川中红层灌区地下水硝酸盐污染特征及影响因素

摘要

为探明川中红层灌区地下水硝酸盐污染特征及影响因素,选取简阳市内典型农业种植区,利用变异函数模型与ArcGIS地统计模块,分析了区内地下水硝酸盐污染空间变异特征,并通过因子分析识别其主要影响因素.研究表明:球状模型为本次插值分析的最优理论模型,块金值为0.067,基台值为0.736,块金效应0.091,研究区地下水硝酸盐分布的空间自相关性较强;区内大部分地区硝酸盐污染严重,约有91.8%的面积遭受硝酸盐污染,农业生产活动与包气带岩性特征加剧了地下水硝酸盐含量的升高;研究区中部金鸡河两侧地下水水力坡度较大,径流强烈,污染物不易富集,河流两侧硝酸盐含量明显较低;因子分析表明,地下水硝酸盐含量主要受地层岩性、地形地貌、pH值和人类活动等因素影响.%In order to verify the pollution distribution and influencing factors of nitrate in groundwater in agricultural irrigation areas in central Sichuan red layer basin,a typical agricultural area in Jianyang city is selected as the study area. Spatial variabili-ty of nitrate pollution in groundwater are analyzed by the model of variogram and the geostatistics of ArcGIS. The influential fac-tors of nitrate pollution are analyzed by factor analysis method. The results show that spherical model is the optimal model for in-terpolation analysis. The main parameters (the nugget,sill and nugget effect are 0.067,0.736 and 0.091 respectively) show a strong spatial self-correlation of nitrate distribution. Most of the area suffers seriously nitrate pollution,and the polluted area ac-counts for about 91.8% of the total area. Agricultural activities and lithology characteristic of vadose zone promote the increase of nitrate in groundwater. The larger groundwater hydraulic gradient and strong runoff in the aquifers on the both sides of the Jinji River in the central study area,are unfavorable for the accumulation of pollutants,resulting in significantly lower nitrate content. Factor analysis shows that the nitrate content in groundwater is mainly controlled by stratigraphic lithology,topography,pH value and human activities,etc.