Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, California 94720-1710, USA.
Environ Sci Technol. 2012 Sep 4;46(17):9342-9. doi: 10.1021/es302274g. Epub 2012 Aug 17.
A new method was developed to quantify concentrations of difficult-to-measure and unidentified precursors of perfluoroalkyl carboxylic (PFCA) and sulfonic (PFSA) acids in urban runoff. Samples were exposed to hydroxyl radicals generated by thermolysis of persulfate under basic pH conditions and perfluoroalkyl acid (PFAA) precursors were transformed to PFCAs of related perfluorinated chain length. By comparing PFCA concentrations before and after oxidation, the concentrations of total PFAA precursors were inferred. Analysis of 33 urban runoff samples collected from locations around the San Francisco Bay, CA indicated that PFOS (2.6-26 ng/L), PFOA (2.1-16 ng/L), and PFHxA (0.9-9.7 ng/L) were the predominant perfluorinated compounds detected prior to sample treatment. Following oxidative treatment, the total concentrations of PFCAs with 5-12 membered perfluoroalkyl chains increased by a median of 69%, or between 2.8 and 56 ng/L. Precursors that produced PFHxA and PFPeA upon oxidation were more prevalent in runoff samples than those that produced PFOA, despite lower concentrations of their corresponding perfluorinated acids prior to oxidation. Direct measurements of several common precursors to PFOS and PFOA (e.g., perfluorooctanesulfonamide and 8:2 fluorotelomer sulfonate) accounted for less than 25% of the observed increase in PFOA, which increased by a median value of 37%. Exposure of urban runoff to sunlight, advanced oxidation processes, or microbes could result in modest, but measurable, increases in concentrations of PFCAs and PFSAs.
开发了一种新方法来量化城市径流中难以测量和未识别的全氟烷基羧酸 (PFCA) 和全氟磺酸 (PFSA) 酸前体的浓度。样品在碱性 pH 条件下通过过硫酸盐热解产生的羟基自由基暴露，并将全氟烷基酸 (PFAA) 前体转化为相关全氟链长的 PFCAs。通过比较氧化前后的 PFCA 浓度，可以推断出总 PFAA 前体的浓度。对从加利福尼亚州旧金山湾周围地点采集的 33 个城市径流样本的分析表明，在进行样品处理之前，PFOS（2.6-26 ng/L）、PFOA（2.1-16 ng/L）和 PFHxA（0.9-9.7 ng/L）是主要检测到的全氟化化合物。在氧化处理后，具有 5-12 个全氟烷基链的 PFCAs 的总浓度中位数增加了 69%，或在 2.8 和 56 ng/L 之间。在氧化后产生 PFHxA 和 PFPeA 的前体比那些产生 PFOA 的前体在径流样本中更为普遍，尽管它们在氧化前的相应全氟酸浓度较低。对 PFOS 和 PFOA 的几种常见前体（例如，全氟辛烷磺酰胺和 8:2 氟代烷烃磺酸盐）进行的直接测量仅占 PFOA 观察到的增加量的不到 25%，PFOA 的中位数增加了 37%。城市径流暴露于阳光、高级氧化过程或微生物可能会导致 PFCAs 和 PFSA 的浓度适度增加，但可测量。
