Assessment of dissolved mercury in surface water along the lower basin of the River Pra in Ghana
The region along the Lower Pra River Basin has been studied for dissolved Hg concentration in the surface water of the river and its tributaries which serve as source of drinking water for communities along the basin. The study area encompassed 6 communities in the Mpohor Wassa East district of the Western Region of Ghana with a population of 122,595. Samples of surface water were collected from locations in the period September 2006 to March 2007 spanning the wet (rainy) seasons and dry seasons chronologically. The seasonal variation in dissolved mercury concentration during the wet and dry seasons in the study area was also investigated. The dissolved Hg concentration in surface water was assessed using cold vapor AAS. The average dissolved Hg concentration in the main river (48.40 ± 26.08 ng/mL) and in the tributaries (27.59 ± 18.23 ng/mL) were above the WHO guideline value of 1.0 ng/mL. The trend in contamination levels along the river Pra suggested incidence of both remote pollution and localized pollution occasioned by artisanal alluvial gold mining activities within this enclave using mobile rigs which constitute rafts with mechanized dredging equipment mounted on them.