Effects of Soil Composition and Mineralogy on the Bioaccessibility of Arsenic from Tailings and Soil in Gold Mine Districts of Nova Scotia

Abstract

Bioaccessibility tests and mineralogical analyses were performed on arsenic-contaminated tailings and soils from gold mine districts of Nova Scotia, Canada, to examine the links between soil composition, mineralogy and arsenic bioaccessibility. Arsenic bioaccessibility ranges from 0.1% to 49%. A weak correlation was observed between total and bioaccessible arsenic concentrations, and the arsenic bioaccessibility was not correlated with other elements. Bulk Xray absorption near-edge structure analysis shows arsenic in these near-surface samples is mainly in pentavalent form, indicating that most of the arsenopyrite (As 1-) originally present in the tailings and soils has been oxidized during weathering reactions. Detailed mineralogical analyses of individual samples identified up to seven arsenic species, the relative proportions of which appear to affect arsenic bioaccessibility. The highest arsenic bioaccessibility (up to 49%) is associated with the presence of calcium-iron arsenate. Samples containing arsenic predominantly as arsenopyrite or scorodite have the lowest bioaccessibility (< 1%). Other arsenic species identified (predominantly amorphous iron arsenates and arsenic-bearing iron(oxy)hydroxides) are associated with intermediate bioaccessibility (1 to 10%). The presence of a more soluble arsenic phase, even at low concentrations, results in increased arsenic bioaccessibility from the mixed arsenic phases associated with tailings and mine-impacted soils.3

An inter-laboratory trial of the unified BARGE bioaccessibility method for arsenic, cadmium and lead in soil

“…These contaminants are associated with a legacy of industrial activities (Gasser et al, 1996;Razo et al, 2006;Rieuwerts et al, 2006;Basta et al, 2007;Laird et al, 2007;Morrison and Gulson, 2007;Romero et al, 2008;Caboche et al,2010;Meunier et al,2010; and natural background geology (Fendorf et al, 2004;Koch et al, 2005;Nathanail et al, 2005;Palumbo-Roe et al, 2005;Cave et al, 2007;Juhasz et al, 2007b;, which are of concern to a number of the countries participating in BARGE.…”

Spatial Distribution of As, Cr, Pb, Cd, Cu, and Zn in the Water and Sediment of a River Impacted by Gold Mining

“…Mine drainage laden with high concentrations of contaminants is an important cause of environmental pollution throughout the world (Andrade et al 2012;Cánovas et al 2012;Carling et al 2013;Caruso and Bishop 2009;Meunier et al 2010;Runkel et al 2012;Sarmiento et al 2011). Extracting and processing of minerals from hard rock mines at an industrial scale can result in tremendous loading of trace elements into streams and rivers.…”

Establishing geochemical baselines in forest soils for environmental risk assessment in the Montague and Goldenville gold districts, Nova Scotia, Canada

“…When dry, any remaining pebbles or roots were removed by hand and the soil was then sieved using stainless steel screens to three separate grainsize fractions: <2 mm, <150 µm, and <63 µm. The <2 mm fraction was chosen for comparison with environmental and human health risk assessment guidelines (Health Canada 2010;CCME 2015), the <150 µm material for use in studies of As bioaccessibility (Meunier et al 2010(Meunier et al , 2011, and the <63 µm fraction for comparison with existing exploration geochemistry data sets (e.g., Carrick Gold Resources 1990; Rencz et al 2006).…”

“…Details on the mineralogy and bioaccessibility of As in these tailings can be found in Walker et al (2009), Meunier et al (2010, Corriveau et al (2011a, 2011b), and DeSisto et al (2011 areas of gold mineralization as a result of glacial dispersion (Goodwin et al 2004). The results of these studies are useful for assessing the pre-mining background concentrations of various elements in tills within the Nova Scotian gold districts.…”

“…Our data suggest that As and Hg concentrations from different grain size fractions are generally not interchangeable, and that human health risk assessments should consider those size fractions that are most relevant to human exposure (cf. Bright et al 2006;Ljung et al 2006;Meunier et al 2010).…”