Volatile Organic Compound Losses from Sewage Sludge-Amended Soils.

Volatile organic compounds (VOCs) applied to soil in sludge have been assumed to disappear quickly and completely. The VOC behavior in sludge-amended soils has been studied previously only in laboratory systems where the sludged soil has been spiked with compounds of interest. Behavior in these systems may not necessarily represent compound behavior in field soils to which contaminated sludge is added. A series of laboratory microcosm experiments were designed therefore to investigate the behavior of toluene, ethyl benzene, o-, m-, and p-xylene applied to soil in contaminated sludge, and factors influencing loss processes. The VOC loss from sludge-amended soil was well described by a simple one step pseudo-first-order model but in certain soils was better described by a two step first-order model. Volatilization was the predominant loss process. Rates of loss depended on sludge application rate, method of sludge application, soil properties, and on compound characteristics. Experiments indicated that spiking sludge-amended soils gave a reasonable indication of VOC loss rates from systems amended with contaminated sludge at least over a period of 23 d. The majority of VOCs applied to soils in sludge volatilizes quickly to the atmosphere over a few to 10s of days with a small fraction lost more slowly. Potential for VOC crop uptake, livestock ingestion, and contamination of ground water (the transfer routes of most concern) is low under routine, managed applications of sewage sludge to agricultural land