Identification of groundwater potential zones (GWPZ) is as equally important as determining the most effective groundwater mapping models for efficient production of reliable GWPZ maps. In this study, relative frequency ratio (RF) with predictor value and analytic hierarchy process (AHP) models, including two RF-AHP hybrid models (HM-A and HM-B) were applied and compared to evaluate their effectiveness and accuracy in groundwater potential mapping. For HM-A model, RF was used to rank the subclasses of groundwater controlling parameter and AHP provided the weight of that parameter. For HM-B, it was vice versa. Eight parameters (slope, geomorphology, lithology, lineament density, drainage density, soil, rainfall and LULC) were considered for this assessment. The RF, AHP, HM-A and HM-B show the AUC value of 72.47%, 60.55%, 71.96% and 49.85%, respectively. The models based on RF-derived ranks show better accuracies (>70%), thus suggesting that ranks have more influence in the performance of models than weights.

Groundwater is a significant source of water across the world and constitutes about 30% of the earth's freshwater. This water source is likely to be contaminated by cyanobacteria that produce secondary metabolites called cyanotoxins. Studies on contamination of groundwater by cyanobacteria have been sketchy with limited information. There is a need for better evidence regarding groundwater contamination by cyanobacteria as their presence in surface water bodies could cause contamination of groundwater via infiltration and percolation during rainfall events or during groundwater-surface water interaction, bank infiltration or water quality exchange. Therefore, this review is aimed at exploring the occurrences and potential sources of cyanotoxins in groundwater. This was achieved by summarising the existing data on the occurrence of cyanobacteria in groundwater and their potential sources across the world. Groundwater cyanobacteria contamination can possibly pose threat to water quality because many of the cyanotoxins produced by cyanobacteria pose a severe threat to human health, animals and the environment. Concentrations of microcystins (MCs) in groundwater have been recorded in China (Chaohu), Saudi Arabia, and China (Huai River Basin), with concentrations of 1.446 μg/L, 1.8 μg/L and 1.07 μg/L, respectively. In humans, exposure to these cyanotoxins can cause symptoms such as vomiting, diarrhea, and skin irritation, to mention a few. This work highlights the importance of providing information or knowledge regarding public health implications of exposure to groundwater contaminated with cyanotoxins and the need to undertake risk management actions through national and international regulation. This review also points out current knowledge gaps, which could lead to future research.

In addition to quantity of water supply for various water uses, water quality is also of concern. The current state of the water quality is not known; neither is its suitability for domestic and agricultural uses. The current study investigated the suitability of the groundwater resource for domestic and agricultural uses in Nwanedi agricultural community. Water samples were collected from the existing boreholes following procedure for standard water sampling. Physicochemical parameters (pH, TDS, EC), anions (Cl⁻, SO₄²⁻, HCO₃, and NO_3--N), cations (Mg, Ca, K, and Na), and HCO₃ were analysed successively. The assay results were used to generate the agricultural water quality parameters (Sodium Adsorption Ratio, Magnesium Adsorption Ratio, Permeability Index, Residual Sodium Carbonates, Sodium percentage, Kelly's Ration and Chloride Index). Also, the communality test was conducted to investigate the suitability of the data for factor analysis and the loading of different parameters on the resultant factors. The assay results indicated that the water quality in the area is relatively fresh and adequate for domestic consumption, although there are infrequent excessive levels of nitrates ranging between 0.52–135.54 mg/l. Similarly, the groundwater was found to be ideal for irrigation (SAR 0.07–0.94 meq/l, MAR 26–48 meq/l, PI (92.5%) Class 1, PI 13–111 meq/l, RSC < −1, and CI = Class 1). The communalities which are the index of the measure of efficiency indicated that all the parameters except K were suitable for FA assessment. The hydrochemical composition is controlled by natural and anthropogenic processes such as on-sight sanitation, agricultural leachates, and domestic effluents. Future comparative studies on how groundwater quality is influenced by climate conditions (dry and wet season) should be conducted in this area.

Globally, the occurrence of cyanobacteria in water currently remains an important subject as they produce cyanotoxins that pose threat to human health. Studies on the contamination of maize meals during mill grinding processes using cyanobacteria-contaminated water have not been conducted. The present study aimed to assess the diversity of cyanobacteria in the samples (process water, uncooked maize meal, and cooked maize meal (porridge)). Polymerized Chain Reaction (PCR) and Advanced digital flow cytometry (FlowCAM) were used to detect and identify cyanobacterial species available in these samples. 16S Primers (forward and reverse) tailed with Universal Sequences were used for amplification and sequencing of full-length 16S rRNA genes from cyanobacteria found in all samples. Cyanobacterial species from order Nostocales, Pseudanabaenales, Oscillatoriales Chroococcales, Synechococcales, and unclassified cyanobacterial order, some of which have the potential to produce cyanotoxins were amplified and identified in process water, raw maize meal and porridge samples using PCR. Images of the genusMicrocystis, Phormidium, andLeptolyngbyawere captured in process water samples using FlowCAM. These findings show the presence of cyanobacteria species in process water used for maize meal and the absence in cooked maize meal. The presence of cyanobacteria in process water is likely another route of human exposure to cyanotoxins.