Effectiveness of wetlands in retaining metals from mine water, South Africa

Abstract

Wetlands are effectively used to treat mine water effluent in South Africa, where they retain toxic metals that can potentially contaminate the environment. Wetlands that are located close to the abandoned tailings dams were chosen and solidified substrate samples were collected for thin section microscopy, X‐ray fluorescence (XRF) and X‐ray diffraction (XRD) analyses. In order to determine the concentration of selected metals in the tailings dams, fine grained samples were collected and leached with a diluted nitric acid and deionised water to simulate leaching by rainwater. The results from the substrate analysis revealed an overall oxide abundance of 71.76 weight percent (%) and an elevated metal concentration, which suggest a crucial role played by pH, redox, wetland sediments and wetland plants in maintaining oxygen circulation and triggering reactions. The study confirmed the efficiency of wetlands in the attenuation of toxic metals from the mine water.

Environmental arsenic in a changing world

“…For example, in the tailings dams the content of some metals such as Cr ranges from 170 to 310 mg L −1 , Co = 10-240 mg L −1 , Cu = 15-254 mg L −1 and lead 6-34 mg L −1 . High uranium rich mine water with acidic pH decants continuously from abandoned mines into streams (Winde, 2006;Hobbs, 2011;Abiye, 2014;Abiye, et al, 2018). The high concentration of polymetallic contaminants in the groundwater was regulated by oxidation, leaching and precipitation processes besides water-rock interaction.…”