Spatial and Temporal Distribution and Source Variation of Heavy Metals in Cultivated Land Soil of Xiangzhou District Based on EBK Interpolation Prediction and GDM Model

Abstract

In order to explore the spatial and temporal changes in spatial patterns and source changes in heavy metals in Xiangzhou District, 395 and 326 soil samples were collected from cultivated soil in Xiangzhou District in November 2009 and November 2019, respectively. The contents of Cr, Pb, As, Hg, and Cd during these two years were measured. The spatial pattern and variation distribution of five types of heavy metals during these two years were obtained by using the empirical Bayesian Kriging (EBK) method. The effect (q-statistic) of 19 environmental factors and 5 types of heavy metals was calculated by using the geographical detector model (GDM), and the changes over the two years were compared. The results showed that compared with that in 2009, the heavy metal contents of Cr, Pb, Hg, and As in Xiangzhou District were decreased as a whole in 2019, whereas the Cd content increased overall. The spatial differentiation of heavy metals in the soil in Xiangzhou District in 2019 was more complicated than that in 2009. Pb, Hg, and Cd in the south and Hg in the central urban area and surrounding areas also increased. The content of each element decreased to the north and northwest. Compared with that in 2009, the explanatory power of natural factors and the distance between pollution enterprises on the single factor of the five soil heavy metal contents in 2019 decreased, and the influence on the contents under the control of single factors decreased significantly. The superposition influence of human activity factors increased, especially the distance between residential land, road, and land for pollution enterprises and environmental factors on soil heavy metal elements. These results indicated that the changes in soil heavy metal sources in 2019 tended to be complex, with structural factors as the main influencing factor. The influence of the emission of polluting enterprises on heavy metal elements decreased, whereas the influence of human activities on heavy metal content increased.