The role of biofilm as a bio-accumulator of Ultraviolet Filters in porous media

Ultraviolet filters (UVFs) are contaminants of emerging concern (CECs) produced and used in large quantities worldwide. They are constituents of a large number of personal care and hygiene products and other consumer goods. Benzophenones, such as benzophenone-3 (BP-3), benzophenone-4 (BP-4) and avobenzone (AVO), are among the most used. These compounds are characterized by being photo-stable and lipophilic. Although it is highly known the lipophilicity of these compounds, their monitoring in porous media is centered in the aqueous phase. Nevertheless, their high logK_ow make foreseeable the accumulation in more lipophilic phases such as biofilm or sedimentary organic matter. For that, in this work we have highly characterized a Managed Aquifer Recharge system with a very intensive monitoring of benzophenones and transformation products in the three phases: water, biofilm and sedimentary organic matter. Furthermore, we have contrasted our results with a numerical model, which was based on the partition of UVFs under equilibrium conditions. Our results show that biofilm acted as an additional environmental compartment favoring the retention and degradation of UVFs in porous media. Indeed, it played a central role in the fate of these compounds, controlling both sorption and biodegradation. With this we believe that the current understanding of the organic compounds fate should incorporate it as a new compartment capable of bio-accumulate these compounds.