pH-dependent aquatic criteria for 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol

Due to their agricultural as well as industrial uses, 2,4-dichlorophenol (2,4-DCP), 2,4,6-trichlorophenol (2,4,6-TCP), and pentachlorophenol (PCP) are ubiquitous in the environment and recognized as priority pollutants in many countries. In this study, effects of pH on toxicity to the crustacean Daphnia magna and the alga Scenedesmus obliquus were investigated. Combined published toxicity data of the three chlorophenols along with; relationships between toxicity and pH reported here were used to establish pH-dependent water quality criteria (WQC). The WQC expressed as a function of pH, also considered intra-species variation and proportions of taxonomic groups. At pH 7.8, the recommended acute exposure water quality criteria (WQC) were 286.2 μg 2,4-DCP/l, 341.5 μg 2,4,6-TCP/l and 11.4 μg PCP/l. The recommended chronic exposure WQC were 16.3 μg 2,4-DCP/l, 54.6 μg 2,4,6-TCP/land 3.9 μg PCP/l.

► The effects of pH on toxicity of CPs to Daphnia magna and Scenedesmus obliquus were studied. ► There were strong correlations between the logarithmic EC50s and pH values for both D. magna and S. obliquus. ► The manipulation of data (intra-species variation or/and proportions of taxonomic groups) is important to the result of WQC.