Abstract
To assess heavy metal pollution and ecological risk, a total of 28 surface paddy soil samples were collected and analyzed around a famous copper smelter in Guixi, China. The results showed that all sites were heavily contaminated by both Cu and Cd, compared with soil background values, whose average concentrations exceeded the standard by 5.7 and 12.3 times, respectively, posing a slight ecological risk related to Cu (potential ecological risk index <40) and an extremely serious ecological risk related to Cd (potential ecological risk index >320). The risks were also demonstrated through the speciation analyses of Cu (CaCl2-Cu 2.63%, acid-soluble Cu 8.67%, and residual Cu 74.17%, on average) and Cd (CaCl2-Cd 47.30%, acid-soluble Cd 45.02%, and residual Cd 28.87%, on average) in the surface paddy soil, including the use of a CaCl2 extraction procedure and the BCR (Community Bureau of Reference) sequential extraction scheme. Several soil properties (residual carbon, cation exchange capacity, and soil texture) were significantly correlated with soil Cd but made a small contribution to their variability with a poor linear fit because of external Cd input to the soil, while soil total potassium largely influenced the soil Cu species except for residual Cu. Therefore, an effective Cu pollution regulation strategy through soil potassium control is suggested for this smelter soil.
Highlights
With rapid urbanization and industrial development, the heavy metal pollution of agricultural soil has been a great challenge all over the world [1,2,3]
These results are basically consistent with the serious combined pollution of Cu and Cd that existed in the soil around this smelter [10]; by contrast, there was a large decline (43.4%) in the TCu concentration in the surface paddy soil in the study area compared to 14 years ago [7] due to the improvement in copper smelting technology and the intensification of heavy metal pollution control [8,10]
Chemical speciation analysis of the soil heavy metals indicated that the surface paddy soil in the study area had high Cd bioavailability, while stable residual Cu (F4-Cu) dominated the Cu in the soil (Figures 3 and 4)
Summary
With rapid urbanization and industrial development, the heavy metal pollution of agricultural soil has been a great challenge all over the world [1,2,3]. A report from the Ministry of Environmental Protection of China (MEP) shows that 19.40% of the investigated cropland soil samples had pollutants exceeding the standard, and most of them were heavy metals [4]. Anthropogenic inputs, such as industrial emissions from nonferrous mining and smelting activities have been regarded as the most important sources of heavy metal pollution in China’s agricultural soils in the past few decades [3,4].
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