Exploratory analysis of trace elements in soils and plants affected by a gossan in the Semiarid

ABSTRACT Trace elements in high concentrations are a huge problem worldwide. Monitoring of natural areas with a high concentration of these elements, such as soils under the influence of gossans, is important since there is little information available. This study aimed to evaluate the pseudo total and available concentrations of Fe, Mn, Pb, and Zn in the soil and its accumulation in native and cultivated plants in the area under the influence of gossan in the Semiarid region in Brazil. Soil samples (0-20 cm) were collected in the North, South, and center areas of the gossan and five transections separated by 1000 m. The pseudo total (EPA3050A) and available concentration (DTPA, Mehlich) of Fe, Mn, Pb, and Zn were determined. In the same points, plant samples were collected and processed to determine the concentration and bioconcentration factor of Fe, Mn, Pb, and Zn. Soils under the influence of the gossan had high Pb and Zn concentration (exceeding soil reference values), indicating that care should be taken in these areas to prevent any risk for the local community. Plants showed different accumulation patterns, with a higher accumulation of trace elements in the shoot (Fe, Mn, Zn), while Pb was primarily accumulated in the roots. Even though soil concentrations were high, plants showed in general, low bioconcentration factor of the potentially toxic elements, except for Zn, indicating that soil conditions limit their availability.摘要 高浓度微量元素已成为全球性的突出环境问题。鉴于当前相关研究资料较为匮乏，对铁帽（gossan）影响区域这类高微量元素含量的自然区域开展监测工作具有重要意义。本研究以巴西半干旱区铁帽影响区域为研究对象，旨在测定该区域土壤中Fe、Mn、Pb、Zn的伪总浓度（pseudo total concentration）与有效态含量，并分析这些元素在本土植物与栽培植物中的富集特征。研究人员在该铁帽区域的北部、南部、中心区域以及间距1000m设置的5条样带上采集了0~20cm土层的土壤样品；采用EPA3050A法测定土壤样品中Fe、Mn、Pb、Zn的伪总浓度，采用二乙三胺五乙酸（DTPA）、梅利奇（Mehlich）提取法测定其有效态含量。在相同采样点位同步采集植物样品并完成前处理，以测定Fe、Mn、Pb、Zn的含量及生物富集系数（bioconcentration factor）。研究结果显示，铁帽影响区域的土壤中Pb与Zn含量显著偏高，超出土壤基准参考值，提示该区域需采取必要防护措施，以规避对当地社区的健康风险。不同植物的元素富集模式存在显著差异：地上部对Fe、Mn、Zn的富集能力更强，而Pb主要富集于植物根部。尽管土壤中微量元素含量偏高，但除Zn外，多数潜在有毒元素的生物富集系数普遍较低，表明土壤环境限制了这些元素的生物有效性。