Water quality and solute sources in the Marsyangdi River system of Higher Himalayan range (West-Central Nepal)

Lisa Ghezzi; Salvatore Iaccarino; Rodolfo Carosi; Chiara Montomoli; Matteo Simonetti; Kabi R Paudyal; Rosa Cidu; Riccardo Petrini

doi:10.1016/j.scitotenv.2019.04.363

Water quality and solute sources in the Marsyangdi River system of Higher Himalayan range (West-Central Nepal)

Sci Total Environ. 2019 Aug 10:677:580-589. doi: 10.1016/j.scitotenv.2019.04.363. Epub 2019 Apr 25.

Authors

Lisa Ghezzi¹, Salvatore Iaccarino², Rodolfo Carosi², Chiara Montomoli³, Matteo Simonetti², Kabi R Paudyal⁴, Rosa Cidu⁵, Riccardo Petrini⁶

Affiliations

¹ Università di Pisa, Dipartimento di Scienze della Terra, via S. Maria 53, 56126 Pisa, Italy.
² Università di Torino, Dipartimento di Scienze della Terra, via Valperga Caluso 35, 10125 Torino, Italy.
³ Università di Torino, Dipartimento di Scienze della Terra, via Valperga Caluso 35, 10125 Torino, Italy; CNR-IGG, via Moruzzi 1, 56124 Pisa, Italy.
⁴ Tribhuvan University, Central Department of Geology, Kirtipur, Kathmandu, Nepal.
⁵ Università di Cagliari, Dipartimento di Scienze Chimiche e Geologiche, Cittadella Universitaria, SS 554 Bivio per Sestu, 09042 Monserrato, CA, Italy.
⁶ Università di Pisa, Dipartimento di Scienze della Terra, via S. Maria 53, 56126 Pisa, Italy. Electronic address: riccardo.petrini@unipi.it.

PMID: 31067479
DOI: 10.1016/j.scitotenv.2019.04.363

Abstract

Surface waters, cold and hot springs were collected in different catchments along the Marsyangdi basin, in the Himalayan Range of West-Central Nepal, during the post-monsoon season in 2017 and analyzed for major ions and trace elements, with the aim of assessing the sources of dissolved species and to contribute in watershed planning. The major element data indicate that surface waters coming from the Tethyan Himalayan Sequence (THS) range from the Ca-Mg-HCO₃ to the Ca-Mg-HCO₃-SO₄ water-types and reflect a two-component mixing of waters from carbonate- and sulfate-bearing sources. The latter component is attributable to sulfide oxidation with minor silicate weathering. In the Greater Himalaya Sequence (GHS), alteration of pedogenetic carbonates formed in response to silicate weathering under a variable CO₂ gas pressure dominates, yielding a Ca-HCO₃ signature. The stability diagram in the K₂O-Al₂O₃-SiO₂-H₂O system and the paired increases in Ca²⁺, Na⁺, K⁺ and silica indicate that degradation of silicate minerals through kaolinization and possibly plagioclase albitization reactions is the main process for hot groundwater. Cold and hot springs define a trend of increasing Li, SiO₂ and Cl^-, suggesting that lithium was leached from silica-rich sources, such as pegmatite dykes and sills occurring in host rocks, and concentrated into halite-bearing salt aquifers. In hot waters Sb, As and Tl exceed the EU and USEPA thresholds. Tl is usually incorporated into pyrite and correlates with Li indicating the occurrence of an ore-bearing zone possibly related to hydrothermal activity at the transition zone between THS and GHS, as suggested by the relatively high Ba, Ni, Cu, Sb, As and Mn contents. The obtained data on water quality have significant implications for people living along the Upper Marsyangdi River in the management of water resources, especially in terms of the enhancement of cold water aquaculture and hot water uses for recreation purposes and tourism.

Keywords: Chemical weathering; Marsyangdi River basin; Nepal; Water geochemistry.