Apportionment of Ambient Primary and Secondary Fine Particulate Matter during a 2001 Summer Intensive Study at the CMU Supersite and NETL Pittsburgh Site

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 (PM 2.5 ) into primary and secondary contributions using PMF2. Input to the PMF2 analysis included the concentrations of PM 2.5 nonvolatile and semivolatile organic material, elemental carbon (EC), ammonium sulfate, trace element components, gas-phase organic material, and NO x , NO 2 , and O 3 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 PM 2.5 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 PM 2.5 . 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 Ambient Primary and Secondary Fine Particulate Matter at the Pittsburgh National Energy Laboratory Particulate Matter Characterization Site Using Positive Matrix Factorization and a Potential Source Contributions Function Analysis

“…In addition, the PSCF analysis ( Figure 6) indicates this factor is also consistently associated with transport to the Pittsburgh area from the west or southwest, consistent with previous observations 7,8,11,23 and consistent with the occurrence of emissions from a large number of SO 2 sources in this region. Facilities in this direction include coal-fired power plants, coke processing industries, steel mills, oil refineries, and other industrial sources located along the Ohio River from Steubenville, 50 km west of Pittsburgh, and other sources along the Ohio River to the south and west of Steubenville ( Figure 1).…”

“…It is assumed that the CMU Nitrate factor would be a subset of the Secondary SVM (Factor 5) reported here. However, the SVM during the time period of both studies was dominated by OM 3,8 and the two sources were not comparable. The CMU PMF metal dataset did not include Al and Si, the elements that dominated in the identification of crustal source in the NETL PMF analysis reported here.…”

“…This is consistent with previous observations for the Pittsburgh urban area. 7,8 As with the diesel source, there was no strong PSCF directional component for the factor attributed to gasoline combustion emissions.…”

“…Approaches to apportion carbonaceous fine particulate matter (PM 2.5 ) include using the ratio of the particulate organic carbon (OC) to elemental carbon (EC) to approximate the extent of secondary formation, 1,2 chemical mass balance, 3 specific organic markers, 4,5 UNMIX 4,6 and Positive Matrix Factorization (PMF). 4,7 The PMF analyses results at the Pittsburgh National Energy Laboratory (NETL) and the Carnegie-Mellon University (CMU) Supersite for a 2001 July intensive study previously reported by Eatough et al 7,8 included the estimation of primary and secondary contributions of fine particulate mass, organic carbonaceous material, and ammonium sulfate using Particle Concentrator-BYU Organic Sampling System (PC-BOSS) multiple samples per day. The source apportionment results obtained from 24-hr integrated samples over a 2-yr period are reported here.…”