Contamination and Soil Biological Properties in the Serra Pelada Mine - Amazonia, Brazil

ABSTRACT Discovered in 1980 and unleashed an utter gold rush of the modern era, Serra Pelada was the largest open-air mine in Brazil. About 80,000 gold prospectors worked there until 1984, when the gold pits were flooded. The environmental impact caused by mining inflicted irreversible damage to the ecosystem, with the formation of a large lake and piles of waste rock and sterile overburden, still evident 28 years after the mine was closed. This study aimed to evaluate the available and pseudo total contents of potentially toxic elements (PTEs), the contamination and pollution levels, and to understand how the biological soil factors are related to the chemical properties of the soil and the available PTE contents in the Serra Pelada - Amazônia, Brazil. Soil was collected from seven areas around the lake: Area 1 - margin of the mine without waste and/or sterile deposits; Area 2 - margin with waste and/or sterile deposits; Area 3 - area with sterile deposit; Area 4 - mine tailings, denominated curimã by the prospectors, from which gold had been extracted; Area 5 - sediment dredged from the lake in the mine pit; Area 6 - area with agroforestry system; Area 7 - riparian forest, unaffected by the artisanal gold extraction process (control treatment). Apart from selenium (Se), all evaluated elements, in at least one of the studied areas, exceeded the contents of the investigation values (defined as the content of a given substance in soil or groundwater above which the human health is under potential direct or indirect risks, considering a standardized exposure scenario) in agricultural areas in Brazil, as determined by the National Council of the Environment. Soil enrichment and contamination with Co, Ba, Mn, and Hg were investigated. Principal component analysis showed that the available levels of PTEs influenced the soil biological properties, in particular basal respiration, indicating that important ecosystem processes are being affected by PTE contamination.

摘要
1980年被发现后，塞拉佩拉达（Serra Pelada）引发了现代史上一场彻头彻尾的淘金热，曾是巴西规模最大的露天金矿。约8万名淘金者在此作业，直至1984年金矿坑被水淹没。采矿活动造成的环境影响给当地生态系统带来了不可逆破坏：形成了大片湖泊，堆积了大量废石与无矿覆盖层，即便在矿山闭坑28年后，这些痕迹仍清晰可见。
本研究旨在评估巴西亚马逊地区塞拉佩拉达矿区土壤中潜在有毒元素（PTEs）的有效态与假全量含量，分析其污染程度，并探究土壤生物因子与土壤化学性质、有效态PTEs含量之间的关联。
研究人员从矿区湖泊周边共7个区域采集土壤样本：区域1——无废石及/或无矿覆盖层堆积的矿坑边缘；区域2——有废石及/或无矿覆盖层堆积的矿坑边缘；区域3——存在无矿覆盖层堆积的区域；区域4——已完成黄金提取、被淘金者称为“库里马（curimã）”的尾矿堆；区域5——矿坑湖底疏浚所得沉积物；区域6——采用农林业复合系统的区域；区域7——未受手工采金活动影响的河岸林（对照组）。
除硒（Se）外，所有被检测元素在至少一个采样区域中的含量均超出了巴西国家环境委员会制定的巴西农业用地调查限值——该限值指在标准化暴露场景下，土壤或地下水中某物质含量超过该值时，人类健康将面临潜在直接或间接风险。本研究同时针对钴（Co）、钡（Ba）、锰（Mn）与汞（Hg）的土壤富集与污染情况展开了分析。
主成分分析结果显示，潜在有毒元素的有效态含量会影响土壤生物特性，尤其是基础呼吸速率，这表明重要的生态系统过程正受到PTE污染的干扰。