in the exhaust were Cr, Fe, Mo, Na, Ca and Al; V, Ba, Co, Cu, Ni, Pb, Mg, Mn, Si, Ti and Zr were also detected. We further investigated potential sources of the ATOFMS-detected metallic compounds using Inductively Coupled Plasma Mass Spectrometry. The potential sources considered were kerosene, engine lubrication oil and abrasion from engine wearing components. An unambiguous source apportionment was not possible because most metallic compounds were detected in several of the analyzed sources.
Keywords: Particulate matter; Aircraft emission; Soot; Metal tracers; Single particle mass spectrometry; Chemical characterization; A-PRIDE;
Time variations of gaseous and reactive mercury in the industrial area of Puertollano (south-central Spain). Temporal cycles with marked variations by Alba Martínez-Coronado; Jose Maria Esbrí; Pablo Higueras (198-207).
Puertollano (48,086 inhabitants) is the largest industrial city in the Castilla-La Mancha region (South-Central Spain). The city is located some 250 km South of Madrid; it was an important coal mining site during the last century and today it is the location of one of the most important Spanish oil refineries and the only refinery located away from the coast. Nowadays the area (which mainly includes the Ojailen valley) has a large open pit coal mine (Encasur), two power plants (Eon and Elcogas) and a petrochemical complex (Repsol) located S and SE from the town. These industries give rise to a complex scenario in terms of mercury emissions to the atmosphere: Repsol, Elcogas and Eon act as discrete sources, while coal mine and dumps acts as a general, diffuse source.The mercury contents in Puertollano town and the related industrial area were characterized during 2010 and 2011 by acquiring stationary data of Gaseous Elemental Mercury (GEM), Reactive Gaseous Mercury (RGM), meteorological parameters and other atmospheric contaminants (NO, NO2, SO2, benzene, toluene, xylene, ozone and PM10). In addition, several Total Gaseous Mercury (TGM) mobile surveys were carried out covering the Ojailen valley.Total Gaseous Mercury (TGM) in the whole valley was in the range 0–24 ng m−3 in all surveys, while higher levels were found near to the coal mine and in the vicinity of a coal power plant that employs clean technology (Elcogas).Tekran data showed low GEM levels during 2010–2011 (1.81 ng m−3 on average), while lower GEM levels were measured during autumn and summer, and maximum levels in spring (7.32 ng m−3 on average). RGM measurements were 0.0088 ng m−3, i.e., significantly lower than background levels in the USA and Europe (0.04 ng m−3). Concentrations of these mercury species' were higher during summer (0.0117 ng m−3).Multiple regression analysis was carried out and good relationships between GEM levels, meteorological parameters and other pollutants were identified. The best GEM predictors were temperature, relative humidity and NO2, whereas the best predictors for RGM were GEM, temperature and ozone. RGM variations seem to be explained predominantly by photoxidation processes, with GEM availability and transport processes of secondary importance.Display Omitted
Keywords: Puertollano; Gaseous elemental mercury; Reactive gaseous mercury; Industrial pollutants; Air quality;
Modeling and analysis of PM2.5 generation for key factors identification in China by Dehong Xia; Binfan Jiang; Yulei Xie (208-216).
Recently, the PM2.5 pollution in China has occurred frequently and caused widely concern. In order to identify the key factors for PM2.5 generation, the formation characteristics of PM2.5 would be revealed. A property of electric neutrality of PM2.5 was proposed under the least-energy principle and verified through electricity-charge calculation in this paper. It indicated that PM2.5 is formed by the effect of electromagnetic force, including the effect of ionic bond, hydrogen bond and polarization. According to the analysis of interactive forces among different chemical components, a simulation model is developed for describing the random process of PM2.5 generation. In addition, an orthogonal test with two levels and four factors has been designed and carried out through the proposed model. From the text analysis, PM2.5 would be looser and suspend longer in atmosphere due to Organic Compound (OC) existing (OC can reduce about 67% of PM2.5 density). Considering that N H 4 + is the only cation in the main chemical components of PM2.5, it would be vital for anions (such as S O 4 2 − and N O 3 − ) to aggregate together for facilitating PM2.5 growing. Therefore, in order to relieve PM2.5 pollution, control strategies for OC and N H 4 + would be enhanced by government through improving the quality of oils and solvent products, decreasing the amount of nitrogenous fertilizer utilization, or changing the fertilizing environment from dry condition to wet condition.
Keywords: PM2.5; Formation characteristics; Electrical neutrality; Ionic bond; Hydrogen bond;
An analytical system enabling consistent and long-term measurement of atmospheric dimethyl sulfide by Sehyun Jang; Ki-Tae Park; Kitack Lee; Young-Sang Suh (217-223).
We describe here an analytical system capable of continuous measurement of atmospheric dimethylsulfide (DMS) at pptv levels. The system uses customized devices for detector calibration and for DMS trapping and desorption that are controlled using a data acquisition system (based on Visual Basic 6.0/C 6.0) designed to maximize the efficiency of DMS analysis in a highly sensitive pulsed flame photometric detector housed in a gas chromatograph. The fully integrated system, which can sample approximately 6 L of air during a 1-hr sampling, was used to measure the atmospheric DMS mixing ratio over the Atlantic sector of the Arctic Ocean over 3 full annual growth cycles of phytoplankton in 2010, 2014, and 2015, with minimal routine maintenance and interruptions. During the field campaigns, the measured atmospheric DMS mixing ratio varied over a considerable range, from <1.5 pptv to maximum levels of 298 pptv in 2010, 82 pptv in 2014, and 429 pptv in 2015. The operational period covering the 3 full annual growth cycles of phytoplankton showed that the system is suitable for uninterrupted measurement of atmospheric DMS mixing ratios in extreme environments. Moreover, the findings obtained using the system showed it to be useful in identifying ocean DMS source regions and changes in source strength.
Keywords: Dimethyl sulfide; Climate feedback; Atmospheric monitoring; Arctic Ocean;