Armitage James M, Macleod Matthew, Cousins Ian T
Department of Applied Environmental Science (ITM), Stockholm University, SE-10691 Stockholm, Sweden.
Environ Sci Technol. 2009 Aug 1;43(15):5830-6. doi: 10.1021/es900753y.
A global-scale multispecies mass balance model was used to simulate the long-term fate and transport of perfluorocarboxylic acids (PFCAs) with eight to thirteen carbons (C8-C13) and their conjugate bases, the perfluorocarboxylates (PFCs). The main purpose of this study was to assess the relative long-range transport (LRT) potential of each conjugate pair, collectively termed PFC(A)s, considering emissions from direct sources (i.e., manufacturing and use) only. Overall LRT potential (atmospheric + oceanic) varied as a function of chain length and depended on assumptions regarding pKa and mode of entry. Atmospheric transport makes a relatively higher contribution to overall LRT potential for PFC(A)s with longer chain length, which reflects the increasing trend in the air-water partition coefficient (K(AW)) of the neutral PFCA species with chain length. Model scenarios using estimated direct emissions of the C8, C9, and C11 PFC(A)s indicate that the mass fluxes to the Arctic marine environment associated with oceanic transport are in excess of mass fluxes from indirect sources (i.e., atmospheric transport of precursor substances such as fluorotelomer alcohols and subsequent degradation to PFCAs). Modeled concentrations of C8 and C9 in the abiotic environment are broadly consistent with available monitoring data in surface ocean waters. Furthermore, the modeled concentration ratios of C8 to C9 are reconcilable with the homologue pattern frequently observed in biota, assuming a positive correlation between bioaccumulation potential and chain length. Modeled concentration ratios of C11 to C10 are more difficult to reconcile with monitoring data in both source and remote regions. Our model results for C11 and C10 therefore imply that either (i) indirect sources are dominant or (ii) estimates of direct emission are not accurate for these homologues.
使用一个全球尺度的多物种质量平衡模型来模拟含8至13个碳（C8 - C13）的全氟羧酸（PFCA）及其共轭碱全氟羧酸盐（PFCS）的长期归宿和迁移。本研究的主要目的是仅考虑直接来源（即制造和使用）的排放，评估每个共轭对（统称为PFCA）的相对长距离迁移（LRT）潜力。总体LRT潜力（大气 + 海洋）随链长而变化，并取决于关于pKa和进入模式的假设。对于链长较长的PFCA，大气迁移对总体LRT潜力的贡献相对较高，这反映了中性PFCA物种的气 - 水分配系数（K（AW））随链长增加的趋势。使用C8、C9和C11 PFCA估计直接排放量的模型情景表明，与海洋运输相关的北极海洋环境质量通量超过间接来源（即前体物质如氟调聚物醇的大气运输以及随后降解为PFCA）的质量通量。非生物环境中C8和C9的模拟浓度与表层海水中现有的监测数据大致一致。此外，假设生物累积潜力与链长呈正相关，C8与C9的模拟浓度比与生物群中经常观察到的同系物模式相符。C11与C10的模拟浓度比在源区和偏远地区都更难与监测数据相符。因此，我们关于C11和C10的模型结果意味着要么（i）间接来源占主导地位，要么（ii）这些同系物的直接排放估计不准确。
