In the passive dosing tests, measured Cw values remained constant during the test period, notably, even after the addition of daphnids (Figure ). DOC concentrations in the solvent spiking test (15-24 mg/L) were higher than those in the passive dosing method (0.8-4.3 mg/L) (Table ). The presence of methanol (0.01 %, v/v) in the exposure medium caused an increase in DOC in the spiking test, whereas the exposure water in the passive dosing test contained a low concentration of DOC. Therefore, the binding of C14-18