Emission influences on air pollutant concentrations in New York state: II. PM2.5 organic and elemental carbon constituents

Abstract

Abstract Analyses of 20-year records of emissions and ambient air pollutant concentrations were combined with receptor modeling to enhance current understanding of the relative contributions of different emission source types to fine particle (PM2.5) elemental carbon (EC) and organic carbon (OC) fractions in New York State. Two receptor models, principal component analysis (PCA) and positive matrix factorization (PMF), were applied to determine trends in source contributions to OC and EC at the principal study site, Pinnacle State Park (PSP), between 2001 and 2015. The PSP results are interpreted in relation to state and regional emission and pollutant trends. Multi-site average SO4 concentrations showed a linear relationship to reductions in anthropogenic emissions of sulfur dioxide (SO2) in New York, surrounding states, and eastern Canada from 6.1 million metric tons in 1995 to 1.0 million metric tons in 2015. On average, 0.5 ± 0.1 μg m-3 sulfate (SO4) originated from natural SO2 emissions or from outside the region. Emission-reduction programs yielded measurable reductions of ambient OC, EC, and SO4 concentrations, but OC and EC improvements at PSP were partly offset by increasing concentrations of biomass-burning OC and EC. Between 2001 and 2015, biomass burning contributions increased the PSP 2001–2003 mean EC and OC concentrations by 13–18% and 23–30%, respectively. With decreases in other source contributions, net total reductions of PSP 2001–2003 mean EC and OC concentrations were 36–58% and 26–45%, respectively. Contributions to PSP EC and OC declined from four source types: (1) fossil-fuel combustion associated with SO2, (2) combustion not associated with SO2 (tentatively identified as mobile sources), (3) crustal OC and EC, and (4) sulfate-associated OC and EC. SO2-associated fossil-fuel and biomass-burning OC and EC concentrations were higher in winter, sulfate and non-SO2 combustion OC and EC concentrations were higher in summer, and crustal OC and EC were higher in spring. Spatial and temporal coherence of mean OC and EC concentrations, which was observed as a constant slope of annual-average OC-vs-EC across sites and years, indicates that multiple sites were influenced by similar emission source types and responded similarly to emission reductions during the study period. The lowest mean annual OC and EC concentrations were recorded at the most remote site, Whiteface Mountain Base (WMB), averaging 1.0 ± 0.05 μg m-3 and 0.2 ± 0.01 μg m-3, respectively; these values may represent regional background concentrations.