Spatial-temporal Variation and Source Change of Heavy Metals in the Cropland Soil in the Industrial City

Abstract

Environmental policy regulation affects the accumulation of heavy metals in soil. Two soil surveys were conducted in farmland in industrial cities. Classical statistical and geostatistical methods were applied to examine the content changes and spatial-temporal distribution characteristics of Cd, Pb, Cu, and Zn in soil. The pollution sources and their contribution rates were further analyzed by a principal component analysis/absolute principal component scores (PCA/APCS) model. The results indicated that the concentrations of Cd, Pb, Cu, and Zn increased during the two periods. The content of Cd and Pb in the spatial distribution decreased from northwest to southeast in both periods. The content of Cu and Zn decreased from north to south in 2011, and gradually decreased from northwest to southeast in 2017. Compared with 2011, the contribution rate of industrial activities increased by 5.58%, 10.4%, and 20.4% for Cd, Cu, and Zn, respectively, but decreased by 19.7% for Pb. The contribution rates of the other factors to Cd and Pb increased by 3.76% and 24.83%, respectively, and decreased by 9.27% and 4.31% for Cu and Zn, respectively. Relevant measures have reduced the accumulation of Pb in regional soil caused by industrial activities, but not Cd, Cu, or Zn. In addition, new Cd and Pb pollution sources need to be paid attention to.