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CHARACTERIZATION OF ACID MINE DRAINAGE AT THE REGOUFE MINE, AROUCA GEOPARK, NORTHERN PORTUGAL

Prof. Paulo Favas, Prof. Joao Pratas

Abstract

The abandoned Regoufe mine is situated in Northern Portugal, in the Arouca Geopark. It was exploited for tungsten by underground mining till the 1970s. The tailings were deposited on the ground. The mine was abandoned without any environmental remediation. Mineralization occur in quartz veins, and consists of wolframite, cassiterite, and several sulfides (arsenopyrite, pyrite, sphalerite), bismuthinite and native bismuth (Bi). The present study aims to characterize the acid mine drainages (AMD) and superficial waters at the Regoufe mine area, based on a bimonthly monitoring scheme for a year. Portable instruments were used to measure water pH, Eh, temperature and electric conductivity (EC) in situ. HCO3 was also measured in situ using the titration method. Laboratory analyses were performed using current analytical methods: atomic absorption spectrometry (AAS) for Ca, Mg, Na and K; coupled graphite furnace AAS for Fe, Mn, Cu, Zn, Cd, Co, Ni, Pb and As; the spectrophotometric method for Cl; SO4 was analyzed by gravimetry. Mine drainage at the Regoufe mine have low pH and significant concentrations of SO4 (444 mg/L), arsenic (669 ?g/L) and metals (e.g., 304 ?g/L Mn; 269 ?g/L Zn; 32.3 ?g/L Cd), while in the superficial natural stream waters outside the mine influence the conductivity and metal concentrations are lower and the pH is close to neutral. The stream waters inside the mine influence have chemical composition between AMD and natural stream waters outside mine influence.

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