Abstract：
The distributions of heavy metals in paddy fields and rice along river valleys were studied to explore the key factors affecting the accumulation of heavy metals in the upstream terraces and downstream plains. Results from 975 sampling sites showed that elevation, growing season and soil organic matter (OM) had significant effects on the content of Cd and Pb in topsoil and rice. The content of Cd (0.47-0.66 mg kg-1) and Pb (49.9-68.6 mg kg-1) in paddy fields with low elevation (30-60 m) in the downstream plains was significantly higher than the content of Cd (0.29-0.38 mg kg-1) and Pb (43.9-56.3 mg kg-1) in the upstream terraces with high altitude (60-90 m). In the double-rice production area, late rice generally produced grains with higher Cd and Pb content than early rice. Soil Cd was positively increased with the content of OM, especially in the downstream plains. When elevation was used for principal component analysis, plains with low elevation were grouped together with high content of total and soluble Cd, OM and Pb in soil, as well as high content of Cd and Pb in late rice. Altitude is one of the key factors affecting Cd content in rice. Although content of Cr (93.7-138.0 mg kg-1) was significantly higher than that of Cd and Pb in soil, content of Cr was lower than that of Cd in rice. These results indicate that paddy fields with elevation of 30-60 m in the downstream plains had high risk to produce late rice with Cd and Pb content exceeding the food safety standard 0.2 mg kg-1, which may be resulted from the driving force of runoff on soil soluble Cd and Pb from terraces to alluvial plains in river valleys.
摘要：
研究了沿河谷的稻田和水稻中重金属的分布，以探索影响上游梯田和下游平原重金属积累的关键因素。975个采样点的结果表明，海拔，生长季节和土壤有机质（OM）对表层土壤和水稻中Cd和Pb的含量有显著影响。下游平原低海拔(30~60m)水田Cd(0.47~0.66mgkg-1)和Pb(49.9~68.6mgkg-1)含量显著高于上游高海拔(60~90m)梯田Cd(0.29~0.38mgkg-1)和Pb(43.9~56.3mgkg-1)含量。在双稻产区，晚稻通常生产的谷物中Cd和Pb含量高于早稻。土壤Cd含量随OM含量呈正增加,尤其是在下游平原。当高程用于主成分分析时，低海拔平原被组合在一起，总Cd和可溶性Cd含量高，土壤中的OM和Pb，晚稻中Cd和Pb含量较高。海拔是影响水稻中Cd含量的关键因素之一。尽管土壤中Cr（93.7-138.0mgkg-1）的含量显着高于Cd和Pb的含量，水稻中Cr含量低于Cd含量。这些结果表明，下游平原海拔30-60m的稻田生产Cd和Pb含量超过食品安全标准0.2mgkg-1的晚稻的风险很高，这可能是由于径流的驱动力所致。从梯田到河谷冲积平原的土壤可溶性Cd和Pb。
