沈阳市城乡结合部土壤-作物系统铅含量水平及其影响因素分析

Pb Concentration in Soil-Plant System and Its Influence Factors in the Combination Area of Urban and Rural of Shenyang City

以沈阳市城乡结合部为研究区域,分析测定了土壤、蔬菜和粮食作物中铅的含量水平,并探讨了土壤有机质、pH值、全磷对铅在土壤-作物系统迁移的影响。结果表明,沈阳市城乡结合部耕作层土壤铅含量平均值为107.35m g·kg-1,是背景值的3.25～15.08倍,土壤铅含量均超过国家土壤质量标准的一级标准(G B15618-1995);蔬菜类可食部分铅含量的超标率是100%(G B14935-94、G B2707-2763-3),其中叶菜类叶子含铅量要远远小于其根系含铅量,根菜类叶子含铅量要大于根含铅量;粮食作物中水稻可食部分没有发现超标现象,而玉米籽粒超标率达7.1%。土壤有机质、pH值及全磷是影响作物铅含量及不同作物不同器官铅分配的重要因素,相关分析结果表明,蔬菜类的叶铅和根铅含量与土壤有机质含量呈显著的正相关关系,与土壤pH值和土壤全磷呈负相关关系,水稻籽实铅与土壤全磷呈正相关关系,尚未发现玉米籽实铅含量与土壤有机质、pH值及全磷具有统计学上的相关性。土壤有机质、pH值及全磷3种因素协同作用是导致不同作物机体铅吸收与分配的不均一性的根本原因。

The distribution character of lead in soil-plant system and its influence factors in connection areas of urban and rural of Shenyang city were studied. The lead concentrations of soils were comparatively higher, with the average being 107.35 mg·kg-1 that was 3.25～15.08 times of background value. Almost all lead concentrations of the soils were higher than the first standard oflead concentration prescribed in the Environmental Quality Standard for Soils (GB15618-1995), which suggested that the soils in the connection of urban and rural area were contaminated seriously not only by point pollution sources, but also by the ubiquitous non-point pollution resources. The leaf vegetables, suchas Chinese cabbage, small cabbage, lettuce, celery and spinach, and the root vegetables, such as white radish, red radish and carrot, were selected in the experiment. The order of enrichment index was root>leaf for leaf vegetables, while that was contrary for the root vegetables. The content of lead in edible part of vegetables were all beyond the standard of lead concentration, while 7.1%in edible part of maize was beyond the Tolerance Limit of Lead in Foods (GB 14935-94)and Categories of Food Hygiene Standards (GB2707-2763-3). The lead concentrations in seed of rice were lower than the standard concentration, mainlydistributed in root with only a little in the seed, and the order of lead concentrations in rice was: root>leaf>stem>seed. Similarly, the order of lead concentration in maize was: root> stalk>seed. These suggested that much lead might be absorbed and leached by the plant fibre. Organic matter, pH, and total phosphate had significant impact on the lead concentration in vegetables and its transfer in different organs. The lead concentrations in leaf and root of vegetables werepositively correlated with organic matter content, but negatively correlated with pH and total phosphate in soil. The lead in seed of rice was positively correlated with total phosphate in soil. There was no statistically significant correlation between lead content in seed of maize and organic matter, pH and total phosphate. Organic matter, pH and total phosphate in soils, cooperated with each other, resulted in different lead concentrations in different organs for different plants.