Abstract: In order to understand the contamination characteristics and bioavailability of heavy metals in the areas with abundant phosphate ore mines, the concentrations of Cd, Cu, Pb and Zn in samples of farmland soils and samples of different crops such as maize, rice and vegetables collected from Yunnan and Guizhou phosphate ore mine areas were determined and then the pollution characteristics of soils were evaluated. The regression equations were used to explore the effect of available heavy metals and soil properties on the quality of the agricultural products. The results show that Pb and Cd were enriched in most soil samples, the average enrichment factors of Cd and Pb reached to 2.31 and 2.39, respectively, compared to the local background values. About 84.8% and 28.3% of soil samples were polluted by Cd and Pb, respectively, and Pb concentrations were markedly higher than that of the farmland soils of other geological high background areas. The average biological accumulation factors of Cd in maize, rice and leaf vegetables were 0.09, 0.17 and 0.32, respectively. The soil Pb bioavailability in the studied area was lower than those in other high background areas. The crops had different abilities to absorb heavy metals, and the Chinese cabbage had the largest absorbing ability to four heavy metals and the absorbing ability of rice to Cd and Pb were higher than those of maize. It is not advised to plant Chinese cabbage in those areas, and the risks of Cd and Pb that exceeding the safety limits in crops should be considered. Correlation analysis and regression equations show that available heavy metals, along with pH, organic matters, and MgO in soils were the key factors affecting the accumulation of heavy metals in crops (P<0.05).

Key words: phosphate ore area, heavy metal, high geological background, bioavailability, quality of agricultural product