典型重工业区与污灌区植物的重金属污染状况及特征

Contamination and Characters of Vegetation Polluted by Heavy Metals in Typical Industrial Regions Subjected to Sewage as Irrigation

对我国几个典型重工业区和污灌区木本植物、水生或湿地植物、农作物以及蔬菜、杂草的重金属污染状况进行了野外调查与采样分析。结果说明,相同条件下,垂柳、紫穗槐和女贞对Mn的吸收量较大,臭椿和紫穗槐对Cr和Zn、爬墙虎对Cu、臭椿对Cd和Pb的吸收能力均较强,而悬铃木、油松、芙蓉等相同条件下叶内浓度却很低。湿地植物对Zn的吸收累积能力接近或已经达到对重金属的“超富集”水平(≥1000mg·kg-1),凤眼莲对Cr和Cu的吸收量分别是其它水生与湿地植物平均值的12与4倍,湿地植物水芹对Ni和Cd的吸收累积明显高于水生植物。蔬菜和水稻对Cd、Cr、Zn的吸收累积量较高。对水稻,这3种元素主要积累在果实部位,说明该类污染土壤种植水稻对人类健康的风险性更大,而在土壤Cd污染严重的情况下种植小麦导致污染的可能性大于玉米。

A field investigation was carried out at some individual sites to evaluate contamination of vegetation by heavy metals, including trees, crops, vegetables and grasses. Results indicated that metal contents differed with plant species. Sweeping willow, amorpha and privet had higher contents of Mn; trees of heaven and amorpha absorbed more Cr and Zn; Boston ivy had higher concentration of Cu, while tree of heaven preferred to absorb higher amount of Cd and Pb from soil under same circumstance. However, another trees, such as chinar, Chinese pine and cottonrose hibiscus (Hibiscus mutabilis) had much less amounts of those metals, possibly due mainly to existing some evading mechanisms in these plants. On the other hand, aquatic plants accumulated high content of Zn, one of them had as high as more than 1000 mg·kg-1 of Zn, while 4 and 12 times of Cr and Cuwere absorbed by waterhyacinth compared with others two aquatic plants. Wetlandplant, cress was capable of accumulating more Ni and Cd than aquatic ones. Rumex acetosa L, later contained over 900 mg·kg-1 of Zn in both of shoots and roots.It may be concluded that phytoremediation is available in China from the results above. Moreover, for paddy rice, since the major portion (24 and 22%) of Cd, Cr and Zn accumulated in fruit parts, a high risk would be taken if growing rice on this sort of contaminated soils. In addition, growing wheat in Cd-contaminated soil would take a higher risk rather than growing maize. These results imply that ecological engineering steps, e.g., correctly selecting crops in agricultural practice could reduce metal contamination in food products, a'hygienic food' could be produced in 'unhygienic environment'.