Characterization of chemical composition and sources of PM2.5 aerosols
Fine particles (PM2.5), ≤2.5 μm, reduce visibility, affect global climate, and human health. Therefore we investigated the chemical composition and sources of PM2.5 aerosols in metropolitan New York (Queens) and two rural locations, Pinnacle State Park (∼350 km to the northwest) and Whiteface Mt (∼390 km north, ∼1.5 km amsl). Daily PM2.5 aerosols were collected on Zeflour filters, July 1, 2001 to June 30, 2002. Filters were analyzed for SO42− by ion-chromatography and by inductively coupled plasma mass spectrometry for Mg, Al, Ca, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Cd, Sb and Pb in water-leached and acid digested aliquots of the aerosols. The highest annual mean concentrations were observed at Queens followed by Pinnacle State Park and Whiteface Mountain. Since the bioavailibility is an important factor in determining the health impact of various species the concentrations of the soluble fraction as well as the total were determined. The soluble fractions at the three sites were essentially the same. The mean solubilities were (%): Mg, 94 ± 21; V, 91 ± 13; Zn, 88 ± 22; As, 87 ± 20; Mn, 83 ± 20; Pb, 83 ± 21; Se, 77 ± 21; Sb, 75 ± 17; Co, 65 ± 16; Fe, 58 ± 21; and Ni, 55 ± 20. The oxides of V, Mn, As, Se and Sb are highly soluble. It appears that these elements were produced during high temperature combustion. The contributions from nearby and distant regional sources were evaluated by correlating the daily-observed concentrations with 3-day backward HYSPLIT 4 air trajectories. At Queens, 44–55% of SO4 2− was transported from the Midwest, whereas ∼60% was transported to Pinnacle State Park and Whiteface Mt. The transported component of trace metals at Queens were (%): Se, ∼50; Ni, Sb and Pb, ∼30–40; Mg, Mn, As, Co and Fe, ∼20–27; and V and Zn, <20 are transported. Based on Positive Matrix Factorization analysis, the emissions from coal and oil-fired power plants motor vehicles, sea salt and soil were the major contributors. The SO42− aerosols contributed up to ∼50% of the PM2.5 mass. Hence, any strategy to minimize the atmospheric PM2.5 mass must curtail emissions from fossil fuel burning.