An investigation of mercury distribution in the soils around gold mining area at Dar-Mali locality, river Nile State, Sudan

Abstract

An artisanal gold mining region located in North of Atbara (Dar-Mali locality), River Nile State, Sudan (17.82289 to 17.82389N and 33.99974 to 34.02127E) has been studied with the aim to evaluate the soil contamination with mercury (Hg) using two parameters; (i) Comparison of the Hg concentration with the mean concentrations in world soils, (ii) Enrichment Factor (EF). The results revealed that, the concentrations of the Hg are varying in the studied area and the highest concentrations were obtained inside the mining basins used for gold extraction (2.62 mg kg-1 soil) it is around 29 times more than mean Hg concentration in world soils, while the lower concentrations are found at recent Nile River terrace (0.10 mg kg-1 soil). The results also indicated that the soil samples collected from inside mining basins had a highest E.F value (352.84) that means, this site must be closed and remediation process should be started immediately. While the E.F value of recent Nile River terrace site was 8.74, means, all studied sites have significant contamination with Hg. The mobility of Hg may have influenced by northeast wind, or water runoff from mining zone to nearest areas at same wind direction or water flow direction.

Mercury pollution in Africa: A review

“…The contamination of the soils of this mining area and the nearby soils is due to the direct spillage during the amalgamation, the wet and dry deposition of the atmosphere, and the runoff of the residues. Again the work of Donkor et al (2006), who also worked in a mining area in Ghana, did not fully confirm the findings made by Okang ' Odumo et al (2014), Ali et al (2018) and Ikingura et al (1997); but the presence of Hg was reported in the soils of areas near the mine site, and large concentrations of THg (4.876 mg.kg -1 dw) and MeHg (0.162 mg.kg -1 dw) were found during the wet season in the soils of the mine site. MeHg was undetectable in soil samples during the dry season, which would be due to the low water content of these soils during the dry season, thus limiting the microbial activities that allow the production of MeHg (Donkor et al, 2006).…”

“…Therefore, the presence of Hg in the areas close to the artisanal gold mining site would be due to the dry deposition process (Ali et al, 2018). However, the concentration of Hg in the sites studied is above the average global concentrations in soils, and this does not exclude the closure of this area to carry out decontamination work (Ali et al, 2018). Podolský et al (2015) measured mercury in the soils of the extraction and smelting zones of certain metals in Namibia and Zambia.…”

“…Therefore, these champions can be useful for monitoring air pollution by Hg. Ali et al (2018) showed mercury contamination of soils in the gold mining area and areas near the locality of Dar-Mali, Nile State of Sudan. The highest concentrations were observed in the soils of the mining area.…”

“…Research is necessary to validate and have a better understanding. Several studies have also reported the presence of mercury in the soils and eggs of certain living species for human consumption (Daso et al, 2015;Nnorom et al, 2012;Ali et al, 2018;Podolský et al, 2015;Noubissie et al, 2016). Daso et al (2015) reported Hg concentrations in the eggshells of the Southern ground hornbill (Bucorvus leadbeateri) and wattled crane (Bugeranus carunculatus) in the Mpumlanga and KwaZulu-Natal areas of South Africa.…”

“…MeHg was undetectable in soil samples during the dry season, which would be due to the low water content of these soils during the dry season, thus limiting the microbial activities that allow the production of MeHg (Donkor et al, 2006). Therefore, the presence of Hg in the areas close to the artisanal gold mining site would be due to the dry deposition process (Ali et al, 2018). However, the concentration of Hg in the sites studied is above the average global concentrations in soils, and this does not exclude the closure of this area to carry out decontamination work (Ali et al, 2018).…”