The occurrence of the antimicrobials triclocarban (TCC) and triclosan (TCS) was investigatedin agricultural soils following land application of biosolids using liquid chromatography–tandem mass spectrometry (LC–MS–MS) with negative ion multimode ionization.The method detection limits were 0.58 ng TCC/g soil, 3.08 ng TCC/g biosolids, 0.05 ng TCS/gsoil and 0.11 ng TCS/g biosolids and the average recovery from all of the sample matriceswas >95%. Antimicrobial concentrations in biosolids from three Michigan wastewatertreatment plants (WWTPs) ranged from 4890 to 9280 ng/g, and from90 to 7060 ng/g, for TCCand TCS respectively. Antimicrobial analysis of soil samples, collected over two years, fromten agricultural sites previously amended with biosolids, indicated TCC was present athigher concentrations (1.24–7.01 ng/g and 1.20–65.10 ng/g in 2007 and 2008) compared toTCS (0.16–1.02 ng/g and from the method detection limit, <0.05–0.28 ng/g in 2007 and 2008).Soil antimicrobial concentrations could not be correlated to any soil characteristic, or to thetime of last biosolids application, which occurred in either 2003, 2004 or 2007. To ourknowledge, our data represent the first report of TCC, and the first comparison of TCC andTCS concentrations, in biosolids-amended agricultural soils. Such information is importantbecause approximately 50% of US biosolids are land applied, therefore, any downstreameffects of either antimicrobial are likely to be widespread.
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