The chemical composition of meltwater-draining Himalayan glacierized basins reflects the dominance of carbonic acid in weathering of silicate and carbonate minerals, yet the role of sulfuric acid-mediated reactions in the mineral weathering and ionic release is still unclear. Here, we present a long-term study (1992-2018) of chemical weathering characteristics of a precipitation-dominated glacierized basin (Dokriani glacier) of central Himalaya. By using new and reprocessed datasets of major ions from the glacial/subglacial zones of the glacier, we suggest that two-thirds of the dissolved load of the meltwater derives from sulfuric acid-mediated weathering of minerals and rocks. We observed a clear control of carbonic acid-mediated reactions in the early ablation periods, while sulfuric acid-mediated reactions dominate in peak and late ablation periods. The slopes and intercepts in best-fit regressions of [*Ca2+ + *Mg2+ vs *SO42- and HCO3-] and [HCO3- vs *SO42-] in meltwater were following the stoichiometric parameters of sulfide oxidation coupled to carbonate dissolution reactions. The glaciers of the central and western Himalaya are in good agreement with the present estimates. We contend that the bedrock lithology has limited or second-order effects over the ionic release from Himalayan glaciers and surmise that these patterns are broadly applicable to the other orogenic systems of the world.

Permafrost degradation is altering biogeochemical processes throughout the Arctic. Thaw-induced changes in organic matter transformations and mineral weathering reactions are impacting fluxes of inorganic carbon (IC) and alkalinity (ALK) in Arctic rivers. However, the net impact of these changing fluxes on the concentration of carbon dioxide in the atmosphere (pCO(2)) is relatively unconstrained. Resolving this uncertainty is important as thaw-driven changes in the fluxes of IC and ALK could produce feedbacks in the global carbon cycle. Enhanced production of sulfuric acid through sulfide oxidation is particularly poorly quantified despite its potential to remove ALK from the ocean-atmosphere system and increase pCO(2), producing a positive feedback leading to more warming and permafrost degradation. In this work, we quantified weathering in the Koyukuk River, a major tributary of the Yukon River draining discontinuous permafrost in central Alaska, based on water and sediment samples collected near the village of Huslia in summer 2018. Using measurements of major ion abundances and sulfate (SO42-) sulfur (S-34/S-32) and oxygen (O-18/O-16) isotope ratios, we employed the MEANDIR inversion model to quantify the relative importance of a suite of weathering processes and their net impact on pCO(2). Calculations found that approximately 80% of SO42- in mainstem samples derived from sulfide oxidation with the remainder from evaporite dissolution. Moreover, S-34/S-32 ratios, C-13/C-12 ratios of dissolved IC, and sulfur X-ray absorption spectra of mainstem, secondary channel, and floodplain pore fluid and sediment samples revealed modest degrees of microbial sulfate reduction within the floodplain. Weathering fluxes of ALK and IC result in lower values of pCO(2) over timescales shorter than carbonate compensation (similar to 10(4) yr) and, for mainstem samples, higher values of pCO(2) over timescales longer than carbonate compensation but shorter than the residence time of marine SO42- (similar to 10(7) yr). Furthermore, the absolute concentrations of SO42- and Mg2+ in the Koyukuk River, as well as the ratios of SO42- and Mg2+ to other dissolved weathering products, have increased over the past 50 years. Through analogy to similar trends in the Yukon River, we interpret these changes as reflecting enhanced sulfide oxidation due to ongoing exposure of previously frozen sediment and changes in the contributions of shallow and deep flow paths to the active channel. Overall, these findings confirm that sulfide oxidation is a substantial outcome of permafrost degradation and that the sulfur cycle responds to permafrost thaw with a timescale-dependent feedback on warming.

Studies on the responses of soil organic carbon (SOC) and nitrogen dynamics to Holocene climate and environment in permafrost peatlands and/or wetlands might serve as analogues for future scenarios, and they can help predict the fate of the frozen SOC and nitrogen under a warming climate. To date, little is known about these issues on the Qinghai -Tibet Plateau (QTP). Here, we investigated the accumulations of SOC and nitrogen in a permafrost wetland on the northeastern QTP, and analyzed their links with Holocene climatic and environmental changes. In order to do so, we studied grain size, soil organic matter, SOC, and nitrogen contents, bulk density, geochemical parameters, and the accelerator mass spectrometry (AMS) 14C dating of the 216-cm-deep wetland profile. SOC and nitrogen contents revealed a general uptrend over last 7300 years. SOC stocks for depths of 0-100 and 0-200 cm were 50.1 and 79.0 kgC m-2, respectively, and nitrogen stocks for the same depths were 4.3 and 6.6 kgN m-2, respectively. Overall, a cooling and drying trend for regional climate over last 7300 years was inferred from the declining chemical weathering and humidity index. Meanwhile, SOC and nitrogen accumulated rapidly in 1110-720 BP, while apparent accumulation rates of SOC and nitrogen were much lower during the other periods of the last 7300 years. Consequently, we proposed a probable conceptual framework for the concordant development of syngenetic permafrost and SOC and nitrogen accumulations in alpine permafrost wetlands. This indicates that, apart from controls of climate, non-climate environmental factors, such as dust deposition and site hydrology, matter to SOC and nitrogen accumulations in permafrost wetlands. We emphasized that environmental changes driven by climate change have important impacts on SOC and nitrogen accumulations in alpine permafrost wetlands. This study could provide data support for regional and global estimates of SOC and nitrogen pools and for global models on carbon -climate interactions that take into account of alpine permafrost wetlands on the northeastern QTP at mid-latitudes.