Publications (11)8.95 Total impact
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Article: Filtration Effectiveness of HVAC Systems at Near-Roadway Schools.
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ABSTRACT: Concern for the exposure of children attending schools located near busy roadways to toxic, traffic-related air pollutants has raised questions regarding the environmental benefits of advanced heating, ventilation, and air conditioning (HVAC) filtration systems for near-road pollution. Levels of black carbon and gaseous pollutants were measured at three indoor classroom sites and at seven outdoor monitoring sites at Las Vegas schools. Initial HVAC filtration systems effected a 31-66% reduction in black carbon particle concentrations inside three schools compared to ambient air concentrations. After improved filtration systems were installed, black carbon particle concentrations were reduced by 74-97% inside three classrooms relative to ambient air concentrations. Average black carbon particle concentrations inside the schools with improved filtration systems were lower than typical ambient Las Vegas concentrations by 49-96%. aseous pollutants were higher indoors than outdoors. The higher indoor concentrations most likely originated at least partially from indoor sources, which were not targeted as part of this intervention © 2012 John Wiley & Sons A/S.Indoor Air 11/2012; · 2.55 Impact Factor -
Article: Predicting areas of high diesel particulate matter emissions in Phoenix, Arizona, using spatial analysis techniques
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ABSTRACT: Growing evidence suggests that inhalation exposure to diesel exhaust, including diesel particulate matter (DPM), causes acute and chronic health effects. As a result, interest in monitoring diesel exhaust has increased. Maps of emissions sources, emissions activity data, and meteorology were combined within a geographic information system (GIS) suitability model to produce a composite map identifying areas where DPM emissions are likely to be high. The results of the GIS model were compared with (i) the locations of existing monitoring sites in Phoenix, Arizona, and (ii) the spatial distribution of population. The results indicate that two existing sites are located in areas where DPM emissions are predicted to be high; however, incorporating meteorology as a factor showed that one site is located upwind of a predicted high DPM area. Consideration of population density showed high density in two areas that appear to be moderately influenced by DPM.De plus en plus de preuves suggèrent que l'exposition à l'inhalation des échappements des diesels, incluant les matières particulaires diesel, entraîne des effets aigus et chroniques sur la santé. L'intérêt dans la surveillance des échappements diesel a donc augmenté. Des cartes des sources des émissions, des données sur les activités d'émissions ainsi que des données météorologiques ont été combinées à un modèle pertinent d'un système d'information géographique (SIG) afin de produire une carte composite montrant les zones où les émissions de matières particulaires diesel sont probablement élevées. Les résultats du modèle SIG ont été comparés (i) aux emplacements des sites de surveillance existants à Phoenix, en Arizona, et (ii) à la distribution spatiale de la population. Les résultats indiquent que deux sites existants sont situés dans les zones où les émissions de matières particulaires diesel devraient être élevées. Toutefois, l'incorporation du facteur météorologie a montré qu'un site est situé en amont d'une zone à émissions de matières particulaires diesel probablement élevées. Le fait de tenir compte de la densité de la population a montré une forte densité dans deux zones qui semblent être modérément influencées par les matières particulaires diesel.Canadian Journal of Civil Engineering 01/2010; 37(2):354-365. · 0.33 Impact Factor -
Article: Source apportionment of fine particulate matter in Phoenix, AZ, using positive matrix factorization.
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ABSTRACT: Speciated particulate matter (PM)2.5 data collected as part of the Interagency Monitoring of Protected Visual Environments (IMPROVE) program in Phoenix, AZ, from April 2001 through October 2003 were analyzed using the multivariate receptor model, positive matrix factorization (PMF). Over 250 samples and 24 species were used, including the organic carbon and elemental carbon analytical temperature fractions from the thermal optical reflectance method. A two-step approach was used. First, the species excluding the carbon fractions were used, and initially eight factors were identified; non-soil potassium was calculated and included to better refine the burning factor. Next, the mass associated with the burning factor was removed, and the data set rerun with the carbon fractions. Results were very similar (i.e., within a few percent), but this step enabled a separation of the mobile factor into gasoline and diesel vehicle emissions. The identified factors were burning (on average 2% of the mass), secondary transport (7%), regional power generation (13%), dust (25%), nitrate (9%), industrial As/Pb/Se (2%), Cu/Ni/V (7%), diesel (9%), and general mobile (26%). The overall contribution from mobile sources also increased, as some mass (OC and nitrate) from the nitrate and regional power generation factors were apportioned with the mobile factors. This approach allowed better apportionment of carbon as well as total mass. Additionally, the use of multiple supporting analyses, including air mass trajectories, activity trends, and emission inventory information, helped increase confidence in factor identification.Journal of the Air & Waste Management Association (1995) 07/2007; 57(6):741-52. · 1.52 Impact Factor -
Article: Analysis and apportionment of organic carbon and fine particulate matter sources at multiple sites in the midwestern United States.
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ABSTRACT: Speciated fine particulate matter (PM2.5) data collected as part of the Speciation Trends Network at four sites in the Midwest (Detroit, MI; Cincinnati, OH; Indianapolis, IN; and Northbrook, IL) and as part of the Interagency Monitoring of Protected Visual Environments program at the rural Bondville, IL, site were analyzed to understand sources contributing to organic carbon (OC) and PM2.5 mass. Positive matrix factorization (PMF) was applied to available data collected from January 2002 through March 2005, and seven to nine factors were identified at each site. Common factors at all of the sites included mobile (gasoline)/secondary organic aerosols with high OC, diesel with a high elemental carbon/OC ratio (only at the urban sites), secondary sulfate, secondary nitrate, soil, and biomass burning. Identified industrial factors included copper smelting (Northbrook, Indianapolis, and Bondville), steel/manufacturing with iron (Northbrook), industrial zinc (Northbrook, Cincinnati, Indianapolis, and Detroit), metal plating with chromium and nickel (Detroit, Indianapolis, and Bondville), mixed industrial with copper and iron (Cincinnati), and limestone with calcium and iron (Bondville). PMF results, on average, accounted for 96% of the measured PM2.5 mass at each site; residuals were consistently within tolerance (+/-3), and goodness-of-fit (Q) was acceptable. Potential source contribution function analysis helped identify regional and local impacts of the identified source types. Secondary sulfate and soil factors showed regional characteristics at each site, whereas industrial sources typically appeared to be locally influenced. These regional factors contributed approximately one third of the total PM2.5 mass, on average, whereas local mobile and industrial sources contributed to the remaining mass. Mobile sources were a major contributor (55-76% at the urban sites) to OC mass, generally with at least twice as much mass from nondiesel sources as from diesel. Regional OC associated with secondary sulfate and soil was generally low.Journal of the Air & Waste Management Association (1995) 06/2007; 57(5):606-19. · 1.52 Impact Factor -
Article: Processes influencing secondary aerosol formation in the San Joaquin Valley during winter.
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ABSTRACT: Air quality data collected in the California Regional PM10/ PM(2.5) Air Quality Study (CRPAQS) are analyzed to qualitatively assess the processes affecting secondary aerosol formation in the San Joaquin Valley (SJV). This region experiences some of the highest fine particulate matter (PM(2.5)) mass concentrations in California (< or = 188 microg/m3 24-hr average), and secondary aerosol components (as a group) frequently constitute over half of the fine aerosol mass in winter. The analyses are based on 15 days of high-frequency filter and canister measurements and several months of wintertime continuous gas and aerosol measurements. The phase-partitioning of nitrogen oxide (NO(x))-related nitrogen species and carbonaceous species shows that concentrations of gaseous precursor species are far more abundant than measured secondary aerosol nitrate or estimated secondary organic aerosols. Comparisons of ammonia and nitric acid concentrations indicate that ammonium nitrate formation is limited by the availability of nitric acid rather than ammonia. Time-resolved aerosol nitrate data collected at the surface and on a 90-m tower suggest that both the daytime and nighttime nitric acid formation pathways are active, and entrainment of aerosol nitrate formed aloft at night may explain the spatial homogeneity of nitrate in the SJV. NO(x) and volatile organic compound (VOC) emissions plus background O3 levels are expected to determine NO(x) oxidation and nitric acid production rates, which currently control the ammonium nitrate levels in the SJV. Secondary organic aerosol formation is significant in winter, especially in the Fresno urban area. Formation of secondary organic aerosol is more likely limited by the rate of VOC oxidation than the availability of VOC precursors in winter.Journal of the Air & Waste Management Association (1995) 01/2007; 56(12):1679-93. · 1.52 Impact Factor -
Article: Wintertime vertical variations in particulate matter (PM) and precursor concentrations in the San Joaquin Valley during the California Regional Coarse PM/Fine PM Air Quality Study.
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ABSTRACT: Air quality monitoring was conducted at a rural site with a tower in the middle of California's San Joaquin Valley (SJV) and at elevated sites in the foothills and mountains surrounding the SJV for the California Regional PM10/ PM2.5 Air Quality Study. Measurements at the surface and n a tower at 90 m were collected in Angiola, CA, from December 2000 through February 2001 and included hourly black carbon (BC), particle counts from optical particle counters, nitric oxide, ozone, temperature, relative humidity, wind speed, and direction. Boundary site measurements were made primarily using 24-hr integrated particulate matter (PM) samples. These measurements were used to understand the vertical variations of PM and PM precursors, the effect of stratification in the winter on concentrations and chemistry aloft and at the surface, and the impact of aloft-versus-surface transport on PM concentrations. Vertical variations of concentrations differed among individual species. The stratification may be important to atmospheric chemistry processes, particularly nighttime nitrate formation aloft, because NO2 appeared to be oxidized by ozone in the stratified aloft layer. Additionally, increases in accumulation-mode particle concentrations in the aloft layer during a fine PM (PM2.5) episode corresponded with increases in aloft nitrate, demonstrating the likelihood of an aloft nighttime nitrate formation mechanism. Evidence of local transport at the surface and regional transport aloft was found; transport processes also varied among the species. The distribution of BC appeared to be regional, and BC was often uniformly mixed vertically. Overall, the combination of time-resolved tower and surface measurements provided important insight into PM stratification, formation, and transport.Journal of the Air & Waste Management Association (1995) 10/2006; 56(9):1267-77. · 1.52 Impact Factor -
Article: Source apportionment of VOCs in the Los Angeles area using positive matrix factorization
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ABSTRACT: Eight 3-h speciated hydrocarbon measurements were collected daily by the South Coast Air Quality Management District (SCAQMD) as part of the Photochemical Assessment Monitoring Stations (PAMS) program during the summers of 2001–03 at two sites in the Los Angeles air basin, Azusa and Hawthorne. Over 30 hydrocarbons from over 500 samples at Azusa and 600 samples at Hawthorne were subsequently analyzed using the multivariate receptor model positive matrix factorization (PMF). At Azusa and Hawthorne, five and six factors were identified, respectively, with a good comparison between predicted and measured mass. At Azusa, evaporative emissions (a median of 31% of the total mass), motor vehicle exhaust (22%), liquid/unburned gasoline (27%), coatings (17%), and biogenic emissions (3%) factors were identified. Factors identified at Hawthorne were evaporative emissions (a median of 34% of the total mass), motor vehicle exhaust (24%), industrial process losses (15%), natural gas (13%), liquid/unburned gasoline (13%), and biogenic emissions (1%). Together, the median contribution from mobile source-related factors (exhaust, evaporative emissions, and liquid/unburned gasoline) was 80% and 71% at Azusa and Hawthorne, respectively, similar to previous source apportionment results using the chemical mass balance (CMB) model. There is a difference in the distribution among mobile source factors compared to the CMB work, with an increase in the contribution from evaporative emissions, though the cause (changes in emissions or differences between models) is unknown.Atmospheric Environment. -
Article: Characterization of non-methane volatile organic compounds sources in Houston during 2001 using positive matrix factorization
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ABSTRACT: Non-methane volatile organic compounds (NMOC) that were most likely to contribute to ozone formation in the Houston, Texas area were measured by Texas Commission on Environmental Quality using AutoSystem Gas Chromatograph. Hourly, integrated NMOC measured between 9 pm and 6 am at the three monitoring sites (Deer Park, Haden Rd., and Clinton Dr.) in Houston were analyzed with Positive Matrix Factorization (PMF). Only NMOC data collected during the nighttime was utilized to minimize the influence of photochemistry, motor vehicles, and biogenic sources. A total of 401–883 samples and 38 to 40 NMOC species measured between July 2001 and October 2001 were analyzed. PMF identified seven sources at Deer Park (flare emissions, industrial source, petrochemical source, natural gas/propane, refinery, isoprene source, and motor vehicle), Haden Rd. (flare emissions, petrochemical source, industrial source, solvent, natural gas/propane, refinery, and motor vehicle), and Clinton Dr. (flare emissions, two industrial sources, refinery, natural gas/propane, motor vehicle, and isoprene source). Five similar source types were found among three sites although the sources were differently located. Conditional probability function analysis using surface wind data and identified source contributions aided the identifications of local point sources by providing indications of likely directions for the sources. The results agreed well with the locations of known local NMOC sources.Atmospheric Environment. -
Article: Reconciliation of the VOC and NOX Emission Inventory with Ambient Data in the Houston, Texas Region
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ABSTRACT: This study, sponsored by the Houston Advanced Research Center (HARC) in support of the Texas Commission on Environmental Quality (TCEQ), was designed to use innovative methods for evaluating and reconciling the emission inventory for the Houston-Galveston area (HGA). The objective of this project was to evaluate the emissions inventory for large point sources in the HGA for 2000 by comparing emissions estimates to ambient data collected during 2000 and 2001, and to make recommendations on possible improvements to the point source inventory. This project focused on sources of non-methane organic compounds (NMOC, often called volatile organic compounds, VOC) that are most likely to contribute to ozone formation, and on oxides of nitrogen (NO x) in the HGA. In particular, the project focused on the 12 highly reactive VOCs or groups of compounds that TCEQ has targeted because of their significant contributions to ozone formation. These compounds and groups include the following: acetaldehyde; formaldehyde; ethylene; propylene; 1,3-butadiene; all butenes (butylenes); isoprene; all pentenes; toluene; all xylenes; all ethyltoluenes; and all trimethylbenzenes. However, due to limitations in the measurement systems, we did not address acetaldehyde and formaldehyde, and ethyltoluenes and trimethylbenzenes were often lumped together. The overall results of this study indicate that the NMOC and NO x point source emission inventory appears to be underestimated and should be evaluated and corrected as necessary. In addition, estimates for non-road sources appear to be high in some areas, particularly for lawn and garden equipment and non-road equipment for Ellington Field. Overall, the speciation profiles used to prepare the emission inventory correlate relatively well with the weight percentages of organic species (and species groups) detected by the ambient monitoring system. However, propylene, n-butane, and ethane were underrepresented and benzene and C-5 paraffins were overrepresented in the emission inventory. The point source emission inventory should be examined to identify the sources that contribute the most mass for the compounds listed above. Both the chemical speciation profiles used to speciate these identified sources, and the speciation profiles used to speciate the point source inventory for refineries and chemical manufacturing should be assessed. -
Article: Estimating Regional Contributions to Atmospheric Haze Using GIS
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ABSTRACT: ArcObjects was used to develop a customized spatial mapping tool to aid in characterizing relationships between air pollutant emissions and downwind air quality observations. The tool, called Emission Impact Potential (EIP), combines backward-trajectory meteorological analyses with emission inventory data to calculate and visualize emissions source regions most likely to impact a specified air pollution monitoring site. EIP generates spatial probability distributions that account for the spatial distribution of emissions and wind trajectory probability distributions. Thus, pollutant emissions that are most likely to affect a measurement location are weighted more heavily in correlation analyses. This analysis approach helps to identify emissions source regions likely to impact specified monitoring sites and to more intelligently target emission reductions to improve downwind air quality. -
Conference Proceeding: Reconciliation of the VOC and NOx Emission Inventory with Ambient Data in the Houston, Texas Region
13th International Emission Inventory Conference "Working for Clean Air in Clearwater";
Top co-authors
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Institutions
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2007
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Michigan State University
East Lansing, MI, USA
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2006–2007
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Sonoma Technology Inc.
Petaluma, CA, USA
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