Effect of exposure to decabromodiphenyl ether and tetrabromobisphenol A in combination with lead and cadmium on soil enzyme activity

- Urease was the most sensitive to the exposure of both FRs and HM.
- BDE209 exhibited a higher eco-toxicological potential to soil enzymatic activity than TBBPA.
- The exposure levels of HM with FRs were in line with our observation on enzymatic activity and speciation of Cd and Pb.

The two most widely used brominated flame retardants (BFRs), decabromodiphenyl ether (BDE209) and tetrabromobisphenol A (TBBPA), co-exist prevalently with heavy metals (HM), at e-waste recycling sites (EWRSs). The laboratory incubation we conducted, which 50 g of dried soil spiked with Pb, Cd, BDE209 and TBBPA, were incubated 180 d in the dark at 25 °C, and kept the soil moisture at 60%. The results demonstrated that the inhibition ratio of 4 kinds of the enzyme (catalase, dehydrogenase, polyphenol oxidase and urease) in the combined of BFRs and HMs treatments were −127%-66%, -72%-49%, -52%-76% and 54%-107% respectively, and in TBBPA or BDE209 contaminant treatments were −135%-18%, -16%-31%, -18%-15% and −17%-83% respectively. Urease was more sensitive to the combined contamination than catalase, dehydrogenase and Polyphenol oxidase. BDE209 exhibited a higher eco-toxicological potential to soil enzymatic activity than TBBPA. The co-existence of HM induces a stronger response of enzymatic activity to the artificial contamination. The availability of the residual fraction in the later stage of incubation, along with the results of principal component analysis demonstrated that there may be different mechanisms responsible for the generation of residual and extractable fractions of HM.