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.

Apportionment of primary and secondary pollutants during a July 2001 intensive study at the National Energy Technology Laboratory is reported. PM2.5 was apportioned into primary and secondary contributions using PMF2, and results were compared with apportionment based on UNMIX 2.3. Input to PMF2 included PM2.5 mass data from four per 24 hour PC-BOSS filters and TEOM, NOx, NO2, O-3, non-volatile, semi-volatile, and volatile organic material, elemental carbon, sulfate, and PIXE determined trace metals. Nine factors were identified in the PMF analysis. Six factors were associated with primary particles from crustal, mobile (gasoline and diesel), and three local sources high in trace metals. Three factors were associated with secondary sources. Two were associated with local emissions dominated by organic material, one was dominated by transported ammonium sulfate. UNMIX was able to identify the two major mobile sources, major local secondary source and transported secondary source. The three major sources of PM2.5 were identified as secondary transported material (dominated by ammonium sulfate) from west and southwest (46%), secondary material formed during mid-day photochemical processes (21%), and primary emissions from diesel (10%) and gasoline (8%) mobile sources. The other five sources accounted for the remaining 15% of the PM2.5. These findings are consistent with the majority of secondary ammonium sulfate in the Pittsburgh area resulting from distant transport, and so decoupled from local activity involving organic pollutants in the metropolitan area. In contrast, the major local secondary sources were dominated by organic material.

Semivolatile organic compounds (SVOCs) are distributed in the atmosphere between the gas- and aerosol-phases. The low vapor pressures of some SVOCs makes thermal extraction and transfer through gas chromatographic (GC) systems difficult. We evaluated a programmable temperature vaporization (PTV) GC inlet, which served as the preconcentration module, and four open-tubular capillaries (Silcosteel- and Siltek-treated stainless steel, Silcosteel-treated stainless steel coated with 100% dimethylpolysiloxane, and deactivated fused silica) as transfer lines in a valveless, whole-sample analytic system. Thermal extraction of C9–C36 n-alkanes at 300 and 320 °C from fused silica and quartz wool in the PTV inlet was equally efficient. Adsorptive losses of C22–C36 n-alkanes to stainless steel surfaces that protruded into the PTV inlet were suspected. Thus, treatment of the outer surfaces of transfer lines is recommended for effective thermal transfer of SVOCs. Transfer efficiencies began to decline after n-C24, n-C28, and n-C30 in Silcosteel-treated stainless steel, deactivated fused silica, and Siltek-treated stainless steel transfer lines, respectively. Thus, quantitative recovery at 320 °C of compounds with vapor pressures less than about 3 × 10−8 Pa is not expected in valveless SVOC thermal desorption systems that use Siltek-treated stainless steel transfer lines and fused silica or quartz wool as preconcentration substrates.

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.

Ammonium nitrate and semivolatile organic compounds (SVOC) are significant components of fine particles in many urban atmospheres. These components, however, are not properly measured by current EPA accepted methods, such as the R&P TEOM monitor, due to loss of semivolatile material (SVM) from particles in the heated environment of the filter during sampling. The accurate determination of semivolatile material is important due to the possible effects of these species on human health, visibility, and global climate change. The concentration and composition of fine particulate material were determined using a combination of continuous and integrated samplers at the Brigham Young University–EPA Environmental Monitoring for Public Access and Community Tracking (BYU–EPA EMPACT) monitoring site in Salt Lake City, Utah over a six–day sampling period (30 January to 4 February) during the winter of 2001. Continuous samples were collected using a RAMS (total PM2.5 mass), a TEOM monitor (nonvolatile PM2.5 mass), an Aethalometer (elemental carbon), a TSI CPC (particle count), and a Nephelometer (light scattering by particles, bsp). Fine particle composition and mass were determined on a three–hour basis using the PC–BOSS diffusion denuder sampler. Total PM2.5 mass–determined with the RAMS agreed with constructed mass determined from the chemical composition measured in collocated PC–BOSS–integrated samples. Results from this study indicate that semivolatile material (ammonium nitrate and semivolatile organic compounds) is a significant component of fine particle mass. Semivolatile organic compounds were the major contributor to light scattering during the six–day sampling period. Semivolatile nitrate, but not organic material, was suggested to be hygroscopic by the nephelometric data. The majority of the SVM observed appeared to be secondary material formed from photochemical reactions of the organic and NOx emissions from mobile sources and wood smoke combustion.

From October 1999 through September 2000, particulate matter (PM) with aerodynamic diameter greater than or equal to2.5 mum (PM2.5) mass and composition were measured at the National Energy Technology Laboratory Pittsburgh site, with a particle concentrator Brigham Young University-organic sampling system and a tapered element oscillating microbalance (TEOM) monitor. PM2.5 measurements had also been obtained with TEOM monitors located in the Pittsburgh, PA, area, and at sites in Ohio, including Steubenville, Columbus, and Athens. The PM data from all these sites were analyzed on high PM days; PM2.5 TEOM particulate mass at all sites was generally associated with transitions from locally high barometric pressure to lower pressure. Elevated concentrations occurred with transport of PM from outside the local region in advance of frontal passages as the local pressure decreased. During high-pressure periods, concentrations at the study sites were generally low throughout the study region. Further details related to this transport were obtained from surface weather maps and estimated back-trajectories using the hybrid single-particle Lagrangian integrated trajectory model associated with these time periods. These analyses indicated that transport of pollutants to the Pittsburgh site was generally from the west to the southwest. These results suggest that the Ohio River Valley and possible regions beyond act as a significant source of PM and its precursors in the Pittsburgh area and at the other regional sites included in this study.

Both annual 24-h average and seasonal diurnal samples collected at NETL during the research program have been analyzed. The fine particulate components determined include PM{sub 2.5} mass, ammonium sulfate, ammonium nitrate, elemental and organic carbonaceous material and trace elements. The analysis of the nitrate and organic material includes both the identification of nonvolatile material retained by the particle collection filter and semi-volatile material lost from the particles during sample collection. The results obtained in these analyses indicate that both the semivolatile and nonvolatile organic material in the fine particles sampled at the NETL site originate from mobile emissions in the local area. However, the majority of the nonvolatile material is associated with primary emissions and the majority of the semi-volatile material is secondary, being formed from photochemical processes in the atmosphere. In contrast, the fine particulate sulfate does not originate from the local area but is transported into the study region, mostly from sources in the Ohio River Valley. These observations have been supported by both detailed meteorological and apportionment analysis of the data.

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 5km 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 40.0μgm−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 24h. 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.

The concentration and composition of PM 2.5 from May to September of 2000 and monthly trends in ambient fine-particulate material concentrations from October 1999 through December 2000 at the National Energy Technology Laboratory's airmonitoring site in Pittsburgh are reported. Twenty four-hour integrated samples were collected using the Particle Concentrator-Brigham Young University Organic Sampling System (PC-BOSS), a multichannel integrated diffusion denuder sampler designed for routine determination of the chemical composition of ambient particulate matter. The fine-particulate pollutants determined were sulfate estimated as ammonium sulfate, nonvolatile organic material, semivolatile organic material lost from particles during sampling, elemental carbon, nitrate estimated as ammonium nitrate, including ammonium nitrate lost from particles during sampling and elemental content determined by PIXE (for a limited number of samples). Episodes with elevated sulfate and organic material (both semivolatile and nonvolatile) concentrations were seen throughout this period. For the purpose of this discussion, an episode was defined as all times when 3 h average TEOM monitor PM 2.5 concentrations exceeded 30 μg/m3. The use of estimated back-trajectories indicated that during the periods for which these elevated concentrations were observed, pollutants were transported predominantly from the Southwest from the Ohio River Valley to the sampling site. For days when fine particulate episodes occurred, back-trajectory computations were derived for time intervals for which PM 2.5 TEOM concentrations exceeded 30 μg/m3. However, for nonepisode days, back trajectories were computed over a 24 h period. Average PC-BOSS–constructed PM 2.5 concentration (including semivolatile components lost from particles during sampling) for the period from October 1999 through December 2000 was 19 μg/m 3 , excluding crustal material concentration.

The first of the U.S. Environmental Protection Agency's (EPA) Particulate Matter (PM) Supersites projects was established in Atlanta, GA, during the summer of 1999 in conjunction with the Southern Oxidants Study. The short‐term primary focus was a one month intensive field campaign to evaluate advanced PM measurement methods for measuring PM mass and the chemical and physical properties of PM. Long‐term objectives are being met through coordination and cooperation with existing programs in Atlanta and the southeastern United States. Three categories of PM instruments were deployed during August 1999: time‐integrated or discrete filter‐based methods like those used in EPA's PM2.5 Chemical Speciation Network; continuous or semicontinuous species specific methods, most of which are still in development; and single particle mass spectrometers, the most advanced methods looking at the chemical composition of single particles. The focus of this paper is on comparison of the discrete filter‐based methods. Samples were collected by 12 discrete filter‐based samplers on an every other day basis during the study period at the Jefferson Street Southeastern Aerosol Research and Characterization (SEARCH) study site. Samples were analyzed for PM2.5 mass, sulfate, nitrate, ammonium, organic carbon, elemental carbon, and trace elements, the latter by XRF. Samplers used a variety of filters; denuder‐filter combinations in the case of nitrate and organic carbon, particle size fractionating devices, and flow rates. Ambient concentrations for most species were sufficiently above detection limits for testing comparability among samplers, with nitrate being the most notable exception for the major components having an average reported value of 0.5 μg/m3. Several trace species, e.g., As and Pb, also were often below limits of detection of the analysis method. Results indicate that real differences exist among the samplers tested for most species, with sulfate and ammonium being the exceptions, under the conditions tested. Differences are due to sampler design, and in the case of elemental carbon, also due to the use of different chemical analysis methods. Comparability among most of the samplers for a given species was: mass (±20%); sulfate (±10%); nitrate (±30–35%); ammonium (±10–15%); organic carbon either with or without denuders (±20%) or including samplers both with and without denuders (±35–45%); elemental carbon (±20 to ±200%, the latter if different analysis methods are used); and minor and trace elements (±20–30%). A net organic carbon‐sampling artifact on quartz‐fiber filters was estimated from the comparison of denuded versus undenuded samples and is in the range of 1–4 μg/m3.

Ammonium nitrate and semi-volatile organic compounds are significant components of fine particles in urban atmospheres. These components, however, are not properly determined with current US EPA accepted methods such as the PM2.5 FRM or other single filter samplers due to significant losses of semi-volatile material (SVM) from particles collected on the filter during sampling. Continuous PM2.5 mass measurements are attempted using methods such as the R&P TEOM monitor. This method, however, heats the sample to remove particle-bound water which also results in evaporation of SVM. Research at Brigham Young University has resulted in samplers for both the integrated and continuous measurement of total PM2.5, including the SVM. The PC-BOSS is a charcoal diffusion denuder based sampler for the determination of fine particulate chemical composition including the semi-volatile organic material. The RAMS is a modified TEOM monitor which includes diffusion denuders and Nafion dryers to remove gas phase material which can be absorbed by a charcoal sorbent filter. The RAMS then uses a "sandwich filter" consisting of a conventional particle collecting Teflon coated TX40 filter, followed by an activated charcoal sorbent filter which retains any semi-volatile ammonium nitrate or organic material lost from the particles collected on the TEOM monitor Teflon coated filter, thus allowing for determination of total PM2.5 mass including the SVM. Recent research conducted by Brigham Young University using these two samplers has indicated the following about semi-volatile organic aerosol:The majority of semi-volatile fine particulate organic material is secondary organic aerosol.This semi-volatile organic aerosol is not retained on the heated filter of a regular TEOM monitor and hence is not measured by this sampling technique. In addition, secondary ammonium nitrate is also lost.Much of the semi-volatile organic aerosol is also lost during sampling from single filter samplers such as the PM2.5 FRM sampler.The amount of semi-volatile organic aerosol lost from single filter samplers can vary from less than 3 that lost from heated TEOM filters during cold winter conditions to essentially all during warm summer conditions.Semi-volatile organic aerosol can only be reliably collected using an appropriate denuder sampler.Either a PM2.5 FRM sampler or the IMPROVE sampler can be easily modified to a denuder sampler with filters which can be analyzed for semi-volatile OC, nonvolatile OC and EC using existing OC/EC analytical techniques.The research upon which these statements are based is summarized in this document. (C) 2003 Elsevier Science Ltd. All rights reserved.

This paper reports on the results from the first 6 months (from November 1999 to April 2000) of an ongoing monitoring study of fine particulate air pollutants at the Department of Energy's Office of Science and Technology (OST) NETL sampling site, 30 km southwest of Pittsburgh city center, Pennsylvania. This study is part of a 2-year sampling program for PM characterization, under the auspices of The University Coal Research Program of the National Energy Technology Laboratory (NETL), US Department of Energy in Pittsburgh, PA, USA. Samples were collected daily with a Particle Concentrator-Brigham Young University Organic Sampling System (PC-BOSS) to determine PM2.3 composition, including the semi-volatile organic compounds (SVOC) and ammonium nitrate lost from particles during sampling. Average fine particulate composition during the 6-month period was: constructed PM2.3, 19.4 μgm−3; ammonium sulfate 4.3 μgm−3; non-volatile organic material, 6.9 μgm−3; elemental carbon, 0.4 μgm−3; SVOC lost from particles during sampling, 6.1 μgm−3; retained ammonium nitrate, 1.4 μgm−3; lost ammonium nitrate, 0.3 μgm−3. Results from the PC-BOSS sampler are also compared with those obtained from a Federal Reference Method PM2.5 sampler, and a Tapered Element Oscillating Microbalance monitor, both of which tended to not measure the semi-volatile particulate matter. SVOC concentrations were highest in the spring. Episodes of fine particulate non-volatile organic material occurred throughout the 6-month period. Average ammonium sulfate concentrations were higher in November and January than the other months for the study period.

The real-time ambient mass sampler (RAMS) is a continuous monitor based on particle concentrator, denuder, drier, and tapered element oscillating microbalance (TEOM) monitor technology. It is designed to measure PM2.5 mass, including the semi-volatile species NH4NO3 and semi-volatile organic material, but not to measure PM2.5 water content. The performance of the RAMS in an urban environment with high humidity was evaluated during the July 1999 NARSTO-Northeast Oxidant and Particles Study (NEOPS) intensive study at the Baxter water treatment plant in Philadelphia, PA. The results obtained with the RAMS were compared to mass measurements made with a TEOM monitor and to constructed mass obtained with a Particle Concentrator-Brigham Young University Organic Sampling System (PC-BOSS) sampler designed to determine the chemical composition of fine particles, including the semi-volatile species. An average of 28% of the fine particulate material present during the study was semi-volatile organic material lost from a filter during particle collection, and 1% was NH4NO3 that was also lost from the particles during sampling. The remaining mass was dominantly nonvolatile (NH4)2SO4 (31%) and organic material (37%), with minor amounts of soot, crustal material, and nonvolatile NH4NO3. Comparison of the RAMS and PC-BOSS results indicated that the RAMS correctly monitored for fine particulate mass, including the semivolatile material. In contrast, the heated filter of the TEOM monitor did not measure the semi-volatile material. The comparison of the RAMS and PC-BOSS data had a precision of +/-4.1 microg/m3 (+/-9.6%). The precision of the RAMS data was limited by the uncertainty in the blank correction for the reversible adsorption of water by the charcoal-impregnated cellulose sorbent filter of the RAMS monitor. The precision of the measurement of fine particulate components by the PC-BOSS was +/-6-8%.

PM2.5 mass was measured daily with three batch samplers, a PM2.5 R&P Partisol-Plus FRM, an Andersen RAAS, and a BYU PC-BOSS, and continuously with a TEOM monitor during July and August 2000. PM2.5 composition was also determined. These data are part of an ongoing PM2.5 characterization program centered around a sampling site at the National Energy Technology Laboratory Pittsburgh campus. The composition and concentrations of PM2.5 were both highly variable during this time period. Likely sources of PM2.5 during low concentration periods were transportation, coal-fired boiler, and other emissions generated in the local area. For these periods, the average concentration of PM2.5 was 13 mug/m(3) and 70% of the PM2.5 mass was carbonaceous material, including semivolatile organic material that was lost in varying degrees from both the TEOM and FRM samplers. In contrast, much higher concentrations of PM2.5 were associated with transport of pollutants to the site. Analysis of meteorological and back-trajectory data suggests that these pollutants were emitted elsewhere during a period of high atmospheric pressure and were subsequently transported to the site with the passage of a frontal system. When the PM2.5 collected at the site originated from the west or southwest, the concentrations averaged 31 mug/m(3) and ammonium sulfate averaged 54% of the PM2.5 mass. Scanning election microscopy and trace element analyses are consistent with the association of high concentration PM2.5 episodes with transport of coke and iron processing, coal-fired boiler, and other emissions from the Ohio River Valley region to the NETL site. Preliminary observations on the use of SEM and PIXE data in source apportionment at the NETL site are given.

Aerosol concentrations of carbonaceous material, sulfate, and nitrate for samples obtained using a newly designed PC-BOSS are reported. The results indicated that PM2.5 composition in Atlanta was dominated by sulfate and organic material, with low concentrations of particulate nitrate. Observed average particulate component concentrations for the 26-day study period were: sulfate, 12.2μg/m3 (17.0μg/m3 as ammonium sulfate); non-volatile organic material, 11.4μg OM/m3 (assumes organic material, OM, is 61% C); semi-volatile organic compounds (SVOC) lost from particles during sampling, 5.3μg OM/m3; filter retained nitrate, 0.1μg/m3 (0.2μg/m3 as ammonium nitrate); nitrate lost from particles, 0.3μg/m3 (0.4μg/m3 as ammonium nitrate); and soot (elemental carbon), 1.5μg/m3. The PC-BOSS particle concentrator efficiency was obtained by comparison of the PC-BOSS sulfate data with sulfate data obtained from the Federal Reference Method (FRM) sampler. A modification of the PC-BOSS design to allow independent determination of this parameter is recommended.