Sorption and degradation of triclosan in sediments and its effect on microbes

•Triclosan sorption is strongly related to total organic carbon contents in sediments.•Degradation of triclosan in sediment is affected by sorption and redox condition.•Triclosan has minor effects on microbes at environmental relevant levels.•The effects of triclosan on microbes can be reduced by sorption.

Sorption and degradation behavior of triclosan (TCS) and its effect on microbes were studied in three sediments spiked at different concentration levels (1, 10, and 100 μg g−1). TCS showed a strong affiliation to all the sediments with linear adsorption coefficients (Kd) that varied from 220 to 1092 L g−1, and the adsorption capacity is related to the total organic carbon (TOC) contents of the sediments. The half-lives of TCS varied from 55 to 239 days, and were longer in sediment with higher Kd. TCS showed minor effect on the activities of fluorescein diacetate hydrolase, dehydrogenase, alkaline phosphatase, and urease in the 1 μg g−1 treatment, but at higher levels, a short-term effect was observed followed by a rapid recovery except the urease activity in sediment with the lowest adsorption capacity. PCA plots of phospholipid fatty acid showed that the phenotypic community in sediments with low TOC were more sensitive to TCS. A positive relation between bacterial biomass and total microbial biomass suggests that changes of bacteria biomass were responsible for changes of total microbial biomass in treatments. Denaturing gradient gel electrophoresis analysis of the 16 S rDNA showed that the bacterial community structure deviated further away from the control at higher TCS concentration levels, with similarity coefficients in Un-weighted Pair Group Mathematics Average clustering between control and 100 μg g−1 treatment varied from 0.38 to 0.73. Both degradation rate and toxic effects of TCS decreased in sediment with higher sorption capacity, which can be attributed to a reduced bioavailablity.