Network Meta-Analysis and Systematic Review of Conditions Facilitating Microbial Biotransformation of 6:2 and 8:2 Fluorotelomer Alcohols to Perfluoroalkyl Carboxylates

Abstract

A network meta-analysis (NMA) was conducted to explore associations between fluorotelomer alcohol (FTOH) transformation and factors affecting perfluoroalkyl carboxylate (PFCA) evolution in synthetic and environmental media. Data were extracted from a total of 14 primary research articles aligned with bench-scale investigations into 6:2 and/or 8:2 FTOH biotransformation; these data were subjected to a random effect NMA to simultaneously evaluate influences of various experimental conditions on biotransformation. Effectiveness rankings were used to summarize experimental conditions promoting FTOH to PFCA transformation from the greatest to least effect on conversion. Results related to atmospheric conditions and/or electron accepting processes (from greatest to least effect on PFCA formation) are as follows: aerobic, nitrate reducing conditions, microoxic, anaerobic (unamended electron acceptor [EA]), sulfate reducing conditions, and iron reducing conditions. A greater association with PFCA formation was observed under mesophilic conditions compared to psychrophilic conditions. Multiple conditions that promote FTOH to PFCA bioconversion in environmental matrices were identified in this study. Several conditions under which transformation is unlikely have also been identified, suggesting the possibility of long-term FTOH retention in impacted media with limited short- and long-chain PFCA mobilization. Our findings further suggest the need for advancing our understanding of FTOH transformation in media receiving excessive nitrogen from anthropogenic sources.