Sources of Arsenic Distribution at Obuasi in Ghana

There have been various studies to establish the potential sources of arsenic responsible for pollution of surface water and groundwater in the Obuasi Municipality of Ghana. This study seeks to provide better understanding of the identified sources and their characteristics in the study area. In the study rock and soil samples were taken from identified active and inactive arsenic storage structures for analyses of their photomicrographs and selected metal content. Results of photo-micrographic study indicate geologic features of arsenic source minerals such as pyrite, arsenopyrite in different states of oxidation. Other minerals present were pyrrhotite, chalcopyrite, sphalerite, stibnite and galena. It suggests significant potential for acid-mine drainage in the study area. Majority of gangue minerals contain acid-buffering or carbonate-bearing rocks/alterations relevant to control the AMD effect they generate whilst others do not and will therefore rely on the acid-buffering effect of the surface water or groundwater constituents. Arsenic and trace element analysis of tailings dams and tailings footprints around surface water and groundwater suggests that the oxidation of arsenic rich minerals reduces as you move away from the water sources and underscores the importance of water to the oxidation and mobility of arsenic in the study area. Acid base accounting of tailings material from Anglogold Ashanti Obuasi Mine Oxide Treatment Plant (OTP) and Sulphide Treatment Plant (STP) confirms the likelihood of acid mine drainage from the tails of the OTP and STP.