This work considered the environmental impact of artisanal mining gold activity in the Migori-Transmara area (Kenya). From artisanal gold mining, mercury is released to the environment, thus contributing to degradation of soil and water bodies. High mercury contents have been quantified in soil (140 μg kg(-1)), sediment (430 μg kg(-1)) and tailings (8,900 μg kg(-1)), as expected. The results reveal that the mechanism for transporting mercury to the terrestrial ecosystem is associated with wet and dry depositions. Lichens and mosses, used as bioindicators of pollution, are related to the proximity to mining areas. The further the distance from mining areas, the lower the mercury levels. This study also provides risk maps to evaluate potential negative repercussions. We conclude that the Migori-Transmara region can be considered a strongly polluted area with high mercury contents. The technology used to extract gold throughout amalgamation processes causes a high degree of mercury pollution around this gold mining area. Thus, alternative gold extraction methods should be considered to reduce mercury levels that can be released to the environment.

Artisanal gold‐mining (AGM) is one of the most important activities in the districts of Migori and Transmara (Kenya). Gold‐mining, however, is known to release vast quantities of arsenic and metals (some of which are very toxic like As, Hg, Cd, or Pb), which poses a serious threat to not only miners but also to the ecosystem and local populations. We, herein, determine the concentrations of arsenic and some heavy metals in several sample types (i.e., ore, soil, river sediment, and mine tailing) collected from the districts of Migori and Transmara. We also employ lichens and mosses as pollution bioindicators. Geostatistical tools and canonical correlation analysis were used to identify the relevant factors that affected arsenic and metal concentrations in the analysed samples. The following concentration ranges were reported in topsoil: As (1–17,250 mg kg−1), Cd (0.01–15.10 mg kg−1), Cu (7–9,238 mg kg−1), Cr (1–214 mg kg−1), Ni (5–766 mg kg−1), Pb (3–1,149 mg kg−1), and Zn (22–1,271 mg kg−1). It was concluded that the ecosystem in both districts was highly polluted by heavy metals whereas the arsenic concentrations in topsoil were among the highest reported worldwide. The results of this study provide new evidence on the impact of AGM on the environment and may further contribute to the design of policy measures with the aim of reducing environmental and human health risks associated to AGM activities.