贵州兴仁煤矿开采旧址重金属Cd、 Hg和As在常见蕨类及其根际土壤中的含量与积累特征研究

本文对贵州兴仁某处煤矿区旧址自然定居的优势蕨类7科10属(分别为蕨菜、华中介蕨、栗蕨、狗脊、芒萁、顶芽狗脊、耳羽岩蕨、光里白、蜈蚣草和岭南铁角蕨)及其根际土壤重金属(Cd、Hg和As)含量进行了调查分析。结果表明,植物根际土壤Cd含量为0. 03～1. 9 mg/kg,超过了国家土壤二级标准; Hg和As含量分别为0. 5～15 mg/kg和537～5 330 mg/kg,均超过了国家土壤三级标准,其中As超标严重。蕨类植物中蜈蚣草富集As效果最佳,地上部分As含量达1 710 mg/kg,转运系数为1. 4。岭南铁角蕨地上部分Cd含量可高达1 490μg/kg,转运系数达56,具有极强的Cd富集能力。通过相关性分析发现,蕨类吸收Cd和As的量与根际土p H呈显著正相关关系(P0. 05),吸Hg量则与p H呈显著负相关(P0. 05)。土壤中重金属的可交换态与蕨类对重金属的吸收总量均呈显著正相关关系(P0. 05)。单因子污染指数法计算结果显示,废渣堆附近土壤Hg和As污染十分严重,其中As污染已扩散到下游区域。潜在生态风险程度评估表明,该煤矿区重金属Cd、Hg和As复合污染严重,其高风险程度应引起相关部门重视。

Concentrations and Accumulation of Cd, Hg and As in Common Pteridophytes and Their Rhizosphere Soils at an Abandoned Coal Mine in Xingren, Guizhou

Concentrations of hazardous elements (Cd, Hg and As) in dominant pteridophytes of 7 families and 10 genera (Pteridium aquilinum, Deparia okuboana, Histiopteris incisa, Woodwardia japonica, Dicranopteris pedata, Woodwardia unigemmata, Woodsia polystichoides, Diplopterygium chinese, Pteris vittata and Asplenium sampsonii) and their rhizosphere soil at a coal mine site of Xingren, Guizhou province, were analyzed. The result showed concentrations of Cd in rhizosphere soils were 0.03-1.90 mg/kg and exceeded the national soil secondary standard. The concentrations of Hg and As were 0.5-15 mg/kg and 537-5 330 mg/kg, respectively, and both exceeded the national soil third-level standard. Among collected pteridophytes, Pteris vittata exhibited a strong enrichment of As, the highest As concentration in their aboveground parts was as high as 1 710 mg/kg and the transport coefficient reached 1.4. The concentration of Cd in aboveground parts of Asplenium sampsonii reached 1.49 mg/kg and the transport coefficient was 56, showing a strong enrichment of Cd. The correlation analysis showed that the amounts of Cd and As accumulated by ferns were positively correlated with the pH of rhizosphere soils (P<0.05) and negatively correlated with Hg (P<0.05). The exchangeable fraction of hazardous elements in soil was positively correlated with their total amounts in ferns (P<0.05). The single factor pollution index showed that soils near the coal mining waste residue were heavily contaminated by Hg and As, and the latter spread to the downstream area. The potential ecological risk assessment showed that the combined pollution of Cd, Hg and As in the coal mining area was at the serious level, demanding public concerns.