| In recent years,there has been frequent pollution in lakes,reservoirs and urban water systems.Eutrophication and black odor of water bodies have attracted widespread attention and become urgent problems in many Chinese cities.Eutrophication can lead to a series of adverse consequences such as algal bloom,which is the main environmental problem facing aquatic ecosystem.Clean and safe water environment is the guarantee of human health.As recreational water,park landscape water has an important impact on public ecological health.In this study,lakes in major urban parks(Harmony Park,Muye Park,Xiangyang Park,Dingguo Lake Park and People’s Park)in Xinxiang City,Henan Province were selected as research objects,and water bodies in different months(March to October)and at different water depths(0.5m,1.0m,1.5m)were continuously monitored.The characteristics of landscape water quality(physical,chemical,heavy metal,algae biological characteristics)and their influencing factors were analyzed.The single factor evaluation method was used to analyze the change of water quality characteristics by referring to the "People’s Republic of China Water Quality Standard for Landscape Recreation Water(GB12941-91)".According to the water quality characteristics of different parks,this paper explores the ways of using aquatic plants to improve the water quality of parks,in order to provide reference for the environmental protection and management of urban park waters.The main research results are as follows:(1)Through the study on the overall characteristics of water in Xinxiang city park landscape,it is found that the physical characteristics of water in Xinxiang City park landscape are generally poor,the chemical characteristics and heavy metal characteristics are medium,and the biological characteristics of algae are poor.In the physical characteristics of water,the average color of water quality was 30.97 pcu,32% exceeding the standard of Class C water.The mean turbidity was 40.50 NTU.The mean value of suspended solids was 23.212 mg/L.Chroma,turbidity and suspended matter are generally larger.In the chemical characteristics of water body,p H,dissolved oxygen and chemical oxygen demand have little change.The mean value of total nitrogen was 0.39 mg/L,and the overall change was not significant.The average value of total phosphorus index was 0.05 mg/L,18.6% exceeded the standard of Class C water,which was generally high and could not meet the demand of recreational water.In the characteristics of heavy metals in water,the average value of total iron is 0.06 mg/L,and 93.6% belong to Class A water,which is generally good.The mean value of total zinc was 0.91mg/L,and Class C water accounted for67.3%.The mean value of total copper was 0.06mg/L,and Class C water accounted for 64.3%.Total zinc and total copper generally belong to Class C water indexes.From the analysis of heavy metals in water,it can be seen that the total iron pollution is light,and the total zinc and total copper pollution is heavy.The algae density varied from 677 to 15303 cells/m L,with great difference.The average density of algae in water is 4229 cells/m L,which is generally high,which is easy to cause blue-green algae bloom phenomenon.In general,high chroma and turbidity,excessive total phosphorus and high algae density are one of the biggest obstacles to landscape water quality.(2)The water quality characteristics of different parks in Xinxiang City are obviously different.The water quality physical indexes of Muye Lake Park are significantly higher than those of the other four parks,Dingguo Lake Park is second only to Muye Park.The p H value of water in People’s Park and Dingguohu Park exceeded the standard.The total nitrogen of water in Dingguohu Park and the total phosphorus of water in Muye Park were significantly higher than other parks.The total zinc and copper in most park water bodies are Class C water.Generally speaking,the water quality characteristics of Xiangyang Park and People’s Park are basically at a medium level.The chroma,turbidity and suspended matter of each water layer in different parks increase with the increase of water layer depth.The total nitrogen in People’s Park increased with the increase of water depth.Makino Park has the highest chemical oxygen demand.The indices of heavy metals in different water layers in different parks varied greatly.(3)According to the results of monthly water quality sampling analysis,the water temperature,color,turbidity and suspended matter of each water layer in different parks all reach the peak value in summer.Among the chemical indexes,dissolved oxygen in each water layer of different parks reaches its lowest point in summer,p H reaches its peak in summer,and total phosphorus increases significantly in summer.As you can see,the most severe pollution is from June to August.Total nitrogen increased gradually from March to July and rapidly from July to September.The COD value was higher in March,and decreased from September to October with the temperature rising gradually from June to August.In the index of heavy metals,the total zinc in each water layer in different parks was higher in May to June,but decreased sharply in July.Total iron peaked in April and declined from August to October;The total copper was high in August and then fell rapidly.The monthly fluctuation of total copper in each park was not obvious.(4)The algae density of different water layers in the park increased first and then decreased with time,and reached its peak in August.The correlation analysis among the environmental driving factors of algae showed that the water temperature was positively correlated with turbidity and suspended matter(P<0.01),and negatively correlated with dissolved oxygen(P<0.01).Turbidity is positively correlated with suspended matter and negatively correlated with dissolved oxygen.There was a significant negative correlation between the suspended matter and dissolved oxygen.p H was positively correlated with total phosphorus(P<0.05).There was significant positive correlation between dissolved oxygen and chemical oxygen demand(P<0.05).(5)Based on principal component analysis,it was found that the main environmental driving factors of algae density change in different water layers were as follows: electrical conductivity,dissolved oxygen and water temperature in 0.5 m water layer;1.0 m water layer is water temperature,dissolved oxygen;The1.5 m water layer is water temperature,dissolved oxygen,total nitrogen,and electrical conductivity.Overall,water temperature and dissolved oxygen are the main factors affecting algae growth.(6)According to the water quality characteristics of different park landscape and the water purification capacity of aquatic plants,the optimal allocation model of aquatic plants in five parks was recommended. |
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