聚二甲基硅氧烷被动加标法在水毒性测试中的应用：现状与进展

PDMS-based passive dosing method and its application in aquatic toxicity tests:Status and perspectives

被动加标(Passive dosing)可维持水中疏水性化合物的恒定浓度,利于准确测定化合物的溶解度、分配系数和毒性效应.相对于传统的主动加标,被动加标可及时补充由于壁吸附、挥发、光解、水解、生物吸收等因素引起的受试化合物损失,维持测试体系中化合物浓度的稳定,增强数据的准确性.聚二甲基硅氧烷(Polydimethylsiloxane,PDMS)是最常用的加标介质,有良好的生物兼容性,已成功用于多种化合物的细胞和生物个体毒性测试,然而在被动加标的发展中也遇到系列瓶颈问题.PDMS被动加标的应用局限于中等疏水性的化合物(lg K_(OW)=3—6),如多环芳烃(PAHs)和部分多氯联苯(PCBs),却极少用于高疏水性化合物(lg K_(OW)>6);主要用于小体系、短时间实验,而与环境更相关的大体系、长时间暴露的应用尚待研究;缺乏定量方法,难以估算测试体系中PDMS对化合物损失的补偿能力;被动加标方法缺乏标准化.因此,未来发展需加强研究化合物从PDMS释放与水体浓度补充的关联,在理论研究基础上完善被动加标技术规范,发展适用于大体系、长时间暴露的被动加标方法.此外,通过被动加标方法有效地结合原位采样与实验室毒性测试,利于在生态风险评价中综合考虑污染物生物可利用性的影响.

Passive dosing has been used to maintain constant concentrations of hydrophobic organic compounds in water, resulting in more accurate measurements of their solubility, partitioning coefficients and adverse effects. Compared with traditional active dosing, passive dosing is advantageous in compensating the loss of chemicals in water due to glassware adsorption,volatilization,photolysis,hydrolysis,and organism uptake etc. As a result,more constant water concentrations and more accurate measurements can be achieved. Polydimethylsiloxane（PDMS） isthe most commonly used material for passive dosing. With high biocompatibility,PDMS has been successfully used for dosing various compounds into water,yet the application of the method has some limitations. So far,passive dosing has been mainly used for chemicals with lg KOWranging from3 to 6,such as polycyclic aromatic hydrocarbons and some polychlorinated biphenyls. On the other hand,its application for highly hydrophobic compounds with lg KOWvalues over 6 was limited. Most studies using passive dosing were conducted in small testing systems with short exposure time,although long term testing in large systems in more environmentally relevant. Moreover,there is no method for quantifying the capacity of PDMS to buffer chemical loss in water,neither the standard guide for using passive dosing methods. Therefore,future development of passive dosing methods should consider the following aspects,including more studies on the relationship between release of chemicals from PDMS and their compensation in water,improving standard guides on the application of passive dosing on the basis of theoretical research,and establishing new methods for long-term and large-system testing. In addition,incorporating in situ sampling and laboratory toxicity testing by using passive sampling and passive dosing simultaneously would help to take bioavailability into consideration in ecological risk assessment.