长三角工业型城乡交错区蔬菜生产系统重金属平衡及健康风险

Balances of Heavy Metals and Healthy Risks in Vegetable Farming System of An Industry-Based Peri-Urban Area in Yangtze River Delta Region

随着中国城市化进程的加快,城乡交错区重金属污染问题越来越受到人们的关注。本文以长三角无锡市城乡交错区某蔬菜基地为例,详细观测了两年期间(2003.7—2005.7)蔬菜生产系统中Cu、Pb、Zn、Cd等重金属元素的平衡状况,其目的是掌握该生产系统重金属的积累趋势,评价系统中土壤和蔬菜的健康风险。结果表明:该系统在管理过程中,重金属的输入途径有施肥和灌溉,有机肥施用是生产系统重金属输入的主要来源,占输入量的88.5%以上。系统重金属年输入量较高,明显高于荷兰农业区水平,而Cu、Pb、Zn等元素年输出量明显较低,占输入量的10%以下,表现为盈余。观测田块土壤中Cu、Pb、Zn、Cd含量均低于农田土壤二级标准但明显高于太湖地区人为土元素背景值,存在积累的趋势。蔬菜中重金属健康风险评价结果表明,在目前的生产条件下,叶菜类蔬菜重金属健康风险较高。

There is growing concern about heavy metal pollution in peri-urban areas with the rapid development of urbanization in China. In this paper, the balances of some heavy metals including Cu, Pb, Zn and Cd at small-scale vegetable fanning system were studied during the years between July 2003 and July 2005 in an industry-based peri-urban area, Wuxi of the Yangtze River Delta region of China in order to judge the trend of heavy metal accumulation in the agricultural eco-system and assess the healthy risk of heavy metals in soils and vegetables. Results showed that organic fertilizers contributed mainly to heavy metal input in the studied system, which accounted for more than 88.5% of the total input of heavy metals. The inputs of heavy metal in the studied area were higher if compared to yearly heavy metal inputs in European agricultural area, while the corresponding outputs of heavy metals were obviously low, only accounting for less than 10% of the total inputs. Consequently, Cu, Pb and Zn balances were positive in all plots. Heavy metal contents in the studied plots were all lower than the limits according to Chinese agricultural soil safety standard level 2, but higher than the background value of Anthrosols in Tai-hu Lake region. Assessment of healthy risk indicated a high risk of heavy metal pollution existed in the leaf vegetables in the studied area.