Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Advanced Analytical Technologies, Überlandstrasse 129, CH-8600, Dübendorf, Switzerland.
Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Advanced Analytical Technologies, Überlandstrasse 129, CH-8600, Dübendorf, Switzerland; RWTH, Aachen University, Institute for Environmental Sciences, Worringerweg 1, D-52074, Aachen, Germany; ETH, Swiss Federal Institute of Technology, Institute of Biogeochemistry and Pollutant Dynamic, Universitätsstrasse 16, CH-8092, Zurich, Switzerland.
Chemosphere. 2019 Jul;226:744-754. doi: 10.1016/j.chemosphere.2019.03.169. Epub 2019 Mar 29.
Short-chain chlorinated paraffins (SCCPs) are polyhalogenated hydrocarbons as are hexachlorocyclohexanes (HCHs) and hexabromocyclododecanes (HBCDs). They all have been classified as persistent organic pollutants (POPs) under the UN Stockholm Convention. Per se such compounds are transformed slowly in the environment, transported over long distances and accumulate in biota. Several Sphingomonadacea strains isolated from HCH dump sites have evolved to express enzymes that can transform HCHs and HBCDs. We hypothesized that LinA2, a dehydrohalogenase expressed in such bacteria, may also transform CPs to chlorinated olefins (COs). Three mixtures of penta- to deca-chlorinated undecanes (C), dodecanes (C) and tridecanes (C) were exposed to LinA2. High-resolution full-scan mass spectra (R∼8'000) of CPs and COs were obtained applying a soft ionization method, enhancing chloride-adduct [M+Cl] formation. A mathematical deconvolution procedure was used to separate interfering spectra to verify that LinA2 indeed catalyzed the conversion of CPs to COs. About 20-40% of the material was transformed in 24 h, about 50-70% was converted in 200 h. A bimodal first-order kinetic model could describe transformations of reactive and persistent CPs. Under the given conditions reactive CPs (τ = 1.4-6.9 h) were converted 30 to 190-times faster than the persistent ones (τ = 150-260 h). Proportions of persistent isomers (p) varied from 60 to 80%. Lower chlorinated homologues contained higher proportions of persistent isomers. In conclusion, SCCP mixtures contain both, material that is readily converted by LinA2, and persistent material that is not or only slowly transformed.
短链氯化石蜡（SCCPs）与六氯环己烷（HCHs）和六溴环十二烷（HBCDs）一样，都是多卤代烃。它们均被联合国《斯德哥尔摩公约》归类为持久性有机污染物（POPs）。此类化合物本身在环境中转化缓慢，可远距离迁移，并在生物群中积累。从 HCH 倾倒点分离出的几种鞘氨醇单胞菌菌株已进化出表达可转化 HCHs 和 HBCDs 的酶。我们假设，LinA2 是在这些细菌中表达的脱卤化酶，也可能将 CPs 转化为氯化烯烃（COs）。三种五氯至十氯十一烷（C）、十二烷（C）和十三烷（C）混合物暴露于 LinA2 中。采用软电离方法获得 CP 和 CO 的高分辨率全扫描质谱（R∼8'000），增强了氯加合物 [M+Cl] 的形成。使用数学解卷积程序分离干扰光谱，以验证 LinA2 确实催化了 CPs 向 COs 的转化。24 小时内约有 20-40%的物质发生转化，200 小时内约有 50-70%的物质发生转化。一阶动力学模型可以描述反应性和持久性 CPs 的转化。在给定条件下，反应性 CPs（τ=1.4-6.9 h）的转化速度比持久性 CPs（τ=150-260 h）快 30-190 倍。持久性异构体（p）的比例从 60%到 80%不等。低氯同系物含有更高比例的持久性异构体。总之，SCCP 混合物既包含易被 LinA2 转化的物质，也包含不易或缓慢转化的持久性物质。
