| 地质高背景区外源污染叠加条件下大白菜对Cd、Pb、Zn累积途径探究 |
| 摘要点击 1221 全文点击 367 投稿时间：2022-09-04 修订日期：2022-10-23 |
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| 中文关键词 地质高背景 Cd、 Pb、 Zn 土壤 大白菜 富集系数 转运系数 |
| 英文关键词 high geological background Cd, Pb, and Zn soil Chinese cabbage enrichment coefficient transfer coefficient |
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| 中文摘要 |
| 黔西北是喀斯特重金属地质高背景区,受历史上土法炼锌影响,区域内大气降尘重金属含量高,土壤污染严重.为探究叶菜类蔬菜重金属的累积途径,以大白菜为供试作物,选择Cd、Pb和Zn含量一致的地质高背景土壤和锌冶炼污染土壤,在锌粉厂污染区和无污染对照区进行盆栽试验,研究露天、覆膜和大棚栽培条件下大白菜重金属含量、富集系数(BCF)和转运系数(TF).结果表明,污染区和对照区大白菜ω(Cd)范围分别在0.10~1.01 mg ·kg-1和0.10~0.91 mg ·kg-1, ω(Pb)为0.31~0.62 mg ·kg-1和0.23~0.37 mg ·kg-1, ω(Zn)为7.50~32.74 mg ·kg-1和4.88~21.79 mg ·kg-1,总体上污染区重金属含量偏高,在地质高背景土壤上种植的大白菜,Cd和Pb基本达到国家食品安全标准限值的要求.受大气沉降的影响,污染区大白菜Pb和Zn含量显著高于对照区,Cd差异不明显.污染土壤弱酸溶态Cd、Pb和Zn占比分别为48%、3.0%和16%,是地质高背景对照土壤的3.15、1.01和1.57倍,受重金属活性的影响,污染土壤种植的大白菜Cd和Zn含量超过国家标准,显著高于对照土壤.污染土壤大白菜Cd、Pb和Zn的BCF根-土壤 显著高于对照土壤,且Cd和Zn的BCF大于Pb; 大白菜Cd和Zn的TF地上部-根 显著高于对照土壤,而Pb的TF地上部-根在污染区显著高于对照区,两个研究区内大白菜Pb含量均表现出:露天>覆膜>大棚.综上,大白菜Cd和Zn的含量受土壤重金属活性的影响大,主要累积途径是根的吸收和转运; 除根系吸收外,大气沉降是Pb的重要累积途径.因此,在地质高背景区,要注意控制外源污染叠加土壤上种植叶菜类作物的Cd和Zn暴露风险,同时,采用大棚种植能有效降低Pb的积累. |
| 英文摘要 |
| Northwest Guizhou is a karst area with a high geological background. Affected by historical soil zinc smelting, the heavy metal content of atmospheric dust in the region is high, and soil pollution is severe. In order to explore the accumulation pathway of heavy metals in leafy vegetables, Chinese cabbage was used as the test crop, and the geological high background soil and zinc smelting-contaminated soil with the same contents of Cd, Pb, and Zn were selected. A pot experiment was carried out in the polluted area of zinc smelting and the non-polluting control area. The heavy metal content, enrichment coefficient (BCF), and transport coefficient (TF) of Chinese cabbage were studied under open-air, plastic mulching film, and greenhouse cultivation conditions. The results showed that the contents of Cd, Pb, and Zn in Chinese cabbage in the polluted area and the control area were 0.10-1.01 and 0.10-0.91 mg·kg-1, 0.31-0.62 and 0.23-0.37 mg·kg-1, and 7.50-32.74 and 4.88-21.79 mg·kg-1, respectively. Overall, the contents of heavy metals in the polluted area were relatively high. The contents of Cd and Pb in Chinese cabbage planted in soil with a high geological background met the requirements of the national food safety standard limits. Affected by atmospheric deposition, the contents of Pb and Zn in Chinese cabbage in the polluted area were significantly higher than that in the control area, and the difference in Cd was insignificant. The proportions of weak acid-soluble Cd, Pb, and Zn in the contaminated soil were 48%, 3.0%, and 16%, respectively, which were 3.15, 1.01, and 1.57 times higher than those in the control soil with a high geological background. Affected by the activity of heavy metals, the contents of Cd and Zn in Chinese cabbage planted in the contaminated soil exceeded the national standard and were significantly higher than those in the control soil. The root-soil BCF of Cd, Pb, and Zn in polluted soil was significantly higher than that in the control soil, and the BCF of Cd and Zn was higher than that of Pb. The TF aboveground root Cd and Zn in Chinese cabbage was significantly higher than in the control soil, whereas the TF aboveground root Pb in the polluted area was significantly higher than that in the control area. The Pb content of Chinese cabbage in the two study areas showed open field>plastic mulching film>greenhouse cultivation. In conclusion, the content of Cd and Zn in Chinese cabbage was greatly affected by the activity of heavy metals in soil, and the main accumulation pathway was root absorption and transportation. In addition to root absorption, atmospheric deposition was an important accumulation pathway of Pb. Therefore, in areas with high geological backgrounds, attention should be paid to controlling the exposure risk of Cd and Zn in leafy vegetables planted on exogenously polluted soils. Additionally, greenhouse cultivation could effectively reduce the accumulation of Pb. |
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