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ABSTRACT: Fine particulate matter (PM2.5) concentrations associated with 202 24-hr samples collected at the National Energy Technology Laboratory (NETL) particulate matter (PM) characterization site in south Pittsburgh from October 1999 through September 2001 were used to apportion PM2.5 into primary and secondary contributions using Positive Matrix Factorization (PMF2). Input included the concentrations of PM2.5 mass determined with a Federal Reference Method (FRM) sampler, semi-volatile PM2.5 organic material, elemental carbon (EC), and trace element components of PM2.5. A total of 11 factors were identified. The results of potential source contributions function (PSCF) analysis using PMF2 factors and HYSPLIT-calculated back-trajectories were used to identify those factors associated with specific meteorological transport conditions. The 11 factors were identified as being associated with emissions from various specific regions and facilities including crustal material, gasoline combustion, diesel combustion, and three nearby sources high in trace metals. Three sources associated with transport from coal-fired power plants to the southeast, a combination of point sources to the northwest, and a steel mill and associated sources to the west were identified. In addition, two secondary-material-dominated sources were identified, one was associated with secondary products of local emissions and one was dominated by secondary ammonium sulfate transported to the NETL site from the west and southwest. Of these 11 factors, the four largest contributors to PM2.5 were the secondary transported material (dominated by ammonium sulfate) (47%), local secondary material (19%), diesel combustion emissions (10%), and gasoline combustion emissions (8%). The other seven factors accounted for the remaining 16% of the PM2.5 mass. The findings are consistent with the major source of PM2.5 in the Pittsburgh area being dominated by ammonium sulfate from distant transport and so decoupled from local activity emitting organic pollutants in the metropolitan area. In contrast, the major local secondary sources are dominated by organic material.
Journal of the Air & Waste Management Association (1995) 04/2008; 58(3):357-68. · 1.52 Impact Factor
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ABSTRACT: Gaseous and particulate pollutant concentrations associated with five samples per day collected during a July 2001 summer intensive study at the Pittsburgh Carnegie Mellon University (CMU) Supersite were used to apportion fine particulate matter (PM2.5) into primary and secondary contributions using PMF2. Input to the PMF2 analysis included the concentrations of PM2.5 nonvolatile and semivolatile organic material, elemental carbon (EC), ammonium sulfate, trace element components, gas-phase organic material, and NO(x), NO2, and O3 concentrations. A total of 10 factors were identified. These factors are associated with emissions from various sources and facilities including crustal material, gasoline combustion, diesel combustion, and three nearby sources high in trace metals. In addition, four secondary sources were identified, three of which were associated with secondary products of local emissions and were dominated by organic material and one of which was dominated by secondary ammonium sulfate transported to the CMU site from the west and southwest. The three largest contributors to PM2.5 were secondary transported material (dominated by ammonium sulfate) from the west and southwest (49%), secondary material formed during midday photochemical processes (24%), and gasoline combustion emissions (11%). The other seven sources accounted for the remaining 16% of the PM2.5. Results obtained at the CMU site were comparable to results previously reported at the National Energy Technology Laboratory (NETL), located approximately 18 km south of downtown Pittsburgh. The major contributor at both sites was material transported from the west and southwest. Some difference in nearby sources could be attributed to meteorology as evaluated by HYSPLIT model back-trajectory calculations. These findings are consistent with the majority of the secondary ammonium sulfate in the Pittsburgh area being the result of contributions from distant transport, and thus decoupled from local activity involving organic pollutants in the metropolitan area. In contrast, the major local secondary sources were dominated by organic material.
Journal of the Air & Waste Management Association (1995) 11/2007; 57(10):1251-67. · 1.52 Impact Factor
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ABSTRACT: Apportionment of primary and secondary pollutants during the summer 2001 Pittsburgh Air Quality Study (PAQS) is reported. Several sites were included in PAQS, with the main site (the supersite) adjacent to the Carnegie Mellon University campus in Schenley Park. One of the additional sampling sites was located at the National Energy Technology Laboratory, located approximately 18 km southeast of downtown Pittsburgh. Fine particulate matter (PM2.5) mass, gas-phase volatile organic material (VOM), particulate semivolatile and nonvolatile organic material (NVOM), and ammonium sulfate were apportioned at the two sites into their primary and secondary contributions using the U.S. Environmental Protection Agency UNMIX 2.3 multivariate receptor modeling and analysis software. A portion of each of these species was identified as originating from gasoline and diesel primary mobile sources. Some of the organic material was formed from local secondary transformation processes, whereas the great majority of the secondary sulfate was associated with regional transformation contributions. The results indicated that the diurnal patterns of secondary gas-phase VOM and particulate semivolatile and NVOM were not correlated with secondary ammonium sulfate contributions but were associated with separate formation pathways. These findings are consistent with the bulk of the secondary ammonium sulfate in the Pittsburgh area being the result of contributions from distant transport and, thus, decoupled from local activity involving organic pollutants in the metropolitan area.
Journal of the Air & Waste Management Association (1995) 10/2006; 56(9):1301-19. · 1.52 Impact Factor
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ABSTRACT: An objective of the Pittsburgh Air Quality Study was to determine the major sources Of PM(2.5) in the Pittsburgh region. Daily 24-hour averaged filter-based data were collected for 13 months, starting in July 2001, including sulfate and nitrate data from IC analysis, trace element data from ICP-MS analysis, and organic and elemental carbon from the thermal optical transmittance (TOT) method and the NIOSH thermal evolution protocol. These data were used in two source-receptor models, Unmix and PMF. Unmix, which is limited to a maximum number of seven factors, resolved six source factors, including crustal material, a regional transport factor, secondary nitrate, an iron, zinc and manganese factor, specialty steel production and processing, and cadmium. PMF, which has no limit to the number of factors, apportioned the PM(2.5) mass into ten factors, including crustal material, secondary sulfate, primary OC and EC, secondary nitrate, an iron, zinc and manganese factor, specialty steel production and processing, cadmium, selenium, lead, and a gallium-rich factor. The Unmix and PMF common factors agree reasonably well, both in composition and contributions to PM(2.5). To further identify and apportion the sources Of PM(2.5), specific OC compounds that are known markers of some sources were added to the PMF analysis. The results were similar to the original solution, except that the primary OC and EC factor split into two factors. One factor was associated with vehicles as identified by the hopanes, PAH's, and other OC compounds. The other factor had strong correlations with the OC and EC ambient data as well as wood smoke markers such as levoglucosan, syringols, and resin acids.
Aerosol Science and Technology 01/2006; 40(10):910-924. · 2.67 Impact Factor
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ABSTRACT: Ambient PM(2.5) composition. data in Pittsburgh, PA have been used with Positive Matrix Factorization (PMF) to determine the major sources of PM(2.5) sampled. This paper describes the use of the potential source contribution function (PSCF) with the PMF-modeled source contributions to locate. the sources in a. grid of 0.1 degrees x 0.1 degrees cells. The domain extends from the Pittsburgh Supersite at 40.40 degrees N, 79.94 degrees W over the range 35 degrees-50 degrees north, latitude and 75 degrees-90 degrees west longitude. Six-hour back trajectories have been obtained from HYSPLIT four times each day for the 13 months of the study for use with PSCE Using the results, higher probability locations are compared with known, locations of specific source types, based on information from the EPA Toxic Release Inventory (TRI) and the EPA AIRS Database. PSCF results for several sources are compared to the conditional probability function (CPF) analysis, which uses 15-minute wind direction data to determine the most probable direction of a source. Using PSCF and CPF together aids in interpretation of potential source regions. The selenium and sulfate factor source locations are regional, while the lead, cadmium, and. specialty steel factor source, locations are local. The gallium-rich and Fe Mn, and Zn factor source locations are potentially both local and regional. The nitrate, vehicle emissions and road dust, wood combustion, vegetative detritus and cooking, and crustal material factor CPF and: PSCF results were inconclusive as sources of these. factors exist. in all directions fro m the site and therefore one would not expect a clear probability field in any one direction.
Aerosol Science and Technology 01/2006; 40(10):952-961. · 2.67 Impact Factor
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ABSTRACT: Dry deposition flux measurements to surrogate surfaces and airborne concentration measurements of Zn-containing, S-rich, and soil particles (analyzed by scanning electron microscopy) and Al, Ba, Br, Ca, Cl, Cu, K, Mg, Mn, Na, Ti, and V (analyzed by neutron activation analysis) were made over southwestern Lake Michigan in July 1994 and January 1995 to determine atmospheric inputs of pollutants to the lake. Samples collected in the summer show that despite relatively low airborne concentrations of particles with physical diameters >8 μm, these particles account for the majority of the dry deposition mass flux. However, this sharp contrast is not found during January when particles with physical diameters of 4−8 μm dominate both the airborne concentration and the flux. Dry deposition velocities (flux divided by airborne concentration) for particles are found to range from 0.0062 cm/s for 0.75-μm particles to 5.4 cm/s for 24-μm particles.
04/1998;
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ABSTRACT: New monitoring technologies have now permitted the measurement of a variety of chemical species in airborne particulate matter with time resolution as high as 10 min to 1 h. There are still species that are measured with longer integration periods such as several hours to a day. These data from different measurement methods produce a data set of mixed time resolution. Traditional eigenvalue-based methods used in solving multivariate receptor models are unable to analyze this kind of data set since these data cannot form a simple matrix. Averaging the high time resolution data or interpolating the low time resolution data to produce data on the same time schedule is not acceptable. The former method loses valuable temporal information and the latter produces unreliable high resolution series because of the invalid assumption of temporal smoothness. In the present work, a solution to the problem of multiple sampling time intervals has been developed and tested. Each data value is used in its original time schedule without averaging or interpolation and the source contributions are averaged to the corresponding sampling interval. For data with the highest time resolution, the contributions are not actually averaged. The contribution series are smoothed by regularization auxiliary equations especially for sources containing very little high resolution species. This new model will be explored using data from the Pittsburgh supersite.
Atmospheric Environment.
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ABSTRACT: The concentration and chemical composition of ambient fine particulate material (PM2.5) is reported for two sampling sites in the Pittsburgh, Pennsylvania metropolitan area: the Department of Energy, National Energy Technology Laboratory (NETL) PM study site south of the city center, and the Carnegie Mellon Pittsburgh Air Quality Study (PAQS) site 5 km east of central Pittsburgh established with funding by the EPA Supersites Program and by DOE-NETL. Data from these sampling sites were characterized by one to three-day episodes with PM2.5 concentrations (constructed from the sum of the chemical components) exceeding 40.0 μg m−3. The episodes were dominated by high concentrations of ammonium sulfate. The fine particle concentrations were compared with meteorological data from surface weather maps and a Hybrid Single Particle Lagrangian Integrated Trajectory model (HYSPLIT model), with back-trajectories estimated over 24 h. High PM2.5 concentrations were associated with transition from a high pressure to a low pressure regime in advance of an approaching frontal system indicating long-range transport of pollutants. In contrast, fine particulate organic material appeared to be dominated by nearby sources. Distinct differences were observed in the diurnal variations in concentration between the two sites. The NETL site showed clear maximum concentrations of semi-volatile organic material (SVOM) during midday, and minimum concentrations of nonvolatile organic compounds in the afternoon. In contrast, the Carnegie Mellon PAQS site showed an absence of diurnal variation in SVOM, but still with minimum concentrations of nonvolatile organic compounds in the afternoon and evening. Neither site showed significant diurnal variation in ammonium sulfate.
Atmospheric Environment.
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ABSTRACT: During the Pittsburgh Air Quality Study (PAQS), July 2001–September 2002, three co-located instruments analyzed the composition of ambient particulate matter (PM): (1) A single particle mass spectrometer, RSMS-3, was deployed to obtain high-temporal-resolution measurements of single particle size (>1.1 μm) and composition which were correlated with meteorological data to identify sources; (2) PM2.5 and PM10 were collected on cellulose filters using high-volume (hi-vol) samplers, followed by microwave-assisted digestion and analysis by inductively coupled plasma–mass spectrometry (ICP–MS). Positive matrix factorization (PMF) was used to identify possible source categories; and (3) a micro-orifice uniform-deposit impactor (MOUDI) obtained size-distributed samples of PM. Several days of MOUDI filters were selected for microwave-assisted digestion and analysis by ICP–MS.In this paper, sources identified using the single particle data were compared to the PMF results for the hi-vol/ICP–MS data. The strengths of each method were combined to hypothesize the most likely sources of various elements in ambient PM in Pittsburgh. In the final results, Mo and Cr are attributed to local specialty steel facilities; Fe, Mn, Zn, and K are attributed to a steel mill SE of the monitoring station; internally mixed Pb-containing particles are attributed to a major source to the NW; and Ga is attributed to coal combustion sources to the NW. There is a notable lack of oil combustion sources.The MOUDI data were used to resolve discrepancies between the single particle and hi-vol/ICP–MS data concerning the detection of Ti and Se. The hi-vol data showed appreciable Ti and Se masses, but RSMS-3 was unable to detect significant numbers of Ti-containing particles because of their large size, while we hypothesize that the volatility of Se caused it to be distributed more evenly over all emitted particles such that the amount of Se in any individual particle is below the limit of detection.
Atmospheric Environment.
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ABSTRACT: This research has developed an integrated model of a dairy farm that predicts monthly ammonia emission factors based on farming practices and climate conditions, including temperature, wind speed, and precipitation. The model can be used to predict the seasonal and geographic variations in ammonia emission factors, which are important for accurately predicting aerosol nitrate concentrations. The model tracks the volume of manure and mass of ammoniacal nitrogen as the manure moves through the housing, storage, application, and grazing stages of a dairy farm. Most of the processes of ammonia volatilization are modeled explicitly, but poorly understood processes are parameterized and tuned to match empirical data. The tuned model has been compared to independent experimental data and is shown to be robust over the range of experimental conditions. We have characterized the differences in emissions resulting from changes in climate conditions and farming practices and found that both of these factors are significant and should be included when developing a national inventory.
Atmospheric Environment.
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ABSTRACT: A microwave-assisted digestion procedure using HNO3, HF, and H2O2 has been developed for analysis of elements in ambient particulate matter (PM). The samples are collected on cellulose filters and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The ICP-MS is calibrated with external standards, and recovery of analytes is tested with NIST SRM 1648 Urban Dust. This method has been used to quantify the airborne concentrations of a large number of elements, including Ag, As, Ba, Be, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, K, Li, Mg, Mn, Mo, Ni, Pb, Rb, Se, Sb, Sr, Ti, Tl, V, and Zn. For the majority of these elements, recovery of the NIST SRM is within 15% of the certified values.
Analytica Chimica Acta.
