Physical and chemical properties, elemental and material snow composition in Rostov-on-Don

To study the current distribution of the heavy metals (HM) levels and iron in the atmospheric precipitation in Rostov-on-Don, an expedition was conducted aimed at simultaneous river water and snow sampling in the Don River, the roadside and park areas. The pH values of the melt-water were characterized by a slightly acidic reaction, and the stale snow in the park had lower values in comparison with the fresh snow. The river water was slightly alkaline, and the concentrations of dissolved migration forms of Pb, Cd, Zn, Ni, Cr, Mn, and Fe did not exceed the MPC. The exception was the Cu content, which exceeded the MPC by 2.4 times. The contents of the dissolved migration forms of Pb, Cd, Zn, Cu, Ni, and Fe in snow exceeded their contents in river waters. The HM and Fe percentage in suspended form in river water and different snow states is calculated and the sequence series are constructed. The analysis showed that in melt-water, in comparison with river water, there is a higher percentage of the HM and iron in the solution. That may be due to the slightly acidic reaction of the snow water medium, which, as is known, promotes the HM and Fe mobilization from the suspension and their transition to the dissolved state. Using electron microscopy and X-ray phase analysis, the suspension composition in the snow of the park zone was studied, which is mainly represented by aggregates of clay minerals, quartz grains, water silicates, feldspars, and organic matter clumps.

Hidden geographies of the ‘Mediterranean migration crisis’

This article explores the hidden geographies of what has been widely referred to as the ‘Mediterranean migration crisis’ of 2015 and 2016. Specifically, it draws on a large-scale analysis of migratory testimonies from across the central and eastern Mediterranean routes, in order to explore the claims or demands posed to European policy-makers by people on the move. Reflecting on the idea that migration forms a subversive political act that disrupts spatialised inequalities and longer histories of power and violence, the article sets out the argument advanced by scholars of the autonomy of migration approach that migration forms a ‘social movement’ involving subjective acts of escape. It makes the case for a move beyond an abstract account of migration as a social movement, to emphasise the importance of an analysis that unpacks the concrete ways in which multiple ‘nonmovements’ expose the hidden geographies of the so-called ‘crisis’. In so doing, it draws attention to two specific ways in which migration forms a political act. First, the article highlights anti-colonial acts that contest the spatialised inequalities of global migration along with longer-standing historical dynamics of exploitation and dispossession that these implicate. Second, it highlights anti-war acts that reject securitised responses to cross-border migration along with longer-standing spatial and historical dynamics of masculinist violence. While imperceptibility remains a critical dimension of many migratory acts, the article concludes that paying attention to the perceptible claims to justice that subversive political acts of migration involve is crucial in understanding the distinct transformations put into motion by people on the move.

Thermodynamic modeling of aqueous migration of chemical elements in irrigation water

Research of migration forms in irrigation water of flooded fields contributes to understanding geochemical barrier formation and functioning. It can improve pollution and nutrification control in the soil-water-plant system since geochemical barriers promote concentrating chemical elements at different depths of a soil cross-section. The research aimed to simulate the aqueous migration of chemical elements and their precipitation in the flooded rice fields’ irrigation water to determine the potential of removing them from the solution at the sorption geochemical barrier. The samples of irrigation water were taken after harvesting in the Poyang Lake basin (China) and analyzed with a standard set of methods for natural water, including ICP-MS and ICP-AES. To assess the migration forms, the HCh software package was used. The thermodynamic values database was supplemented with free energies of formation of metal complexes with fulvic and humic acids for standard conditions. Modeling has shown that most of the considered chemical elements migrate in positively charging simple ions. The main agents of complexation with humic substances are Fe, Ca, and U. Kaolinite potentially precipitates from the irrigation water. Results show that sorption of positively charged simple ions and MoO42− on clay minerals should be under special attention.