Hydrochemical Characteristics and Quality Assessment of Groundwater in Patuakhali District, Southern Coastal Region of Bangladesh

Groundwater quality is important as it is the main factor determining its suitability for drinking, domestic, agricultural, and industrial purposes. Hydrogeochemical characteristics of groundwater in coastal aquifers of Patuakhali district have been investigated based on different indices for assessing its utility and to evaluate the factors influencing groundwater quality. A total of 18 groundwater samples were collected from tube wells having depth between 244 and 365 m and were analyzed for physicochemical parameters, including temperature, pH, electric conductivity (EC), total dissolved solids (TDS), salinity; major ion concentrations such as Na+, K+, Ca2+, Mg2+, Cl-, SO4 (2-), NO3 (-), HCO3 (-), Br-; and trace element concentrations such as As, Pb, Li, Rb, Ba, Be, Co, Mn, Ti, Cd, and Se. The results revealed that the groundwater is slightly alkaline and brackish in nature. The trends of dominant cations and anions are Na+ > Ca2+ > Mg2+ > K+ and HCO3 (-) > Cl- > SO4 (2-) > NO3 (-) > Br-, respectively and Na-Cl-HCO3 is the dominant groundwater type. Ion exchange and seawater plays a significant role in the geochemistry of the groundwater and signatures of Br-/Cl- ratio showed evidence of mixing of seawater in the southern part of study area. The samples analyzed were also classified with different indices, diagram, and permissible limit i.e., EC, TDS, chloride content, soluble sodium percentage or Na %, sodium adsorption ratio, residual sodium carbonate, magnesium adsorption ratio, Kelley's ratio, Wilcox diagram, USSL diagram and results showed that groundwater is not suitable for drinking and irrigation purpose. However, except for Se and As, the trace metals concentration are within permissible limit.