桂北典型锰矿区周边土壤重金属污染状况及主要植物富集特征

Heavy metal pollution assessment of a typicalmanganese mine tailing and heavy metal enrichment characteristics of dominant plant species in North Guangxi

关键词:  土壤重金属, 锰矿区, 污染评价, 富集植物, 转运系数

Key words:  soil heavy metal, manganese mining area, pollution assessment, accumulator plant, translocation factor

摘要:

为探究桂北某典型锰矿尾库区周边土壤和农作物重金属污染状况,筛选适合该地区污染土壤修复的植物材料,该研究在矿区周边采集了9种农作物和23种主要植物及其根际土壤,并测定了Cd、Mn、Cr、Pb和Zn 5种重金属含量,采用单因子污染指数法和综合污染指数法评价了矿区农田土壤、农作物中重金属的生态风险,通过计算植物对重金属的富集和转运系数评估其应用潜力。结果表明:(1)研究区土壤Cd、Mn污染最为严重,单因子污染指数分别为18.53、147.09,达到重度污染级别。(2)研究区花生和小白菜等作物可食用部位中的Cd、Cr、Pb含量均超过食品国家安全标准(GB 2762—2017)中的阈值,具有较高健康风险。(3)23种主要植物中青葙、鬼针草、一点红、蜈蚣草等对多种重金属转运系数大于1,具备富集型植物特征; 一把伞南星、蓖麻、千里光等根部重金属含量较高,转运系数较低,具备根部囤积型植物特征; 响铃豆、筒轴茅、苣荬菜等富集的重金属含量相对较低,且在重金属污染土壤中能健康生长,具备规避型植物特征。该研究结果表明,研究区土壤存在较严重的Cd/Mn复合污染,青葙等植物用于修复该复合污染土壤极具应用潜力。

Abstract:

In order to assess the heavy metal pollution of soils and crops around a typical manganese mine tailing in North Guangxi, and to select suitable plant materials for the remediation of heavy metal pollution in this area, nine crop samples, 23 dominant plant species and their rhizosphere soils, were collected. The contents of Cd, Mn, Cr, Pb and Zn of the samples were analyzed. The ecological risks of heavy metals in the soils and crops were evaluated using the single factor and comprehensive pollution index. The bioconcentration and translocation factors of the dominant plant species were calculated. The results were as follows:(1)Cd and Mn were the dominant pollutants in the soils of the studied area. The values of single factor pollution index of Cd and Mn reached 18.53 and 147.09 respectively.(2)The contents of Cd, Cr and Pb in crops such as Arachis hypogaea and Brassica chinensis exceeded the threshold values in the National Food Safety Standards(GB 2762—2017), which had great health risks.(3)Among the 23 dominant plant species, thetranslocation factors of Celosia argentea, Bidens pilosa, Emilia sonchifolia and Eremochloa ciliaris for several heavy metals were greater than one, indicating that they have the characteristics of metal accumulating plants. The heavy metal contents in roots of Arisaema erubescens, Ricinus communis, and Senecio scandens were relatively higher, while their translocation factors were relatively lower, indicating that they were root hoarding plant. The metal contents in the shoots and roots of Crotalaria albida, Rottboellia exaltata and Sonchus arvensis were relatively lower, while they kept healthy in the contaminated soil, indicating that they were elusive plants. The results show that the soils in the studied area are seriously polluted by Cd and Mn, and Celosia argentea is a potential plant material for the remediation of the co-contaminated soil.