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UPTAKE AND PHOTODEGRADATION OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN SORBED TO GRASS FOLIAGE
Citation:
McCrady, J. AND S. Maggard. UPTAKE AND PHOTODEGRADATION OF 2,3,7,8-TETRACHLORODIBENZO-P-DIOXIN SORBED TO GRASS FOLIAGE. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/J-94/162 (NTIS PB94160488), 1993.
Description:
Plant uptake rates were determined for airborne 2,3,7,8-TCDD using grass foliage. he primary elimination mechanisms for 2,3,7,8-TCDD from grass, photodegradation and volatility, were measured in natural sunlight, filtered sunlight which reduced UV-B radiation, and in the dark. apid sorption of 2,3,7,8-TCDD vapor to grass resulted in an initial uptake rate constant of 1750 h-1. hotodegradation of 2,3,7,8-TCDD and volatility of 2,3,7,8-TCDD from the foliage back into the air were both significant eliminate-on mechanisms. he photodegradation half-life of 2,3,7,8-TCDD sorbed to grass and exposed to natural sunlight was 44 h (ka = 0.0156 h-1). The half-life resulting from volatility of 2,3,7,8-TCDD from the grass foliage was 128h k2 = 0.0054 h-1) . A two-compartment uptake and clearance model was used to estimate a theoretical air-to-grass bioconcentration factor of 7.9 x 106 (vol./vol.) . The uptake and elimination rates and the bioconcentration factor for 2,3,7,8-TCDD and grass are compared to results reported for 1,2,3,4-TCDD and azalea (18). he rapid photodegradation of 2,3,7,8-TCDD sorbed to grass indicates this elimination mechanism should be considered when estimating plant contamination from 2,3,7,8-TCDD.