Speciation of mercury in mine waste: case study of abandoned and active gold mine sites at the Bibiani–Anwiaso–Bekwai area of South Western Ghana

Abstract

Speciation determines toxicity, transport pathways and residence time of a metal in different compartments of the environment. This study investigated the speciation of mercury in soils, derived from sites known for dumping of mine wastes in the Bibiani-Anwiaso-Bekwai district, a gold mining community of the Western Region of Ghana. Soil samples were taken from the surface; depths of 20, 40 and 60 cm from mine waste at both abandoned and active mine sites. Each sample was analysed for total mercury, organic mercury and elemental mercury. After sample treatment, digestion and reduction with stannous chloride (SnCl(2)), total mercury content was determined using the Inductively Coupled Plasma-Optical Emissions Spectrometer (ICP-OES). Organic mercury content was determined employing a differential technique after disposing of elemental mercury by heating. Total mercury content in samples ranged from 0.067 to 0.876 mg/kg for surface soils. The same soil of depths 20, 40 and 60 cm had total mercury from 0.102 to 1.066, 0.037 to 4.037 and 0.191 to 4.998 mg/kg, respectively. For organic mercury, concentrations range from 0.012 to 0.260 mg/kg for surface soil. Soil depths of 20, 40 and 60 cm had organic mercury concentrations from 0.016 to 0.653, 0.041 to 1.093 and 0.101 to 2.546 mg/kg respectively. Elemental mercury concentrations in surface soils, soils at depths of 20, 40 and 60 cm ranged from 0.043 to 0.780; 0.017 to 0.749; 0.014 to 2.944 and 0.009 to 2.452 mg/kg respectively. Among the sites studied, only galamsey tailings (GM) showed a trend of increasing total mercury level with increasing depth. For the other sites, trends were not defined. There has been no defined trend for elemental mercury with depth at any of the sampling sites. Just as with total mercury, it was only GM that showed an increasing trend of organic mercury concentration with depth.

Assessment of the Impact of Solid Waste Dumpsites on Some Surface Water Systems in the Accra Metropolitan Area, Ghana

“…Zinc levels were below the detection limits in all the waters sampled at the various sites. It is not clear why the very low level of the metal in the rivers despite the recorded values of zinc in the leachates from the dumpsites located close to the rivers [26]. This will need further investigation to ascribe reasons to the very low values of zinc.…”

Distribution of chemical forms of mercury in sediments from abandoned ponds created during former gold mining operations in Colombia

“…It is very well supported by the relative abundance of OM, which provided more binding sites in the present study in both the regions (Cambell et al, 1988;Krupadam et al, 2007). The study on fractionation indicates high contents and proportions of Hg-e (ranging from 83.25 -148.3 ng g -1 ) (Hg 0 , Fe and Mn oxides), which is a typical character of mining sites that receive direct contributions of Hg 0 during gold recovery processes (Cesar et al, 2011., Nartey et al, 2012, Lusilao-Makiese et al, 2016Green et al, 2019). However, Hg 0 has low solubility and mobility and it tends to concentrate in the areas near the discharge site (Van Straaten 2000).…”

Contamination from mercury and other heavy metals in a mining district in Ghana: discerning recent trends from sediment core analysis

“…Various activities linked to segments of the Ghanaian economy have been implicated in issues of chemical contamination. For instance, mining operations in Ghana, which predates the 19th century, over the years have caused contamination from heavy metals in the local environment (Bamford et al 1990;Amonoo-Neizer et al 1995;Ahmad and Carboo 2000;Antwi-Agyei et al 2009;Nartey et al 2012). The applications of pesticides and fertilizers in agriculture, the use of various insecticides for agricultural and public health reasons, as well as poor waste management practices have all introduced various groups of chemical contaminant into the environment in Ghana (Awumbila 1996;Ntow et al 2006;Obiri-Danso et al 2011;Hogarh et al 2014).…”