Development of regional water quality criteria of lead for protecting aquatic organism in Taihu Lake, China

Lead is a widely distributed priority controlled heavy metals in aquatic system, its toxicity to aquatic organisms affected by water quality parameters. This study investigated the acute toxicity of lead (Pb) to the aquatic organisms in Taihu Lake under various water hardness, corresponding regional water quality criteria were derived. The acute toxicity experimental results revealed that the toxicity of Pb to aquatic organisms increased with water hardness. The Pb toxicity has a highest toxicity at water hardness 50 mg/L (expressed as CaCO3), especially for Palaemon modestus where the 96 h LC50 value was 0.024 mg/L. The hazardous concentration for 5% of biological species (HC5) values were determined via species sensitivity distribution (SSD) method as 94.0 μg/L, 222.3 μg/L and 375.8 μg/L for Pb at water hardness 50, 150, and 250 mg/L, respectively. The assessment factor (AF) value was set at 2, followed by the current SSD framework where European commission recommend a fixed AF of 5–1. Thus, the predicted no effect concentration (PNEC) values was 47.0 μg/L, 111.2 μg/Land 187.9 μg/L at water hardness 50, 150, and 250 mg/L, respectively. Meanwhile, the short-term water quality criteria of Pb for Taihu lake aquatic organisms were derived as 111.2 μg/L at water hardness 150 mg CaCO3/L. The long-term water quality criteria were derived as 4.3 μg/L by using acute/chronic ratio 51.29. When the derived value was used for Taihu Lake, 2.7% of the sampling sites in Taihu Lake was exceeded this criterion. The results of this study can provide technical methods and basic information for deriving Pb regional water quality criteria for protecting native aquatic organisms, in China