Impact of dissolved humic acid on the bioavailability of acenaphthene and chrysene assessed by membrane-based passive samplers

Abstract

Dissolved organic carbon (DOC) is known to reduce the bioavailability of hydrophobic organic compounds (HOCs) in aqueous environments. This reduction occurs as a result of adsorption to DOC, apparently reducing the freely dissolved concentration of HOCs. In the present study, triolein-embedded cellulose acetate membrane (TECAM) and Japanese medaka (Oryzias latipes) were used to measure the uptake of acenaphthene and chrysene in the presence of commercial humic acid (HA) at different concentrations (0–15 mg C·L−1) under controlled laboratory conditions. Apparent uptake rate constants for PAHs in TECAM and medaka were compared and DOC-water partition coefficients (K DOCs) of two PAHs were calculated with different sampling methods by model fit. Results showed that HA present in water significantly reduced the uptake of PAHs in TECAM and medaka. The obtained values of log K DOC of acenaphthene and chrysene measured by TECAM were 4.63 and 5.83, respectively, whereas biologically determined values were 4.52 and 5.76, respectively. These log K DOC values were comparable to earlier published K DOCs toward commercial HA, thereby indicating that TECAM accumulated only the freely dissolved fraction of chemicals and uptake PAHs in a manner similar to that of fish. All these results suggested that the TECAM method can provide a good means for assessing the impact of DOC on bioavailability of PAHs in the aqueous environment.