Mineralogy of smelter- and mining- derived particles in semi-arid soils and their potential mobilization during wildfires
Abstract
High levels of inorganic contaminants were found in semi-arid topsoils and soil biomass samples near the Tsumeb copper smelter in northern Namibia: up to 5800 ppm Cu, 1920 ppm As, 4880 ppm Pb, 3310 ppm Zn, 81 ppm Cd, 7.66 ppm Hg. Contamination occurs as particulates derived from mining activities (grains of ore minerals windblown from tailing disposal sites) or from smelting processes (metal-rich slags, dusts from flue-gas cleaning).
Based on mineralogical investigation of these metal(loid)-bearing particulates, laboratory set-up was designed to simulate wildfire conditions. It was demonstrated that contaminants are partially released into the environment especially at temperatures above 700 degrees C.
In contrast to other contaminants, Hg derived from sulphide phases was released into the atmosphere at temperatures 350 degrees C corresponding to low-severity wildfire conditions.