[Translocation Characteristics of Heavy Metals in Soil-Rice Systems Under Conventional Field Planting Environment].

The migration of heavy metal elements in the soil-rice system is a complex process， and it is important to clarify the processes of heavy metal uptake and enrichment in rice under conventional field cultivation environments to ensure food safety. In this study， we analyzed the migration characteristics and influencing factors of heavy metals in the soil-rice system by systematically collecting rice plants and soil samples in representative areas in Hechuan District， Chongqing City， China. The results showed that the paddy field soil in the study area was acidic on the whole. The spatial distribution of heavy metal elements was relatively uniform， and the enrichment degree of Cd was higher than those of other elements. Some samples exceeded the screening value of the risk of soil pollution in agricultural land， and the rate of exceedance of the standard at location was 26.67%. Among the different parts of the rice plant， the content and enrichment characteristics of Cd and Cu were in the order root > stem > leaf > grain， the content and enrichment characteristics of Zn were in the order stem > root > leaf > grain， and those of other heavy metals were in the order of root > leaf > stem > grain. The enrichment capacity of rice roots， stems， leaves， and grains was significantly stronger for Cd in soil than for other elements. The Cd content in grains was mainly controlled by the transport of Cd from soil to root and from root to stem. The analysis of factors affecting heavy metal content and migration in rice grains showed that the heavy metal contents in grain were not significantly affected by the total contents of heavy metals in soil. The factors of MgO， CaO， K₂O， Fe₂O₃， S， Mn， pH and C_org could affect the uptake of heavy metals by rice grains by influencing the environment of the rice roots and the bioavailability of heavy metals. pH showed a more prominent effect. To ensure food security production in the study area， heavy metal migration to rice should be reduced through soil pH adjustment， organic fertilizer application， and water control.