Water Quality Improving Technics And Effect Evaluation In Guizi Lake

Guizi Lake in Yidu City is an important water source for agricultural production and people’s lives in Yidu City.It has multiple functions such as water conservancy and flood control,aquaculture,climate regulation,and tourism development.However,in recent decades,with the continuous increase of urban population and the rapid development of agricultural and fishery production,the water environment of Guizi Lake has gradually deteriorated.At the same time,Guizi Lake has uneven distribution of water resources in time and space,and the lake morphology and spatial pattern have been damaged and severely degraded.,Serious water pollution,destruction of biodiversity and other issues.Therefore,studying the characteristics of Guizi Lake water environment,scientifically formulating Guizi Lake water quality improvement technical system,And evaluating its restoration effects are of great significance to Guizi Lake water pollution control and other.This study first investigates the water environment quality and pollution sources of Guizi Lake,and uses the single factor index method to evaluate the water environment quality.It is concluded that the water environment quality of Guizi Lake is severely polluted.Comparing three months,the pollution is the most serious in the wet period and the normal water period.However,the dry season is the lowest.As far as the water quality pollution sharing rate is concerned,TP has the largest contribution,followed by TN and COD_Mn.The external source pollution of Guizi Lake mainly includes domestic pollution,agricultural non-point source pollution,livestock and poultry breeding pollution,and industrial pollution.The degree of pollution was in the order of livestock and poultry farming pollution>domestic pollution>agricultural pollution>industrial pollution,COD_Mn was 434.79t/a,TN was 88.158t/a,NH₃-N was 30.512 t/a,and TP was 31.64t/a.Based on the analysis of the endogenous pollution of Guizi Lake,the high content of total nitrogen,total phosphorus and organic matter in the sediments of Guizi Lake are mainly concentrated on the surface.The endogenous pollution of Guizi Lake mainly comes from the release of nutrients rich in sediment,fish purse seine and the litter of lake aquatic plants.Based on the problems and characteristics of Guizi Lake’s water environment,scientifically formulate a water quality improvement technical system.Guizi Lake’s water quality improvement is based on the basic principles of“comprehensive renovation,technology integration,and long-term operation”,and adopts“source control and pollution interception,optimization of structure,internal source control,and self-purification“Strengthen”the governance concept,scientifically design a four-system coupling water quality improvement technical system.The system mainly includes four parts（1）The source control pollution interception system,through the shore pollution interception,from the source to reduce the discharge of pollutants.（2）Lake bed space reconstruction system,through the removal of fish ponds,connecting Guizi Lake water system,restoring the original form of the lake,dredging lake sediments,and improving the lake bed space structure.（3）The lakeside wetland system,focusing on the implementation of bank slope improvement and plant planting in areas that have a greater impact on the water quality control section.（4）The biological community restoration system is based on the principle of"biological manipulation"to rebuild the complete ecological chain of the lake ecosystem.The Guizi Lake Demonstration Area is selected as the research object,and the area where the water quality improvement technology is adopted in the demonstration area is set as the monitoring section.The water quality of the demonstration area is evaluated through the comprehensive pollution evaluation method and the comprehensive nutritional status evaluation method.The comprehensive pollution index fluctuates more in the normal period.Large,relatively stable during the wet and dry periods.In general,the comprehensive pollution index of the demonstration area has changed from an overall state of severe pollution to a state of light pollution.The comprehensive nutritional status index varies from 41 to 61,and it is generally in a light-to-moderate pollution state.The average comprehensive eutrophication index is the largest in the high water period,indicating that there are still different degrees of eutrophication pollution in the high water period.By comparing the content and removal rate of various physical and chemical indicators in different hydrological periods,it is concluded that each nutrient indicator has been reduced to a certain extent,and it is believed that the water environment quality of Guizi Lake Demonstration Area has been significantly improved.In order to further explore the temporal and spatial variability of water quality in the Guizi Lake Demonstration Area,the time-varying characteristics and spatial differences of the water quality indicators in the Demonstration Area were analyzed.It can be seen that the overall decline trend of the water quality indicators in different hydrological periods is obvious,TN dry period>normal water period>wet water Period,NH₃-N high water period>normal water period>dry period,nitrate nitrogen high water period>dry period>normal water period,TP normal water period>high water period>dry period,COD_Mn high water period>normal water period>dry period,Chl-a high Water period>normal water period>dry period;from the perspective of spatial volatility,all water quality indicators are gradually reduced from the entrance to the exit of the lake in the demonstration area.In order to explore the mechanism of water quality improvement in different areas of the demonstration area,the SPSS software was used to divide the demonstration area into a severely polluted area,a moderately polluted area,and a lightly polluted area.The heavily polluted area is located from the west inlet to the lotus planting area outside the cascade pond.Insoluble substances in the body have a good sedimentation effect,but the content of soluble nutrients is still high;the moderately polluted area is a buffer zone from deep water to shallow water,a certain flow rate and a multi-level compound fish system promote nitrogen and phosphorus in the plant The nutrient salts are transferred to fish,and the soluble nutrient salts have been better removed;the lightly polluted area is the combination area of aquatic plant populations,and the emergent plants and submerged plants in the lake can produce O₂ through photosynthesis and transport it to the plants.Everywhere,the sediment around the root system is oxidized and decomposed to achieve a good purification effect.Through a one-way variance（ANOVA）analysis,the results show that total nitrogen,ammonia nitrogen,dissolved oxygen,and chlorophyll are significantly different in different ecological areas in the demonstration area.Nitrate nitrogen,total phosphorus,p H,and permanganate index are in different ecological areas in the demonstration area.There is no significant difference.