A first continuous three-year temperature record from the dimictic arctic–alpine Lake Tarfala, northern Sweden

Arctic lakes are exposed to warming during increasingly longer ice-free periods and, if located in glaciated areas, to increased inflow of meltwater and sediments. However, direct monitoring of how such lakes respond to changing environmental conditions is challenging not only because of their remoteness but also because of the scarcity of present and previously observed lake states. At the glacier-proximal Lake Tarfala in the Kebnekaise Mountains, northern Sweden, temperatures throughout the water column at its deepest part (50 m) were acquired between 2016 and 2019. This three-year record shows that Lake Tarfala is dimictic and is overturning during spring and fall, respectively. Timing, duration, and intensity of mixing processes, as well as of summer and winter stratification, vary between years. Glacial meltwater may play an important role regarding not only mixing processes but also cooling of the lake. Attribution of external environmental factors to (changes in) lake mixing processes and thermal states remains challenging owing to for example, timing of ice-on and ice-off but also reflection and absorption of light, both known to play a decisive role for lake mixing processes, are not (yet) monitored in situ at Lake Tarfala.Peer reviewe

Thermodynamic stability of waste glasses compared to leaching behaviour

The thermodynamic stability of products obtained from the high-temperature treatment of municipal solid wastes and their associated residues (bottom ash, fly ash, filter cake, optional additives) can be estimated by calculation of their free energy of hydration ΔGhydr by a polyhedral approach. This approach has been applied on a series of 23 samples originating from high-temperature treatment processes operated under a range of conditions, and 3 thoroughly characterised standards. For vitreous or vitrocrystalline samples, it is demonstrated that Si and Ca contents clearly control their thermodynamic stability, and that the type of incineration process plays only a minor role. Silicon directly influences the durability of the samples, while Ca governs the pH during corrosion, which in turn affects the thermodynamic stability. It is also shown that there is a tight inverse relationship between the calculated thermodynamic stability of the samples and their rates of dissolution under aggressive conditions of corrosion. Attempts to compare the results to the large literature database of results obtained from nuclear high-level waste glasses, their proxies and other analogs (ancient and commercial glasses) are limited by sample preparation constraints. It is however concluded that the calculated thermodynamic stability of these “waste glasses” offers a valid estimate for their relative quality and, in turn, for their durability