4种短链全氟化合物替代物在城市污水处理厂的污染特征研究

全氟辛烷羧酸(perfluorooctanoic acid,PFOA)和全氟辛烷磺酸(perfluorooctyl sulfonate,PFOS)等长链全氟化合物(perfluorinated compounds,PFCs)具有持久性、生物累积性和毒性,近年来发现一些短链PFCs具有相对较短的半衰期,可以成为PFOA和PFOS的替代品,这些物质包括C4和C6结构的PFCs,如全氟丁烷羧酸(perfluorobutanoic acid,PFBA)、全氟己烷羧酸(perfluorohexanoic acid,PFHx A)、全氟丁烷磺酸(perfluorobutyl sulfonate,PFBS)和全氟己烷磺酸(perfluorohexyl sulfonate,PFHx S)。为解析我国城市污水厂短链PFCs污染水平和地域分布特征,本研究调查了我国不同地区17座城市污水处理厂的进水、二沉出水和污泥中4种短链PFCs的分布和浓度水平。结果表明4种短链PFCs、PFOA和PFOS在17座污水厂进水中检出率均为100%(6种目标物单体浓度范围:0.19~274.72 ng·L-1);污泥中PFOS和PFOA检出率为100%(PFOS:2.08~72.31 ng·g-1,PFOA:1.03~24.81 ng·g-1),PFBA、PFHx A检出率为100%(0.60~3.33 ng·g-1),PFBS和PFHx S的检出率分别为42.11%和63.16%。在污水厂进水中,将PFOA和PFOS与其同类的短链PFCs浓度进行比较,发现短链PFCs分别相对于PFOA和PFOS的比例最高可达93.47%和94.57%。4种短链PFCs、PFOA和PFOS的地域分布差异明显,总浓度呈现出华东、华南地区高于西北、东北、华北地区的趋势,其中华东地区调查的污水处理厂浓度最高。污水厂4种短链替代物主要通过污水排放,不同污水厂的日排放总量(污泥和出水)为0.25~273.07 g·d-1,万吨水排放量范围为0.04~1.37 g。研究将为我国全氟化合物替代物污染和控制提供数据基础和科学依据。

Pollution Characteristics of Four Short Chain Perfluorinated Compound Substitutes in Municipal Wastewater Treatment Plant

Perfluorooctanoic acid (PFOA), perfluorooctyl sulfonate (PFOS) and other long-chain perfluorinated compounds (PFCs) are the persistent, bio-accumulative and environmentally toxic chemical compounds. In recent years, some short-chain PFCs with relatively short half-life could be substituted for PFOA and PFOS, including C4 and C6 compounds such as perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), perfluorobutyl sulfonate (PFBS) and perfluorohexyl sulfonate (PFHxS). In order to determine the concentrations and distributions of short chain PFCs in various regions of China, the influent, secondary effluent and sludge samples of 17 municipal wastewater treatment plants (WWTPs) were investigated. This study revealed that the detection rates of four short chain PFCs, PFOA and PFOS in influents were 100% (0.19-274.72 ng L^-1). Meanwhile, the detection rates of PFOA and PFOS in sludge were also 100% (PFOS: 2.08-72.31 ng g^-1, PFOA: 1.03-24.81 ng g^-1). At the same time, the detection rates of PFBA and PFHxA were 100% (0.60-3.33 ng g^-1), and however, the detection rates of PFBS and PFHxS were 42.11% and 63.16%. Comparing short chain PFCs with PFOS and PFOA in influent, it was observed that the ratio of short chain perfluorocarboxylic acids (PFCAs) to PFOA and the ratio of short chainperfluorinated sulfonic acids (PFSAs) to PFOS were 93.47% and 94.57%.The concentrations of four short chain PFCs, PFOA and PFOS were significantly different in different regions. Generally, the total concentrations of PFCs in east China and south China were higher than those of northwest, northeast and north China, and the highest was in east China. The four short chain PFCs in wastewater treatment plants are mainly discharged through sewage water. Their total daily discharge (through sludge and effluent) from the different wastewater treatment plants was 0.25-273.07 g d^-1, and the discharge per ten thousand tons of water was 0.04-1.37 g. The study will provide a scientific basis for the control of the short chain substitutes of PFCs in China.