Water Quality Criteria And Ecological Risk Assessment In Tai Lake,China By Studies 2,4,6-Trichlorophenol,Copper And Ammonia

Water quality criteria and ecological risk study,the significant component of water management system,laid scientific basis for environmental managers and decision makers.Compared with that in developed countries,studies of water quality criteria and ecological risk in home were lagged behind.In addition,site-specific researches that considering the physic-chemical parameters and aquatic biota were remained to be developed.Chemical selection,lack of chronic toxicity data,absence of studies that based on spatial-temporal dimensions et al were stubborn concerns in water quality criteria and ecological risk study.In this study,focusing on the main ecology services and its key drivers in Tai Lake,water quality criteria and ecological risk studies were performed by considering the environmental processes and species sensitivities of aquatic organisms to chemicals.Taking 2,4,6-trichlorophenol,copper and ammonia as the examples,this study was exploring approaches that existed in the current research,in order to contribute to the perfecting of water management system and improving methodologies in water quality criteria and ecological risk.Criteria of 2,4,6-trichlorophenol for protection of aquatic organisms in Tai Lake were derived by considering the aquatic biota.Chronic data for Daphnia Magna was supplemented by performing the 21d chronic test,besides,two-step extrapolation method was used to derive the chronic data of Carassius auratus,Limnodrilus hoffmeisteri and tadpole of Rana amurensis.Pooled slope between toxicity data and pH was derived.Using the species sensitivity distribution,criteria of 2,4,6trichlorophenol at pH 7.8 were obtained.Considering the relationship between toxicity and criteria,water quality criteria for protecting aquatic organisms in Tai Lake were expressed with functions of pH,LnCMC=0.926pH-1.077 and LnCCC=0.926pH-3.576.In order to take physic-chemical parameters in site-specific areas into consideration,water effect ratio method and biotic ligand model were used to derive the criteria of copper in Tai Lake.Results showed that simultaneous CMC and CCC outputted by BLM for protecting aquatic organisms from copper were 42.83 μg/L and 26.61 μg/L,while criteria derived by WER method were 8.83μg/L and 2.74 μg/L.Taking ammonia as an example,information of ammonia exposure in Tai Lake in 37 sites in February and September 2014 Tai Lake and in three key sections in 2004～2015 Tai Lake were gathered.Hazard quotient method and probabilistic method were applied to assess the spatial～temporal risk of ammonia in Tai Lake.Our study showed that the average acute and chronic HQs of ammonia in February were 0.08 and 0.13,and 2.3 and 4.0 in September,respectively.In probabilistic risk assessment,the probabilities of ammonia exceeding threshold value increased from 0.04%and 1.97%in February to 52.37%and 92.05%in September,respectively.Although significant risk was suggested in wet season,the overall probabilities of ammonia exceeding threshold value in three key sections of Tai Lake showed a decreasing trend from 2004 to 2015,implying possible mitigation effect of the eutrophication control practice implemented in key sections of Tai Lake.