Abstract:

There are prominent problems of heavy metal pollution due to mining, smelting and plant accumulation in northern Guizhou Province, where is rich in manganese resources. In order to screen out the pioneer plants that adapt to soil heavy metal pollution in the study area, the concentration of Mn, Cb, Pb, Cu, Zn, Cr and Hg in soils and 13 dominant plants of the Xiangjiang manganese mining area were determined. The Nemeiro pollution index, bioconcentration factor (BCF) and transfer coefficients (BTF) were used to evaluate the soil heavy metal pollution risks and plant enrichment characteristics. The results showed that Mo, Cu, Cd and Zn had varying degree of pollution, with the single factor pollution indexes of 264.09, 5.18, 3.38, 1.57, 2.31 and 2.40, respectively. Furthermore, the Nemerow index was 188.40, which indicated that the mining area was severely polluted and manifested a compound pollution status with Hg and Cd as the leading contaminants, followed by Mn-Cr-Cu-Zn. The BCF and BTF of Cd in the Hypolepis punctata, Phytolacca americana, Amaranthus spinosus and Xanthium sibiricum were exceeding 1. The concentration of Mn in Phytolacca chinensis, Conyza canadensis and Polygonum lapathifolium far exceeded the upper range of most terrestrial plants. These three plants had excellent tolerance and enrichment characteristics in the high Mn environment. The BCF values of Mn and Zn in the aboveground part of Phytolacca americana reached 1.30 and 1.83, respectively, indicating it belongs to Mn, Cd, and Zn-enrichment plants; the BCF value of Mn in Hypolepis punctata was greater than 1, but the BTF was much less than 1, which belonged to a hoarding plant. Gynostemma pentaphyllum and Eclipta prostrata had BCF values lower than 1 for other elements except Zn and Mn, which belonged to evasive plants. The contents of Mn, Cr, Cd, and Cu in soils of the study area were significantly positively correlated with the contents of Zn, Cd, and Hg in plant roots (P<0.05). The four high-concentration metal elements of Mn, Cr, Cd, and Cu could help to promote the accumulation of Zn, Cd and Hg in plants; The contents of Zn in soils were significantly negative correlated with the contents of Hg in plant roots (P<0.01), suggesting they had a stress inhibition effect. The plants including Phytolacca americana, Conyza canadensis, Polygonum lapathifolium and Xanthium sibiricum had a strong compound enrichment capacity for heavy metals, and could be used to serve as pioneer plants for pollution control in the study area.

Key words: manganese mine, heavy metal, dominant plants, enrichment characteristics, pollution evaluation, soil remediation

摘要：

黔北地区锰矿资源丰富,开采、冶炼和堆积过程导致区域土壤重金属污染问题突出,为筛选适应该区域修复土壤重金属污染的先锋植物,对贵州湘江锰矿区土壤及13种优势植物地上部和根部中Mn、Cb、Pb、Cu、Zn、Cr和Hg含量进行了测定分析,分别采用单因子和内梅罗污染指数法、富集和转运系数对土壤污染风险及植物富集特征进行评价。结果表明,锰矿区环境土壤中Hg、Cd、Cr、Mn、Cu和Zn存在不同程度的污染,单因子污染指数分别为264.09、5.18、3.38、1.57、2.31和2.40,内梅罗综合污染指数达188.40,远超重度污染水平限值,形成了以Hg、Cd为主导,Mn-Cr-Cu-Zn伴生的复合污染区域特征。13种优势植物中姬蕨（Hypolepis punctata）、垂序商陆（Phytolacca americana）、刺苋（Amaranthus spinosus）、苍耳（Xanthium sibiricum）对Cd的富集系数和转运系数值均超过1;Mn在垂序商陆（Phytolacca americana）、小蓬草（Conyza canadensis）和酸模叶蓼（Polygonum lapathifolium）中的富集量远超正常植物限值,3种植物在高浓度Mn环境中均具有良好的耐性和富集特征。垂序商陆地上部对Mn和Zn的BCF值分别达1.30和1.83,属Mn、Cd、Zn的富集型植物;姬蕨对Mn的BCF大于1,但BTF远小于1,属囤积型植物;绞股蓝（Gynostemma pentaphyllum）和鳢肠（Eclipta prostrata）对除Zn、Mn外的其余元素的BCF均小于1,属规避型植物。研究区土壤中Mn、Cr、Cd、Cu质量分数分别与植物根部Zn、Cd、Hg质量分数呈显著正相关关系（P<0.05）,Mn、Cr、Cd、Cu四类高浓度金属元素有助于促进植物对Zn、Cd和Hg的富集;土壤中Zn质量分数与植物根部Hg质量分数呈极显著负相关关系（P<0.01）,存在胁迫抑制。垂序商陆、小蓬草、酸模叶蓼、苍耳具有较强的重金属综合富集能力,可作为治理该地区环境污染的先锋植物。

关键词: 锰矿, 重金属, 优势植物, 富集特征, 污染评价, 土壤修复