Most glaciers worldwide are undergoing climate-forced recession, but the impact of glacier changes on biogeochemical cycles is unclear. This study examines the influence of proglacial sediment weathering on meltwater chemistry at the early stages of glacier recession in the High Arctic of Svalbard. Scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) in combination with a wide range of geochemical analyses were used in this study. The SEM-EDS analyses of sediments collected in front of Werenskioldbreen show general degradation of pyrite and carbonate grains with age. The outer parts of pyrite grains have a gradual decrease in sulphur and gradual increase in iron oxides due to pyrite oxidation. This process was less advanced in the proglacial zone younger than 100 years compared to older sites such as the terminal moraine from the Little Ice Age. In both the proglacial zone and the terminal moraine, physical weathering of mineral grains, including formation of microcracks and microfractures, clearly enhanced pyrite oxidation. A consequence of proglacial sediment weathering is that the river chemistry is strongly affected by carbonate dissolution driven by sulphuric acid from sulphide oxidation. Also, reactive iron oxides, a product of sulphide oxidation, are mobilized in the proglacial zone. The results of this study show that proglacial weathering in the High Arctic of Svalbard is strongly coupled to river geochemistry, especially during the early stages of proglacial exposure after glacier recession.

Riverbank filtration (RBF), a managed aquifer recharge (MAR) technique utilised at the river–groundwater interface, can enhance groundwater quantity and quality, thus improving water supply security. However, it demands targeted local and regional monitoring strategies to understand how recharge efficiency and water quality benefits may vary with seasonal and short-term, event-based river flow fluctuations, upstream contaminant inputs, and site-specific aquifer heterogeneity. We evaluated river water–groundwater mixing and groundwater residence times to enhance the knowledge of aquifer recharge dynamics at the RBF site near Tarnów, Poland, serving as a critical drinking water source in this region. By coupling environmental tracers (stable water isotopes, chloride concentration, water temperature and specific electrical conductance) with high-resolution hydrological, meteorological and groundwater abstraction records, we show that RBF is the dominant recharge mechanism for the system that constitutes over 90 % of year-round yield from the production wells near the riverbank. Based on this example, we present a transferable and practical methodology for managing RBF systems efficiently: a multi-tracer, Ensemble End-Member Mixing Analysis (EEMMA) based workflow that covers at least one hydrological year, checks for local biases, and combines discrete water samples with continuous monitoring of physicochemical and hydrometeorological data, thus providing a robust and cost-effective template for recharge-source assessment. Such a framework determines both quantitative and qualitative status of abstracted groundwater and facilitates proactive responses to upstream pollution events and/or rapid hydrological shifts, which are crucial for sustainable water resource management internationally.