基于雷达图的鄱阳湖湿地水质评价

Water Quality Assessment of Poyang Lake Wetland Using Radar-Type Charts

采用雷达图的方法来评价鄱阳湖湿地的水质状况,验证其在鄱阳湖湿地水质评价中的可行性。基于鄱阳湖湿地30个采样点的实测水质数据,选取溶解氧(DO)、高锰酸盐指数(CODMn)、叶绿素a(Chl-a)、氨氮(NH+4-N)、总磷(TP)、总氮(TN)及重金属铜(Cu)、铅(Pb)为水质评价因子,构建水质雷达图对鄱阳湖湿地进行水质评价,雷达图红色区域的面积大小和形状能直观反映采样点的水质状况及主要的污染因子,并基于雷达图红色区域的面积大小计算雷达图水质指数。结果显示,鄱阳湖湿地水体的主要污染物为氮、磷营养盐、重金属及Chl-a;自然保护区及周边湿地的水质较好,而河口附近湿地的水质最差;雷达图水质指数与内梅罗指数、主成分水质指数的评价结果间存在显著的相关性,表明其能较客观地反映鄱阳湖湿地的水质状况。与传统方法以单一数值呈现水质评价结果相比,水质雷达图以可视化的方式、多维度地呈现采样点的水质状况,其结果更直观易懂,尤其有助于增强公众对水环境污染的认知和关注度,为水质评价及评价结果的展示提供方法上的借鉴。

Poyang Lake wetland provides important wintering habitats for many migratory bird species and spawning grounds for many fish species.Regular monitoring and water quality assessment provides critical information to support the rational development of water pollution control strategies.Previous assessments of water quality focused mainly on Poyang Lake and neglected the surrounding wetlands.In this study,radar chart-like figures were constructed to display water quality parameters for assessing and visualizing water quality in Poyang Lake wetland.The results were compared with water quality assessments based on the Nemerow index and the principal component water quality index to verify the feasibility of radar chart based water quality assessment and water resource management in the Poyang Lake wetland.The radar chart was created based on eight water quality variables obtained at 30 sampling sites in the Poyang Lake wetland during September and October of 2016,including dissolved oxygen(DO),chemical oxygen demand using permanganate(CODMn),chlorophyll-a(Chl-a),ammonia nitrogen(NH+4-N),total phosphorus(TP),total nitrogen(TN),Cu and Pb.The eight water quality variables were arranged radially as the axes with equal distances between each other.Each variable value was plotted along its individual axis and connected together to form a figure.The size and shape of the radar chart figure visually indicates the main pollutants and overall water quality.Water quality in the Poyang Lake wetland displays high spatial heterogeneity.Water quality near river discharges to Poyang Lake was poor,whereas water quality in or near nature reserves was good.TP,TN and Chl-a were the main pollutants affecting water quality at most sampling sites,and water quality near river discharges was affected by heavy metal pollution.A water quality index was then calculated based on the red area in radar chart figures.The assessment results based on the radar chart water quality index(RCWQI)correlated significantly with those derived from the Nemerow and principal component water quality indices,indicating that the radar chart is a reliable alternative tool for water quality assessment in the Poyang Lake wetland.The water quality radar chart allows rapid,multidimensional visualization of water quality and has good potential for quickly comparing water quality at different locations,facilitating visualization of water quality at public meetings and increasing public interest in water resource protection.