RJCES Vol 3 [1] February 2015 29 | P age © 2015 AELS, INDIA ORIGINAL ARTICLE Seasonal trends in Groundwater Arsenic levels in Obuasi Municipality and its vicinity, Ghana A. Donkor, 1* G Kumi-Amoah, 2 V. K. Nartey 1 , B. Dubey 3* , N. Attandoh 1 1 . Department of Chemistry, University of Ghana, Legon, Accra, Ghana 2 . Environmental Science Programme, University of Ghana, Legon, Accra, Ghana 3 . Environmental Engineering, School of Engineering, 50 Stone Road East, University of Guelph, Guelph, Ontario, Canada N1G2W1 Email: bkdubey@ufl.edu and augdonkor@gmail.com ABSTRACT Gold mining in Ghana has a long history. It is hypothesized that, the mining of gold from Birimiam rock rich in arsenopyrite ore leads to the release of arsenic (As) and therefore, could contaminate groundwater resources in and around Obuasi Municipality. Groundwater samples totaling 220 were collected from locations within and outside the municipality both during the dry and rainy periods. Measured total As ranged from 1.32 to 12.27 µg L -1 and 0.30 to 20.90 µg L -1 in the samples collected in the wet and dry seasons respectively. The high concentrations in the wet period are the result of infiltration and percolation of flood water containing dissolved As through the rock layers. This further suggested that the observed levels of As in the water is coming from both human activities (mining) and natural sources. The dry-season value is the result of As mineral dissolution. However, As co-varied very weakly with the determined concentrations of other trace elements (Fe, Cu, Pb, and Zn) as well as some water-quality parameters except for pH, alkalinity and hardness. This indicated that many of these parameters had little influence on the ambient levels of As in the groundwater. Additionally, the recorded numbers in the study except Site 9 [20.9 µg L -1 (wet), 12.27 µg L -1 (dry)] do not exceed the WHO guideline maximum value of 10 µg L -1 for drinking water. In contrast with well-known As contaminated environments like Bangladesh and West Bengal in India where As ranges from <0.5 to 3200 µg L -1 , the measured dissolved As in the groundwater is very low, which is supposedly believed to be due to the removal of As from the water by iron oxides unlike these nations where As is re-mobilized in solution. Finally, the study revealed that the inhabitants in the Obuasi municipality and its vicinity are not at risk of As poisoning. Though, As concentrations are low in the wells except Site 9, yet the fear of long term accumulation can result in an epidemic with time as boreholes/wells are not regularly monitored. Keywords: Arsenic, Gold, Groundwater, Land use, Mining, Water Quality. Received 12.11.2014 Accepted 29.12.2014 © 2015 AELS, INDIA INTRODUCTION Arsenic (As) is a known toxin, carcinogen and mutagen. Traces of As is found in our food, water, air and soil, a growing public concern. Being environmental toxicants and carcinogens, arsenicals affect both human and animal health. Thus, today As contamination of natural resources is one of the major public health problems in many countries. Chronic exposure to As can result in health risks diseases like vascular diseases, jaundice, cancers of the skin, lung, and bladder. Like mercury, As remains permanent in the environment; it cannot be transformed from the toxic to non-toxic form however, it cycles through the environment [1,2]. Arsenic is the chief component of more than 200 minerals of which the most common is arsenopyrite, FeAsS. Residual and waste materials generated by mining activity represent a significant anthropogenic source of environmental As contamination. Other human activities are combustion, fuels, wood preservation, use of As based pesticides, etc., besides natural processes such as weathering reactions, biological activity and volcanic emissions. These actions are responsible for the emission of As into the atmosphere, from where it redistributes on the earth’s surface by rain and dry fall- out. Arsenic is also mobilized by dissolution in water, with aquatic and soil/sediment concentrations being controlled by variety of input and removal mechanisms [3]. In most mining areas in Ghana particularly Obuasi, until the introduction of the bio-oxidation (BIOX) technology of extracting gold, the processing of the ore for gold involved the crushing and grinding of ore to fine powder followed by dissolution and precipitation of free gold. During the ore preparation by roasting, sulphur dioxide and As Research Journal of Chemical and Environmental Sciences Res J. Chem. Environ. Sci. Vol 3 [1] February 2015: 29-39 Online ISSN 2321-1040 CODEN: RJCEA2 [USA] ©Academy for Environment and Life Sciences, INDIA Website: www.aelsindia.com/rjces.htm R R R J J J C C C E E E S S S