Xu Lin, Liu Nannan, Pei Siyao, Jiang Fengjiao, Zhao Rusong, Li Na, Cai Yaqi
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 330106, China.
Environ Sci Technol. 2025 Jul 15;59(27):13983-13991. doi: 10.1021/acs.est.5c02698. Epub 2025 Jul 1.
This study systematically investigated profiles of siloxanes in the photovoltaic (PV) production industry of China and their influences on methylmercury (MeHg) generation. The ubiquitous distribution of 21 siloxanes in PV production additives/accessories [<LOD-626 μg/g, detection frequency (df) = 6.7-100%, = 45] indicated their potential environmental emission, which was confirmed by wide detection (<LOD-14.6 mg/L, df = 30-100%, = 10) of siloxanes and their hydrolysis product [MeSi(OH)] in wastewaters from ten PV production facilities. Overall, annual siloxanes usage (59-463 thousand tonnes) during PV production accounted for 3.9-30% of their total consumption in China. Annual mass loads (389 tonnes) in PV production wastewater were 1.7 times those (from personal care products) in national domestic wastewater. In MeHg-containing (4.35-185 ng/L) wastewaters of PV production, concentrations of ∑siloxanes were positively correlated ( = 0.44, < 0.05) with MeHg/THg ratios, suggesting potential contribution of Si-CH bonds to mercury methylation. Laboratory experiments in simulated PV wastewater indicated that compared with dimethylsiloxanes, other methylsiloxanes and methylsilanol containing electrophilic groups (phenyl, vinyl, and hydroxyl) would lead to 1.3-7.1 times larger abiotic mercury methylation fractions (0.14-4.0% after 18 h incubation) by accelerating the cleavage of Si-CH. In addition, both hydrolysis of Si-O bonds (in acidic conditions) and generation of Si-F bonds (in F-rich wastewater) could accelerate mercury methylation by introducing electrophilic groups.
本研究系统调查了中国光伏（PV）生产行业中硅氧烷的概况及其对甲基汞（MeHg）生成的影响。21种硅氧烷在光伏生产添加剂/配件中的普遍分布[<检测限-626μg/g，检测频率（df）=6.7-100%，n=45]表明它们可能向环境排放，这在十个光伏生产设施废水中硅氧烷及其水解产物[MeSi(OH)]的广泛检测[<检测限-14.6mg/L，df=30-100%，n=10]中得到了证实。总体而言，光伏生产过程中硅氧烷的年使用量（59-46.3万吨）占中国其总消费量的3.9-30%。光伏生产废水中的年质量负荷（389吨）是全国生活污水中（来自个人护理产品）的1.7倍。在含MeHg（4.35-185ng/L）的光伏生产废水中，总硅氧烷浓度与MeHg/THg比值呈正相关（r=0.44，p<0.05），表明Si-CH键对汞甲基化有潜在贡献模拟光伏废水的实验室实验表明，与二甲基硅氧烷相比，其他含亲电基团（苯基、乙烯基和羟基）的甲基硅氧烷和甲基硅烷醇通过加速Si-CH的裂解，会导致非生物汞甲基化分数大1.3-7.1倍（孵育18小时后为0.14-4.0%）。此外，Si-O键的水解（在酸性条件下）和Si-F键的生成（在富含F的废水中）都可以通过引入亲电基团来加速汞甲基化。
