三峡库区中低产土壤重金属含量及其与小麦吸收的关系

三峡库区中低产土壤的Hg,As,Cr,Pb,Cu五个重金属含量（除渝北区外），均在国家土壤环境质量标准内，属自然背景值一级标准。Cd和Zn高于全国土壤中的平均含量和背景值含量，属二级标准。土壤的重金属含量与土壤母质类型，pH值，阳离子交换量，有机质，无定形铁和物理性粘粒有关，同时存在一定的地域分布。重庆近郊的土壤所有重金属含量相对较高。土壤重金属的可给态或有效性含量极低，锌和铜不是过量，而是不足。小麦籽粒中As,Cr,Pb,Zn,Cu含量低于国家食品对重金属限量标准和小麦籽粒背景值标准，Hg,Cd含量高于国家规定标准。籽粒中的Cu,Zn含量是小麦茎叶中的2.0-2.2倍，而茎叶中的Hg,Pb,As,Cr,Cd含量明显高于籽粒。

LEVELS OF HEAVY METALS IN LOW-MIDDLE YIELD SOILS AND THEIR EFFECTS ON WHEAT UPTAKE IN THREE GORGES RESREVOIR AREA

The low-middle yield soils are the most important soil resources in Three Gorges Reservoir Area after the construction of Three-Gorge Project. It is basically guaranteed that the produced potential of these soils are synthetically improved and used, in which the immigrations may live and work in peace and contentment. This paper deals with the level of heavy metals in low-middle yield soils and their effects on wheat uptake in the Three-Gorge Reservoir Area. The results show that the content of Hg, As, Cr, Pb and Cu in low-middle yield soils all falls into the quality standards of soil environment in China, and belongs to the first quality standard of natural backdrop content. The content of Cd and Zn in the soils is higher than the average content in soils and natural backdrop content in China, and falls into second quality standards. The content of heavy metals in the soils are related with types of soil parents, pH value, cation exchange capacity, content of organic matter, amorphous iron and physical clay. The heavy metals in the soils are distributed regionally. The content of all heavy metals in suburbs of Chongqing municipality is higher than in out-suburb. The availability of soil heavy metals is very low. The content of As, Cr, Pb, Zn and Cu in wheat seed grain in the area is lower than permissive standard of heavy metals in food in China and backdrop content in wheat seed grain, but content of Hg and Cd is higher. The content of Cu and Zn in seed is 2 times of those in the stem and leaf. But, contents of Hg, Pb, As, Cr and Cd in the stem and leaf are higher than in the seed.