Abstract:

To better understand the geochemical characteristics and influencing factors of the selenium-enriched soils of the arable land around the stone coal mine,144 topsoil samples were collected from the cultivated land around Huibu stone coal mine in Changshan County, Zhejiang Province, and 20 sugarcane samples, 6 soil vertical profile samples, 5 rock samples, 3 surface water samples were collected at the same time. The contents of Se, organic matter, As, Cd, Cu, Pb, Zn, Ni, Hg and Cr were determined to explore the geochemical characteristics of Se rich soil. The results showed that Se content mainly concentrated in the range of 0.47-1.34 mg/kg in surface soil, with an average content of 0.87 mg/kg, which was much higher than that average value of Zhejiang Province, and the high value area of Se content was consistent with the strike of stone coal mine in Huibu. Se content decreased with the increasing depth along the vertical profile of soil. 89.58% of the soil samples and 65% of the sugarcane samples reached the Se enrichment standard, but there was an ecological risk that the contents of Cd and other major heavy metals in soil and agricultural products exceeded the state standard. The average content of Se was the highest (1.31 mg/kg) in the $\epsilon$₁h of soil stratum, and the lowest (0.64 mg/kg) in the O_1-2. The average selenium content in dry field was slightly higher than that in paddy field without significant difference(p>0.05). The highest average selenium content was that of coarse bone soil, followed by that of limestone soil and paddy soil, and that of red soil was the lowest. The selenium content in soil had been affected by geological background, soil type and organic matter. The main factors for the formation of selenium rich soil had been regarded as the stone coal bed, black rock series and carbonate rocks, and a small part was related to human activities such as mining.

Key words: selenium-rich soil, geochemical characteristics, black rock series, influencing factors