Department of Chemistry, University of Toronto, Toronto, Ontario, Canada.
Environ Sci Technol. 2010 May 1;44(9):3305-10. doi: 10.1021/es9028183.
Wastewater treatment plants (WWTPs) have been identified as a major source of perfluorocarboxylates (PFCAs) to aqueous environments. The observed increase in PFCA mass flows from WWTP influent to effluent suggests the biodegradation of commercial fluorinated materials within the WWTP. Commercial fluorinated surfactants are used as greaseproofing agents in food-contact paper products as well as leveling and wetting agents. As WWTPs are likely the major fate of these surfactants, their biodegradation may be a source of PFCA production. One class of commercial surfactants, the polyfluoroalkyl phosphates (PAPs), have been observed in WWTP sludge. While PAPs have been shown to degrade into PFCAs in a rat model, the present study investigates their microbial fate to determine whether the biodegradation of PAPs within a WWTP-simulated system will contribute to the load of PFCAs released. PAPs are applied commercially in mixed formulations of different chain lengths and substitution at the phosphate center. The effect of chain length and phosphate substitution on the biodegradation of PAPs was investigated by incubating mixtures of 4:2, 6:2, 8:2, and 10:2 monosubstituted PAPs (monoPAPs) in an aerobic microbial system and by separately incubating the 6:2 monoPAP and 6:2 disubstituted PAP (diPAP) for 92 days. Headspace sampling revealed production of the fluorotelomer alcohols (FTOHs) from the hydrolysis of the PAP phosphate ester linkages. Analysis of the aqueous phase revealed microbial transformation of the PAPs to the final PFCA products was possible. The majority of the oxidation products observed were consistent with previous investigations that have suggested fluorotelomer precursor compounds degrade predominantly via a beta-oxidation-like mechanism. However, in this study, the detection of odd-chain PFCAs suggests that other pathways may be important. The present study demonstrated microbially mediated biodegradation of PAPs to PFCAs. This observation, together with the diPAP concentrations observed in WWTP sludge, suggest PAPs-containing commercial products may be a significant contributor to the increased PFCA mass flows observed in WWTP effluents.
污水处理厂 (WWTP) 已被确定为向水生环境中排放全氟羧酸 (PFCAs) 的主要来源之一。从 WWTP 进水到出水的 PFCA 质量流量增加表明，商业含氟材料在 WWTP 中发生了生物降解。商业含氟表面活性剂被用作食品接触纸制品的防油剂，以及平整剂和润湿剂。由于 WWTP 很可能是这些表面活性剂的主要归宿，因此它们的生物降解可能是 PFCA 产生的一个来源。一类商业表面活性剂，即多氟烷基磷酸酯 (PAPs)，已在 WWTP 污泥中被发现。虽然已经证明 PAPs 在大鼠模型中会降解为 PFCAs，但本研究调查了它们的微生物命运，以确定 WWTP 模拟系统中 PAPs 的生物降解是否会导致释放的 PFCAs 负荷增加。PAPs 以不同链长和磷酸酯中心取代的混合配方在商业上应用。通过在好氧微生物系统中孵育 4:2、6:2、8:2 和 10:2 单取代 PAP（单 PAPs）的混合物，并分别孵育 6:2 单 PAP 和 6:2 双取代 PAP（双 PAP）92 天，研究了链长和磷酸酯取代对 PAP 生物降解的影响。顶空采样显示，通过 PAP 磷酸酯键的水解产生了全氟代醇 (FTOH)。对水相的分析表明，PAP 向最终 PFCA 产物的微生物转化是可能的。观察到的大多数氧化产物与先前的研究一致，这些研究表明，氟代前体化合物主要通过类似于β-氧化的机制降解。然而，在这项研究中，奇数链 PFCAs 的检测表明其他途径可能很重要。本研究证明了 PAP 经微生物介导转化为 PFCAs。这一观察结果，再加上 WWTP 污泥中观察到的双 PAP 浓度，表明含 PAP 的商业产品可能是导致 WWTP 出水中 PFCA 质量流量增加的一个重要因素。
