Geospatial and statistical approaches to nitrate health risk and groundwater quality assessment of an alluvial aquifer in SE Nigeria for drinking and irrigation purposes

Abstract

In agricultural districts, like Ogbaru in southeastern Nigeria, water supplies are under obvious threats from human activities. Therefore, continuous monitoring and assessment of water quality suitability for drinking, domestic, and irrigation purposes are encouraged to keep check of the effects of water contaminants. In this paper, several quality water assessment tools were integrated to determine the suitability of the groundwater in Ogbaru for drinking and irrigation uses and to assess the ingestion and dermal health risks of nitrate occurrence. The majority of the physicochemical parameters analyzed in this study were within their respective standard limits. However, groundwater quality index classified 52.63% of the groundwaters as excellent water and 47.37% as good water. Overall index of pollution, on the other hand, classified 84.21% as excellent water and 15.79% as acceptable water. The pH ranged from 5.4 to 6.8, indicating that the groundwater is acidic. Most irrigation water quality assessment indices (SAR, Na%, PS, KR, RCO, CAI-1 and 2) revealed that the groundwater samples are suitable for irrigation. However, magnesium hazard and permeability index grouped the majority of the water samples as unsuitable resources for irrigation uses. The nitrate health risk assessment (mean score = 1.371) indicated that children are exposed to higher non-carcinogenic health risk due to ingestion of contaminated groundwater than the other populations. It was observed that 21.05% of the groundwater samples had the highest concentrations of the analyzed chemical species. Multivariate statistical methods (hierarchical cluster analysis and factor analysis) efficiently aided the contaminant source apportionment. Based on the findings of this paper, it is advised that adequate regulatory strategies and water treatment techniques be adopted in the area to protect and sustain the groundwater quality and public health.