CHEMICAL CHARACTERISATION OF ACID MINE DRAINAGE FROM VALEA ȘESEI TAILING DAM (NW OF ROMANIA) AND ITS IMPACT ON SURFACE WATER QUALITY

Abstract

The acid mine drainage (AMD) can be a major source of water and soil pollution. To evaluate the chemical composition of the AMD and its impact on surface waters, a total of 132 water samples, both surface and waste waters, were collected during four field campaigns in November 2018, December 2018, March 2019 and April 2019. There were also collected several samples from the tailing dam material and sediments from the rivers where acidic waters are discharged. The physico-chemical parameters (pH, redox potential, electrical conductivity, total dissolved salts and salinity) were measured by a portable multiparameter (WTW multi350i, Germany), while the dissolved ions (NO₂^-, NO₃^-, Br^-, F^-, Cl^-, PO₄^3-, SO₄^2-, Li⁺, Na⁺, NH₄⁺, K⁺, Mg²⁺ and Ca²⁺) were analysed by ion chromatography and the metal content (Cu, Zn, Fe, Cr, Cd, Ni, Pb) was determined by atomic absorption spectrometry. Most of the water samples had an acidic pH, with high electrical conductivity values (up to 9,360 µS/cm). The waters had a high level of SO₄^2- (up to 8141.8 mg/l), Fe (up to 1,216.2 mg/l), Cu (up to 71.9 mg/l) and Zn (up to 61.98 mg/l). The tailing dam material was characterised by high levels of Fe (39.87 – 40.72 g/kg), Zn (81.3 – 241.1 mg/kg), Cu (343.5 – 942.3 mg/kg) and Pb (41.4 – 77.1 mg/kg). The analyses indicated the negative impact of AMD discharge in surface waters, which proved to have high levels of SO₄^2- and heavy metals.