The fate of fipronil in modular estuarine mesocosmsElectronic supplementary information (ESI) available: table of GC-ECD and GC-ITMS retention times, RT, for fipronil analytes; mass spectra of fipronil, fipronil desulfinyl, fipronil sulfide, fipronil sulfone and fipronil amide; and aqueous product distribution of fipronil in estuarine mesocosms over the experimental timescale. See http://www.rsc.org/suppdata/em/b3/b307304a/
The degradation and corresponding product manifold for the pesticide fipronil was determined in three replicate estuarine mesocosms. Aqueous fipronil concentrations rapidly decreased over the 672 h timescale of the experiment (95% removal). Loss was apparently first-order in fipronil, although there appeared to be a change in the removal mechanism after 96 h that corresponded to a dramatic slowdown in its disappearance. The reduction product of fipronil, fipronil sulfide, was not detected in the water column; however, it formed rapidly in sediments and was identified as the major product of fipronil degradation in the system (20% yield at 672 h, with respect to initial fipronil concentration). Fipronil sulfone is thought to form primarily via biological oxidation; and, although it was generated rapidly in the water column (10% yield), only trace amounts were detected in the sediment (1% yield). The direct photolysis product of fipronil, fipronil desulfinyl, was present in all samples; it formed rapidly in the water column (4% yield) and partitioned into the sediment phase (7% yield) over the course of the experiment. The mass balance on fipronil and associated products was 42% at 672 h.