Study On Water Environment Health Of Urban Wetland Park Based On The Landscape Key Ecological Process

Wetland is known as the kidney of the earth,an important part of the construction of the Sponge City,and the health of urban wetland ecosystem plays an important role in promoting the construction of ecologically civilized cities.As we have known,the Chengdu Bailuwan National Wetland Park,Qinglonghu Wetland Park and Beihu Wetland Park are important ecosystems of the Three Lakes,Eight Wetlands and Hundred Ditches in the ecological zone around the Chengdu city.Based on the healthy landscape of these wetlands,it is considered as a great significance to accelerate the construction of a beautiful and livable park city demonstration area that implements the new development concept.As the most important dynamic scale in landscape ecology,landscape process plays an important role in the formation and development of landscape structure and function.However,there are very few reports on the landscape health research of urban wetland parks based on ecological processes.Based on the above backgrounds,we conducted the health analysis on the water environment and related elements of four typical urban wetland parks in China and the United States（including Bailuwan,Qinglonghu and Beihu Wetland Park in Chengdu,and Capitol Lake in U.S.）based on the key process of landscape ecology.The temporal and spatial dynamics of key ecological parameters in wetland water and soil environment are compared,and their differences of the water environment（i.e.,state and process）of four urban wetland parks in China and the United States are investigated,and the landscape process health evaluation system of urban wetland parks is revealed.After analysis,this study has obtained the five conclusions as following:1)Based on the Technical Regulations of Lake（Reservoir）Eutrophication Evaluation Method and Classification（Zongzhanshengzi[2001]No.090）,our study showed that the comprehensive nutritional status index[i.e.,TLI（∑）]in Bailuwan and Qinglonghu Wetland Park are 63.52 and 63.15,respectively,which thus were classified as middle eutropher;while the water body in Beihu Wetland Park is classified as light eutropher（TLI（∑）=57.01）.In addition,based on the national standard as the Surface Water Environmental Quality Standard（GB 3838-2002）,the dissolved oxygen（DO）in the water bodies of Bailuwan,Qinglonghu and Beihuhu are 6.73,8.43 and 6.10 mg/L,respectively,the water-quality of Bailuwan and Beihu are thus classified as the Class II,while Qinglonghu is classified as the Class I.Besides,the average TP values of Qinglonghu and Beihue are less than or equal to 0.1 mg/L,so their water quality can be classified as Class I;while the water quality of Bailuwan is less than 0.1 mg/L,so can be classified as Class II.2)Based on the national standard as the Surface Water Environmental Quality Standard（GB 3838-2002）,the analysis shows that the content of most of the heavy metal elements in our study are within the standard limit of Level I～II,indicating that the water bodies of the three wetland parks in Chengdu are not polluted by heavy metal such as arsenic/As,cadmium/Cd,copper/Cu,mercury/Hg,lead/Pb,selenium/Se and zinc/Zn.However,the Cr,Fe,and Mn in the water body of Bailuwan Wetland Park are V or exceed the limit,indicating that the water body is seriously polluted by Chromium/Cr,Iron/Fe and Manganese/Mn;while the Beihu Wetland Park is polluted by Fe,indicating that it needs further treatment to achieve Class V water-quality standards.According to the national standard as the Soil Environmental Quality:Soil Pollution Risk Control Standards for Construction Land（Trial）（GB 36600-2018）,the investigation shows that,except for the content of Cr in soil and sediment in the three wetland parks in Chengdu,it is rated as the second type of land for management and control.The other studied metals are the first type of land used for the screening value,indicating that most of the metals in the soil and sediments of the three wetland parks in Chengdu are within the lower limit,and only the content of Cr in this study has a control risk.3)According to the Second National Soil Survey Nutrient Classification Standard,we analyzed the soil and sediment nutrient classification showing that the soil total nitrogen（TN）of the three wetland parks in Chengdu is classified as the Level III（i.e.,high level）,and the organic matter（OM）is classified as the Level III（for Bailuwan and Qinglonghu）and LevelⅣ（for Beihu;i.e.,middle）,available phosphorus（AP）and quick-acting potassium（QP）are classified as the LevelⅠ（i.e.,very high）andⅡ（i.e.,high）,respectively;while the total nitrogen（TN）in the sediment is classified as the LevelⅢ.Moreover,the available phosphorus（AP）and quick-acting potassium（QP）are at Level I to III,while the organic matter（OM）in the sediment is at level IV.4)The pCO₂ and FCO₂ of the four wetland parks in China and the United States showed significant seasonal changes.Specifically,the pCO₂ and FCO₂ of the Qinglonghu water body showed the trend as increased-decreased-increased,while the Beihu showed a significant first increase and then decrease.In addition,the monthly changes of pCO₂ and FCO₂ in Capitol Lake also increased first and then decreased,but reached the highest in December and reached the lowest in May and November.On the whole,the seasonal variation of pCO₂ and FCO₂ in the three wetland parks in Chengdu has a negative correlation with that in Capitol Lake,LA,USA.During the study period,the pCO₂ and FCO₂ of the four wetland parks in China and the United States showed obvious daily changes.Analysis shows that,the daily fluctuations of CO₂ in the water bodies of the four wetland parks may be caused by aquatic metabolism,and are mainly affected by factors such as solar radiation,lake nutrition and water temperature influences.5)The calculation of the FCO₂ content in the four urban wetland parks shows that since many previous studies have neglected the high daily variability of pCO₂,the current regional and global CO₂ emission estimates may be a big uncertainty.Therefore,accurate measurement of carbon content in wetland water/soil plays an important role in the correct evaluation of wetland functions,and is also an important basis for the management department to formulate relevant policies and measures.More importantly,exploring the landscape health problems of wetland parks under the active management of human beings has important theoretical and practical significance for coordinating the water purification,rainwater storage,ecological restoration and climate regulation of urban wetland parks,as well as the ecological design of new urban wetland parks.