270 OCCURRENCE OF ALUMINIUM AND BERYLLIUM IN THE OKAVANGO DELTA BOTSWANA: HUMAN HEALTH RISKS Oarabile Mogobe, Wellington R. L. Masamba, Edwin Mosimanyana, Ketlhatlogile Mosepele Okavango Research Institute, University of Botswana. P/Bag 285, Maun, Botswana. omogobe@ori.ub.bw; wmasamba@ori.ub.bw; emosimanyana@ori.ub.bw; kmosepele@ori.ub.bw; ABSTRACT The Okavango River runs through 3 countries; Angola, Namibia and Botswana and is a major source of water for drinking and other domestic uses for the basin communities in the riparian states. Developments in the 3 countries, e.g. agriculture, tourism, mining, power generation industries, etc., are putting pressure on the river’s water quality which threatens both human and overall ecosystem health. Data is therefore needed to monitor changes of water quality as a result of both natural and anthropogenic sources. The objective of this study was to quantify the concentration levels of aluminium (Al) and beryllium (Be) at three sites (Mohembo East, Sepopa and Guma) of the Okavango Delta’s panhandle, study the influence of water discharge and pH on concentration of these metals and evaluate the human health risks associated with their occurrence. Surface water samples were collected in triplicates every three weeks from 3 sampling sites between July 2014 and October 2015. Samples were preserved with nitric acid and stored in the laboratory before analysis. Direct analysis with ICP-OES was used to determine their concentrations. Al values ranged from 0.032 – 0.305mg/L at Mohembo East; 0.005 – 0.333 mg/L at Sepopa and 0 – 0.151mg/L for Guma. Be concentrations ranged between 0 – 0.008mg/L at all three sites. There were no significant differences (P>0.05) between the three sites in concentrations of these metals. Seasonal variations in metal concentrations were observed for both metals, with the highest concentrations occurring around October, coinciding with lowest water levels. In accordance with the WHO regulatory limits for drinking water, the mean concentrations of both Al and Be, and the calculated hazard quotient(HQ) which was less than 1, do not pose any long term human health threats. However, both metals need to be monitored because concentrations above 200µg/L for Al and 4µg/L for Be (WHO acceptable limits) were exceeded at times at these sampling sites, which may cause acute toxicity to humans and aquatic organisms. From this study, we concluded that both aluminium and beryllium exist in the Okavango River at concentrations comparable to world river values. We recommend a more comprehensive monitoring programme for toxic metals in the Okavango River to ensure protection of both human and ecosystem health. Keywords: Aluminium, Beryllium, Okavango, Water quality, Human health 1. INTRODUCTION The Okavango River in Botswana (one of two perennial rivers in the country) is considered a pristine water source by the people of North West District (Mazvimavi and Mmopelwa, 2006) and some scientists who have studied or reviewed the water quality of the river system (Mackay et al., 2011; Masamba and Mazvimavi, 2008; Masamba and Muzila, 2005; Mmualefe and Torto, 2011; West et al., 2015). Most studies however, have based these conclusions on levels of basic water quality parameters such as electrical conductivity, pH, turbidity, dissolved oxygen, nitrogen, phosphorus, microbiological indicators and a few metal ions. The few studies that investigated toxic metals in the delta (e.g. Masamba and Mazvimavi, 2008; Masamba and Muzila, 2005), focussed on the common toxic metals (lead, chromium, cadmium and mercury) and evaluated their effects on ecosystem health. Monitoring of metals in aquatic environments is critical for both human and ecosystem protection (Batayneh, 2011; Genthe et al., 2013; Muhammad et al., 2011) . Ecotourism is the major income earner around the Okavango Delta, and prudent ecosystem management is therefore important. The river is a source of water for domestic use, including drinking, for 8.7% of the people living in the area around the delta (CSO, 2011). Therefore the river requires protection from pollutants, especially toxic metals which have not received much attention yet. Data on concentration levels of toxic metals, their mobility, sources and health risks in the Okavango River is scarce, as mentioned, especially for aluminium and beryllium. These metals have not been studied well in the Okavango River, but they have a fascinating hydrochemistry and pose serious human health risks, if present at high concentrations. Aluminium and Beryllium have a similar chemistry in the aquatic environments, probably because of their small ionic size and ease of hydrolysis (Neal, 2003). Aluminium is ubiquitous in the environment, amphoteric in nature and exists in different chemical forms. The monomeric form, which is predominant in acidic and near neutral pH waters is toxic to aquatic organisms (Guibaud and Gauthier, 2003; Ščančar and Milačič, 2006). Toxicity of aluminium to humans is associated with long term exposures (chronic), and manifests in the nervous system as Parkinson’s dementia and Alzheimer’s diseases (Dzulfakar et al., 2011). Beryllium is one of the most toxic elements to humans as well as aquatic organisms (Armiento et al., 2012; Calabrese et al., 1985; Neal, 2003). It is also known to be a group 1 carcinogen (IARC, 1993). 3 rd International Conference - Water resources and wetlands. 8-10 September, 2014 Tulcea (Romania); Available online at http://www.limnology.ro/wrw2016/proceedings.html Editors: Petre Gâştescu, Petre Bretcan; ISSN: 2285-7923; Pages:270-277; Open access under CC BY-NC-ND license