Studies on arsenic rich mine dumps .1. Effect on the surface soil.

The effect of abandoned mine dumps on the terrestrial environment was assessed by determining the soil pH, organic content, exchangeable and total concentrations of heavy metals in the surface soil at three selected sites namely at the mine dumps (MD), adjacent to mine dumps (AMD) and at a site near the river stream about 400 m from the mine dumps (NR). The soil pi. at the mine dumps was very low (2.08 +/- 0.22) and pH at NR was (4.02 +/- 0.12). Soil samples at MD contained total elemental concentrations (mg/g) of arsenic (9.53 +/- 0.25), Se (0.10 +/- 0.02), Fe (15.6 +/- 3.7), Cu (0.54 +/- 0.05), Ni (0.97 +/- 0.03), Co (0.08 +/- 0.01), Mn (0.84 +/- 0.08), Zn (0.33 +/- 0.04) and Pb (0.34 +/- 0.04. The exchangeable cations (acetate extraction) at MD (mg/g) were As (0.84 +/- 0.07), Fe (2.30 +/- 0.06), Cu (0.36 +/- 0.02), Ni (0.45 +/- 0.04), Mn (0.46 +/- 0.02) and Zn (0.27 +/- 0.02). No mobile form of Pb was detected at the sites. Although, the total elemental concentrations in the soil decreased with the increasing distance from the mine dumps, the fraction of respective exchangeable cations increased.