Gillis, J. D., Price, G. W. and Stratton, G. W. 2014. Detection and degradation of organic contaminants in an agricultural soil amended with alkaline-treated biosolids. Can. J. Soil Sci. 94: 595-604. The agricultural use of wastewater biosolids is a common practice in many countries, but concerns exist regarding the presence of organic wastewater contaminants that remain in the land-applied biosolids. The objective of this study was to determine if contaminants present in biosolids are detectable in soil following land application. A suite of organic contaminants were monitored by gas chromatograph with mass spectrometer in agricultural soil samples from a site amended with increasing rates of alkaline-treated biosolids. Triclosan, a common antimicrobial agent, was detected at levels greater than the reporting limit in an environment-controlled incubation study and validated through in situ field samples from soils receiving the same alkaline-treated biosolid. A rapid decrease in triclosan concentration was observed during the first few weeks of the incubation study, with concentrations decreasing from 92±26 to 20±2 ng g^-1 (average 78% decrease) after 4 mo. The field results indicate that triclosan in fall-applied may persist overwinter. However, a rapid decrease in triclosan concentration during the spring and summer months led to levels lower than predicted following the spring application, and levels below our reporting limit (up to 85% decrease) by the end of the study. Removal is posited to be through aerobic microbial degradation.