滇池夏季营养盐空间分布特征研究

Spatial Distribution of Nutrients during Summer in Dianchi Lake

基于2014年8月滇池外海空间23个采样点的水质采样数据,考虑化学需氧量(COD)、悬浮颗粒物(SS)、总磷(TP)、溶解性总磷(DTP)、总氮(TN)、溶解性总氮(DTN)、叶绿素a(Chla)七种理化变量并加入空间坐标信息,采用K-means聚类分析方法将采样点划分为三组,并对加入空间坐标信息前后的变量进行聚类效果分析,应用相关性分析方法分析聚类后不同组中各测点水质指标之间的相关性,结合七个水质指标的熵权评价结果研究了水质的空间分布特征。结果表明,加入空间坐标信息后的聚类可避免聚类后同组点的空间分布分散的情况,有助于优化常规的水质监测点位;各水质指标之间并不存在明显相关性,叶绿素a的空间差异明显,呈现出北高南低的空间分布特征,这与流域上的营养盐排放主要集中在东北部区域,并随水流由北向南对流扩散有关。

Based on the water quality data of 23 sampling points in Waihai,the main part of Dianchi Lake,monitored on August 2014,considering seven physicochemical variables such as chemical oxygen demand（COD）,suspended solids（SS）,total phosphorus（TP）,dissolved total phosphorus（DTP）,total nitrogen（TN）,dissolved total nitrogen（DTN）,chlorophyll a（Chla）and coordinate information,k-means clustering analysis method was used to divide the sampling sites into three groups with or without coordinate information.The difference between those two results of cluster analysis was compared.Correlation analysis method was applied to analyze the correlation between different water quality variables in different groups.And then the entropy weight evaluation method was used to analyze the distribution of water quality.The results show that the clustering analysis with coordinate information can avoid that the spatial distribution of monitoring points that are discontinuity in the group.There is no obvious correlation between different water quality variables.The spatial difference of chlorophyll a is obvious,and the concentration of chlorophyll a in the north of Waihai is much higher than that in the south,which is mainly related to the discharge of nutritive salt in the northeast region and transfer from the north to the south area under the advection and diffusion.