Abstract: Through the investigation and sampling analysis of the polluted paddy soil around the gangue yard in three coal mines in midwestern Guizhou province, the impact of heavy metal accumulation and migration on the ecological environment in polluted farmland was discussed. The results showed that the content of Cd and Hg in polluted paddy soil in coal mining area was higher than the soil pollution risk screening value of 2.20~9.30 times and 0.34~2.48 times for agricultural land, respectively; which the content of Cd in 86.7% of farmland was higher than the control value of soil pollution risk of agricultural land. So the element that causes heavy metal pollution in farmland around the coal gangue yard was Cd first, Hg second, and Cu and Cr third. The content of Cd in the drainage from contaminated farmland around gangue yard was exceeded the limit of class III water quality standard of surface water or the standard of farmland irrigation water quality, and the content of Hg in drainage was exceeded class III water quality standard of surface water, so the heavy metal that affected the change of water quality was mainly Cd, followed by Hg. In addition, the contents of Cd, Hg and As in rice in the survey area were 0.74~1.77 times, 0.45~1.35 times and 0.50~1.16 times of the limit value of pollutants in the national food safety standard, respectively; and the exceeding rates of Cd, Hg and As were 73.3%, 33.3% and 20.0%, respectively, which indicated significant Cd pollution and a certain degree of Hg pollution occured in rice from the polluted paddy soil in coal mine areas.

Key words: coal mine area, gangue yard, farmland, heavy metals, pollution risk