Behavior of sewage sludge-derived PAHs on pasture

A field experiment was setup to investigate the retention of PAHs by pastur e grass following sludge application. In addition to information on compoun d-specific loss rates, the influence of meteorological variables and sludge -pasture contact time gn the weathering process were investigated. The rate s of loss were compound specific with half-lives ranging from <1 to 10 d. T he lighter PAHs were rapidly lost from the grass surface primarily by volat ilization. For the intermediate and heavier PAHs, loss was slower with rain playing an important role in the weathering process. Growth dilution was a lso important in reducing the contaminant levels in the grass. The effect o f sludge-pasture contact time prior to weathering by rain on the residual l evels remains unclear. In terms of risk of exposure, there is the potential for persistent organic contaminants to be introduced into the grazing anim al food chain if sewage sludge is applied to pasture land.