虽然平衡分配(EqP)方法已被证明可以通过沉积物毒性测试有效预测沉积物中的非离子有机化学物质对底栖生物的不利影响,在使用相同物种的纯水和全沉积物毒性测试中,仅进行了有限数量的研究,并验证了基于EqP的毒性评估的有效性。为了进一步检查EqP方法在广泛的疏水性中应用的有效性,我们使用一种流行的水生甲壳类动物物种进行了吸附/解吸实验以及纯水和沉积物毒性测试,大型水蚤(48小时),和底栖物种Hyalellaazteca(96h)为六种典型的多环芳烃(PAHs),具有三到五个环和胺衍生物:蒽,菲,荧蒽,芘,苯并[a]芘,二苯并[a,h]蒽,和1-氨基芘。确定了线性吸附系数,其范围为2.7×102(菲)和1.2×104L/kg(苯并[a]芘),这在很大程度上取决于疏水性,而在解吸测试中,水溶液浓度在24小时后保持稳定。作为在仅水暴露系统中进行急性毒性测试的结果,蒽和二苯并[a,h]发现蒽对这两种物种都无毒,而中位数效应/致死浓度(EC50/LC50)被确定为从0.66(苯并[a]芘)到330μg/L(菲),对于D.magna和H.azteca,从11(1-氨基芘)到180μg/L(菲),分别。在这些化合物中,三种多环芳烃和三种,四,每个五个戒指,和1-氨基芘进行了沉积物-水毒性测试。在沉积物-水测试中,菲和芘的LC50是H.azteca纯水测试的3至6倍,而D.magna的EC50是1.1至2.0倍。相比之下,苯并[a]芘(BaP)在沉积物-水毒性测试中的EC50/LC50比H.azteca和D.magna的仅水测试高5倍以上。1-氨基芘的EC50/LC50值在沉积物-水和仅水毒性测试中相似,D.magna和H.azteca的范围从21到28μg/L和8.8到11μg/L,分别。研究了两种代表性PAHs的基于体残基的EC50/LC50(ER50/LR50),芘,还有BaP.在D.magna和H.azteca的仅水毒性测试中,两种物种中pyr的ER50/LR50分别高出2.3和11倍。分别,虽然沉积物-水毒性试验中的BaP没有计算沉积物-水毒性试验中的BaP,沉积物-水测试中的最高体浓度低于仅水中毒性测试中的ER50/LR50。尽管实验结果与本研究中选定的PAHs基于EqP方法的预测沉积物毒性值相当,对于H.azteca,EqP方法存在菲和芘被略微低估的风险(菲1.4-1.9倍,芘3.7-6.1倍)。这些结果重申,水溶性差的化学物质的生物利用度对沉积物毒性很重要,应进一步研究暴露途径,以避免通过EqP方法低估和高估。
While the equilibrium partitioning (EqP) method has been demonstrated to effectively predict the adverse effects of nonionic organic chemicals in sediment on benthic organisms by sediment toxicity tests, only a limited number of studies have been performed both in water-only and whole-sediment toxicity tests using the same species and verified the validity of EqP-based toxicity assessment. To further examine the validity of the EqP method for application in a wide range of hydrophobicity, we conducted sorption/desorption experiments and both water-only and sediment toxicity tests using a popular aquatic crustacean species, Daphnia magna (48 h), and benthic species Hyalella azteca (96 h) for six typical polycyclic aromatic hydrocarbons (PAHs) with three to five rings and an amine derivative: anthracene, phenanthrene, fluoranthene, pyrene, benzo[a]pyrene, dibenzo[a,h]anthracene, and 1-aminopyrene. The linear sorption coefficient was determined and ranged from 2.7 × 102 (phenanthrene) and 1.2 × 104 L/kg (benzo[a]pyrene) highly depending on the hydrophobicity while the aqueous concentrations were stable after 24 h in the desorption test. As result of acute toxicity tests in the water-only exposure system, anthracene and dibenz[a,h]anthracene were found to be nontoxic to both species, while median effect/lethal concentrations (EC50/LC50) were determined as ranging from 0.66 (benzo[a]pyrene) to 330 μg/L (phenanthrene), and from 11 (1-aminopyrene) to 180 μg/L (phenanthrene) for D. magna and H. azteca, respectively. Among these compounds, three PAHs with three, four, and five rings each, and 1-aminopyrene were subjected to sediment-water toxicity tests. In the sediment-water tests, the LC50 of phenanthrene and pyrene was three to six times higher than that of the water-only tests for H. azteca while the EC50 was 1.1 to 2.0 times higher for D. magna. In contrast, the EC50/LC50 of benzo[a]pyrene (BaP) in the sediment-water toxicity test was more than 5 times higher than that in the water-only test for both H. azteca and D. magna. The EC50/LC50 values of 1-aminopyrene were similar in both the sediment-water and the water-only toxicity tests, ranging narrowly from 21 to 28 μg/L and 8.8 to 11 μg/L for D. magna and H. azteca, respectively. The EC50/LC50 based on the body residue (ER50/LR50) was investigated for two of the representative PAHs, pyrene, and BaP. The ER50/LR50 of pyrene in both species was 2.3 and 11 times higher in the water-only toxicity test for D. magna and H. azteca, respectively, while those of BaP in the sediment-water toxicity test were not calculated for the sediment-water toxicity tests, and the highest body concentration in the sediment-water tests was lower than the ER50/LR50 in the water-only toxicity test. Although the experimental results were comparable with the predicted sediment toxicity values based on the EqP method for the selected PAHs in this study, there is a risk of phenanthrene and pyrene being slightly underestimated (1.4-1.9 fold for phenanthrene and 3.7-6.1 fold for pyrene) by the EqP method for H. azteca. These results reaffirm that the bioavailability of poorly water-soluble chemicals is important for sediment toxicity and that the exposure pathway should be further investigated to avoid under- and overestimation via the EqP method.