Fate of triclosan and evidence for reductive dechlorination of triclocarban in estuarine sediments
The biocides triclosan and triclocarban are wastewatercontaminants whose occurrence and fate in estuarine sedimentsremain unexplored.Weexamined contaminant profiles in 137Cs/7Be-dated sediment cores taken near wastewater treatmentplants in the Chesapeake Bay watershed (CB), Maryland andJamaica Bay (JB),NewYork. In JB, biocide occurrences trackedthe time course of biocide usage and wastewater treatmentstrategies employed, first appearing in the 1950s (triclocarban)and 1960s (triclosan), and peaking in the late 1960s and1970s (24 ( 0.54 and 0.8 ( 0.4 mg/kg dry weight, respectively).In CB, where the time of sediment accumulation was not aswell constrained by 137Cs depth profiles, triclocarban was onlymeasurable in 137Cs-bearing sediments, peaking at 3.6(0.6 mg/kg midway through the core and exceeding 1 mg/kg in recentdeposits. In contrast, triclosan concentrations were low ornot detectable in theCBcore. Analysis ofCBsediment by tandemmass spectrometry produced the first evidence for completesequential dechlorination of triclocarban to the transformationproducts dichloro-, monochloro-, and unsubstituted carbanilide,which were detected at maxima of 15.5 ( 1.8, 4.1 ( 2.4,and0.5(0.1 mg/kg, respectively. Concentrations of all carbanilidecongeners combined were correlated with heavy metals ( R 2>0.64, P <0.01), thereby identifying wastewater as the principalpathway of contamination. Environmental persistence overthe past 40 years was observed for triclosan and triclocarbanin JB, and for triclocarban's diphenylurea backbone in CBsediments.