Hydrogeological controls on groundwater manganese: Spatial distribution, health risks, and well-depth suitability in two aquifers systems of Bangladesh

Abstract

Manganese (Mn) contamination in groundwater is an emerging public health concern in Bangladesh, particularly in rural communities. The main objective of this study was to evaluate the spatial patterns of Mn contamination across diverse hydrogeological settings, estimate human health risks, and identify suitable groundwater sources in shallow aquifers. A total of 132 groundwater samples were collected from shallow tube wells using a purposive sampling technique and analyzed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) following standard procedures. The spatial patterns of groundwater contamination were depicted using ArcGIS version 10.8.2, while surface elevation and tube-well depth were incorporated into linear regression models to examine the influence of topographic factors on Mn distribution. Moreover, human health risks were evaluated using the Chronic Daily Intake (CDI), Hazard Quotient (HQ), and Hazard Index (HI) equations. The results showed that Jaypurhat had substantially higher Mn contamination, with approximately 76.67% and 91.67% of groundwater samples exceeding the former WHO and current Bangladesh drinking-water guideline values, respectively. Elevation showed only a weak positive relationship with Mn concentration in Jaypurhat, whereas tube-well depth had a strong negative relationship with Mn concentration in Chandpur, indicating that deeper tube wells contained lower Mn concentrations. The health risk assessment showed that Jaypurhat had considerably higher Mn-related health risks than Chandpur, particularly for children, while the suitable-depth analysis indicated that safer groundwater abstraction is more depth-dependent in Chandpur than in Jaypurhat. These findings suggest that the relevant authorities should implement regular groundwater quality monitoring and promote safer groundwater management practices to reduce Mn-related human health risks.