• Temporal and spatial trends of fine particulate matter composition in Fairbanks, Alaska

      Nattinger, Kristian C.; Simpson, William R.; Guerard, Jennifer J.; Cahill, Catherine F. (2016-08)
      Fairbanks, AK experiences extreme winter pollution episodes that result in violations of the Fine Particulate (PM₂.₅) National Ambient Air Quality Standards and pose significant health risks for inhabitants. We analyzed the 2006-2014 wintertime (November 1 to the end of February) PM₂.₅ composition from four sampling sites in the Fairbanks North Star Borough (FNSB) to provide insight into sources and trends. We developed conversions for particulate carbon measurements that were sampled/analyzed with different methods to allow quantitative comparisons. Using these conversions, we found excellent mass closure between PM₂.₅ mass concentration reconstructed from particulate composition and directly measured PM₂.₅ mass concentration. The North Pole Fire Station #3 site (NPFS3) PM₂.₅ mass concentration is nearly double the concentration at other sites in the FNSB and significantly different (t-test on log normalized data, 95% conf.). We observe significant differences (t-test, 95% conf.) in the PM₂.₅ composition between the NPFS3 site and all other sites for most components. Comparison to source profiles indicates that the difference in SO₄²⁻/PM₂.₅ and organic carbon (OC)/PM₂.₅ ratios is attributable to greater use of wood heat in the areas surrounding the NPFS3 site than in Fairbanks. This interpretation is supported by the results of the Home Heating Survey, which found a greater reported use of wood for heat in North Pole than in Fairbanks. Interannual variability is observed in the PM₂.₅ composition. The increase in fuel oil price in 2009 is correlated with an increase in OC/PM₂.₅ ratio and a decrease in the SO₄²⁻/PM₂.₅. The interannual variability of the SO₄²⁻/PM₂.₅ and NH₄⁺/PM₂.₅ ratios are correlated. The particles appear to be neutralized until 2010 when a drop in NH₄⁺ is not accompanied by as large of a drop in anions leaving the particles acidic. The mean sulfur oxidation ratio is 5%, attributable to primary and possible secondary oxidation of SO₂. The results of our analysis supports modeling results that wood smoke contributes a large fraction to the Fairbanks area PM₂.₅. Our work also identified changes in the concentration, composition and spatial distribution of PM₂.₅ that may help air quality managers in identifying effective PM₂.₅ control strategies.