Pollution Characteristics And Ecological Risk Assessment In Yangquan Section Of The Tao River

With the progress of ecological civilization construction,ecological sustainable development has become the goal of human unremitting pursuit.In the process of ecological civilization development,there will inevitably be contradiction between human and nature,and various ecological risks in the process of ecological civilization development is an important link in the pursuit of ecological sustainable development.As an important natural ecosystem,rivers provide ecosystem health,climate regulation,biodiversity and other ecological services for human beings.With the rapid development of economy,river ecological environment has been seriously damaged,such as river morphology simplification,river velocity slowing down,body self-purification capacity weakening,water pollution and so on.The distribution characteristics of river pollutants and river ecological riskassessment have become a hot research topic.Based on the theory of ecological risk assessment,this paper evaluates the ecological risk of Taohe River according to the ideas of risk identification,risk assessment and risk control.Taking Taohe River as an example,the environmental characteristics such as small runoff,slow flow rate,poor self-purification capacity and small environmental capacity are studied.On the basis of the preliminary field investigation,the destructiveness of pollution caused by human activities was evaluated with the help of species sensitivity analysis method,and the most typical pollutants were found out,and the analysis results were obtained.Finally,on the basis of the results of pollutant assessment,the problems faced by the river ecology are deeply discussed and analyzed,and suggestions and measures for optimization and improvement are put forward.The achievements of this research are as follows:（1）In terms of the distribution characteristics of pollutants in Tao River,most ion concentrations show a"low-high-low"pattern.The results show that the ion concentration in Tao River is enriched from the upstream to the middle reaches,and diluted from the middle to the downstream.In terms of the chemical characteristics of single ionic water,the order of anionic concentration in Tao water is as follows:SO₄>Cl>HCO₃>NO₃,the content of SO₄^2-is 228 times that of NO₃^-,the order of cation is Ca²⁺>Mg²⁺>Na⁺>K⁺,and the content of Ca²⁺is three times that of K⁺.The main anion composition of Taohe is rich in SO42-,accounting for 75%of the total anion.The main cations in the water are rich in Ca²⁺and Mg²⁺,accounting for 72%of the total cations.Therefore,the dominant ions in Taohe river are Ca²⁺,Mg²⁺and SO₄^2-.Among them,Ca²⁺,Mg²⁺and SO₄^2-have the largest values in Yihuan Village,which is caused by excessive drainage of mine water caused by the tributaries of the upstream passing through several coal mine areas.（2）A small amount of heavy metal Cd in Tao River exceeds the level I standard limit of Surface Water Environmental Quality Standard,which is a threat to Tao River.In terms of the variation trend of water quality inspection values,heavy metals Ni,Cu and Cd have similar trends,and the highest values all appear in TH^-5.According to the distribution of on-site sampling points,the highest values are located in Potou Village,because there are industrial enterprises in the basin.The high concentration of heavy metals Ni,Cu and Cd in this area is influenced by the discharge of wastewater from industrial activities.（3）A species sensitivity distribution（SSD）model was constructed to simulate and evaluate the species sensitivity distribution.By comparing R2,RMSE and P-value（K-S test）,the SSD curve fitting of Logic-tic distribution model was the best.（4）The river ecology was evaluated by single factor and safety valve value methods.The results of single factor evaluation method showed that heavy metal Cd exceeded the standard at some points in the upper reaches of taohe River,and the whole Taohe River showed a clean-medium pollution level.Due to the small number of tributaries in the upper reaches of Taohe River,the discharge of heavy metal in the upper reaches of Taohe River had certain ecological risks.The safety threshold of cadmium was 0.3380,and the safety threshold was less than 1.The result indicated that there was no obvious ecological risk of heavy metal cadmium to the Biological zone of Taohe River under the current situation.（5）Based on the situation of Tao River,the paper provide the pollution prevention and control of taohe river basin and the comprehensive control of river channel,and provide some suggestions on the protection of biological diversity in engineering measures,biological measures,environmental protection measures and management measures.