Water Environment Assessment And Pollution Source Analysis In Qilu Lake Basi

Qilu Lake is the largest lake in Tonghai,from the West River system of the Pearl River basin,is located in the middle of the Pearl River basin slightly to the northeast,the surface runoff of the surrounding watershed are converging into Qilu Lake,is one of the nine plateau lake basin,the area has a high population density,and is subject to greater resource and environmental constraints.In recent years,with the rapid development of modern urbanization,Qilu Lake water resources are increasingly polluted,clarify the source of its water pollution,is conducive to an in-depth understanding of the plateau lake basin water pollution,to provide reference for the watershed water pollution prevention work.This paper is based on the water environment pollution of Qilu Lake as the starting point of the study,the water quality of its 2022 staged testing,the use of Arc Gis inverse distance weighting spatial method interpolation of pollutant indicators monitoring results for spatial and temporal distribution characteristics analysis;then on this basis from the water quality and water eutrophication two aspects of the lake water environment for a comprehensive evaluation;finally the watershed for the point source and surface source pollution load Finally,the pollution load from point and surface sources is estimated,the main pollutants causing water pollution and their sources are identified,and countermeasures for pollution control are proposed in response to the analysis results.The main conclusions are as follows:(1)Among the inorganic chemical indicators,the spatial distribution of SD shows a gradually increasing trend from west to east,and the temporal changes are better in the order of abundance than in the dry period,i.e.the transparency of the lake body is greater in the flooding period than in the non-flooding period;the p H concentration of the lake body is higher and shows an increasing trend from southwest to northeast,and the concentration in the dry period is higher than in the abundance period.The spatial distribution characteristics of the organic chemical indicators TP,TN and NH3-N show a decreasing trend from southwest to northeast in all sub-periods,and the concentration value is greater in the rich water period than in the dry water period;DO concentration basically meets the target demand,and the concentration increases from southwest to northeast,and is higher in the dry water period than in the rich water period;COD spatial distribution is more uniform,and the concentration is higher in both water periods.The water quality at the inlet of each river has a significant influence on the concentration of organic matter indicators.(2)The water quality evaluation results show that the water quality of Qilu Lake does not reach the water function zone Ⅲ water quality requirements,belongs to the poor V water quality,in a heavy water pollution state.The results of the single factor index method show that the pollutant indexes in the evaluation,except DO in the dry period to achieve the Ⅲ water standard,the other six indicators are in the poor V.A,B,C zoning are poor V water quality.The evaluation results of the Nemero integrated pollution index method show that the water quality of Qilu Lake in all water periods did not reach the Ⅲ standard,and there is no difference in the evaluation of each division is poor V water quality.The results of the water column nutrient evaluation show that Qilu Lake is in a moderate eutrophic state.Based on the nutrient status index values,the calculated scores ranged from 59.95 to 86.16,with 62.5% of the monitoring points in the dry water period evaluated to be in a moderate eutrophication state and 37.5% in a severe eutrophication state.There is no significant difference between the two water periods;from the nutrient status index values,the calculated scores range from 58.74 to 84.68,and most of the sites have no significant difference in the calculated values and nutrient status between the two water periods,and the overall state is moderate eutrophication.(3)According to the estimation results of the different pollution sources of Qilu Lake in terms of generation,emission and entry into the lake and the structural characteristics of water pollution in the basin,among the various pollution sources in Qilu Lake basin in2022,agricultural surface source pollution is the main source of water pollution in Qilu Lake basin;among the indicators of different water pollutants TN and COD have a greater impact on the water environment,five main suggestions are made: adjusting farmland planting structure,implementing farmland weight loss and efficiency projects,preventing the discharge of receding water from farmland,promoting agricultural efficient watersaving irrigation projects and strictly saving water to reduce waste of resources.