Abstract

Laboratory incubation studies were conducted to assess the persistence of ten volatile organic compounds (VOCs) in seven soils treated with 3% dw of anaer-obically digested municipal sludge. The VOCs were probable municipal sludge contaminants and the soils represented wide ranges of constituents likely to sorb organic compounds, e.g., organic carbon (1.3 to 12%) and clay (7 to 50%). The VOCs were spiked into soils at 50 mg kg-1 dw of soil, except for trichloro-ethylene and chloroform which were at 2.5 mg kg-1 dw. Three general patterns of VOC losses from soils were identified: (1) complete volatilization at room temperature within 24 h, (2) complete volatilization/degradation within 144 to 288 h, and (3) incomplete volatilization/degradation within 288 h. All VOC losses were consistent with first-order kinetics and indicated a combination of a rapid initial kinetic (0 to 4 h) followed by a slower kinetic. The slower kinetic was assumed to be more relevant to field VOC losses than the rapid kinetic, and first-order half-lives were calculated using the 4- to 288-h experimental data. The half-lives ranged from 5.5 to 1,926 h with a median value of 70 h, and generally increased with increasing boiling points of the VOCs and with increasing organic carbon contents of the soils. These laboratory findings indicate that VOCs in land-applied sludge are unlikely to represent a hazard to agriculture.

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