Gold Mining Impacts on Soil Quality: A Comparative Study of Two Sites from the Romanian Apuseni Mountains

Soil contamination due to gold mining persists in time post-closure, but comparative data contrasting long-closed versus recently suspended operations are scarce. This study aims to compare soil quality between two distinct mining environments located onto Aries River Basin in the Romanian Apuseni Mountains: a closed decades ago gold mining operation (Baia de Aries) and a recently closed mining site (Roșia Montană).

Eight soil samples were collected in Winter 2021 along the Aries River and its tributary corridors (four per site). Major elements (Fe, Na, Mg, K and Ca) were analyses by Inductively Coupled Plasma Optical Emission Spectrometer (5300 Optima DV, PerkinElmer, MA, USA), while trace elements (Ni, Cr, Cu, Zn, Cd, Pb, Mn, Al, and As) were determined by Inductively Coupled Mass Spectrometer (ELAN DRC II, PerkinElmer, MA, USA). Hg content was measured by cold-vapor atomic fluorescence spectrometry (CV-AFS, Hydra-AF Mercury Analyzer, Teledyne Leeman Labs, Hudson, NY, USA). Soil pollution degree was assessed using individual indices (Contamination Degree, Cd; Geo-accumulation Index, Igeo) and complex contamination indices (Contamination factor, CF; Pollution Load Index, PLI).

Cu, Zn, Pb and Ni were the primarily contaminants at both sites, even though the enrichment levels varied. Roșia Montană samples exhibits higher contamination levels than those from Baia de Arieș. Mean CF values were 35,2± 16,7 (Strong pollution) for Roșia Montană and 18,9±5,30 (considerate pollution) for Baia de Arieș, respectively, mean PLI 1,2±0,6 (moderate pollution), PLI 1,0±0,2 (baseline to moderate pollution).

Despite decades of closure, the historical mining area of Baia de Arieș remains considerably polluted, whereas the more recent exploitation site from Roșia Montană presented severe levels of pollution. These findings highlight the persistence of soil contamination from gold mining and underscore the need for remediation strategies based on element-specific risks and contamination levels.