The impact of glacier retreat on Andean high wetlands: Assessing the geochemical transfer and sediment provenance in the proglacial area of Huayna-Potosí (Bolivia)

Abstract

The accelerated decline of tropical Andean glaciers is affecting the water cycle of mountains in the region. In the Cordillera Real (Bolivia) on the Huayna-Potosí peak (6088 m a.s.l.), the rapid retreat of the Oeste Glacier is exposing new rock outcrops and glacial materials. Changes in the hydrological regime by glacier retreat are likely to modify the supply of sediments and subsequently affect the geochemical transfer of particle-bound elements within proglacial and downstream ecosystems. To address this issue, a sampling campaign in the proglacial area of Huayna-Potosí aimed to identify and collect sediments from the primary active landforms. To characterise elemental transfer and identify sediment provenance using fingerprinting techniques, streambed sediments were collected along the main stream from the glacier tongue at 5002 m a.s.l. to a wetland shallow lake at 4700 m a.s.l.. Geomorphological features control the production of fine particles and the distribution of particle-bound geochemical elements. Complex processes of solubilization, mobilisation, and retention govern the elemental transfer. Significant increases in 238U, as well as some major elements, were observed in the surface lake sediments, while Pb, Cr, and Cu decreased, and 137Cs was not detected. The spatial distribution patterns of geochemical elements and the assessment of the sediment provenance indicate that deglaciation fosters geochemical processes and the elemental transfer dynamics in the wetlands. Moraines and colluvium were found to be the primary contributors to sediment yield (93 %) while the rich organic soils in swamps contributed the least (7 %). The enhanced supply of sediments to the shallow lake in parallel to glacier decline may affect water quality and bring about further changes in the wetlands. Identifying primary sediment sources is essential for water management. Our findings enhance understanding of the compositional characteristics of mobilised sediment and their variations, aiding in more effective resource management to preserve these high-altitude wetlands.