Release of tetrabromobisphenol A (TBBPA)-derived non-extractable residues in oxic soil and the effects of the TBBPA-degrading bacterium Ochrobactrum sp. strain T

Tetrabromobisphenol A (TBBPA) forms large amount of non-extractable residues (NER) in soil. However, the stability of TBBPA-NER with TBBPA degrader in soil had not been determined. In this study, a C-14-tracer was used to follow the release and alteration of TBBPA-derived NER during 214 days of incubation in oxic soil and in the presence or absence of the TBBPA-degrading bacterium Ochrobatrum sp. strain T. In the absence of strain T, 1.89% of the TBBPA and its metabolites were slowly released from the NER, with TBBPA as the predominant component, accompanied by 2.47% mineralization by day 91 of the incubation. The addition of active cells strongly stimulated the release and mineralization of NER (10.93% and 4.64%, respectively), reduced the amount of the ester-linked fraction, and transformed NER from humin-bound to HA-bound forms. Cells added to the soil in sterilized form had much smaller effects on the stability and internal alterations of NER. Among the ester-linked compounds, 47.4% consisted of TBBPA; two metabolites were so detected. These results provide new information on the stability and internal transformation of TBBPA-NER in soil during its long-term incubation and underlines the importance of microbial TBBPA degraders in determining the composition of NER in soil.