基于地统计学和GIS技术的坡豪湖氨氮浓度空间变异特征分析

Spatial Variation Analysis of Ammonia Nitrogen Concentration in Pohao Lake Based on Geostatistics and GIS Technology

在以喀斯特地貌为主的桂西北地区,坡豪湖是广西极为罕见的大面积的风景秀丽的湖泊。由于人类活动逐渐频繁,坡豪湖水环境状况受到影响。为了解坡豪湖水质的状况,在实地采样与测样的基础上,基于地统计学半方差理论和GIS软件Kring空间插值方法,对坡豪湖水体中氨氮进行空间变异特征分析。结果表明:指数模型是氨氮浓度的最优半方差拟合模型;氨氮浓度的块金系数(C0/C+C0)=0.4076,在25%~75%之间,表现出变量氨氮浓度空间自相关程度中等,具有较强的空间自相关,可进行空间插值;空间分布上,氨氮浓度大致呈现出湖西部高于东部,且自湖中心向南北增高的变化趋势,在湖东北小部分处氨氮浓度值偏高;结合地表水环境质量标准,坡豪湖大部分水域即78.18%面积的氨氮浓度符合国家二级标准,适用于水产养殖,11.94%面积的水质氨氮浓度符合国家一级水质标准,9.88%面积的水质氨氮浓度值在国家三级标准和四级范围之内。

In the northwestern part of Guangxi,which is dominated by karst landforms,Pohu Lake is a very large and scenic lake.As human activities become more and more frequent,the environment of Pohao Lake is affected.Under the field sampling and sampling measurement,this study analyzes the spatial variation of ammonia nitrogen concentration in Pohao Lake by the Geostatistics semi-variance theory and Kriging spatial interpolation method of GIS to understand the water quality.The results indicates that the optimal semivariogram model ammonia nitrogen concentration is Exponential model.The nugget coefficient of ammonia nitrogen concentration(C0/C+C0) is 0.407 6,between 25% and 75%,showing moderate spatial autocorrelation on ammonia nitrogen concentration,which is possible to do the spatial interpolation.In spatial distribution,the ammonia nitrogen concentration in the western part of the lake is higher than that in the eastern part,and increases gradually from the center of the lake to the north and south.And the value of ammonia nitrogen concentration in the north of the lake is the highest.Integrating with environmental quality standards of surface water,the most lake area,namely 78.18%,meets the national second-level standard and it is suitable for human drinking and aquaculture.The 11.94% of the area meets the national one-level,and the 9.88% of the area is within the national three-level and four-level.