Identification of 4-Hydroxycumyl Alcohol As the Major MnO_2-Mediated Bisphenol A Transformation Product and Evaluation of Its Environmental Fate

摘要

Bisphenol A (BPA), an environmental contaminant with weak estrogenic activity, resists microbial degradation under anoxic conditions but is susceptible to abiotic transformation by manganese dioxide (MnO_2). BPA degradation followed pseudo-first- order kinetics with a rate constant of 0.96 (±0.03) min~(-1) in the presence of 2 mM MnO_2 (0.01796 w/w) at pH 7.2. 4-hydroxycumyI alcohol (HCA) was the major transformation product, and, on a molar basis, up to 64% of the initial amount of BPA was recovered as HCA. MnO_2 was also reactive toward HCA, albeit at 5-fold lower rates, and CO_2 evolution (i.e., mineralization) occurred. In microcosms established with freshwater sediment, HCA was rapidly biodegraded under oxic, but not anoxic conditions. With a measured octanol-water partition coefficient (Log K_(ow)) of 0.76 and an aqueous solubility of 2.65 g L~(-1), HCA is more mobile in saturated media than BPA (Log K_(ow), = 2.76; aqueous solubility = 0.31 g L~(-1)), and therefore more likely to encounter oxic zones and undergo aerobic biodegradation. These findings corroborate that BPA is not inert under anoxic conditions and suggest that MnO_2-mediated coupled abiotic-biotic processes may be relevant for controlling the fate and longevity of BPA in sediments and aquifers.