A new hazard assessment workflow to assess soil contamination from large and artisanal scale gold mining

by Selleckchem | Sep 04 2023

Gold mining activities are undertaken both at large and artisanal scale, often resulting in serious 'collateral' environmental issues, including environmental pollution and hazard to human and ecosystem health. Furthermore, some of these activities are poorly regulated, which can produce long-lasting damage to the environment and local livelihoods. The aim of this study was to identify a new workflow model to discriminate anthropogenic versus geogenic enrichment in soils of gold mining regions. The Kedougou region (Senegal, West Africa) was used as a case study. Ninety-four soil samples (76 topsoils and 18 bottom soils) were collected over an area of 6,742 km2 and analysed for 53 chemical elements. Robust spatial mapping, compositional and geostatistical models were employed to evaluate sources and elemental footprint associated with geology and mining activities. Multivariate approaches highlighted anomalies in arsenic (As) and mercury (Hg) distribution in several areas. However, further interpretation with enrichment factor (EFs) and index of geoaccumulation (IGeo) emphasised high contamination levels in areas approximately coinciding with the ones where artisanal and small scale mining (ASGM) activities occur, and robust compositional contamination index (RCCI) isolated potentially harmful elements (PHE) contamination levels in very specific areas of the Kedougou mining region. The study underlined the importance of complementary approaches to identify anomalies and, more significantly, contamination by hazardous material. In particular, the analyses helped to identify discrete areas that would require to be surveyed in more detail to allow a comprehensive and thorough risk assessment, to investigate potential impacts to both human and ecosystem health.

Comments:

The study aimed to develop a new workflow model to distinguish between anthropogenic (caused by human activities) and geogenic (naturally occurring) enrichment in soils within gold mining regions. The Kedougou region in Senegal, West Africa, was selected as a case study. The researchers collected a total of 94 soil samples, including 76 topsoils and 18 bottom soils, covering an area of 6,742 km2. These samples were then analyzed for 53 different chemical elements.

To assess the sources and distribution of these elements, the researchers employed robust spatial mapping, compositional analysis, and geostatistical modeling techniques. Multivariate approaches were used to identify anomalies in the distribution of arsenic (As) and mercury (Hg) in various areas. However, to gain a more comprehensive understanding of contamination levels, enrichment factors (EFs) and the index of geoaccumulation (IGeo) were also utilized. These additional analyses revealed high contamination levels in areas where artisanal and small-scale mining (ASGM) activities were concentrated.

Furthermore, a robust compositional contamination index (RCCI) was used to isolate the contamination levels of potentially harmful elements (PHE) in specific areas of the Kedougou mining region. This index helped to identify discrete areas that required more detailed surveys to enable a comprehensive risk assessment. The purpose of these surveys would be to investigate potential impacts on both human and ecosystem health.

The study highlighted the significance of employing complementary approaches to identify anomalies and contamination caused by hazardous materials. By combining different analytical methods, the researchers were able to pinpoint areas of high contamination and assess the potential risks to the environment and local communities more effectively. The findings emphasize the need for improved regulation and monitoring of mining activities, particularly in regions where artisanal and small-scale mining takes place, to mitigate the adverse environmental and health impacts associated with gold mining.