Assessment of hydrochemical characteristics and trace metals of Punpun River water – a tributary of the Ganga River

Abstract

This manuscript presents the first inventory of dissolved ions (cations and anions) and trace metals (Pb, Mn, Cr, Co, Ni, Cu and Zn) in the Punpun River water to assess its irrigational suitability, pollution sources and hydrogeochemical processes. For this, the physicochemical parameters and trace metals in river water were analysed in the pre- and post-monsoon seasons. The results showed that the concentrations of cations and anions were Ca2+ > Na+ > Mg2+ > K+ and HCO3− > SO42- > Cl− > NO3− > PO43-, respectively, in both the pre- and post-monsoon seasons. However, trace metal concentration in pre- and post-monsoon followed the trend of Pb > Mn > Cr > Ni > Cu > Zn > Co and Pb > Ni > Mn > Cr > Zn > Co > Cu, respectively. The results reveal that combined effects of rock weathering and evaporation-concentration influence hydrochemistry, along with anthropogenic factors like industrial effluents, urban domestic sewage and agricultural runoff. Piper and Durov plots suggest that the river water is dominated by Ca–Mg–HCO3− type, and the processes were governed by simple ion dissolution and mixing. However, the Gibbs plot shows that silicate and carbonate weathering govern the hydrochemical properties. Irrigational indices like sodium adsorption ratio, %Na, residual sodium carbonate, Kelly's ratio, magnesium hazard, and trace metals indicate that most of the water samples are suitable for irrigation. Comprehensive pollution index values suggest that the river water quality ranges from sub-clean to slightly to moderately polluted. HIGHLIGHTS The dominant cation and anion in the Punpun River water were Ca2+ and HCO3−, respectively.; The Punpun River water is influenced by silicate and carbonate weathering.; Different water processes indicate ion dissolution and mixing.; Sodium adsorption ratio, %Na, residual sodium carbonate, Kelly's ratio and MH irrigational indices show that most river water is suitable for irrigation.; Comprehensive pollution index value shows that river water falls into a slightly to moderately polluted category.;

Keywords

• hydrochemistry
• punpun river
• surface water
• trace metal
• water quality index