Investigation into groundwater and stream water quality affected by an active coal washing plant, Shahrood, northeast Iran

The stream water and groundwater at Alborz Sharghi has poor quality due to the generation of acid mine drainage in the low grade coal wastes that produces problems of transporting suspended solids and dissolving heavy metals to the receiving waters and soils. The oxidation of pyrite and release of the oxidation products from a low grade coal waste dump to groundwater and stream water was investigated by geochemical and hydrogeochemical techniques at Alborz Sharghi coal washing plant, in the Shahrood region, north-east Iran. Hydrogeochemical analysis of water samples indicates that the metal concentrations in the stream waters were low. However, direct contact of stream water with one of the low grade coal waste dumps caused an increase in the EC, and the concentrations of SO4, Fe, Na and Cu. Moreover, the pH of the water showed no considerable change. The results of the analysis of groundwater samples indicate that the pH varies from 7.41 to 7.51. The concentrations of the toxic metals were low. The concentration of SO4 is slightly above than its standard concentration in potable water. It seems that, the groundwater less affected by the coal washing operation in the study area. Geochemical analysis of the sediment samples shows that Fe concentration decreases gradually downstream the waste dump with pH rising. Sulphate concentration decreases rapidly downstream direction. Copper, Zn and Co concentrations decrease with distance from the waste dump due to a dilution effect by the mixing of uncontaminated sediments. These elements, in particular, Zn are considerably elevated in sediment sample collected at the nearest distance to the waste dump. Type of the water samples were determined to be calcium-sulphate based on the highest concentrations of inions and cations represented in stiff diagrams. There is no doubt that the investigation of water quality affected by coal washing plant in the Alborz Sharghi is a basic task in the development of an appropriate water remediation plan.

Keywords:

Water quality analysis , Alborz Sharghi , acid mine drainage , coal washing wastes