全氟辛酸(PFOA)厌氧生物可降解性

Anaerobic Biodegradability of Perfluorooctanoic Acid(PFOA)

全氟辛酸(PFOA)的可生物降解性对阐明其环境归趋具有重要意义.根据前人的还原降解研究成果,采用PFOA摩尔回收率、氟离子浓度、乙酸根浓度、2H-PFOA[F(CF_2)_6CHFCOOH]浓度和短链(<C8)全氟羧酸(PFCAs)浓度的变化等作为指标,研究PFOA的厌氧可生物降解性.结果表明,活菌降解样中PFOA摩尔回收率由培养期初(3d)的101%±5%降至培养期末(250 d)的85.6%±3.9%,而氟离子浓度则由培养期初(3 d)的0.59 mg·L^(-1)±0.02 mg·L^(-1)增至培养期末(250 d)的0.63 mg·L^(-1)±0.02 mg·L^(-1),且检出了一定量的乙酸根、2H-PFOA和短链PFCAs,但是这却和其对照样中相应指标的变化类似,且不存在显著性差异.由此可见,尽管热力学计算结果表明还原脱氟产生的热量足够维持微生物生命活动,但在本研究的实验条件下却并没有发现PFOA可被生物降解的证据.

Perfluorooctanoic acid（ PFOA）,one of the most typical representatives of perfluoroalkyl surfactants（ PASs）,has relatively high detection rate and level of pollution,and the accumulation of PFOA in the environment has been a serious threat to human health and security of the whole ecological environment. Therefore,studies on anaerobic biodegradability of PFOA are very important for elucidation of its environmental fate. This study used anaerobic sludge from municipal sewage treatment plant（ WWTP） and 5. 0mg·L- 1vitamin B12（ VB12） as catalysts for the degradation of PFOA in the anaerobic environment. The anaerobic biodegradability of PFOA was examined by liquid chromatography tandem mass spectrometry（ LC-MS / MS） and ion chromatography while some indictors,such as molar recoveries of PFOA as well as concentrations of fluoride,acetate,2H-PFOA（ F（ CF_2）_6CHFCOOH）,and shorter chain（ C8） perfluorocarboxylates（ PFCAs） etc.,were selected according to the reductive degradation results reported by predecessors.The results indicated that the molar recoveries of PFOA significantly decreased from 101% ± 5% at the initial incubation（ 3 d） to85. 6% ± 3. 9% at the end of incubation（ 250 d）,while fluoride concentrations significantly increased from 0. 59 mg·L^-1± 0. 02mg·L^-1at the initial incubation（ 3 d） to 0. 63 mg·L^-1± 0. 02 mg·L^-1at the end of incubation（ 250 d） in biodegradation samples.Meanwhile,certain amounts of acetate,2H-PFOA,and short-chain PFCAs,the products of reductive degradation of PFOA reported by precursors,were detected in biodegradation samples. However,there was no significant difference between these indicators in biodegradation samples and their corresponding controls. Therefore,no evidences were found to certify the anaerobic biodegradability of PFOA under the conditions described in present study,though the microorganisms were able to obtain enough energy for growth from reductive defluorination of PFOA in the thermodynamic aspects.