Role of sediment in solute acquisition in the Himalayan glacier meltwater stream, Gangotri glacier, Uttarakhand, India

• Published in: Hydrological processes Vol. 35; no. 1
• Main Authors: Sharma, Mukesh K., Thayyen, Renoj J., Shyamlal
• Format: Journal Article
• Language: English
• Published: Hoboken, USA John Wiley & Sons, Inc 01-01-2021; Wiley Subscription Services, Inc
• Subjects: Calcite; Contact melting; Creeks & streams; Dissolution; dissolution experiment; Dissolving; Evolution; Fluvial sediments; Gangotri glacier; Glacial streams; Glacier melting; Glaciers; Headwaters; Hydrogen; Hydrogen ion concentration; Hydrogen ions; Hydrologic processes; Hydrology; Ion concentration; Low temperature; Meltwater; Microparticles; Minerals; pH effects; River beds; Riverbeds; Rivers; Seasonal variations; Seasonality; Sediment; Sediments; solute acquisition; Solutes; Surface properties; Suspended sediments; Water chemistry; Wetting; India
• ISSN: 0885-6087; 1099-1085
• DOI: 10.1002/hyp.14018

Low temperature in‐stream solute acquisition in a glacial environment with very high suspended sediment is critical for downstream evolution of water chemistry. Present work is carried out on 18 km headwater reach from Gomukh (snout of the Gangotri glacier) to Gangotri along River Bhagirathi, India for understanding the hydrological processes controlling the solute acquisition in the glacial environment. This is the first attempt to conduct dissolution experiments with river bed sediments and meltwater considering different operating variables namely; contact time, seasonality, different sediment particle sizes, different sediment dose, effect of pH, wetting and crushing of bed sediments of the glacial stream. The role of sediment in low temperature solute acquisition process is characterized by sudden release of ions from the sediment in initial few seconds. Equilibrium time was observed to be 600 s (10 min). Further progressive increase in EC was observed from Gomukh to Gangotri, suggesting change in sediment surface characteristics/or source. Higher dissolution was observed from the bed sediments collected in June. It is found that the dissolution increases with increase in sediment doses but decreases with an increase in sediment particle size fraction. Higher solute acquisition was observed from crushed sediment because of an abundance of very fine particles having fresh, aggressive/reactive mineral surfaces which are capable of dissolution. The solute released from wetted sediment is significantly lower than the fresh sediment, which may be attributed to the destruction of microparticles adhering to mineral grains, the removal of fresh reactive surface sites, dissolution of rapidly weathered minerals such as calcite and evolution towards to equilibrium of the solution. Further, higher dissolution was observed with decrease in pH, which may be attributed to the availability of more hydrogen ion concentration of the solution, which favours more solute acquisition from sediment into meltwater.
Significant difference observed between Gangotri glacier meltwater chemistry with that of Alpine glacier system. Alpine system is dominated CO2 dissolution while Gangotri system is dominated by sulphide oxidation.
Highest SO42− 1095 μeq/L in meltwater of Gangotri glacier was in comparable with that from experiment clearly indicating the role of sediment in the meltwater chemistry.
Continuum of high p(CO2) closed system conditions in proglacial stream of Gangotri Glacier also confirmed by the dissolution experiment.