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Environmental fate and transformation of fluorotelomer compounds in landfill leachate Hamid, Hanna


Fluorotelomer compounds (FTCs) and their transformation products are routinely detected in landfill leachate, their environmental fate and transformation in leachate are unknown. This study focused on measuring bio- and phototransformation of spiked FTCs in landfill leachate, using lab-scale experiments under environmentally relevant conditions. Spiked 8:2 fluorotelomer alcohol (FTOH) and 6:2 fluorotelomer sulfonate (FTS) and their known biotransformation products were quantified in sediment-leachate microcosms and their headspaces over 90 days. The results showed that 8:2 FTOH and 6:2 FTS persisted (half-life >>30 d) in landfill leachate-sediment microcosms. Slower biotransformation led to significant partitioning of semi-volatile 8:2 FTOH to the gas phase, suggesting that landfills may act as secondary sources for semi-volatile FTOHs in the environment. C6 – C8 and C4 – C6 perfluorocarboxylic acids (PFCAs) were the most abundant products for 8:2 FTOH and 6:2 FTS, respectively. The effect of organic carbon and ammonia concentrations in 6:2 FTS biotransformation and PFCA formation were investigated with sediment microcosms, to which deionized water (DI) and various amounts of leachate were added. Greater biotransformation of 6:2 FTS was observed in leachate added microcosms, compared to DI microcosms, likely reflecting substrate dependency of 6:2 FTS biotransformation. Substrate limiting conditions in DI microcosms resulted in a slightly higher formation of (C4 – C6) PFCAs compared with leachate added microcosms. To understand roles of microbial communities (e.g., heterotrophic, autotrophic) in 6:2 FTS biotransformation and PFCA production, experiments were carried out with specific substrates (i.e., glucose, ammonia) and ammonia-oxidizing inhibitor (allylthiourea) using inoculum prepared from sediment. Both heterotrophic and autotrophic bacteria were able to biotransform 6:2 FTS to varying extents. Greater biotransformation of 6:2 FTS and C4 – C6 PFCAs formation were observed in the presence of ammonia oxidizers, indicating that biological nitrification is likely to increase 6:2 FTS biotransformation and PFCA production. Phototransformation of 6:2 FTS and PFCA production were investigated in leachate under simulated sunlight. The results showed that 6:2 FTS was undergoing indirect photolysis in leachate (half-life of ∽15 days), suggesting indirect photolysis of 6:2 FTS is likely a relevant transformation pathway in sunlit aquatic environments.

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