Bioaccumulation Kinetics of Model Pharmaceuticals in the Freshwater Unionid Pondmussel, Sagittunio subrostratus

摘要

Bioaccumulation of ionizable pharmaceuticals has been increasingly studied, with most reported aquatic tissueconcentrations in field or laboratory experiments being from fish. However, higher levels of antidepressants have been observedin bivalves compared with fish from effluent‐dominated and dependent surface waters. Such observations may be important forbiodiversity because approximately 70 of freshwater bivalves in North America are considered to be vulnerable to extinction.Because experimental bioaccumulation information for freshwater bivalves is lacking, we examined accumulation dynamics inthe freshwater pondmussel, Sagittunio subrostratus, following exposure to a model weak acid, acetaminophen (mean (±SD) =4.9 ± 1 μg L~(–1)), and a model weak base, sertraline (mean (±SD) = 1.1 ± 1.1 μg L~(–1)) during 14‐day uptake and 7‐day depurationexperiments. Pharmaceutical concentrations were analyzed in water and tissue using isotope dilution liquid chromatography–tandem mass spectrometry. Mussels accumulated two orders of magnitude higher concentrations of sertraline (31.7 ± 9.4 μgg~(–1))compared to acetaminophen (0.3 ± 0.1 μgg~(–1)). Ratio and kinetic‐based bioaccumulation factors of 28,836.4 (L kg~(–1)) and 34.9 (Lkg~(–1)) were calculated for sertraline and for acetaminophen at 65.3 (L kg~(–1)) and 0.13 (L kg~(–1)), respectively. However, after 14 dayssertraline did not reach steady‐state concentrations, although it was readily eliminated by S. subrostratus. Acetaminophenrapidly reached steady‐state conditions but was not depurated over a 7‐day period. Future bioaccumulation studies of ionizablepharmaceuticals in freshwater bivalves appear warranted.