SEM-EDS and water chemistry characteristics at the early stages of glacier recession reveal biogeochemical coupling between proglacial sediments and meltwater

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.

Combustion wastes from thermal power stations and household stoves: A comparison of properties, mineralogical and chemical composition, and element mobilization by water and fertilizers

Wood and coal combustion generate wastes, which may negatively influence the environment. However, studies concerning coal combustion products serving as soil additives are currently in progress. Hence, this study was conducted to compare properties (mineralogy, metallic element content, and rare earth element content) of combustion wastes of different genesis (ash and soot after wood and coal combustion in households, ash from thermal power stations) and to assess possible risk posed to the soil environment when used as soil additive. This study demonstrated the diversity of chemical and mineralogical features of ashes of household genesis originating from thermal power stations. Ash from household stoves showed a higher concentration of metallic elements (i.e., Zn) compared to those originating from thermal power stations. Antimony (Sb) content in household ash can serve as an indicator of plastic (polyethylene) combustion, which is legally prohibited. Leaching tests using water and common mineral fertilizers showed that ammonium sulfate mobilizes metallic elements (Cu, Zn, Pb) more significantly than potassium nitrate or deionized water. The leaching of metallic elements from household stove's ash certainly excludes the possibility of applying the ash as a soil additive even when the ash contains a source of beneficial elements for plants (i.e., Ca).