Long-term environmental impact at an abandoned gold–silver enrichment plant: A case study in Mitsero, Cyprus

Abstract

The abandoned gold–silver enrichment plant of Mitsero village is located in Cyprus and is an example of the long-term environmental impact of mining activity when no rehabilitation measures are undertaken. We conducted a study at a plant that has been abandoned for 70years to investigate potential environmental contamination and, if discovered, describe the extent of the contamination. Soil and water samples were collected from five potentially-polluted zones and the results are summarized as follows: soil pH of samples collected from inside the abandoned enrichment plant was low, around 3.4 to 5.4, while samples from the tailings were extremely low, ranging between 1.9 and 2.0. The tailing samples also exhibit high leachability of metals, particularly for Cu, Fe, Zn, Cr, Pb and Mn when subjected to the SPLP. Furthermore, the samples from the tailings also contain high cyanide levels of 25.05mg/kg and 45.85mg/kg, which are well-above allowable limits of 0.9mg/kg (Canadian Environmental Quality Guidelines, 2007). It is particularly interesting that no arsenic leachability was measured for the tailings, although arsenic is present in these samples as determined by XRF analysis. Our results indicate that the low pH environment combined with high leachability of metals is reflected in the quality of water samples collected from the ephemeral stream: high levels of metals were detected in the water samples measured using ICP-OES. While the pH of the water samples was neutral (7.6), aqueous concentrations of Cu, Fe, Zn, As, Cr, Pb and Mn ranged between 173.95μg/l and 3678.8μg/l. Thus, our findings indicate that areas of the site contain significant concentrations of metals and cyanide, leading us to conclude that, in conjunction with the low soil pH in those same areas, the potential exists to form acidic runoff (regardless of the pH of the rain itself) capable of leaching metals, thus mobilizing the contaminants. That the contamination, particularly the presence of cyanide, is still found some 70years after closure makes a compelling argument for remediation of such legacy sites.