Occurrence and spatio-seasonal distribution of organophosphate tri- and di-esters in surface water from Dongting Lake and their potential biological risk.

In this study, 24 surface water samples were collected from Dongting Lake, China, in the wet and dry seasons, then the concentrations, composition profiles and spatio-seasonal variations of nine organophosphate triesters (OPEs) and five organophosphate diesters (Di-OPs) were determined. Significantly higher total OPE concentrations (∑OPEs) were observed in the wet season (49.5-148 ng L) than in the dry season (5.00-45.7 ng L) suggesting higher input via tributaries discharge as well as wet deposition in the studied region. Whereas lower levels of TnBP and (triphenyl phosphate (TPHP) in wet season reflected their possible degradation under solar irradiation. Comparable levels of total Di-OPs (∑Di-OPs) were found in the wet season (3.41-13.9 ng L) and dry season (1.01-12.3 ng L). Tri(2-chloroethyl) phosphate and tris(2-chloroisopropyl) phosphate were the main OPE components, while diphenyl phosphate, di-n-butyl phosphate and bis(1,3-dichloro-2-propyl) phosphate were the main Di-OP components. High levels of OPEs and Di-OPs were found in Datong Lake suggesting possible local emissions potentially related to fishery activity in the land-locked lake. Samples at river mouths to the lake also have higher levels of target OPEs and Di-OPs, the results disclosed obvious discharges from tributaries in Hunan Province. Negligible non-carcinogenic and carcinogenic risks were determined based on the measured concentrations in source waters. A limited ecological risk aquatic organisms in the Dongting Lake was identified, with most risk from TPHP.