Hydrogeochemical investigations of arsenic-rich groundwater using multivariate statistical analysis

Multivariate statistical analysis has been applied to assess the chemical characteristics of high arsenic groundwater from central-southern part of Bangladesh. A total of 43 shallow groundwater samples were collected and analyzed. The groundwater is almost neutral. The results of cations and anions trends are Na>Ca>Mg>K and HCO3>Cl>SO4>NO3, respectively. Alkalinity has significant positive correlation with Mg, Ca and K, which suggest silicate weathering as the major processes of controlling groundwater geochemistry. The significant positive correlation between Na and Cl indicates the seawater intrusion into groundwater. R-mode cluster allows variables into four groups. Alkalinity, Mg, K in the first, Ca in the second and Na and Cl in the third cluster, indicate silicate weathering, carbonate dissolution and seawater intrusion, respectively. R-mode factor analysis allows variables into four components having eigen values more than 1 which represent 72.5% of total variances. Component 1 is positively loaded with K, Mg, P and Alkalinity suggesting the silicate weathering. Component 2 positively loaded with Na and Cl, suggests seawater influences into groundwater. Component 3 positively loaded with Ca, suggest the carbonate dissolution. The Q-mode cluster analysis indicates that the as shows highest concentrations with highest Fe concentrations and lowest Mn concentration, suggesting the relatively high anoxic conditions of aquifer.