Real-world emission factors for different vehicle types and their contributions to roadside air p... more Real-world emission factors for different vehicle types and their contributions to roadside air pollution are needed for air-quality management. Tunnel measurements have been used to estimate emission factors for several vehicle types using linear regression or receptor-based source apportionment. However, the accuracy and uncertainties of these methods have not been sufficiently discussed. This study applies four methods to derive emission factors for different vehicle types from tunnel measurements in Hong Kong, China: (1) simple linear regressions (SLR); (2) multiple linear regressions (MLR); (3) positive matrix factorization (PMF); and (4) EMission FACtors for Hong Kong (EMFAC-HK). Separable vehicle types include those fueled by liquefied petroleum gas (LPG), gasoline, and diesel. PMF was the most useful, as it simultaneously seeks source profiles and source contributions. Diesel-, gasoline-, and LPG-fueled vehicle emissions accounted for 52%, 10%, and 5% of PM2.5 mass, respecti...
Personal monitoring for fine particulate matter (PM) was conducted for adults (48 subjects, 18-63... more Personal monitoring for fine particulate matter (PM) was conducted for adults (48 subjects, 18-63years of age) in Hong Kong during the summer and winter of 2014-2015. All filters were analyzed for PM mass and constituents (including carbonaceous aerosols, water-soluble ions, and elements). We found that season (p=0.02) and occupation (p<0.001) were significant factors affecting the strength of the personal-ambient PM associations. We applied mixed-effects models to investigate the determinants of personal exposure to PM mass and constituents, along with within- and between-individual variance components. Ambient PM was the dominant predictor of (R=0.12-0.59, p<0.01) and the largest contributor (>37.3%) to personal exposures for PM mass and most components. For all subjects, a one-unit (2.72μg/m) increase in ambient PM was associated with a 0.75μg/m (95% CI: 0.59-0.94μg/m) increase in personal PM exposure. The adjusted mixed-effects models included information extracted from...
Journal of the Air & Waste Management Association (1995), Jan 9, 2015
Geological samples were collected from 27 representative locations in the Athabasca Oil Sands Reg... more Geological samples were collected from 27 representative locations in the Athabasca Oil Sands Region (AOSR) in Alberta, Canada. These samples were resuspended onto filter substrates for PM2.5 and PM10 size fractions. Samples were analyzed for 229 chemical species, consisting of elements, ions, carbon, and organic compounds. These chemical species are normalized to gravimetric mass to derive individual source profiles. Individual profiles were grouped into six categories typical of those used in emission inventories: paved road dust, unpaved road dust close to and distant from oil sand operations, overburden soil, tailings sands, and forest soils. Consistent with their geological origin, the major components are minerals, organic and elemental carbon, and ions. The sum of five major elements (i.e., Al, Si, K, Ca, and Fe) and their oxidized forms account for 25‒40% and 45‒82% of PM mass, respectively. Si is the most abundant element, averaging 17-18% in the Facility (oil sand operatio...
Source profiles (fractional mass abundances and uncertainties) for use in chemical mass balance (... more Source profiles (fractional mass abundances and uncertainties) for use in chemical mass balance (CMB) source apportionment are reported for soil dust from unpaved roads and desert lands. The objectives were to add to the library of source composition profiles available for CMB studies, and to provide data on the variation in wind-blown dust composition between particle sizes and geographical locations. Samples were resuspended and sampled through PM 1 , PM 2.5 and PM 10 inlets onto filters, then chemically analyzed for 40 elements, seven ions and eight carbon fractions. Air quality management would benefit from technology that can distinguish soil dust from sites in different geographical locations and sites with different land uses. Five geographical clusters representing Ft Bliss, TX, Dona Ana County, NM, Ft Irwin, CA, the west desert and the Canyonlands, UT, were examined. Distinctive differences were found between sites within a cluster and these differences were comparable to the differences between cluster averages. Some sites showed small differences in chemical composition between particle sizes, but these differences were less than the differences observed between nearby geographical locations. Dust emissions from sites with uniform geology have distinctive source profiles that may be useful for CMB receptor modeling. Heterogeneous regions, defined by land management boundaries, will require extensive field sampling to develop representative composite source profiles.
Journal of the Air & Waste Management Association, 2007
The US. Department of Energy Gasoline/Diesel PM Split Study was conducted to assess the sources o... more The US. Department of Energy Gasoline/Diesel PM Split Study was conducted to assess the sources of uncertainties in using an organic compound-based chemical mass balance receptor model to quantify the relative contributions of emissions from gasoline (or spark ignition [SI]) and diesel (or compression ignition [CI]) engines to ambient concentrations of fine particulate matter (PM 2.5) in California's South Coast Air Basin (SOCAB). In this study, several groups worked cooperatively on source and ambient sample collection and quality assurance aspects of the study but worked independently to perform chemical analysis and source apportionment. Ambient sampling included daily 24-hr PM 2.5 samples at two air qualitymonitoring stations, several regional urban locations, and along freeway routes and surface streets with varying proportions of automobile and truck traffic. Diesel exhaust was the dominant source of total carbon (TC) and elemental carbon (EC) at the Azusa and downtown Los Angeles, CA, monitoring sites, but samples from the central part of the air basin showed nearly equal apportionments of CI and SI. CI apportionments to TC were mainly dependent on EC, which was sensitive to the analytical method used. Weekday contributions of CI exhaust were higher for Interagency Monitoring of Protected Visual Environments (IMPROVE; 41 Ï® 3.7%) than Speciation Trends Network (32 Ï® 2.4%). EC had little effect on SI apportionment. SI apportionments were most sensitive to higher molecular weight polycyclic aromatic hydrocarbons (indeno[123-cd]pyrene, benzo(ghi)perylene, and coronene) and several steranes and hopanes, which were associated mainly with high emitters. Apportionments were also sensitive to choice of source profiles. CI contributions varied from 30% to 60% of TC when using individual source profiles rather than the composites used in the final apportionments. The apportionment of SI vehicles varied from 1% to 12% of TC depending on the specific profile that was used. Up to 70% of organic carbon (OC) in the ambient samples collected at the two fixed monitoring sites could not be apportioned to directly emitted PM emissions. IMPLICATIONS The apportionments of CI and SI exhaust were most sensitive to the specific CI and SI source profiles that are used and the analytical method for EC. The IMPROVE carbon fractions (four OC and three EC fractions) could not be used for apportionment because of rapid changes in the atmosphere that altered the distributions among the carbon fractions. The apportionment of CI was mainly dependent on EC and could not be obtained by organic markers alone. However, CI vehicles were the dominant source of EC, and EC was a reasonable surrogate of PM emissions from CI vehicles in the SOCAB. Semivolatile organic compounds, which are major components of ultrafine particles and are precursors of secondary organic aerosols, were emitted in far greater quantities than particulate organic compounds by both SI and CI vehicles.
Journal of the Air & Waste Management Association, 2007
The U.S. Department of Energy Gasoline/Diesel PM Split Study examined the sources of uncertaintie... more The U.S. Department of Energy Gasoline/Diesel PM Split Study examined the sources of uncertainties in using an organic compound-based chemical mass balance receptor model to quantify the contributions of spark-ignition (SI) and compression-ignition (CI) engine exhaust to ambient fine particulate matter (PM 2.5). This paper presents the chemical composition profiles of SI and CI engine exhaust from the vehicle-testing portion of the study. Chemical analysis of source samples consisted of gravimetric mass, elements, ions, organic carbon (OC), and elemental carbon (EC) by the Interagency Monitoring of Protected Visual Environments (IMPROVE) and Speciation Trends Network (STN) thermal/optical methods, polycyclic aromatic hydrocarbons (PAHs), hopanes, steranes, alkanes, and polar organic compounds. More than half of the mass IMPLICATIONS We examined several factors that contribute to variations in chemical composition of PM 2.5 emissions from in-use diesel and gasoline vehicles in California's South Coast Air Basin. These factors included model year, mileage accumulation, vehicle test cycles, composition of lubrication oils, and variations in sampling and analytical methods. Distinctive differences were found in the abundances of specific chemical species in diesel and gasoline exhaust, but the variations among individual exhaust profiles were large. These variations should be considered when applying specific profiles in receptor modeling or emission inventory development and in estimating the uncertainties associated with the results.
Journal of the Air & Waste Management Association, 2006
This study tested the feasibility of using pyrolysis (Py)-gas chromatography (GC)/mass spectromet... more This study tested the feasibility of using pyrolysis (Py)-gas chromatography (GC)/mass spectrometry (MS) to obtain organic chemical species data suitable for source apportionment modeling of soil-derived coarse particulate matter (PM 10) dust on ambient filters. A laboratory resuspension apparatus was used with known soils to generate simulated receptor filter samples loaded with ϳ0.4 mg of PM 10 dust, which is within the range of mass loading on ambient filters. Py-GC/MS at 740°C generated five times more resolvable compounds than were obtained with thermal desorption GC/MS at 315°C. The identified compounds were consistent with literature from Py experiments using larger samples of bulk soils. A subset of 91 organic species out of the 178 identified Py products was used as input to CMB8 software in a demonstration of source apportionment using laboratory-generated mixtures simulating ambient filter samples. The 178 quantified organic species obtained by Py of soil samples is an improvement compared with the 38 organic species obtained by thermal desorption of soils and the four functionally defined organic fractions reported by thermal/ optical reflectance. Significant differences in the concentration of specific species were seen between samples from different sites, both geographically distant and close, using analysis of variance and cluster analysis. This feasibility study showed that Py-GC/MS can generate useful source profile data for receptor modeling and justifies continued method development.
Journal of the Air & Waste Management Association, 2001
This paper presents and discusses the results obtained from the gravimetric and chemical analyses... more This paper presents and discusses the results obtained from the gravimetric and chemical analyses of the 24-hr average dichotomous samples collected from five sites in the El Paso-Cd. Juarez air quality basin between August 1999 and March 2000. Gravimetric analysis was performed to determine the temporal and spatial variations of PM 2.5 (particulate matter less than 2.5 µm in diameter) and PM 2.5-10 (particulate matter less than 10 µm but greater than 2.5 µm in diameter) mass concentrations. The results indicate that ~25% of the PM 10 (i.e., PM 2.5 + PM 2.5-10) concentration is composed of PM 2.5. Concurrent measurements of hourly PM concentrations and wind speed showed strong diurnal patterns of the regional PM pollution. Results of X-ray fluorescence (XRF) elemental analyses were compared to similar but limited studies performed by the Texas Natural Resource Conservation Commission (TNRCC) in 1990 and 1997. Major elements from geologic sources-Al, Si, Ca, Na, K, Fe, and Ti-accounted for 35% of the total mass concentrations in the PM 2.5-10 fraction, indicating that geologic sources in the area are the dominant PM sources. Levels of toxic trace elements, mainly considered as products of anthropogenic activities, have decreased significantly from those observed in 1990 and 1997.
Journal of the Air & Waste Management Association, 2012
This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Journal of the Air & Waste Management Association, 2007
In celebration of the 100th anniversary of the Air & Waste Management Association, this review ex... more In celebration of the 100th anniversary of the Air & Waste Management Association, this review examines the history of air quality management (AQM) in the United States over the last century, with an emphasis on the ambient standards programs established by the landmark 1970 Clean Air Act (CAA) Amendments. The current CAA system is a hybrid of several distinct air pollution control philosophies, including the recursive or circular system driven by ambient standards. Although this evolving system has resulted in tremendous improvements in air quality, it has been far from perfect in terms of timeliness and effectiveness. The paper looks at several periods in the history of the U.S. program, including: (1) 1900-1970, spanning the early smoke abatement and smog control programs, the first federal involvement, and the development of a hybrid AQM approach in the 1970 CAA; (2) 1971-1976, when the first National Ambient Air Quality Standards (NAAQS) were set and implemented; (3) 1977-1993, a period of the first revisions to the standards, new CAA Amendments, delays in implementation and decision-making, and key science/policy/legislative developments that would alter both the focus and scale of air pollution programs and how they are implemented; and (4) 1993-2006, the second and third wave of NAAQS revisions and their implementation in the context of the 1990 CAA. This discussion examines where NAAQS have helped drive implementation programs and how improvements in both effects and air quality/control sciences influenced policy and legislation to enhance the effectiveness of the system over time. The review concludes with a look toward the future of AQM, emphasizing challenges and ways to meet them. The most significant of these is the need to make more efficient progress toward air quality goals, while adjusting the system to address the growing intersections between air quality management and climate change.
ponderosa) is commonly seen in temperate/boreal forests and one of America's abundant tree specie... more ponderosa) is commonly seen in temperate/boreal forests and one of America's abundant tree species, covering approximately 27 million acres of land. The wood was prepared in the form of dried sticks. US 48 0.07 0.28 6.0 ± 0.4 250 Ponderosa Pine Needles See above. The needles were removed from the trees and dried for combustion. US 50 0.6 3.8 7.3 ± 0.8 250 White Pine Needles White Pine (Pinus strobes) has soft blue-green needles borne in groups of five. It is the state tree of Maine and Missouri. The needles were removed from the trees and dried for combustion.
We treated human lung epithelial cells, type BEAS-2B, with 10-80 µg/cm 2 of dust from soils and r... more We treated human lung epithelial cells, type BEAS-2B, with 10-80 µg/cm 2 of dust from soils and road surfaces in the western United States that contained particulate matter (PM) < 2.5 µm aerodynamic diameter. Cell viability and cytokine secretion responses were measured at 24 hr. Each dust sample is a complex mixture containing particles from different minerals mixed with biogenic and anthropogenic materials. We determined the particle chemical composition using methods based on the U.S. Environmental Protection Agency Speciation Trends Network (STN) and the National Park Service Interagency Monitoring of Protected Visual Environments (IMPROVE) network. The functionally defined carbon fractions reported by the ambient monitoring networks have not been widely used for toxicology studies. The soil-derived PM 2.5 from different sites showed a wide range of potency for inducing the release of the proinflammatory cytokines interleukin-6 (IL-6) and IL-8 in vitro. Univariate regression and multivariate redundancy analysis were used to test for correlation of viability and cytokine release with the concentrations of 40 elements, 7 ions, and 8 carbon fractions. The particles showed positive correlation between IL-6 release and the elemental and pyrolyzable carbon fractions, and the strongest correlation involving crustal elements was between IL-6 release and the aluminum:silicon ratio. The observed correlations between low-volatility organic components of soil-and road-derived dusts and the cytokine release by BEAS-2B cells are relevant for investigation of mechanisms linking specific air pollution particle types with the initiating events leading to airway inflammation in sensitive populations.
The ratio of organic mass (OM) to organic carbon (OC) in PM 2.5 aerosols at US national parks in ... more The ratio of organic mass (OM) to organic carbon (OC) in PM 2.5 aerosols at US national parks in the IMPROVE network was estimated experimentally from solvent extraction of sample filters and from the difference between PM 2.5 mass and chemical constituents other than OC (mass balance) in IMPROVE samples from 1988 to 2003. Archived IMPROVE filters from five IMPROVE sites were extracted with dichloromethane (DCM), acetone and water. The extract residues were weighed to determine OM and analyzed for OC by thermal optical reflectance (TOR). On average, successive extracts of DCM, acetone, and water contained 64%, 21%, and 15%, respectively, of the extractable OC, respectively. On average, the non-blank-corrected recovery of the OC initially measured in these samples by TOR was 115 ± 42%. OM/OC ratios from the combined DCM and acetone extracts averaged 1.92 and ranged from 1.58 at Indian Gardens, AZ in the Grand Canyon to 2.58 at Mount Rainier, WA. The average OM/OC ratio determined by mass balance was 2.07 across the IMPROVE network. The sensitivity of this ratio to assumptions concerning sulfate neutralization, water uptake by hygroscopic species, soil mass, and nitrate volatilization were evaluated. These results suggest that the value of 1.4 for the OM/OC ratio commonly used for mass and light extinction reconstruction in IMPROVE is too low.
The chemical mass balance (CMB) receptor model has apportioned volatile organic compounds (VOCs) ... more The chemical mass balance (CMB) receptor model has apportioned volatile organic compounds (VOCs) in more than 20 urban areas, mostly in the United States. These applications di!er in terms of the total fraction apportioned, the calculation method, the chemical compounds used in the calculation, the apportionment units, and the source pro"les applied. Nevertheless, they show similar results for VOC fractions contributed by di!erent sources. Gasoline vehicle exhaust, liquid gasoline, and gasoline evaporation contribute up to 50% or more of the ambient VOCs in many of these studies. Relative motor vehicle source contributions determined by CMB were similar to or larger than their proportions in emissions inventories. Coatings and solvent contributions from CMB were much lower than the proportions attributed to these sources in current emissions inventories. Several measurement and reporting conventions would facilitate CMB analyses of VOC data sets.
Sources of PM 2.5 at the Fresno Supersite during high PM 2.5 episodes occurring from 15 December ... more Sources of PM 2.5 at the Fresno Supersite during high PM 2.5 episodes occurring from 15 December 2000-3 February 2001 were estimated with the Chemical Mass Balance (CMB) receptor model. The ability of source profiles with organic markers to distinguish motor vehicle, residential wood combustion (RWC), and cooking emissions was evaluated with simulated data. Organics improved the distinction between gasoline and diesel vehicle emissions and allowed a more precise estimate of the cooking source contribution. Sensitivity tests using average ambient concentrations showed that the gasoline vehicle contribution was not resolved without organics. Organics were not required to estimate hardwood contributions. The most important RWC marker was the water-soluble potassium ion. The estimated cooking contribution did not depend on cholesterol because its concentrations were below the detection limit in most samples. Winter time source contributions were estimated by applying the CMB model to individual and average sample concentrations. RWC was the largest source, contributing 29-31% of measured PM 2.5. Hardwood and softwood combustion accounted for 16-17% and 12-15%, respectively. Secondary ammonium nitrate and motor vehicle emissions accounted for 31-33% and 9-15%, respectively. The gasoline vehicle contribution (3-10%) was comparable to the diesel vehicle contribution (5-6%). The cooking contribution was 5-19% of PM 2.5. Fresno source apportionment results were consistent with those estimated in previous studies.
The chemical mass balance (CMB) receptor model was applied to the chemically speciated diurnal pa... more The chemical mass balance (CMB) receptor model was applied to the chemically speciated diurnal particulate matter samples acquired at nine locations in California's South Coast Air Basin (SOCAB) during the summer and fall of 1987 as part of the Southern California Air Quality Study (SCAQS). Source profiles applicable to the Los Angeles area were used to apportion PM,, and PM,, (particles with aerodynamic diameters < 2.5 and 10 pm, respectively) to primary paved road dust, primary construction dust, primary motor vehicle exhaust, primary marine aerosol, secondary ammonium
Emission inventories can serve as a basis for air quality management programs. The focus has been... more Emission inventories can serve as a basis for air quality management programs. The focus has been mainly on building inventories for criteria pollutants including particulate matter (PM). Control efforts in developing countries are mostly limited to total suspended particles (TSP) and/or PM 10. Since the adverse effects of PM 10 depend on its chemical composition, it is important to control emissions of toxic species. The first step is to identify key pollution sources and estimate quantities of various chemical species in emissions. This paper presents a speciated PM 10 emission inventory for Delhi, the capital and one of the most polluted cities in India. An established PM 10 inventory for Delhi in conjunction with source profiles was used to estimate emissions of major PM 10 components including organic and elemental carbon (OC and EC, respectively), sulphates (SO 4 2-), and nitrates (NO 3-), as well as selected toxic trace metals (i.e., Pb, Ni, V, As, and Hg), some of which are subject to India's National Ambient Air Quality Standards (NAAQS). For the base year of 2007, emission estimates for PM 10 mass, OC, EC, SO 4 2-, and NO 3 are 140, 22, 6.4, 2.8, and 2.1 tonnes/day (TPD; 1 tonne = 1000 kg), respectively. Emissions of Pb, Ni, V, As, and Hg are estimated to be 203, 43, 37, 26, and 9.4 kg/day, respectively. This inventory underestimated Pb and Hg emissions because sources of PM 10 from unorganized secondary lead smelters are not specifically identified and gas-to-particle conversion of Hg is not accounted for.
Real-world emission factors for different vehicle types and their contributions to roadside air p... more Real-world emission factors for different vehicle types and their contributions to roadside air pollution are needed for air-quality management. Tunnel measurements have been used to estimate emission factors for several vehicle types using linear regression or receptor-based source apportionment. However, the accuracy and uncertainties of these methods have not been sufficiently discussed. This study applies four methods to derive emission factors for different vehicle types from tunnel measurements in Hong Kong, China: (1) simple linear regressions (SLR); (2) multiple linear regressions (MLR); (3) positive matrix factorization (PMF); and (4) EMission FACtors for Hong Kong (EMFAC-HK). Separable vehicle types include those fueled by liquefied petroleum gas (LPG), gasoline, and diesel. PMF was the most useful, as it simultaneously seeks source profiles and source contributions. Diesel-, gasoline-, and LPG-fueled vehicle emissions accounted for 52%, 10%, and 5% of PM2.5 mass, respecti...
Personal monitoring for fine particulate matter (PM) was conducted for adults (48 subjects, 18-63... more Personal monitoring for fine particulate matter (PM) was conducted for adults (48 subjects, 18-63years of age) in Hong Kong during the summer and winter of 2014-2015. All filters were analyzed for PM mass and constituents (including carbonaceous aerosols, water-soluble ions, and elements). We found that season (p=0.02) and occupation (p<0.001) were significant factors affecting the strength of the personal-ambient PM associations. We applied mixed-effects models to investigate the determinants of personal exposure to PM mass and constituents, along with within- and between-individual variance components. Ambient PM was the dominant predictor of (R=0.12-0.59, p<0.01) and the largest contributor (>37.3%) to personal exposures for PM mass and most components. For all subjects, a one-unit (2.72μg/m) increase in ambient PM was associated with a 0.75μg/m (95% CI: 0.59-0.94μg/m) increase in personal PM exposure. The adjusted mixed-effects models included information extracted from...
Journal of the Air & Waste Management Association (1995), Jan 9, 2015
Geological samples were collected from 27 representative locations in the Athabasca Oil Sands Reg... more Geological samples were collected from 27 representative locations in the Athabasca Oil Sands Region (AOSR) in Alberta, Canada. These samples were resuspended onto filter substrates for PM2.5 and PM10 size fractions. Samples were analyzed for 229 chemical species, consisting of elements, ions, carbon, and organic compounds. These chemical species are normalized to gravimetric mass to derive individual source profiles. Individual profiles were grouped into six categories typical of those used in emission inventories: paved road dust, unpaved road dust close to and distant from oil sand operations, overburden soil, tailings sands, and forest soils. Consistent with their geological origin, the major components are minerals, organic and elemental carbon, and ions. The sum of five major elements (i.e., Al, Si, K, Ca, and Fe) and their oxidized forms account for 25‒40% and 45‒82% of PM mass, respectively. Si is the most abundant element, averaging 17-18% in the Facility (oil sand operatio...
Source profiles (fractional mass abundances and uncertainties) for use in chemical mass balance (... more Source profiles (fractional mass abundances and uncertainties) for use in chemical mass balance (CMB) source apportionment are reported for soil dust from unpaved roads and desert lands. The objectives were to add to the library of source composition profiles available for CMB studies, and to provide data on the variation in wind-blown dust composition between particle sizes and geographical locations. Samples were resuspended and sampled through PM 1 , PM 2.5 and PM 10 inlets onto filters, then chemically analyzed for 40 elements, seven ions and eight carbon fractions. Air quality management would benefit from technology that can distinguish soil dust from sites in different geographical locations and sites with different land uses. Five geographical clusters representing Ft Bliss, TX, Dona Ana County, NM, Ft Irwin, CA, the west desert and the Canyonlands, UT, were examined. Distinctive differences were found between sites within a cluster and these differences were comparable to the differences between cluster averages. Some sites showed small differences in chemical composition between particle sizes, but these differences were less than the differences observed between nearby geographical locations. Dust emissions from sites with uniform geology have distinctive source profiles that may be useful for CMB receptor modeling. Heterogeneous regions, defined by land management boundaries, will require extensive field sampling to develop representative composite source profiles.
Journal of the Air & Waste Management Association, 2007
The US. Department of Energy Gasoline/Diesel PM Split Study was conducted to assess the sources o... more The US. Department of Energy Gasoline/Diesel PM Split Study was conducted to assess the sources of uncertainties in using an organic compound-based chemical mass balance receptor model to quantify the relative contributions of emissions from gasoline (or spark ignition [SI]) and diesel (or compression ignition [CI]) engines to ambient concentrations of fine particulate matter (PM 2.5) in California's South Coast Air Basin (SOCAB). In this study, several groups worked cooperatively on source and ambient sample collection and quality assurance aspects of the study but worked independently to perform chemical analysis and source apportionment. Ambient sampling included daily 24-hr PM 2.5 samples at two air qualitymonitoring stations, several regional urban locations, and along freeway routes and surface streets with varying proportions of automobile and truck traffic. Diesel exhaust was the dominant source of total carbon (TC) and elemental carbon (EC) at the Azusa and downtown Los Angeles, CA, monitoring sites, but samples from the central part of the air basin showed nearly equal apportionments of CI and SI. CI apportionments to TC were mainly dependent on EC, which was sensitive to the analytical method used. Weekday contributions of CI exhaust were higher for Interagency Monitoring of Protected Visual Environments (IMPROVE; 41 Ï® 3.7%) than Speciation Trends Network (32 Ï® 2.4%). EC had little effect on SI apportionment. SI apportionments were most sensitive to higher molecular weight polycyclic aromatic hydrocarbons (indeno[123-cd]pyrene, benzo(ghi)perylene, and coronene) and several steranes and hopanes, which were associated mainly with high emitters. Apportionments were also sensitive to choice of source profiles. CI contributions varied from 30% to 60% of TC when using individual source profiles rather than the composites used in the final apportionments. The apportionment of SI vehicles varied from 1% to 12% of TC depending on the specific profile that was used. Up to 70% of organic carbon (OC) in the ambient samples collected at the two fixed monitoring sites could not be apportioned to directly emitted PM emissions. IMPLICATIONS The apportionments of CI and SI exhaust were most sensitive to the specific CI and SI source profiles that are used and the analytical method for EC. The IMPROVE carbon fractions (four OC and three EC fractions) could not be used for apportionment because of rapid changes in the atmosphere that altered the distributions among the carbon fractions. The apportionment of CI was mainly dependent on EC and could not be obtained by organic markers alone. However, CI vehicles were the dominant source of EC, and EC was a reasonable surrogate of PM emissions from CI vehicles in the SOCAB. Semivolatile organic compounds, which are major components of ultrafine particles and are precursors of secondary organic aerosols, were emitted in far greater quantities than particulate organic compounds by both SI and CI vehicles.
Journal of the Air & Waste Management Association, 2007
The U.S. Department of Energy Gasoline/Diesel PM Split Study examined the sources of uncertaintie... more The U.S. Department of Energy Gasoline/Diesel PM Split Study examined the sources of uncertainties in using an organic compound-based chemical mass balance receptor model to quantify the contributions of spark-ignition (SI) and compression-ignition (CI) engine exhaust to ambient fine particulate matter (PM 2.5). This paper presents the chemical composition profiles of SI and CI engine exhaust from the vehicle-testing portion of the study. Chemical analysis of source samples consisted of gravimetric mass, elements, ions, organic carbon (OC), and elemental carbon (EC) by the Interagency Monitoring of Protected Visual Environments (IMPROVE) and Speciation Trends Network (STN) thermal/optical methods, polycyclic aromatic hydrocarbons (PAHs), hopanes, steranes, alkanes, and polar organic compounds. More than half of the mass IMPLICATIONS We examined several factors that contribute to variations in chemical composition of PM 2.5 emissions from in-use diesel and gasoline vehicles in California's South Coast Air Basin. These factors included model year, mileage accumulation, vehicle test cycles, composition of lubrication oils, and variations in sampling and analytical methods. Distinctive differences were found in the abundances of specific chemical species in diesel and gasoline exhaust, but the variations among individual exhaust profiles were large. These variations should be considered when applying specific profiles in receptor modeling or emission inventory development and in estimating the uncertainties associated with the results.
Journal of the Air & Waste Management Association, 2006
This study tested the feasibility of using pyrolysis (Py)-gas chromatography (GC)/mass spectromet... more This study tested the feasibility of using pyrolysis (Py)-gas chromatography (GC)/mass spectrometry (MS) to obtain organic chemical species data suitable for source apportionment modeling of soil-derived coarse particulate matter (PM 10) dust on ambient filters. A laboratory resuspension apparatus was used with known soils to generate simulated receptor filter samples loaded with ϳ0.4 mg of PM 10 dust, which is within the range of mass loading on ambient filters. Py-GC/MS at 740°C generated five times more resolvable compounds than were obtained with thermal desorption GC/MS at 315°C. The identified compounds were consistent with literature from Py experiments using larger samples of bulk soils. A subset of 91 organic species out of the 178 identified Py products was used as input to CMB8 software in a demonstration of source apportionment using laboratory-generated mixtures simulating ambient filter samples. The 178 quantified organic species obtained by Py of soil samples is an improvement compared with the 38 organic species obtained by thermal desorption of soils and the four functionally defined organic fractions reported by thermal/ optical reflectance. Significant differences in the concentration of specific species were seen between samples from different sites, both geographically distant and close, using analysis of variance and cluster analysis. This feasibility study showed that Py-GC/MS can generate useful source profile data for receptor modeling and justifies continued method development.
Journal of the Air & Waste Management Association, 2001
This paper presents and discusses the results obtained from the gravimetric and chemical analyses... more This paper presents and discusses the results obtained from the gravimetric and chemical analyses of the 24-hr average dichotomous samples collected from five sites in the El Paso-Cd. Juarez air quality basin between August 1999 and March 2000. Gravimetric analysis was performed to determine the temporal and spatial variations of PM 2.5 (particulate matter less than 2.5 µm in diameter) and PM 2.5-10 (particulate matter less than 10 µm but greater than 2.5 µm in diameter) mass concentrations. The results indicate that ~25% of the PM 10 (i.e., PM 2.5 + PM 2.5-10) concentration is composed of PM 2.5. Concurrent measurements of hourly PM concentrations and wind speed showed strong diurnal patterns of the regional PM pollution. Results of X-ray fluorescence (XRF) elemental analyses were compared to similar but limited studies performed by the Texas Natural Resource Conservation Commission (TNRCC) in 1990 and 1997. Major elements from geologic sources-Al, Si, Ca, Na, K, Fe, and Ti-accounted for 35% of the total mass concentrations in the PM 2.5-10 fraction, indicating that geologic sources in the area are the dominant PM sources. Levels of toxic trace elements, mainly considered as products of anthropogenic activities, have decreased significantly from those observed in 1990 and 1997.
Journal of the Air & Waste Management Association, 2012
This article may be used for research, teaching, and private study purposes. Any substantial or s... more This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae, and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand, or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
Journal of the Air & Waste Management Association, 2007
In celebration of the 100th anniversary of the Air & Waste Management Association, this review ex... more In celebration of the 100th anniversary of the Air & Waste Management Association, this review examines the history of air quality management (AQM) in the United States over the last century, with an emphasis on the ambient standards programs established by the landmark 1970 Clean Air Act (CAA) Amendments. The current CAA system is a hybrid of several distinct air pollution control philosophies, including the recursive or circular system driven by ambient standards. Although this evolving system has resulted in tremendous improvements in air quality, it has been far from perfect in terms of timeliness and effectiveness. The paper looks at several periods in the history of the U.S. program, including: (1) 1900-1970, spanning the early smoke abatement and smog control programs, the first federal involvement, and the development of a hybrid AQM approach in the 1970 CAA; (2) 1971-1976, when the first National Ambient Air Quality Standards (NAAQS) were set and implemented; (3) 1977-1993, a period of the first revisions to the standards, new CAA Amendments, delays in implementation and decision-making, and key science/policy/legislative developments that would alter both the focus and scale of air pollution programs and how they are implemented; and (4) 1993-2006, the second and third wave of NAAQS revisions and their implementation in the context of the 1990 CAA. This discussion examines where NAAQS have helped drive implementation programs and how improvements in both effects and air quality/control sciences influenced policy and legislation to enhance the effectiveness of the system over time. The review concludes with a look toward the future of AQM, emphasizing challenges and ways to meet them. The most significant of these is the need to make more efficient progress toward air quality goals, while adjusting the system to address the growing intersections between air quality management and climate change.
ponderosa) is commonly seen in temperate/boreal forests and one of America's abundant tree specie... more ponderosa) is commonly seen in temperate/boreal forests and one of America's abundant tree species, covering approximately 27 million acres of land. The wood was prepared in the form of dried sticks. US 48 0.07 0.28 6.0 ± 0.4 250 Ponderosa Pine Needles See above. The needles were removed from the trees and dried for combustion. US 50 0.6 3.8 7.3 ± 0.8 250 White Pine Needles White Pine (Pinus strobes) has soft blue-green needles borne in groups of five. It is the state tree of Maine and Missouri. The needles were removed from the trees and dried for combustion.
We treated human lung epithelial cells, type BEAS-2B, with 10-80 µg/cm 2 of dust from soils and r... more We treated human lung epithelial cells, type BEAS-2B, with 10-80 µg/cm 2 of dust from soils and road surfaces in the western United States that contained particulate matter (PM) < 2.5 µm aerodynamic diameter. Cell viability and cytokine secretion responses were measured at 24 hr. Each dust sample is a complex mixture containing particles from different minerals mixed with biogenic and anthropogenic materials. We determined the particle chemical composition using methods based on the U.S. Environmental Protection Agency Speciation Trends Network (STN) and the National Park Service Interagency Monitoring of Protected Visual Environments (IMPROVE) network. The functionally defined carbon fractions reported by the ambient monitoring networks have not been widely used for toxicology studies. The soil-derived PM 2.5 from different sites showed a wide range of potency for inducing the release of the proinflammatory cytokines interleukin-6 (IL-6) and IL-8 in vitro. Univariate regression and multivariate redundancy analysis were used to test for correlation of viability and cytokine release with the concentrations of 40 elements, 7 ions, and 8 carbon fractions. The particles showed positive correlation between IL-6 release and the elemental and pyrolyzable carbon fractions, and the strongest correlation involving crustal elements was between IL-6 release and the aluminum:silicon ratio. The observed correlations between low-volatility organic components of soil-and road-derived dusts and the cytokine release by BEAS-2B cells are relevant for investigation of mechanisms linking specific air pollution particle types with the initiating events leading to airway inflammation in sensitive populations.
The ratio of organic mass (OM) to organic carbon (OC) in PM 2.5 aerosols at US national parks in ... more The ratio of organic mass (OM) to organic carbon (OC) in PM 2.5 aerosols at US national parks in the IMPROVE network was estimated experimentally from solvent extraction of sample filters and from the difference between PM 2.5 mass and chemical constituents other than OC (mass balance) in IMPROVE samples from 1988 to 2003. Archived IMPROVE filters from five IMPROVE sites were extracted with dichloromethane (DCM), acetone and water. The extract residues were weighed to determine OM and analyzed for OC by thermal optical reflectance (TOR). On average, successive extracts of DCM, acetone, and water contained 64%, 21%, and 15%, respectively, of the extractable OC, respectively. On average, the non-blank-corrected recovery of the OC initially measured in these samples by TOR was 115 ± 42%. OM/OC ratios from the combined DCM and acetone extracts averaged 1.92 and ranged from 1.58 at Indian Gardens, AZ in the Grand Canyon to 2.58 at Mount Rainier, WA. The average OM/OC ratio determined by mass balance was 2.07 across the IMPROVE network. The sensitivity of this ratio to assumptions concerning sulfate neutralization, water uptake by hygroscopic species, soil mass, and nitrate volatilization were evaluated. These results suggest that the value of 1.4 for the OM/OC ratio commonly used for mass and light extinction reconstruction in IMPROVE is too low.
The chemical mass balance (CMB) receptor model has apportioned volatile organic compounds (VOCs) ... more The chemical mass balance (CMB) receptor model has apportioned volatile organic compounds (VOCs) in more than 20 urban areas, mostly in the United States. These applications di!er in terms of the total fraction apportioned, the calculation method, the chemical compounds used in the calculation, the apportionment units, and the source pro"les applied. Nevertheless, they show similar results for VOC fractions contributed by di!erent sources. Gasoline vehicle exhaust, liquid gasoline, and gasoline evaporation contribute up to 50% or more of the ambient VOCs in many of these studies. Relative motor vehicle source contributions determined by CMB were similar to or larger than their proportions in emissions inventories. Coatings and solvent contributions from CMB were much lower than the proportions attributed to these sources in current emissions inventories. Several measurement and reporting conventions would facilitate CMB analyses of VOC data sets.
Sources of PM 2.5 at the Fresno Supersite during high PM 2.5 episodes occurring from 15 December ... more Sources of PM 2.5 at the Fresno Supersite during high PM 2.5 episodes occurring from 15 December 2000-3 February 2001 were estimated with the Chemical Mass Balance (CMB) receptor model. The ability of source profiles with organic markers to distinguish motor vehicle, residential wood combustion (RWC), and cooking emissions was evaluated with simulated data. Organics improved the distinction between gasoline and diesel vehicle emissions and allowed a more precise estimate of the cooking source contribution. Sensitivity tests using average ambient concentrations showed that the gasoline vehicle contribution was not resolved without organics. Organics were not required to estimate hardwood contributions. The most important RWC marker was the water-soluble potassium ion. The estimated cooking contribution did not depend on cholesterol because its concentrations were below the detection limit in most samples. Winter time source contributions were estimated by applying the CMB model to individual and average sample concentrations. RWC was the largest source, contributing 29-31% of measured PM 2.5. Hardwood and softwood combustion accounted for 16-17% and 12-15%, respectively. Secondary ammonium nitrate and motor vehicle emissions accounted for 31-33% and 9-15%, respectively. The gasoline vehicle contribution (3-10%) was comparable to the diesel vehicle contribution (5-6%). The cooking contribution was 5-19% of PM 2.5. Fresno source apportionment results were consistent with those estimated in previous studies.
The chemical mass balance (CMB) receptor model was applied to the chemically speciated diurnal pa... more The chemical mass balance (CMB) receptor model was applied to the chemically speciated diurnal particulate matter samples acquired at nine locations in California's South Coast Air Basin (SOCAB) during the summer and fall of 1987 as part of the Southern California Air Quality Study (SCAQS). Source profiles applicable to the Los Angeles area were used to apportion PM,, and PM,, (particles with aerodynamic diameters < 2.5 and 10 pm, respectively) to primary paved road dust, primary construction dust, primary motor vehicle exhaust, primary marine aerosol, secondary ammonium
Emission inventories can serve as a basis for air quality management programs. The focus has been... more Emission inventories can serve as a basis for air quality management programs. The focus has been mainly on building inventories for criteria pollutants including particulate matter (PM). Control efforts in developing countries are mostly limited to total suspended particles (TSP) and/or PM 10. Since the adverse effects of PM 10 depend on its chemical composition, it is important to control emissions of toxic species. The first step is to identify key pollution sources and estimate quantities of various chemical species in emissions. This paper presents a speciated PM 10 emission inventory for Delhi, the capital and one of the most polluted cities in India. An established PM 10 inventory for Delhi in conjunction with source profiles was used to estimate emissions of major PM 10 components including organic and elemental carbon (OC and EC, respectively), sulphates (SO 4 2-), and nitrates (NO 3-), as well as selected toxic trace metals (i.e., Pb, Ni, V, As, and Hg), some of which are subject to India's National Ambient Air Quality Standards (NAAQS). For the base year of 2007, emission estimates for PM 10 mass, OC, EC, SO 4 2-, and NO 3 are 140, 22, 6.4, 2.8, and 2.1 tonnes/day (TPD; 1 tonne = 1000 kg), respectively. Emissions of Pb, Ni, V, As, and Hg are estimated to be 203, 43, 37, 26, and 9.4 kg/day, respectively. This inventory underestimated Pb and Hg emissions because sources of PM 10 from unorganized secondary lead smelters are not specifically identified and gas-to-particle conversion of Hg is not accounted for.
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Papers by Judith Chow