A Study of Atmospheric Deposition of Air Toxics to the Waters of Puget Sound
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Air pollutants can be deposited in many forms such as rain, snow, and gases. Urban centers are major sources of combustion-derived particulate matter, black carbon, and volatile organic carbon to the atmosphere. Expansion of urban centers in the 20th Century, especially in coastal areas, and their concomitant influence on land use, vehicular traffic, and industrial growth have been responsible for major outputs of combustion-derived hydrocarbon to the atmosphere and fallout of such carbon-rich particulate matter over the urban airsheds. This, in turn, has led to local health effects on human populations and a decrease in the quality of regional hydrological cycling. Due to continuous coastal development and increase in population in Puget Sound, Washington, it is vital to determine what the impacts of such growth have had on air and water quality and if greater needs in regulation are needed to curtail emissions. A bi-weekly deposition study of atmospheric particulate matter at seven sites around the Puget Sound (from urban to rural) have been performed for the purpose of developing appropriate regional and temporal estimates of contaminant fluxes to the surface of Puget Sound. The present study focuses on anhydrosugars, molecular markers of biomass combustion, in atmospheric particles to characterize the sources of combustion-derived materials. These are then compared to combustion-derived condensed hydrocarbon (PAH) concentrations and their signature ratios. Sample series were extracted for anhydrosugars and analyzed via gas chromatography mass spectrometry. All stations showed temporal variability in fluxes of levoglucosan, a major biomass combustion anhydrosugar, over the four months studied (Aug-Nov, 2008), with values ranging close to two orders of magnitude (15-450 uGu/m2.day). Replicate sampling at different stations during the study period showed a good reproducibility (<15% variability). Regional similarities were observed with major fluxes reported (230-450 μg/m2.day) in September to mid-October. This peak follows the occurrence of major wildfire events reported in the Pacific Northwest during August-September. A second smaller peak in November suggests the start of winter and domestic heat-derived wood burning. Levoglucosan concentrations are not correlated to pyrogenic PAHs in all but one rural station suggesting a predominant biomass source of combustion at that site. A specific PAH ratio associated with biomass combustion (1,7 DMP/[1,7+2,6 DMP]) was positively correlated to levoglucosan at all stations confirming the usefulness of this ratio for tracing non fossil fuel sources of pyrogenic PAHs in natural environments.
Aguirre, Danielle (2009). A Study of Atmospheric Deposition of Air Toxics to the Waters of Puget Sound. Available electronically from