Distribution,Ecological Risk Assessment And Adsorption Mechanism Of Phenolic Compounds In Weihe River

Phenoliccompounds are a kind of weakly acidic organic compounds with polarity and ionization,which have potential carcinogenic,teratogenic and mutagenic function.They can enter the organism body through different ways,and are widespread in the aquatic environment.For their high hydrophobicity,they can be transferred from the water phase to the solid phase,and can be dissolved into the water phase from the depositional state in the river water environment.The migration and transformation of phenolic compounds between different phases can be affected by different environmental factors(e.g.pH?ionic strength,temperature,natural dissolved organic matter,etc.).The Weihe River is an important river in the northwest of China for its major role in the development ofthe Guanzhong-tianshui economic zone.So understanding the distribution characteristics,environmental ecological risks,migration and transformation of phenolic compounds in Weihe River isof great significance to the prevention and control of organic pollution in Weihe water environment and the protection of ecological environment.In this study,32 sampling points were set up in the Shaanxi section of Weihe River.The concentrations of 11 phenolic compounds in water samples and sediments samples from Weihe River were measured.The distribution characteristics of phenolic compounds inWeiheRiver were analysed,and the environmental ecological risk assessment was also carried out based on the toxicity of phenols to aquatic organisms.The influence of dissolved natural organic matter on the adsorption characteristics of phenol compounds to sediment were studied by indoor static adsorption experiment.The main conclusions are as follows:(1)The proportion of chlorophenols in water and sediments of phenolic compounds in the Weihe River(Shaanxi section)is significantly higher than that in non-chlorophenols.The content of phenolic compounds was decreased slightly from upstream to downstream in the water samples,the concentration of phenolic pollutants in sediments in Xi'an section is higher than that in the upper and lower reaches of Shaanxi section.The level of phenolic pollution in Weihe River is higher than that many rivers in south part China and below the Yellow River,Songhua River and Liaohe River.Compared with other polluted rivers in the world,the concentrations of phenolic compounds in the Weihe River were at a moderate level.(2)To assess the ecological risk of the soluble phenolic compounds in Weihe River,a method of species sensitivity distribution curve was applied.The results showed that there were 4-chloro-3-cresol,2,4-dichlorophenol and 2,4,6-trichlorophenolwith chronic ecological risksin the Weihe river basin,which needed to take some measures to reduce risks.The rest of the phenol compounds did not produce chronic ecological risk on aquatic organisms and have a low potential risk.(3)According to adsorption kinetic experiments,the fitting correlation coefficients of the three models for three phenolic compounds are above 0.9.In comparison,Two-compartment first-order model perform better than Pseudo-first-order model and Pseudo-second model in description of phenol and 2,4-dichlorophenol kinetic adsorption.The Pseudo first-order kinetics of 2,4,6-trichlorophenol fit better.In experiments of isothermal adsorption,both Langmuir and Freundlich have good fitting results,and three phenolic compounds more in line with nonlinear adsorption.(4)With increasing pH,sediment absorption of phenols was inhibited to varying degrees.Increased ionic strength can promote the adsorptionof phenols.Increase system temperature within a certain rangeaccelerate the adsorption of 2,4-dichlorophenol and 2,4,6-trichlorophenol by sediments,but inhibits the adsorption of phenol by sediments.The three phenolic compounds were more suitable for nonlinear adsorption when the temperature changes.(5)In the presence of natural dissolved organic matter amino acids and fulvic acid,the adsorption of phenol by sediments can be significantly promoted.Glucose has a greater effect on the adsorption of 2,4-dichlorophenol and 2,4,6-trichlorophenol.The isothermal adsorption of three phenols in the presence of different NDOMs was more consistent with the nonlinear adsorption.