Chemical Mass Balance Method Research Articles

Ensemble-trained source apportionment of fine particulate matter and method uncertainty analysis

An ensemble-based approach is applied to better estimate source impacts on fine particulate matter (PM2.5) and quantify uncertainties in various source apportionment (SA) methods. The approach combines source impacts from applications of four individual SA methods: three receptor-based models and one chemical transport model (CTM). Receptor models used are the chemical mass balance methods CMB-LGO (Chemical Mass Balance-Lipschitz global optimizer) and CMB-MM (molecular markers) as well as a factor analytic method, Positive Matrix Factorization (PMF). The CTM used is the Community Multiscale Air Quality (CMAQ) model. New source impact estimates and uncertainties in these estimates are calculated in a two-step process. First, an ensemble average is calculated for each source category using results from applying the four individual SA methods. The root mean square error (RMSE) between each method with respect to the average is calculated for each source category; the RMSE is then taken to be the updated uncertainty for each individual SA method. Second, these new uncertainties are used to re-estimate ensemble source impacts and uncertainties. The approach is applied to data from daily PM2.5 measurements at the Atlanta, GA, Jefferson Street (JST) site in July 2001 and January 2002. The procedure provides updated uncertainties for the individual SA methods that are calculated in a consistent way across methods. Overall, the ensemble has lower relative uncertainties as compared to the individual SA methods. Calculated CMB-LGO uncertainties tend to decrease from initial estimates, while PMF and CMB-MM uncertainties increase. Estimated CMAQ source impact uncertainties are comparable to other SA methods for gasoline vehicles and SOC but are larger than other methods for other sources. In addition to providing improved estimates of source impact uncertainties, the ensemble estimates do not have unrealistic extremes as compared to individual SA methods and avoids zero impact days.

Source Contributions to Atmospheric Gases and Particulate Matter in the Southeastern United States

A new approach for determining the contributions of emission sources to concentrations of particulate matter and gases is developed using the chemical mass balance (CMB) method and the U.S. EPA's National Emission Inventory (NEI). The approach apportions combined gas-phase and condensed-phase concentrations of individual compounds as well as PM(2.5) mass. Because the NEI is used to provide source emission profiles for CMB analysis, the method generates information on the consistency of the NEI with ambient monitoring data. The method also tracks secondary species to primary source emissions, permitting a more complete accounting of the impact of aggregated source types on PM(2.5) mass concentrations. An example application is presented using four years of monitoring data collected at eight sites in the Southeastern Aerosol Research and Characterization (SEARCH) network. Including both primary and secondary species, area sources contributed 2.0-3.7 μg m(-3) (13-26%), point sources contributed 3.0-4.6 μg m(-3) (22-33%), and mobile sources contributed 1.0-6.0 μg m(-3) (9-42%) to mean PM(2.5) mass concentrations. Whereas the NEI generally accounts for the ambient concentrations of gases and particles, certain anomalies are identified, especially related to carbonaceous compounds and dust.

Study of particles dispersion method joined with Chemical Mass Balance method

Study of particles dispersion method joined with Chemical Mass Balance method

Size-resolved source apportionment of carbonaceous particulate matter in urban and rural sites in central California

Abstract Very little is currently known about the relationship between exposure to different sources of ambient ultrafine particles (PM0.1) and human health effects. If human health effects are enhanced by PM0.1’s ability to cross cell membranes, then more information is needed describing the sources of ultrafine particles that are deposited in the human respiratory system. The current study presents results for the source apportionment of airborne particulate matter in six size fractions smaller than 1.8 μm particle diameter including ultrafine particles (PM0.1) in one of the most polluted air basins in the United States. Size-resolved source apportionment results are presented at an urban site and rural site in central California’s heavily polluted San Joaquin Valley during the winter and summer months using a molecular marker chemical mass balance (MM–CMB) method. Respiratory deposition calculations for the size-resolved source apportionment results are carried out with the Multiple Path Particle Dosimetry Model ( MPPD v 2.0), including calculations for ultrafine (PM0.1) source deposition. Diesel engines accounted for the majority of PM0.1 and PM1.8 EC at both the urban and rural sampling locations during both summer and winter seasons. Meat cooking accounted for 33–67% and diesel engines accounted for 15–21% of the PM0.1 OC at Fresno. Meat cooking accounted for 22–26% of the PM0.1 OC at the rural Westside location, while diesel engines accounted for 8–9%. Wood burning contributions to PM0.1 OC increased to as much as 12% of PM0.1 OC during the wintertime. The modest contribution of wood smoke reflects the success of emissions control programs over the past decade. In contrast to PM0.1, PM1.8 OC had a higher fraction of unidentified source contributions (68–85%) suggesting that this material is composed of secondary organic aerosol (SOA) or primary organic aerosol (POA) that has been processed by atmospheric chemical reactions. Meat cooking was the largest identified source of PM1.8 organic carbon (OC) at the Fresno site (12–13%) while diesel engines were the largest identified PM1.8 OC source at the rural site (5–8%). Wood burning contributions to PM1.8 OC increased during the wintertime at both sites (6–9%) but were relatively small during the summertime (∼1%). As expected, diesel engines were the dominant source of PM0.1 EC respiratory deposition at both the urban and rural site in both summer and winter (0.01–0.03 μg PM0.1 EC deposited per m3 air inhaled). Meat cooking accounted for 0.01–0.025 μg PM0.1 OC deposited per m3 air inhaled while diesel fuel accounted for 0.005–0.013 μg PM0.1 OC deposited per m3 air inhaled. Minor contributions from wood burning, motor oil, and gasoline fuel were calculated at levels

Source apportionment of ambient PM10 in urban areas of Wuxi, China

A total of 168 PM10 samples were collected during the year of 2005 at eight sites in the city of Wuxi in China. Fifteen chemical elements, three water-soluble ions, total carbon and organic carbon were analyzed. Six source categories were identified and their contributions to ambient PM10 in Wuxi were estimated using a nested chemical mass balance method that reduces the effects of colinearity on the chemical mass balance model. In addition, the concentrations of secondary aerosols, such as secondary organic carbon, sulfate and nitrate, were quantified. The spatially averaged PM10 was high in the spring and winter (123 μg·m−3 and low in the summer-fall (90 μg·m−3). According to the result of source apportionment, resuspended dust was the largest contributor to ambient PM10, accounting for more than 50% of the PM10 mass. Coal combustion (14.6%) and vehicle exhaust (9.4%) were also significant source categories of ambient PM10. Construction and cement dust, sulfates, secondary organic carbon, and nitrates made contributions ranging between 4.1% and 4.9%. Other source categories such as steel manufacturing dust and soil dust made low contributions to ambient PM10.

Real-Time Methods for Estimating Organic Component Mass Concentrations from Aerosol Mass Spectrometer Data

We use results from positive matrix factorization (PMF) analysis of 15 urban aerosol mass spectrometer (AMS) data sets to derive simple methods for estimating major organic aerosol (OA) component concentrations in real time. PMF analysis extracts mass spectral (MS) profiles and mass concentrations for key OA components such as hydrocarbon-like OA (HOA), oxygenated OA (OOA), low-volatility OOA (LV-OOA), semivolatile OOA (SV-OOA), and biomass burning OA (BBOA). The variability in the component MS across all sites is characterized and used to derive standard profiles for real-time estimation of component concentrations. Two methods for obtaining first-order estimates of the HOA and OOA mass concentrations are evaluated. The first approach is the tracer m/z method, in which the HOA and OOA concentrations are estimated from m/z 57 and m/z 44 as follows: HOA ∼ 13.4 × (C(57) - 0.1 × C(44)) and OOA ∼ 6.6 × C(44), where C(i) is the equivalent mass concentration of tracer ion m/z i. The second approach uses a chemical mass balance (CMB) method in which standard HOA and OOA profiles are used as a priori information for calculating their mass concentrations. The HOA and OOA mass concentrations obtained from the first-order estimates are evaluated by comparing with the corresponding PMF results for each site. Both methods reproduce the HOA and OOA concentrations to within ∼30% of the results from detailed PMF analysis at most sites, with the CMB method being slightly better. For hybrid CMB methods, we find that fixing the LV-OOA spectrum and not constraining the other spectra produces the best results.

Contribution of Primary and Secondary Sources to Organic Aerosol and PM2.5 at SEARCH Network Sites

Chemical tracer methods for determining contributions to primary organic aerosol (POA) are fairly well established, whereas similar techniques for secondary organic aerosol (SOA), inherently complicated by time-dependent atmospheric processes, are only beginning to be studied. Laboratory chamber experiments provide insights into the precursors of SOA, but field data must be used to test the approaches. This study investigates primary and secondary sources of organic carbon (OC) and determines their mass contribution to particulate matter 2.5 µm or less in aerodynamic diameter (PM2.5) in Southeastern Aerosol Research and Characterization (SEARCH) network samples. Filter samples were taken during 20 24-hr periods between May and August 2005 at SEARCH sites in Atlanta, GA (JST); Birmingham, AL (BHM); Centerville, AL (CTR); and Pensacola, FL (PNS) and analyzed for organic tracers by gas chromatography-mass spectrometry. Contribution to primary OC was made using a chemical mass balance method and to secondary OC using a mass fraction method. Aerosol masses were reconstructed from the contributions of POA, SOA, elemental carbon, inorganic ions (sulfate [SO4 2−], nitrate [NO3 −], ammonium [NH4 +]), metals, and metal oxides and compared with the measured PM2.5. From the analysis, OC contributions from seven primary sources and four secondary sources were determined. The major primary sources of carbon were from wood combustion, diesel and gasoline exhaust, and meat cooking; major secondary sources were from isoprene and monoterpenes with minor contributions from toluene and β-caryophyllene SOA. Mass concentrations at the four sites were determined using source-specific organic mass (OM)-to-OC ratios and gave values in the range of 12–42 µg m−3. Reconstructed masses at three of the sites (JST, CTR, PNS) ranged from 87 to 91% of the measured PM2.5 mass. The reconstructed mass at the BHM site exceeded the measured mass by approximately 25%. The difference between the reconstructed and measured PM2.5 mass for nonindustrial areas is consistent with not including aerosol liquid water or other sources of organic aerosol.

Quantification of self pollution from two diesel school buses using three independent methods

We monitored two Seattle school buses to quantify the buses’ self pollution using the dual tracers (DT), lead vehicle (LV), and chemical mass balance (CMB) methods. Each bus drove along a residential route simulating stops, with windows closed or open. Particulate matter (PM) and its constituents were monitored in the bus and from a LV. We collected source samples from the tailpipe and crankcase emissions using an on-board dilution tunnel. Concentrations of PM 1, ultrafine particle counts, elemental and organic carbon (EC/OC) were higher on the bus than the LV. The DT method estimated that the tailpipe and the crankcase emissions contributed 1.1 and 6.8 μg m −3 of PM 2.5 inside the bus, respectively, with significantly higher crankcase self pollution (SP) when windows were closed. Approximately two-thirds of in-cabin PM 2.5 originated from background sources. Using the LV approach, SP estimates from the EC and the active personal DataRAM (pDR) measurements correlated well with the DT estimates for tailpipe and crankcase emissions, respectively, although both measurements need further calibration for accurate quantification. CMB results overestimated SP from the DT method but confirmed crankcase emissions as the major SP source. We confirmed buses’ SP using three independent methods and quantified crankcase emissions as the dominant contributor.

PCBs and PCDD/DFs in waste oil illegally dumped and neglected for more than 20 years

Quantification of polychlorinated biphenyls (PCBs), polychlorinated-dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in waste oil by high resolution gas chromatography-high resolution mass spectrometry (HRGC-HRMS), and profiling of their congeners and homologues were described. Waste oil packed in drums which were estimated to have been exposed to the weather for more than 20 years were found by the illegal dumping patrol in 2006. PCBs were detected in all of 12 waste oil samples examined, with concentrations in the range of 0.0032–22 μ g/g. The main pollution sources of the waste oil samples were presumed to be KC300, KC400 and/or KC500 by principal component analysis (PCA) and a chemical mass balance (CMB) method. The concentrations of PCDDs and PCDFs (PCDD/DFs) in the illegally dumped waste oil ranged from 1.1 to 360 pg/g and 1.3 to 110 pg/g, respectively. The ratios of toxicity equivalency quantity (TEQ) of PCDDs and PCDFs to Co-PCBs were lower than those of Yusho rice oil. Consequently, it was determined that even after 20 years of exposure to the weather, no PCB denaturation occurred. However, it was confirmed that low-chlorinated biphenyls in corroded drums would have evaporated into the atmosphere.

Estimation of Source Contribution for PM10 by Chemical Mass Balance(CMB) in Busan

PM10 samples were collected from July 2007 to Oct. 2007 at Gwaebopdong(inland area) and Dongsamdong(coastal area), in Busan. This paper investigates the contribution of emission sources to PM10 mass in Busan. Source apportionment results derived from the chemical mass balance(CMB) method. A source profiles applied in this study is organized to minimize the collinearity among sources type via statistical method. Source profiles applied in this study utilized a measured value of fine particle directly sampled from metropolitan area such as Seoul and Incheon, After a CMB modeling, sulfate and nitrate related sources among those contributing to PM10 in Busan showed high contribution by 36.53% in Gwaebopdong and 42.02% in Dongsamdong.

Fine Particle Sources and Cardiorespiratory Morbidity: An Application of Chemical Mass Balance and Factor Analytical Source-Apportionment Methods

BackgroundInterest in the health effects of particulate matter (PM) has focused on identifying sources of PM, including biomass burning, power plants, and gasoline and diesel emissions that may be associated with adverse health risks. Few epidemiologic studies, however, have included source-apportionment estimates in their examinations of PM health effects. We analyzed a time-series of chemically speciated PM measurements in Atlanta, Georgia, and conducted an epidemiologic analysis using data from three distinct source-apportionment methods.ObjectiveThe key objective of this analysis was to compare epidemiologic findings generated using both factor analysis and mass balance source-apportionment methods.MethodsWe analyzed data collected between November 1998 and December 2002 using positive-matrix factorization (PMF), modified chemical mass balance (CMB-LGO), and a tracer approach. Emergency department (ED) visits for a combined cardiovascular (CVD) and respiratory disease (RD) group were assessed as end points. We estimated the risk ratio (RR) associated with same day PM concentrations using Poisson generalized linear models.ResultsThere were significant, positive associations between same-day PM2.5 (PM with aero-dynamic diameter ≤ 2.5 μm) concentrations attributed to mobile sources (RR range, 1.018–1.025) and biomass combustion, primarily prescribed forest burning and residential wood combustion, (RR range, 1.024–1.033) source categories and CVD-related ED visits. Associations between the source categories and RD visits were not significant for all models except sulfate-rich secondary PM2.5 (RR range, 1.012–1.020). Generally, the epidemiologic results were robust to the selection of source-apportionment method, with strong agreement between the RR estimates from the PMF and CMB-LGO models, as well as with results from models using single-species tracers as surrogates of the source-apportioned PM2.5 values.ConclusionsDespite differences among the source-apportionment methods, these findings suggest that modeled source-apportioned data can produce robust estimates of acute health risk. In Atlanta, there were consistent associations across methods between PM2.5 from mobile sources and biomass burning with both cardiovascular and respiratory ED visits, and between sulfate-rich secondary PM2.5 with respiratory visits.

Concentration and Characteristics of Polychlorinated Biphenyls in the Sediments of Sea and River in Nagasaki Prefecture, Japan

Environmental pollution with polychlorinated biphenyls (PCBs) continues in Japan due to their high persistency, although their manufacture and use have already been prohibited. In this study, PCBs in sediments at 67 sites in Nagasaki Prefecture were determined by GC-MS, and their profiles were compared with those of commercial PCBs (Kanechlor KC300-600). The concentrations of PCBs in the sediments of sea and river areas in Nagasaki Prefecture were found to be up to 2.5 and 0.035 μg/g, respectively. Higher concentrations of PCBs in the sediments of the sea compared to those from river were observed (except area D vs N). The profile of PCB homologues in the sediments of the sea areas was similar to that of Kanechlor KC600, whereas the profile of PCB homologues in the river sediments was similar to that of Kanechlor KC500. Moreover, the source contribution was estimated by a chemical mass balance (CMB) method using the composition ratio of major congeners of Kanechlor. As a result, it was found that the contributions of KC600 and KC500 were higher in sea sediments (ca. 60%) than in river sediments (ca 50%).

Nationwide study of dioxins in the freshwater fish Carassius auratus ( gibelio) langsdorfii (crucian carp) in Japan: Concentrations and estimation of source contribution ratios

We investigated dioxin concentrations in freshwater fish in Japan by standardizing species to detect subtle decreasing trends of dioxin concentrations in the future with the reinforcement of regulations. The fish studied were crucian carp ( Carassius auratus ( gibelio) langsdorfii), an omnivorous species. Fish and sediments were collected from 14 rivers and lakes located in remote areas, agricultural areas, and small and large cities throughout Japan. The total toxic equivalent (TEQ) dioxin concentrations at the three remote sites were about 20% of the concentrations at the other 11 sites, which all had similar concentrations. The average concentrations in fish collected from these 11 sites were 0.69 pg TEQ g −1 wet wt. (95% CI 0.52–0.85) or 57.3 pg TEQ g −1 fat (95% CI 47.9–66.7). There were notable differences in congener profiles of polychlorinated p-dibenzodioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) between sampling areas. A chemical mass balance method was used to estimate the proportions of dioxin contributions from different sources. The sampling areas were classified into four groups on the basis of the predominant source of dioxin contamination: a combustion group, a chlornitrofen herbicide group, a chlornitrofen and pentachlorphenol herbicide group, and a remote group. The congener profiles of dioxin like polychlorinated biphenyls (DL-PCBs) were almost the same in all areas and close to those in Kanechlor, which indicates that pollution from PCB products has spread throughout Japan. From samples collected during the spawning season, it was determined that about 20% of the dioxins in adult females were transferred to the eggs, resulting in higher dioxin concentrations in adult males than in females. Biota–sediment accumulation factors (BSAFs) of 2,3,7,8-substituted PCDDs/DFs for crucian carp were larger than those of non-2,3,7,8-substituted congeners, and BASFs decreased with increasing number of chlorines. The BSAFs of DL-PCBs were 10 times greater than those of PCDDs/DFs, and BSAFs of mono- ortho type DL-PCBs were higher than those of non- ortho types.

Estimation of the emission factors of PAHs by traffic with the model of atmospheric dispersion and deposition from heavy traffic road

In order to consider the total atmospheric loadings of the PAHs (polycyclic aromatic hydrocarbons) from traffic activities, the emission factors of PAHs were estimated and from the obtained emission factors and vehicle transportation statistics, total atmospheric loadings were integrated and the loadings into the water body were estimated on a regional scale. The atmospheric concentration of PAHs was measured at the roadside of a road with heavy traffic in the Hiroshima area in Japan. The samplings were conducted in summer and winter. Atmospheric particulate matters (fine particle, 0.6-7 microm; coarse particle, over 7 microm) and their PAH concentration were measured. Also, four major emission sources (gasoline and diesel vehicle emissions, tire and asphalt debris) were assumed for vehicle transportation activities, the chemical mass balance method was applied and the source partitioning at the roadside was estimated. Furthermore, the dispersion of atmospheric particles from the vehicles was modelled and the emission factors of the sources were determined by the comparison to the chemical mass balance results. Based on emission factors derived from the modelling, an atmospheric dispersion model of nationwide scale (National Institute of Advanced Industrial Science and Technology - Atmospheric Dispersion Model for Exposure and Risk assessment) was applied, and the atmospheric concentration and loading to the ground were calculated for the Hiroshima Bay watershed area.

Pinnacles and Pitfalls for Source Apportionment of Potential Health Effects From Airborne Particle Exposure

Since its origins in the 1970s, source apportionment using receptor modeling has improved to a point where both the chemical mass balance and various methods of factor analysis have been applied to many urban and regional data sets to infer major sources or source classes influencing airborne particle concentrations. Recently the factors from the latter analyses have been combined with regression techniques using human health endpoints to infer source influence on health effects. This approach is attractive for air quality management when the composition of particles is known, since it provides, in principle, a means of quantifying major source influence on health consequences. The factor-based analyses have been used for both epidemiological and toxicological studies with some success. While the method is useful in many ways, it also has important limitations that include failing to identify specific sources, misidentification from comingled source factors, and inconsistency or unreasonableness of results from the same locations using different factor techniques. Examples of ambiguities evolving from these limitations are cited in this article. Ambiguity found in the literature is fostered by loosely worded terminology that does not distinguish statistically based factors from actual sources, and from health impacts inferred by single centrally located air monitors, which are assumed to represent actual exposure or dosage to airborne particles.

Estimating Outdoor and Indoor Contributions of Particulate Matter to Personal Exposure Using a Chemical Mass Balance Method

P-324 Introduction: The Centers for Disease Control/National Center for Health Statistics (CDC/NCHS) collects and analyzes data describing the health of the U.S. population, such as the National Health Interview Survey (NHIS), a household interview survey of ∼100,000 respondents each year, and Natality data for ∼4 million births each year. The Environmental Protection Agency (EPA) maintains several databases that monitor environmental factors. Geographically linking CDC/NCHS health information and EPA environmental data could enhance our understanding of the effects of environment on health; such linkages, however, have been limited. Furthermore, as air pollution monitors are not located in all U.S. counties, comprehensive exposure data are unavailable, particularly for simultaneous exposure to multiple pollutants. This study describes and evaluates potential linkages between two CDC/NCHS datasets and EPA air pollution data. Methods: After linking 2001–2003 NHIS and 2002 Natality files to corresponding annual county-level averages of exposures for 6 pollutants (fine [PM25] and coarse [PM10] particles, O3, SO2, NO2, CO), the authors compare demographic and health characteristics for people living in areas with extensive air pollution data to those with limited pollution data to determine the impact of this differential linkage on observed associations between air pollution and health outcomes. For each dataset, 2 linked subsets based on exposure availability were defined: (a) linked to PM25 or (b) linked to all pollutants. Results: About 70% of records were linked to county-level PM25 data; about one-third were linked to all pollutants. Linkage differed by most available demographic factors (e.g., race, ethnicity, poverty, region/state) and health indicators (poor health status, smoking, overweight), but not all (e.g. low birthweight). The unadjusted odds ratios and 95% confidence intervals for poor health status (NHIS) and a 10 ug/m3 change in PM25 exposure were similar for the 2 linked subsets ([a] 1.26, 1.23–1.30; [b] 1.24, 1.19–1.29). After adjustment for race and poverty status, the associations weakened but remained both elevated and similar. In contrast, there was no overall effect of PM25 on mean birthweight (Natality) among term infants, but the adjusted effect varied both by linkage and state: e.g. New York (a) −111.3 g (-166g,-56g), (b) −50g, (-76g,-25g); California (a)-29g (-43g,-15g), (b)-28g (-41g,-15g); and Texas (a) 120g (69g,170g), (b) −317g (-367g,-267g). Discussion/Conclusions: Linked CDC/NCHS - EPA files have limited geographical coverage of exposure to pollutants. Preliminary analyses of NHIS suggest that linked files may provide consistent inference. The Natality results, however, suggest that inferences could vary by geographic area or outcome.

Validation of an efficient non-negative matrix factorization method and its preliminary application in Central California

Positive matrix factorization (PMF) techniques have been applied in many environmental studies. The commercial version of the PMF method has a relatively moderate practical limit for the size of the input data matrix, since the computer memory and time needed for the commercial method increases quadratically with the number of elements of solution matrices. To extend the applications of the PMF techniques to large datasets, we exercised alternative methods that demand less computer memory and time. One such method, called non-negative matrix factorization (NMF) here, is extremely memory efficient, compared with the commercial PMF method. Both NMF and PMF methods are sensitive to the initialization of solution matrices, and the use of random numbers in the initialization usually starts with a large prediction error, and requires a number of model runs with different random seeds. A novel, chemical mass balance method (ROC) is introduced here to provide a reasonable initialization for the NMF method for large data sets. Both NMF and ROC methods were validated with an ideal Cross example and the benchmark example of the commercial PMF method. The NMF-ROC method was further evaluated, in terms of computer time and the prediction error, in the preliminary application to a data set that contains particle-phase polar organic compounds analyzed for a number of samples collected in Central California during the California Regional PM 10/PM 2.5 air quality study (CRPAQS, 1999–2001). The NMF-ROC method was demonstrated to perform better than the NMF, PMF and PMF-ROC methods in the CRPAQS data set. This performance enhancement is expected to be magnified for larger data sets.

Estimation of Enhancing Improvement for Ambient Air-Quality during Street Flushing and Sweeping

This investigation addressed the source apportionment of aerosol particles using both the receptor and dispersion models. Factor analysis and chemical mass balance (CMB) models were two receptor modeling techniques employed to categorize the possible sources in Kaohsiung district. The ISCST3 dispersion model was also used to evaluate improvements in ambient-air quality. Factor analysis revealed that road sweeping resulted in a variation of approximately 10% in the compositions of TSP and PM10. The mass fractions of TSP explained by the CMB model were 60-70% before flushing, 35-37% after flushing, 71-83% before sweeping, and 80-120% after sweeping. The CMB method identified six possible sources of TSP as: combustion sources (53.2 ± 11.1%), street dust (12.4 ± 9.3%), nitrate (4.9 ± 1.2%), sulfate (2.9 ± 0.8%), sea salt (1.0 ± 0.3%), and gasoline cars (0.4 ± 0.6%). The simulation results of ISCST3 model showed that road flushing improved annual PM10 from 1.5-2.1% at the 11 monitoring stations operated around Kaohsiung City. After road flushing, the ratios and concentrations of TSP for street dust and combustion sources were reduced. For TSP, road sweeping increased the concentrations of street dust within 30 m downwind of the sampling sites (both sites located downwind at 5 and 30 meters); but reduced it at 200 m downwind. Factor analysis showed rates of street dust for TSP were lower than 28% before street sweeping; lower than 17% after street sweeping. The CMB model revealed that contributed rates of street dust for TSP were lower than 22% before street sweeping, and lower than 34% after street sweeping. The ISCST3 model showed air quality improvements for PM10 in urban areas were greater than in industrial areas. Moreover, the maximum improvement in the annual mean PM10 was around 2 μg/m3.

Chemical mass balance when an unknown source exists

AbstractA chemical mass balance method is proposed for the case where the existence of an unknown source is suspected. In general, when the existence of an unknown source is assumed in statistical receptor modeling, unknown quantities such as the composition of an unknown source and the contributions of assumed sources become unidentifiable. To estimate these unknown quantities avoiding the identification problem, a Bayes model for chemical mass balance is constructed in the form of composition without using prior knowledge on the unknown quantities except for natural constraints. The covariance of ambient observations given in the form of composition is defined in several ways. Markov chain Monte Carlo is used for evaluating the posterior means and variances of the unknown quantities as well as the likelihood for the proposed model. The likelihood is used for selecting the best fit covariance model. A simulation study is carried out to check the performance of the proposed method. Copyright © 2004 John Wiley & Sons, Ltd.

Aerosol pollution in some Chinese cities (IUPAC Technical Report)

Abstract Emissions caused by the use of coal and by traffic have caused serious photochemical smog and aerosol pollution with unique characteristics in most Chinese cities. This report gives an overview of aerosol concentrations in China based on data obtained from both the literature and recent research by the authors. The results show that TSP (total suspended particulate) and PM-10 (particles with aerodynamic diameter 10 µm) concentrations frequently exceed the National Ambient Air Quality Standard and that ambient aerosol concentrations constitute a serious air pollution problem. PM-2.5 concentrations are also high and account for 60 % of the PM-10 mass. Organic carbon and sulfate are the most abundant components of PM-2.5, while crustal elements represent a minor portion.Nitrate concentrations are almost the same as sulfate in summertime, which implies that NOx control is very important in lowering fine particle concentrations and in improving air visibility. The chemical mass balance (CMB) method was applied in Beijing to identify the sources of PM-2.5. The main sources include fugitive dust, coal burning/industrial processes, traffic emissions, and secondary aerosol produced by atmospheric chemical conversion.