Physicochemical properties of pit-water from ishiagu lead/ zinc (Pb/Zn) mine as an index for alkaline classification of the mine drainage

The nature and chemical composition of mine pit-water was investigated in Ishiagu lead/zinc (Pb/Zn) mine in southeastern, Nigeria. Laboratory determination of some physicochemical parameters namely, temperature, total dissolved solids (TDS), conductivity , chloride, pH, alkalinity, hardness, sulphate and dissolved metal constituents like calcium and magnesium were assessed in the three mine pits using standard methods. The results showed that Ishiagu Pb/Zn mine is slightly acidic with moderate levels of dissolved metal constituents. Seasonal variation observed in the parameters indicate higher levels for pH (6.7-8.1), alkalinity (36.4--115.3mg/l) and sulphate (6.8-84.4) in the wet season when compared with corresponding values, pH (6.1-7.3), alkalinity (31.3- 98.4mg/l) and sulphate (6.1-78mg/l) in the dry season. The consistently the higher levels of pH, alkalinity, hardness, calcium, magnesium, total dissolved solids (TDS) and conductivity in more than 66% of the mine pits (mine 1and mine 3) investigated across the season is an indication of changing state of the mine pit-water to more alkaline mine drainage. This phenomenon is attributable to preponderance and buffering effect of carbonate minerals in the area.