Spatio-temporal Variation And Evaluation Of Surface Water Quality In Fujin National Wetland Park

Fujin National Wetland Park is located in the northern part of Heilongjiang Province,in the hinterland of Sanjiang Plain,about 50 kilometers southwest of Fujin City.The park is an ecological scenic spot that integrates scenic sightseeing,recreation and humanistic education.With the rapid development of economy,the continuous impact of human activities and the deterioration of the water environment,it has a negative impact on the aquatic ecosystem.Therefore,it is very important to monitor and master the changes of the water environmental conditions in the park.In this study,20 sampling sites were set up in Fujin National Wetland Park.Water samples were collected in May 2022(spring),July 2022(summer)and September2022(autumn)respectively,and the main physicochemical indexes of water quality were determined.A variety of methods were used to conduct comprehensive analysis of the test results,including: Comprehensive pollution index method,Nemerow index method,gray correlation method,comprehensive nutrient state index and single factor index method.Finally,the main factors affecting water quality were explored through principal component analysis and cluster analysis to provide scientific basis for protecting the water environment of wetland park.The main conclusions of this paper are as follows:(1)The water environment indicators in Fujin National Wetland Park have the difference of spatial and temporal distribution.The p H is acidic in spring and autumn and alkaline in summer.The content of dissolved oxygen in summer is generally lower than that in spring and autumn,while the concentration of permanganate,BOD5,ammonia nitrogen,total nitrogen,total phosphorus and chlorophyll a in summer is higher than that in spring and autumn.The concentrations of potassium permanganate,BOD5,ammonia nitrogen,total nitrogen and total phosphorus near the water inlet and outlet of the park were higher than those of other sample points,the concentrations of dissolved oxygen near the water outlet of the park and the northern farmland were higher than those of other sample points,and the concentrations of chlorophyll a in the water inlet and outlet of the park were lower than those of other sample points.(2)According to the analysis of single factor index,the water quality evaluation grade of spring and autumn was Class Ⅳ,and that of summer was poor class Ⅴ.In general,all samples of dissolved oxygen(DO)reached the national quality Class Ⅰwater standard,most samples of high bornate index(CODMn),total nitrogen(TN), total phosphorus(TP)reached the national quality Class Ⅴ water standard,and most samples of five-day biochemical oxygen demand(BOD5)reached the national quality Class Ⅳ water standard.Most samples of ammonia nitrogen(NH4-N)reached the national quality Class III water standard,and most samples of chlorophyll a(Chla)were lower than 10μg/L.The water quality evaluation grade of most sampling sites in spring and autumn was Class Ⅳ,and the water quality evaluation grade of summer was poor Class Ⅴ.The main indexes affecting water quality were chlorophyll a and total nitrogen.The sample sites that failed to meet the water standard of Class Ⅳ-Ⅴwere mainly located at the water inlet of farmland backwater entering the park and other areas affected by agricultural non-point source pollution,most of which were in summer.(3)The overall water quality of Fujin National Wetland Park was slightly eutrophication.According to the results of comprehensive pollution index,85%,15%and 80% of the sample points reached class Ⅱ in spring,summer and autumn respectively.Nemerow pollution index method shows that the comprehensive evaluation grade is excellent 95% in spring,excellent 30% in summer and excellent75% in autumn.The gray correlation method showed that the water quality of Fujin National Wetland Park in spring,summer and autumn was the surface water environmental quality standard Class Ⅴ.The comprehensive nutritional status index shows that the overall water quality of the park is slightly eutrophication.(4)Nutrient salt is the key factor affecting the water quality of Fujin National Wetland Park.Through principal component and cluster analysis,it can be concluded that the main physicochemical factors affecting the water quality of Fujin National Wetland Park are NH4-N,BOD5,TP and TN,and the increase of the content of these nutrients makes the water environment of the park appear eutrophication.Therefore,the control of agricultural non-point source pollution,the import of nutrients,and the regular monitoring of water quality should be the focus of park management.