Appraisal and evaluation of Hydrochemical Processes in the Aquifer System of the South Eastern Coastal Area of Bangladesh

Abstract

Hydrochemical study of groundwater in the aquifer system of the southeast coastal area of Bangladesh was carried out to investigate the processes of groundwater hydrochemistry as well as the suitability of groundwater for drinking purposes. Water samples from tube wells (depths 6.5–165 m) were collected and examined several water quality parameters to describe the hydrogeochemical characteristic. Most of the water samples were found as fresh and soft water with few numbers of hard and brackish water. The overall sequence of cation and anion throughout the study area are Ca2+> Na+> Mg2+> K+ and HCO3−> CO3−> NO3−> SO42−> Cl− respectively. Maximum water quality parameters satisfy the drinking water quality standard proposed by WHO. Piper diagram suggests that Ca2+- Mg2+- HCO3− (80%) and Ca2+- Na+- HCO3− (20%) facies are the predominant water type. Gibb’s plot implies a rock dominant inheritance that regulates the groundwater chemistry. The most significant hydrochemical processes in the study area are carbonate weathering and cation exchange. 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 shows weathering and leaching of parent rocks are the leading environmental sources, while intensive farming incorporating the extensive use of pesticides and fertilizers might be another anthropogenic component that influences the groundwater hydrochemistry.