HR: 1340h
AN: A43C-0059    [Abstracts]
TI: Mercury Flux Studies on Urban Surface Covers
AU: * Gabriel, M C
EM: mark.c.gabriel@ua.edu
AF: The University of Alabama, Department of Civil and Environmental Engineering, Box 870205, Tuscaloosa, AL 35487 United States
AU: Williamson, D G
EM: dwilliamson@coe.eng.ua.edu
AF: The University of Alabama, Department of Civil and Environmental Engineering, Box 870205, Tuscaloosa, AL 35487 United States
AB: In an effort to advance the state-of-art understanding of mercury's global transport, a study was conducted to measure and evaluate the in-situ flux of total mercury from common urban surfaces (weathered blacktop, compact soil, grass, street runon) with spatial (3 km radius) and seasonal change, and quantify the affect of irrigation on flux from blacktop and street runon. Additional experiments examined the relative flux contribution from each surface under uniform meteorological conditions. Average seasonal flux (ng/m2-hr) measurements are as follows: 0.569 (Winter) 0.274 (Spring) for grass; 0.0910 (Winter) 0.612 (Spring) for blacktop; 1.750 (Winter) 7.451 (Spring) for soil. Relatively high terrestrial adsorption/deposition (-1.5 ng/m2-hr) occurred for grass during the early morning (3am to 7 am) in Winter. No adsorption occurred for soil in either season. Using multi-regression analyses, statistically significant (p = 0.05) time series relationships were found between Hg flux and (1) UV and total solar radiation (2) surface temperature and (3) surface moisture for each cover type. For Winter flux contribution studies, 76% of total Hg (mass) emitted at this site came from soil, 14% from grass, and 10% from blacktop. In the Spring study, emissions increased an additional 3% for soil and grass. Artificial irrigation experiments were performed on blacktop and street runon to (1) determine if wet deposition delivers a pool of oxidized mercury that is available for reduction and release, and (2) simulate release mechanisms of Hg during wet weather events. No statistically significant difference (p = 0.05) in flux was found when de-ionized (DI) and rain water were separately applied to blacktop and street runon. This suggests that oxidized mercury forms in rainwater do not increase flux for blacktop and street runon during wet weather events. However, DI and rainwater create, on average, a 7-fold increase in flux immediately after irrigation from preexisting mercury on these surfaces. Geochemical Hg de-sorption and physical displacement of air-containing-Hg by H20 are the primary methods of Hg release and resulting flux. Our analyses also show that no statistically significant spatial variability in flux exists for the studied urban area on this scale.
DE: 1065 Trace elements (3670)
DE: 0312 Air/sea constituent fluxes (3339, 4504)
DE: 0315 Biosphere/atmosphere interactions
DE: 0330 Geochemical cycles
DE: 0345 Pollution--urban and regional (0305)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting