Toxicology and Environmental Research and Consulting, The Dow Chemical Company, Midland, MI, USA.
Department of Chemistry, Trent University, Peterborough, ON, Canada.
Chemosphere. 2018 Mar;195:325-335. doi: 10.1016/j.chemosphere.2017.12.071. Epub 2017 Dec 12.
We investigated the response times of eight volatile methylsiloxanes (VMSs) in environmental systems at different scales from local to global, with a particular focus on overall loss rates after cessation of emissions. In part, this is driven by proposals to restrict the use of some of these compounds in certain products in Europe. The GloboPOP model estimated low absolute Arctic Contamination Potentials for all VMSs and rapid response times in all media except sediment. VMSs are predicted to be distributed predominantly in air where they react with OH radicals, leading to short response times. After cessation of emissions VMSs concentrations in the environment are expected to decrease rapidly from current levels. Response times in specific water and sediment systems were evaluated using a dynamic QWASI model. Response times were sensitive to both physico-chemical properties and environmental characteristics. Degradation was predicted to play the most important role in determining response times in water and sediment. In the case of the lowest molecular weight VMSs such as L2 and D3, response times were essentially independent of environmental characteristics due to fast hydrolysis in water and sediment. However, response times for the other VMSs are system-specific. They are relatively short in shallow water bodies but increase with depth due to the diminishing role of volatilization on concentration change as volume to surface area ratio increases. In sediment, degradation and resuspension rates also contribute most to the response times. The estimated response times for local environments are useful for planning future monitoring programs.
我们研究了在不同尺度（从局部到全球）的环境系统中，八种挥发性甲基硅氧烷（VMS）的响应时间，特别关注排放停止后总体损失率。部分原因是，欧洲有提议限制某些产品中使用这些化合物。GloboPOP 模型估计所有 VMS 的绝对北极污染潜力较低，除沉积物外，所有介质的响应时间都较快。VMS 预计将主要分布在空气中，在空气中它们与 OH 自由基反应，导致较短的响应时间。排放停止后，环境中的 VMS 浓度预计将从目前水平迅速下降。使用动态 QWASI 模型评估了特定水和沉积物系统中的响应时间。响应时间对物理化学性质和环境特征均敏感。降解被预测为在水中和沉积物中确定响应时间的最重要因素。对于 L2 和 D3 等最低分子量的 VMS，由于在水和沉积物中快速水解，响应时间基本与环境特征无关。但是，其他 VMS 的响应时间是特定于系统的。它们在浅水体内较短，但随着深度的增加而增加，因为随着体积与表面积比的增加，挥发对浓度变化的作用减弱。在沉积物中，降解和再悬浮速率也对响应时间贡献最大。对局部环境的估计响应时间可用于规划未来的监测计划。
