Impact of gold mining associated with mercury contamination in surface soil of San Martin de Loba, south of Bolivar (Colombia)

Human activities have increased mercury (Hg) contamination of terrestrial environments, especially gold mining areas. The aim of this study was to evaluate total Hg concentrations (T-Hg) in surface soil samples of San Martin de Loba, south of Bolivar (Colombia), to determine their Hg contamination level. For that purpose, 202 surface soil samples were collected. T-Hg levels were measured by electrothermal atomization and atomic absorption spectroscopy. The T-Hg surface soil concentrations ranged between 0.002 and 23.83 μg/g, with a median value of 3.40 ± 0.36 μg/g, which is slightly higher than the international Hg soil levels. The geo accumulation index for soils reached values greater than 5, indicating extreme pollution (Class 6) in 17% of samples, while 70% was Class 5 (strongly to extremely polluted). This study also provides a risk map to evaluate potential negative repercussions. In conclusion, the municipality of San Martin de Loba can be considered as a strongly polluted area with high Hg content. Technology used to extract gold through amalgamation processes causes a high degree of Hg pollution around this gold mining area. Therefore, alternative extraction methods should be considered to reduce Hg levels that can be released into the environment and affect human health. (author)