Abstract
Water containing high concentrations of nitrate is unfit for human consumption and, if discharging to freshwater or marine habitats, can contribute to algal blooms and eutrophication. The level of nitrate contamination in groundwater of two densely populated, agro-industrial areas of the Cameroon Volcanic Line (CVL) (Banana Plain and Mount Cameroon area) was evaluated. A total of 100 samples from boreholes, open wells and springs (67 from the Banana Plain; 33 from springs only, in the Mount Cameroon area) were collected in April 2009 and January 2010 and analyzed for chemical constituents, including nitrates. The average groundwater nitrate concentrations for the studied areas are: 17.28 mg/l for the Banana Plain and 2.90 mg/l for the Mount Cameroon area. Overall, groundwaters are relatively free from excessive nitrate contamination, with nitrate concentrations in only 6 % of groundwater resources in the Banana Plain exceeding the maximum admissible concentration for drinking water (50 mg/l). Sources of NO3− in groundwater of this region may be mainly anthropogenic (N-fertilizers, sewerage, animal waste, organic manure, pit latrines, etc.). Multivariate statistical analyses of the hydrochemical data revealed that three factors were responsible for the groundwater chemistry (especially, degree of nitrate contamination): (1) a geogenic factor; (2) nitrate contamination factor; (3) ionic enrichment factor. The impact of anthropogenic activities, especially groundwater nitrate contamination, is more accentuated in the Banana Plain than in the Mount Cameroon area. This study also demonstrates the usefulness of multivariate statistical analysis in groundwater study as a supplementary tool for interpretation of complex hydrochemical data sets.
Highlights
Nitrate contamination in groundwater is a common problem in many part of the world arising from diffuse reasons, e.g., intensive agriculture, unsewered sanitation in densely populated areas or from non-point sources such as irrigation of land by sewage effluents
Endeley et al (2001) in a study of water sources around Mount Cameroon made up of weathered volcanic and sedimentary rocks like the Banana Plain showed that these waters did contain trace elements and a dominance of Na? and K? as major cations closely associated with nitrates
The study areas are located along the Cameroon Volcanic Line, with the Banana Plain located in Mbanga, NjombePenja, (4°300–4°530N; 9°370–9°500E) in the Mungo Division, 70 km north of Douala, economic capital of Cameroon
Summary
Nitrate contamination in groundwater is a common problem in many part of the world arising from diffuse reasons, e.g., intensive agriculture, unsewered sanitation in densely populated areas or from non-point sources such as irrigation of land by sewage effluents. Shallow aquifers in agricultural fields are highly vulnerable to nitrate contamination, due to the widespread application of fertilizers and manure (Bohlke 2002; Kyoung-Ho et al 2009). Some of the major concerns of nitrate contamination/loading to both groundwater and surface water systems include health risks to humans through drinking water (i.e., methemoglobinemia and potential carcinogenic effects) and degradation of the local ecosystems (i.e., excessive plant and algal growth) (Murgulet and Tick 2008). Extensive research has indicated that agricultural practices may cause nitrate contamination to be high so as to exceed the maximum acceptable level for drinking water (Bohlke 2002). Ako et al (2011) reported about nitrate contamination of groundwater and surface water resources in the Banana Plain. Endeley et al (2001) in a study of water sources around Mount Cameroon made up of weathered volcanic and sedimentary rocks like the Banana Plain showed that these waters did contain trace elements and a dominance of Na? and K? as major cations closely associated with nitrates
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