太原盆地浅层地下水中富集元素空间变异特点

SPATIAL VARIATION OF ENRICHED ELEMENTS IN SHALLOW GROUNDWATER IN TAIYUAN BASIN

利用统计学结合GIS研究太原盆地浅层地下水中As、F、Cr^6＋、Cl、Fe、Mn6种元素的空间变异特征，空间变异性所用拟合理论模型主要是球状模型和指数模型．结果表明：太原盆地浅层地下水Fe浓度超过地下水Ⅲ类标准样品，占总样品数的45．8％，Mn占48．4％，F占27％，As占24．9％o，C1占24．7％，Cr^6＋。占16．3％．其质量浓度均呈对数正态分布．半方差分析表明，6种元素都存在块金效应，变程为2～33．8km，其中Cl，Fe，F，Mn块金系数值与基台系数值的比值小于25％，说明系统具有强烈的空间相关性，结构性因素（地质条件、气候、含水层性质、土壤类型等）占主导地位；As，Cr^6＋块金系数与基台系数比值在25％～75％之间，则说明系统变量具有中等的空间相关性，结构性因素与随机性因素（人为因素、特殊的地质条件等）共同发挥作用．

Geological survey revealed that elements As, F, Cr^6＋, Cl, Fe and Mn are present in high concentrations in shallow groundwater in Taiyuan basin, affecting water utilization. Geostatlstlcal methods combined with GIS were used in this article to investigate origin and occurrence of these elements. Both spherical model and exponential model were used. Data indicate that. （1） the percentage of groundwater samples, 45.8% of Fe, 48.4%of Mn, 27% of F, 24. 9% of As, 24.7%of Cl and 16.3% of Cr^6＋ were over the national groundwater standard grade Ill. The concentrations of the six elements showed logarithmic normal distribution. （2） an obvious nugget effect was found for all six elements with a range between 2 and 33.8 km. （3） for F, Cl, Fe and Mn, the ratio of nugget value to sill value was less than 25, indicating that they are spatially correlated and structural factors such as geological setting, climate, aquifer characteristics and soil type control the distribution. （4） for As and Cr6＋, the ratio of nugget value to sill value is 25%-75, which indicated that their distribution is moderately spatial correlative; random factors such as human activities, special geological conditions （faults） are controlling factors.