Lithological and hydrological controls on water composition: evaporite dissolution and glacial weathering in the south central Andes of Argentina (33°–34°S)

Abstract

Lithological and hydrological influence on fluvial physical and chemical erosion was studied in a glacierized sedimentary basin with high evaporite presence. Suspended particulate matter (SPM), total dissolved solids (TDS) and major ion concentrations were analysed for 2 years of different hydrologic condition: (i) 2009–2010, Q = 100% average; and (ii) 2010–2011, Q = 60% average. Annual hydrograph was simple regime‐type with one peak in summer related to snow melting. The intra‐annual SPM and TDS variations were directly and inversely associated to Q, respectively. Snow chemistry showed continental influence (Na+/Ca2+ = 0.17), and atmospheric input of TDS was <1% of the total exported flux. River water was highly concentrated in Ca2+ and SO42− (~4 mmol l−1) and in Na+ and Cl− (~3 mmol l−1). Ca2+/SO42− and Na+/Cl− molar ratios were ~1 and related to Q, directly and inversely, respectively. Major ion relationships suggest that river chemistry is controlled by evaporite (gypsum and halite) dissolution having a summer input from sulfide oxidation and carbonate dissolution, and a winter input from subsurface flow loaded with silicate weathering products. This variation pattern resulted in nearly chemostatic behaviour for Ca+, Mg2+ and SO42−, whereas Na+, Cl− and SiO2 concentrations showed to be controlled by dilution/concentration processes. During the 2009–2010 hydrological year, the fluxes of water, SPM and TDS registered in the snow melting–high Q season were, respectively, 71%, 92% and 67% of the annual total, whereas for equal period in 2010–2011, 56% of water, 86% of SPM and 54% of TDS annual fluxes were registered. The SPM fluxes for 2009–2010 and 2010–2011 were 1.19 × 106 and 0.79 × 106 t year−1, whereas TDS fluxes were 0.68 × 106 and 0.55 × 106 t year−1, respectively. Export rates for 2009–2010 were 484 t km2 year−1 for SPM and 275 t km2 year−1 for TDS. These rates are higher than those observed in glacierized granite basins and in non‐glacierized evaporite basins, suggesting a synergistic effect of lithology and glaciers on physical and chemical erosion. Copyright © 2014 John Wiley & Sons, Ltd.

Sensitivity of chemical weathering and dissolved carbon dynamics to hydrological conditions in a typical karst river

“…The regression coefficient b in the relationship between C and Q has a physical interpretation. If b = 0, the catchment behaves entire chemostatically; and if b = −1, Q is the only controller on C, constant solute fluxes being diluted by variable fluxes of water 27 . However, when b > 0, no dilution effect is present, because large amounts of inputs are induced by high discharge.…”

“… 22 24 25 26 . Riverine DIC and DOC concentrations are often, closely, associated with variations in hydrology 27 28 , as well as variations in sources and fluxes of dissolved carbon 26 29 . Detailed information on dissolved carbon dynamics with respect to hydrological conditions is still scarce, and relevant controlling processes are largely unknown.…”

Spatial characteristics and controlling factors of chemical weathering of loess in the dry season in the middle Loess Plateau, China

“…Furthermore, anthropogenic activities may accelerate the denudation rate. Because seasonal variation of water solutes and discharge was significant (León and Pedrozo, ; Singh et al, ; Ran et al, ) and eolian dust played a potential significant role in controlling seasonal variations of river water chemistry (Jin et al, ), uncertainties of the above calculation may also exist. Therefore, to accurately monitor the processes of modern chemical weathering of loess, and to catch the signature of some extreme events, such as sandstorm and rainstorm in the MLP, the densely time‐series water sampling strategy should be advocated.…”

The impact of extreme El Niño events on modern sediment transport along the western Peruvian Andes (1968–2012)

“…Circle centres indicate the locations of hydro-sedimentological stations, while their size is proportional to the SSY. Red and lead circles represent data from this study and the literature 29 – 38 , respectively. The black dotted line separates the Pacific and Atlantic watersheds.…”