Bachelor Thesis

Basin lithology influences the isotopic composition of riverine sulfate in alpine rivers within the Western Himalayan Mountains

Niklas Linder (04/2026-03/2027)

Chemical weathering controls many element cycles, including the sulfur cycle, which directly affects the carbon and oxygen cycles. To quantify these fluxes, sulfur reaction pathways must first be understood. Sulfur isotopes in riverine sulfate help identify the weathered end members: pyrite, formed mainly by microbial activity, has lower δ³⁴S values than evaporites such as gypsum and anhydrite. Alpine rivers are ideal for this. Rising mountains expose large amounts of weatherable rock, and small tributary catchments drain few rock types, so they approximate single end members. Sulfate is precipitated as barite and measured on a Thermo Delta V mass spectrometer. I analysed samples from the Western Himalaya (Alaknanda, Bhagirathi, Pabbar, Tons, Yamuna and tributaries) to compare the Lesser Himalayan Series (LHS), Higher Himalayan Crystalline Series (HHCS) and Tethyan Sedimentary Series (TSS). I compare my results with one study from the same area and one from another river draining the same units.