Xu Yiping, Spurlock Frank, Wang Zijian, Gant Jay
Department of Environmental Sciences, University of California, Riverside, California 92521, USA.
Environ Sci Technol. 2007 Dec 15;41(24):8394-9. doi: 10.1021/es071911c.
Sediment toxicity from hydrophobic organic compounds (HOCs) is complicated by chemical partitioning among multiple phases and sediment-specific bioavailability. In this study, we used three hydrophobic pyrethroid insecticides as test compounds and derived 10-d median lethal concentrations (LC50s) for Chironomus tentans in three different sediments. The LC50s were expressed using HOC concentrations on a bulk sediment basis (C(S)), organic carbon (OC)-normalized sediment basis (C(S-OC)), porewater basis (C(PW)), dissolved organic carbon (DOC)-normalized porewater basis (C(PW-DOC)), and freely dissolved porewater basis (C(free)). The bulk phase C(S) and C(PW) yielded highly variable LC50s across sediment types, whereas the use of normalized concentrations C(S-OC) and C(PW-DOC) generally reduced variability due to sediment type but not that due to aging. In contrast, LC50s based on C(free) were essentially independent of sediment conditions. The sediment pore water samples contained approximately 20-90 mg L(-1) DOC, and the C(free) expressed as a percentage of the total bulk pore water concentration ranged from 9 to 28% for fenpropathrin (mean = 19%), 8 to 18% for bifenthrin (mean = 13%), and 3 to 8% for cyfluthrin (mean = 6%) across the different sediments. These results indicate thatthe use of C(free) reduces uncertainties caused by sediment variables such as OC properties and aging effects.
疏水性有机化合物（HOCs）造成的沉积物毒性因多相之间的化学分配和沉积物特定的生物可利用性而变得复杂。在本研究中，我们使用三种疏水性拟除虫菊酯杀虫剂作为测试化合物，并得出了三种不同沉积物中摇蚊的10天半数致死浓度（LC50s）。LC50s分别以沉积物总量基础上的HOC浓度（C(S)）、有机碳（OC）归一化沉积物基础上的浓度（C(S-OC)）、孔隙水基础上的浓度（C(PW)）、溶解有机碳（DOC）归一化孔隙水基础上的浓度（C(PW-DOC)）以及自由溶解孔隙水基础上的浓度（C(free)）来表示。沉积物总量相的C(S)和C(PW)在不同沉积物类型中产生的LC50s变化很大，而使用归一化浓度C(S-OC)和C(PW-DOC)通常会降低因沉积物类型导致的变异性，但不会降低因老化导致的变异性。相比之下，基于C(free)的LC50s基本与沉积物条件无关。沉积物孔隙水样品中DOC含量约为20 - 90 mg L(-1)，在不同沉积物中，甲氰菊酯的C(free)占总孔隙水浓度的百分比范围为9%至28%（平均 = 19%），联苯菊酯为8%至18%（平均 = 13%），氯氟氰菊酯为3%至8%（平均 = 6%）。这些结果表明，使用C(free)可减少由沉积物变量（如OC性质和老化效应）引起的不确定性。
