Study On Water Environment Quality Of Dongyu River And Estuary Area In The Lake Based On Diatom And Chironomid

The Dongyu River,located in the southwest of Shandong Province,is one of the national stations for monitoring the water volume of the river flowing into the Nansi Lake.Its water environment has an important impact on the water quality of the Nansi Lake and the safety of water transfer from the South-to-North Water Transfer Project.In order to discuss the water quality of the Dongyu River and the estuary of the lake,it provides a scientific basis for the ecological restoration and management of the water environment of the Dongyu River and the estuary of the lake.In this paper,using the water samples and sediment samples collected from the Dongyu River and the estuary estuaries in May2013 by the research group,the characteristics of the community of mosquitoes and diatoms and the quality of the water environment were analyzed.According to the significant water environment factors affecting the community structure characteristics of Chironomus spp.And diatoms,the water environment status and water quality evaluation results reflected by diatoms and Chironomus spp.Were analyzed and compared,and the differences and reasons between the two were evaluated.The main findings are as follows:(1)The analysis of the improved Nemero pollution index shows that the overall water quality of the Dongyu River and the estuary of the lake is in the category?to?water bodies,and the quality of the water environment is poor.The main physical and chemical factors that exceed the standard are NH₄⁺-N,TP,Hg.The water pollution at the junction of Dongyu River and estuary area in the lake is the most serious.It belongs to category?water body and is a key watershed for governance.The water quality of the middle and upper reaches of the Dongyu River and the northeast of the estuary into the lake is good,meeting the water quality requirements of Class III water bodies;about 67%of the remaining water bodies belong to Class IV water bodies,and Class IV to V water bodies account for about 80%of the total watershed.The reason for the water pollution in the study area is that the middle and lower reaches of the Dongyu River are agricultural farming areas,and the N and P in pesticides penetrate into the river water through groundwater infiltration is the main environmental factor causing water pollution in the middle and lower reaches of the East Fish River.At the same time,the discharge of production and domestic wastewater along the coast is another main reason;the estuary of the lake is located at the junction of the East Fish River and the South Four Lakes.The water body is affected by the river and the lake,and it is connected to the Beijing-Hangzhou Canal and the fishing boats dock.The water environment is seriously affected by human activities.(2)A total of 2101 larvae of larvae of mosquitoes were collected from 15 sampling points in Dongyuhe and Ruhu estuaries,which belonged to 20 genera of 3 subfamilies and a total of 30 species.The subsoil stone shells of the rock mosquitoes in the bottom of the study area are mainly composed of Chironomus plumosus-type,Dicrotendipes nervosus-type,Glyptotendipes pallens-type,Tanytarsus mendax-type,Cricotopus sylvestris-type,Propsilocerus akamusi-type.74.89%of the fossil species.Among them,Chironomus plumosus-type,Glyptotendipes pallens-type and Cricotopus sylvestris-type are the dominant species in the study area,accounting for 49.93%of the whole watershed,almost distributed throughout the whole watershed.At the sampling point N-4,no species of Chironomus were found.Biological evaluation results show that the study area as a whole belongs to the"light pollution-medium pollution"grade.The RDA results show that NH₄⁺-N is a significant factor that affects the composition and distribution of rock mosquitoes.(3)Species of diatoms are mainly epiphytic benthic diatoms.The main dominant genera are Cyclotella meneghiniana,Fragilaria fasciculata,Fragilaria ulna,Amphora libyca,Cocconeis placentula,which together account for 63.36%of the total watershed.The water quality evaluation results based on the biological evaluation index of diatoms show that the whole water body in the study area is in a light pollution-medium pollution state.Because the estuary of the lake is the junction of the Dongyu River and the Nansi Lake,and it is connected to the Beijing-Hangzhou Canal,the river disturbance is large,making it difficult for the diatoms in the sediment to be completely retained,resulting in the diatom species and genera in this area.There are fewer species than the Dongyu River Basin.RDA results show that among all water environment factors,only NH₄⁺-N and DO reached significant levels,explaining the diatom variability of 29.9%and 16.4%,respectively,indicating that the water body in the study area is mainly affected by nutrients.About 60%of the water bodies have poor water environment quality and belong to the category?water quality status,which is mainly located in the middle and lower reaches of the East Fish River and part of the water area of the estuary area of the lake;The water quality is good and meets the water quality requirements of Class III water bodies;the water quality at the junction of Dongyu River and Shaoyang Lake is the worst,reaching Class V water quality status.(4)The water quality evaluation results based on the biological indexes of Chironomid and diatoms all show that the water quality in the study area is in a state of light pollution-medium pollution.This indicates that diatoms and rock mosquitoes are sensitive aquatic organisms reflecting water quality.As far as the Dongyu River is concerned,there is a certain difference between the area indicated by the mosquito community and the area reflected by the diatom.The diatom is more sensitive than the mosquito to respond to changes in water quality.