小尺度下某铀尾矿库周边土壤铀污染与空间自相关性研究

Study on Uranium Pollution and Spatial Autocorrelation of Soil around Uranium Tailing Bank on Small Scale

  • 摘要: 对某铀尾矿库周边44 km2范围内的土壤进行采样,采用空间自相关分析技术结合地统计学的方法,实现小尺度下铀尾矿库周边土壤铀的空间自相关性与变异性研究。地统计学结果显示,土壤中铀含量的均值是当地背景值的2.9倍。通过单因子污染指数计算可知,所测样本中清洁样品数占总样品数的0.5%,轻度污染样品数占22.16%,中度污染样品数占46.76%,重度污染样品数占31.03%。通过空间自相关分析得到铀的全局Moran’s I为0.154 3,Z值为2.066 4,显著性大于1.96,表明铀尾矿库周边土壤中的铀有正的空间自相关性,存在空间聚集性。通过局域自相关分析得到铀空间关联的局域指标(LISA)聚集图,探讨区域内每个单元与相近单元属性的相关水平。半方差函数计算结果显示,铀为强相关性,与空间自相关分析结果类似。根据局部自相关分析结果,将研究区划分为禁止耕作区、综合治理区、重点治理区、重点防护区,建议有关部门进行分区管理。

     

    Abstract: The soil samples in the 44 km2 range around a tailing bank were sampled. The spatial autocorrelation analysis and geostatistics method were used to study the spatial autocorrelation and variability of uranium in the soil around uranium tailing bank. The results of geostatistics method show that the mean value of uranium content in soil is 2.9 times of the local background value. According to the single-factor pollution index, the proportion of clean samples in the samples taken is 0.5%, that of mild pollution is 22.16%, that of moderate pollution is 46.76%, and that of heavy pollution is 31.03%. According to the spatial autocorrelation analysis, the global Moran’s I of the uranium is 0.154 3, the Z value is 2.066 4, and the significance is greater than 1.96, indicating that the uranium in the soil around the uranium tailing bank has positive spatial autocorrelation and spatial aggregation. The local indicators of spatial association (LISA) aggregation map of uranium were obtained by means of local autocorrelation analysis, and the correlations between the properties of each unit and similar units in the area were discussed. The results of the semi-variance show that uranium is strongly correlated with the results of spatial autocorrelation analysis. According to the results of local autocorrelation analysis, the study area is divided into no-till farming area, comprehensive management area, key control area and key protection area. And it is suggested that the concerned departments carry out zoning management according to different pollution degrees.

     

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