Assessing ecological risk of organophosphate esters released from sediment with both of total content and desorbable content

This study introduced fractions (labile, stable-adsorbed, tight-adsorbed fractions) of organophosphate esters (OPEs) into ecological risk assessment to evaluate the potential risks of organophosphate esters that released from sediment, and conduct a case study to verify it. The content of desorbable fractions was get from adsorption-desorption experiments. Adsorption process can be divided into fast sorption, gradual sorption, and final equilibrium stage, and labile, stable-adsorbed, tight-adsorbed fractions were formed during adsorption. Approximately 86.21% labile, 73.41% stable-adsorbed, and 43.01% tight-adsorbed TPhP-D can be desorbed from sediments in desorption experiments. According to the results, the value of hazard quotient (HQ) that calculated by desorbable fractions reduced by 13.88% than HQ calculated by the sum of fractions, and result of 29.76% decrease for ∑HQs. The isotherm results demonstrated that the contents of labile and stable-adsorbed fractions increased faster than tight-adsorbed fraction when the concentration of contaminant in water increased from 50 to 400 μg/L, which means ecological risk in areas with high concentration of contaminants are higher than the discreet value. In case study, an additional hotspot was found in areas, where characterized with high proportion of labile fraction, when ecological risk was calculated by desorbable fractions. Indicating that revised ecological risk assessment takes both of total content and desorbable content into consideration.