RP12 Application of Spatially Explicit Techniques in Ecological Risk Assessment
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(CAL-1117-833827) Modeling exposure of mercury dispersion in Richland and Lexington Counties, South Carolina, US.

Calle, N.¹, Alava, J.J.^{2, 3}, ¹ Department of Environmental Health Science, Arnold Public Health School, University of South Carolina, Columbia, South Carolina, USA² Center for Coastal Environmental Health and Biomolecular Research (CCEHBR)/NOAA/NOS/NCCOS, Charleston, South Carolina, USA³ School of the Environment, University of South Carolina, Columbia, South Carolina, USA

ABSTRACT- A Gaussian plume dispersion model was used to estimate the cumulative exposure of mercury concentrations of local industries located in Richland and Lexington Counties and their surroundings areas. An estimate of the mean exposure of mercury concentrations for women and children under five years old, two of the most vulnerable subpopulations due to mercury exposure, were calculated. The Gaussian plume model was run assuming constant emission rate, constant wind velocity and direction for slightly stable atmospheric conditions. The maximum estimated mercury concentration was extremely lower (0.51 ng/m³) than the observed average mercury concentrations (12,860 ng/m³ ; range = 360–64,900 ng/m³) from the station SC-19 located in Richland County. This scenario suggested that industrial local contributions are smaller since the monitoring station measures the overall mercury concentrations from different local sources other than industries, regional and global mercury concentrations contributions and the existing natural background concentrations, in addition to the limitations of the model which could underestimate the results. The study showed that mean exposure mercury concentration, for different atmospheric conditions scenarios, range from 3.43 x 10-4 to 8.71 x 10^-2 ng/m³) for children and 3.56 x 10^-4 to 6.77 x 10^-2 ng/m3 for women in Richland County and from 3.75 x 10^-3 to 3.86 x 10^-2 ng/m³ for children and from 4.41 x 10^-3 to 4.51 x 10^-2 ng/m³ for women. These concentrations were below of the elemental mercury permissible levels in ambient air (15 x 103 ng/m³ for 24 hours exposure) indicated by the World Health Organization. This model was useful to assess the impact of industrial mercury emissions to the expose population.

Key words: Gaussian dispersion model, Exposure concentration, Air emissions, Mercury