Effect of Residual NAPLs on the Transport of Bisphenol A and Bisphenol S in Saturated Porous Media

Endocrine disrupter, like bisphenol A (BPA) and bisphenol S (BPS), is frequently detected in the subsurface environment, imposing threats to the groundwater quality and public health. However, current understanding of environmental fate and transport of BPA/BPS is still not clear, especially with respect to those in the subsurface media with trapped non-aqueous phase liquids (NAPLs). In this study, the effect of residual NAPLs on the retention and transport of BPA/BPS in the saturated sand and soil media was investigated using column experiments. The results showed that residual NAPLs (i.e., xylene and perchloroethylene (PCE)) inhibited the transport of BPA in the sand columns, and the inhibit effect of xylene was greater than that of PCE. While the presence of NAPLs showed little influence on the transport of BPS in the sand columns, in soil A (sandy soil), the residual NAPLs had similar effect on the retention and transport of BPA and BPS. Both BPA and BPS showed higher retention in the soil B columns than in the sand and soil A columns due to soil B's higher organic matter contents, which can strongly sorb BPA/BPS. The presence of residual NAPLs reduced the retention of BPA/BPS in the soil B columns because the NAPLs blocked the sorption sites of the soil organic matter for BPA/BPS. This study demonstrates the importance of residual NAPLs, types of media, properties of contaminants, and their interactions to the fate and transport of BPA/BPS in saturated porous media.