Appraisal and Evaluation of Hydrogeochemical Processes in the Aquifer System of the South Eastern Coastal Area of Bangladesh

Abstract

A hydrogeochemical study of groundwater in the aquifer system of the southeastern coastal area of Bangladesh was carried out to investigate the processes of groundwater hydrogeochemistry as well as the suitability of groundwater for drinking purposes. Water samples from tube wells (depths 6.5–165 m) were collected and examined for several water quality parameters to describe the hydrogeochemical characteristics. Most of the water samples were found to be fresh and soft water with few numbers of hard and brackish water. The overall sequence of cation and anion throughout the study area is Ca²⁺> Na⁺> Mg²⁺> K⁺ and HCO₃⁻ > CO₃⁻ > NO₃⁻ > SO₄^2-> Cl^−, respectively. Maximum water quality parameters satisfy the drinking water quality standard proposed by WHO. The piper diagram suggests that Ca²⁺-Mg²⁺-HCO₃⁻ (80%) and Ca²⁺-Na⁺-HCO₃⁻ (20%) facies are the predominant water types. Gibb's plot implies a rock-dominant inheritance that regulates the groundwater chemistry. The most significant hydrogeochemical processes in the study area are carbonate weathering. Correlation analysis recommends that TDS, EC, Na⁺, Ca²⁺, Cl⁻, and SO₄²⁻ are strongly correlated with each other, indicating their contribution to water mineralization. The principal component analysis (PCA) and cluster analysis show that weathering and leaching of parent rocks are the leading environmental sources that influence the groundwater hydrochemistry.