Toxicity assessment of typical polycyclic aromatic hydrocarbons to Daphnia magna and Hyalella azteca in water-only and sediment–water exposure systems

While the equilibrium partitioning (EqP) method has been demonstrated to effectively predict adverse effects of nonionic organic chemicals in sediment on benthic organisms by toxicity tests, only a limited number studies have performed both water-only and whole-sediment tests using same species verified validity EqP-based assessment. To further examine EqP for application wide range hydrophobicity, we conducted sorption/desorption experiments popular aquatic crustacean species, Daphnia magna (48 h), Hyalella azteca (96 h) six typical polycyclic aromatic hydrocarbons (PAHs) with three five rings an amine derivative: anthracene, phenanthrene, fluoranthene, pyrene, benzo[a]pyrene, dibenzo[a,h]anthracene, 1-aminopyrene. The linear sorption coefficient was determined ranged from 2.7 × 102 (phenanthrene) 1.2 104 L/kg (benzo[a]pyrene) highly depending hydrophobicity while aqueous concentrations were stable after 24 h desorption test. As result acute exposure system, anthracene dibenz[a,h]anthracene found be nontoxic median effect/lethal (EC50/LC50) as ranging 0.66 330 ?g/L (phenanthrene), 11 (1-aminopyrene) 180 D. H. azteca, respectively. Among these compounds, PAHs three, four, each, 1-aminopyrene subjected sediment-water tests. In LC50 phenanthrene pyrene times higher than that EC50 1.1 2.0 magna. contrast, EC50/LC50 benzo[a]pyrene (BaP) test more 5 values similar narrowly 21 28 8.8 based body residue (ER50/LR50) investigated two representative PAHs, BaP. ER50/LR50 2.3 respectively, those BaP not calculated highest concentration lower Although experimental results comparable predicted selected this study, there is risk being slightly underestimated (1.4–1.9 fold 3.7–6.1 pyrene) azteca. These reaffirm bioavailability poorly water-soluble important pathway should avoid under- overestimation via method.