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SOLAR RADIATION DOSE AND PHOTOTOXICITY OF POLYCYCLIC AROMATIC HYDROCARBONS: A CASE STUDY
Citation:
Diamond, S A., D. R. Mount, AND S. L. Stark. SOLAR RADIATION DOSE AND PHOTOTOXICITY OF POLYCYCLIC AROMATIC HYDROCARBONS: A CASE STUDY. Presented at SETAC Annual Meeting, Austin, TX, November 9-13, 2003.
Description:
The toxicity of polycyclic aromatic hydrocarbons increases by as much as three orders of magnitude in the presence of solar radiation. The risk of this photoactive toxicity is thus based on both tissue concentrations of potentially photo activated compounds and the levels of subsequent (or simultaneous) sunlight exposure, specifically the ultraviolet (UV) wavelength range. Levels of exposure to solar radiation are determined by location, date, time of day, weather, landscape features that may reduce incoming sunlight, and water column components that absorb UV radiation. Over the last several years we have conducted studies at PAH contaminated sites in St. Louis Harbor, near Duluth, MN, USA. As part of these studies UV exposure has been measured and modeled extensively. Global Information Systems (GIS) models that incorporate landscape features were used in conjunction with additional, complex solar radiation models, field measurement of vegetation, water column UV attenuation, and historical weather data to characterize the UV radiation climate at the site. In general, estimated UV exposure, indexed to wavelengths known to activate most PAHs, ranged by over an order of magnitude with highest exposures estimated for open water areas of the site. Depending on location, landscape features reduced exposure by up to 70%. Attenuation in the water column was consistent across time and location and, at a depth of 10cm, reduced exposure by approximately 90%. Over a thirty year period (1961 to 1990) cloud cover reduced exposure by an average of 25 % between April 1 and September 30, although year to year variability was extensive. These weather data also provide a means to incorporate probabilities into PAH phototoxicity risk assessment. Dose estimates for the site will be presented visually and also quantitatively for selected scenarios and endpoints based on laboratory research.