TITLE:
Evaluation of Concentrations and Dispersion of Heavy Metals in Soils Surrounding Artisanal and Small-Scale Gold Mining in Chunya District, Mbeya
AUTHORS:
Fredrick P. Girenga, Nelson Mpumi, Ruth L. Moirana, Revocatus L. Machunda
KEYWORDS:
Heavy Metals, Tailing Heaps, Lateral Mobility, Permissible Limit, Environmental Risks, Human Health
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.13 No.11,
November
26,
2025
ABSTRACT: Heavy metal contamination from Artisanal and Small-Scale Gold Mining (ASGM) is increasingly recognized as a global issue, impacting soil quality and public health. In Tanzania, while ASGM activities significantly bolster local economies, they also pose serious environmental risks. This study examined the levels and dispersion of heavy metals, specifically mercury (Hg), lead (Pb), arsenic (As), zinc (Zn), and cadmium (Cd) in the Chunya district. Soil samples were collected from both active and abandoned tailing heaps and analysed by Atomic Absorption Spectroscopy (AAS), with the results compared to the WHO/FAO (2008) guidelines for agricultural soils. The findings revealed alarming concentrations of Hg across all sampling points, ranging from 0.88 to 3.72 mg∙kg−1. In contrast, 48 out of 51 sampling points exhibited higher Cd levels between 0.98 and 4.42 mg/kg, exceeding the safe limits of 0.5 mg∙kg−1 for Hg and 0.8 mg∙kg−1 for Cd. In contrast, the negative control site showed much lower levels (0.03 mg∙kg−1 for Cd and 0.43 mg∙kg−1 for Hg). A notable decrease in heavy metal concentrations was observed with increasing distance from the tailing heaps (0 m to 200 m). Soil pH and electrical conductivity significantly influenced the mobility of these contaminants, with higher concentrations found near lower tailing heaps. The elevated levels of Hg and Cd present substantial risks to human health and ecosystems, highlighting the urgent need for effective remediation strategies. Furthermore, the gold mining industry must innovate technologies that minimize heavy metal release during extraction processes to mitigate environmental harm.