Heavy metal levels and physical parameters of drainage ways and wells in three mining areas in Ghana

Abstract

Levels of heavy metals (mercury, arsenic, cadmium, iron, zinc and manganese) and physical parameters (total suspended solids, total dissolved solids, conductivity and hydrogen ion concentration) of water sources (drainage ways and wells) associated with mining of gold, diamond and quarrying of granite were assessed for contamination. The results show that in the gold mining area of Tarkwa, Hg levels decreased downstream from 5.40 (x10-3) mg/l to 2.80 (x10-3) mg/l. Arsenic levels, in contrast, ranged from 6.70 to 9.00 mg/l with no indication of any gradient. Iron levels, like Hg, decreased downstream, varying from 6.25 through 5.38 to 3.50 mg/l. In the diamond mining area of Akwatia, no Hg was found in the water samples. Arsenic levels were quite high with a mean value of 10.20±1.70 mg/l. The stream sample registered the highest level of iron at 18.0 mg/l. At the quarry site in Accra, contrary to expectation, Hg was detected in an appreciable concentration of 5.20 (x10-3) mg/l in one of the water samples. Arsenic levels were also high ranging from 9.10 to 19.10 mg/l. On the physical parameters analysed, the total suspended solids measured were low for the three locations with no significant variation (65.2±7.6 mg/l) except one sample from the quarry area which recorded 124 mg/l. Conductivity was highest in the quarry samples (331-11,450 mS/cm) followed by the gold mining area (164-188 mg/l), and then the diamond mining area (30-111 mg/l). Hydrogen ion concentration (pH) were normal for all the samples ranging between 6.05 to 7.79 indicating a generally neutral aquatic environment for the three mining areas studied.



JOURNAL OF THE GHANA SCIENCE ASSOCIATION Volume 1 Number 1, July (1998) pp. 113-117