河北板蓝根产地土壤-植物中镉铅汞砷含量特征及其污染评价

Assessment of Cd, Pb, Hg and As contamination in soils and plants in Isatis indigotica cultivated regions in Hebei Province

  • 摘要: 采用野外调查和室内分析相结合的方法,研究了河北省安国市和蔚县板蓝根产地土壤-植物中Cd、Pb、Hg、As含量特征及其在菘蓝中的累积特性,并对板蓝根产地土壤和草药中Cd、Pb、Hg、As污染状况进行了评价,为该地区安全、合理地发展中草药生产提供数据支撑和科学依据。结果表明,安国市和蔚县板蓝根产地土壤中重金属Cd、Pb、Hg、As含量差异不大,土壤重金属含量的变异系数在11.70%~97.65%。以《土壤环境质量标准》(GB 15618-1995)一级标准值进行评价,综合污染指数评价结果显示45%板蓝根种植区土壤Cd、Pb、Hg、As污染等级为警戒限,其他处于清洁水平;而以《土壤环境质量标准》二级标准值进行评价,种植区单项污染指数及综合污染指数结果均 < 0.7,土壤环境清洁。此外,菘蓝地上部(大青叶)Cd、Pb、Hg、As平均含量分别为0.22 mg·kg-1、0.89 mg·kg-1、0.04 mg·kg-1、0.25 mg·kg-1,对重金属的富集能力表现为Cd > Hg > Pb > As;菘蓝地下部(板蓝根)Cd、Pb、Hg、As含量均值分别为0.14 mg·kg-1、0.57 mg·kg-1、0.04 mg·kg-1、0.26 mg·kg-1,对重金属的富集能力表现为Cd > Hg > As > Pb。所有菘蓝样品中Pb、Hg、As含量均未超出《药用植物及制剂进口绿色行业标准》(WM2-2001),大青叶9.09%样品中Cd超标,且Cd平均污染指数>0.7,属警戒限污染等级。因此,在中药材GAP(良好的农业规范)产地环境质量评价时,除板蓝根产地土壤完全符合土壤环境质量二级标准外,也不应忽视板蓝根和大青叶吸收和累积重金属的自身特性。

     

    Abstract: Concentrations of Cd, Pb, Hg and As in soils and plants in Isatis indigotica cultivated regions of Anguo City and Yuxian County in Hebei Province were analyzed and the bioconcentration factors of I. indigotica from different regions discussed. The study would provide data support and scientific basis for further studies of safe and rational development in crude Chinese drugs. The results showed that the contents of Cd, Pb, Hg and As in soil varied little in I. indigotica cultivated regions of Anguo City and Yuxian County in Hebei Province, with a range of coefficient of variation of 11.70%-97.65%. In the evaluation of the levels of soil contamination based on Class 1 standard for Cd, Pb, Hg and As of the Environmental Quality Standard for Soils (GB 15618-1995), and the Nemerow index background values of heavy metals were used as assessment standard. The range of Nemerow index of 45% soil samples from I. indigotica cultivated regions was 0.7-1.0, which suggested that the soils in the study areas were at an alarming level of pollution. When Class 2 quality standard was used, both the single pollution index and the Nemerow index did not exceed 0.7, which suggested that the investigated soils were generally safe for cultivation of I. indigotica. In addition, the average contents of Cd, Pb, Hg and As in shoots of I. indigotica were respectively 0.22 mg·kg-1, 0.89 mg·kg-1, 0.04 mg·kg-1 and 0.25 mg·kg-1, with accumulation capacity rank of Cd > Hg > Pb > As. The average contents of Cd, Pb, Hg and As in roots of the herb were respectively 0.14 mg·kg-1, 0.57 mg·kg-1, 0.04 mg·kg-1 and 0.26 mg·kg-1, with accumulation capacity trend of Cd > Hg > As > Pb. The concentrations of Pb, As and Hg did not exceed the safety limitation based on the Green Trade Standards for Import-Export of Medicinal Plants Preparations (WM2-2001). However, the contamination index of Cd in shoots of I. indigotica was higher than 0.7 and Cd level in 9.09% of the plant samples exceeded the safety limitation, indicating that the levels of Cd in the herbs in both regions were at an alarming level of pollution. It was therefore recommended to follow Class 2 standard of soil quality set in the Environmental Quality Standard for Soils. The accumulation characteristics of heavy metals in roots and shoots of I. indigotica should also be of significant concern in GAP (good agricultural practices) soil quality evaluation.

     

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