Photochemical degradation of short-chain chlorinated paraffins in aqueous solution by hydrated electrons and hydroxyl radicals
Photochemical degradation of short-chain chlorinated paraffins in aqueous solution by hydrated electrons and hydroxyl radicals
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DOI：
10.1016/j.chemosphere.2022.134732
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发表时间：
2022-05-17
期刊：
影响因子：
8.8
通讯作者：
Aeppli, Christoph
中科院分区：
文献类型：
--
作者：
DiMento, Brian P.;Tusei, Cristina L.;Aeppli, Christoph
短链氯化石蜡（SCCP）是多氯烷烃（C-10-C-13，氯含量为40-70%）的复杂混合物，被归类为持久性有机污染物。然而，在其环境退化方面，特别是在地表沃茨光化学降解的有效性和机制方面，存在着知识空白。光化学产生的水合电子（e（（aq））（-））已被证明在环境相关条件下比羟基自由基（（OH）-O-中心点）更有效地降解高度氯化的化合物，羟基自由基可以降解广泛的有机污染物。本研究旨在评估e（（aq））（-）和（OH）-O-中心点降解短链氯化石蜡的潜力。为此，在实验室条件下研究了短链氯化石蜡模型化合物的降解情况，即光化学生成e（（aq））（-）或（OH）-O-中心点。由此产生的短链氯化石蜡e（（aq））（-）降解速率常数与众所周知的氯化农药处于同一数量级。实验中的存在下的OH产生类似或更高的二级速率常数。所调查的短链氯化石蜡的e（（aq））（-）和（OH）-O-中心点降解速率常数的趋势与其他氯化化合物的趋势一致，氯含量越高，e（（aq））（-）的降解速率常数就越高，而（OH）-O-中心点的降解速率常数就越低。在氯碳比约为0.6以上时，e（（aq））（-）二级速率常数高于（OH）-O-中心点反应的速率常数。该研究的结果还表明，短链氯化石蜡很可能在阳光照射下的表面沃茨中容易发生降解，而溶解的有机物作为光化学产生的e（（aq））（-）和（OH）-O-中心点的来源，会促进短链氯化石蜡的降解。
Short-chain chlorinated paraffins (SCCPs) are a complex mixture of polychlorinated alkanes (C-10-C-13, chlorine content 40-70%), and have been categorized as persistent organic pollutants. However, there are knowledge gaps about their environmental degradation, particularly the effectiveness and mechanism of photochemical degradation in surface waters. Photochemically-produced hydrated electrons (e((aq))(-)) have been shown to degrade highly chlorinated compounds in environmentally-relevant conditions more effectively than hydroxyl radicals ((OH)-O-center dot), which can degrade a wide range of organic pollutants. This study aimed to evaluate the potential for e((aq))(-) and (OH)-O-center dot to degrade SCCPs. To this end, the degradation of SCCP model compounds was investigated under laboratory conditions that photochemically produced e((aq))(-) or (OH)-O-center dot. Resulting SCCP degradation rate constants for e((aq))(-) were on the same order of magnitude as well-known chlorinated pesticides. Experiments in the presence of & BULL;OH yielded similar or higher second-order rate constants. Trends in e((aq))(-) and (OH)-O-center dot degradation rate constants of the investigated SCCPs were consistent with those of other chlorinated compounds, with higher chlorine content producing in higher rate constants for e((aq))(-) and lower for (OH)-O-center dot. Above a chlorine:carbon ratio of approximately 0.6, the e((aq))(-) second-order rate constants were higher than rate constants for (OH)-O-center dot reactions. Results of this study furthermore suggest that SCCPs are likely susceptible to degradation in sunlit surface waters, facilitated by dissolved organic matter as a source of photochemically produced e((aq))(-) and (OH)-O-center dot.