Morphology, Mineralogy, and Chemistry of Ocherous Precipitate Aggregates Downstream of an Abandoned Mine Site

Mineral precipitates forming downstream of abandoned and/or uncontrolled mine sites generally act as scavengers for heavy metals, such as As and Sb, leaking from the sites. This study reports the morphology of ocherous precipitate aggregates downstream of Ayuta, an abandoned antimony mine site in Tochigi Prefecture, Japan, because its morphology differs significantly from those reported previously. The morphology of this aggregate consists of stacked, small terraces enclosed by numerous connected rimstone dams, although on a smaller scale compared to typical terrace landscapes. The rimstone pools contained ocherous spheroids precipitates at the bottom. Additionally, stream water and ocherous aggregates collected from the site were investigated for mineralogy and chemistry. As (0.07–0.17 μg/L) and Sb (0.02 μg/L) levels in the stream water were determined, and the distributions of As and Sb in the mineral phases of the precipitate were estimated using a sequential extraction procedure. The investigations revealed that As was adsorbed by iron-bearing ocherous precipitate aggregates, especially ferrihydrite that formed on the stream bank at concentrations, comparable to those reported by other studies (85 mg/kg). This adsorption contributed to the natural attenuation of As in the stream. Sb in the aggregate consisted of ultra-fine silt and clay-size particles of stibnite ore transported from the surrounding area and/or secondary minerals transported by groundwater and surface water.

ASSESSMENT OF TRACE METALS CONTAMINATION ON SOIL FROM ABANDONED ARTISANAL TIN MINING PADDOCK IN BARKIN-LADI AREA OF PLATEAU STATE

The overwhelming rate of environmental degradation activated by the cruel mining operation associated with the unguided and incessant activities of artisans instigates this study. This study aimed at assessing the extents of trace metals contamination on soil resulting from the abandoned tin mining operation in Barkin Ladi Local Government Area of Plateau State. The abandoned mine site was delineated, and three samples were taken from the soil with respect to 0-15cm and 16-30cm horizontal depth. The three samples were tested and analyzed for heavy metals concentration such as Pb, Cr, As, Zn, Cd, Cu, and Fe at the Analytical Laboratory of the National Metallurgical Development Agency, Jos Nigeria. The result was subjected to the tolerable standard limit of the Federal Ministry of Environment for metals constituent in soil. Findings from the study reveal that the soil samples in both 0-15cm and 16-30cm depth show concentrations that were far above the limit set by the Federal Ministry of Environment of Nigeria for Pb, Cd, Zn, Cu, Cr, and Ar, with the exception of Fe. The study recommends among others that; to ensure sustainable management of minerals with enforceable regulations in a sector dominated by stray mines, strengthening of current policy using command and control measures built on accountability and polluter pay principles to avert cases of dead trap and soil pollution as well as aesthetic destruction of the landscape is the way forward.