Rain gardens are efficient nature-based solutions (NBSs) for the sustainable management of surface run-off in urban areas. The functionality of a rain garden in an urban environment depends on the resistance of plant and soil components to anthropogenic stressors. In temperate climates, the negative effects of de-icing chemicals applied in wintertime are one of the major anthropogenic stressors for the rain gardens’ ecosystem. The research aimed to study the effect of a NaCl-based de-icer in the mesocosm experiment, where materials of soil mixtures (seven parts by volume of quartz or carbonate sand and three parts by volume of loam or peat), plants (Hemerocallis hybrida), de-icer dose (529 mg L⁻¹ for Cl⁻ and 472 mg L⁻¹ for Na⁺ concentrations), and irrigation period simulated typical conditions for the Moscow city—the largest world megapolis with permanent snow cover during the wintertime. For all soil mixtures, a short-term negative impact of salinization on soil health included a decrease in microbial biomass (4–7-times) and basal respiration (2–3.6-times). After six months, soil health indicators recovered by 80–90% in the peat and carbonate sand mixture, whereas the negative effects on the quartz sand and loam mixtures remained irreversible (1.3 and 3 times lower than the control, respectively). The chlorophyll content of the plants on all soil mixtures was reduced compared to the control plants (37.1 ± 4.1 vs. 39.9 ± 1.2 SPAD units). The worst plat condition was observed for soil mixtures based on quartz sand. In this variant, the negative effect of salinization coincided with low nutrient content. In our results, the ash content was up to three times less compared to the initial state, as well as to the other materials. Plants grown in mixtures based on loam were more resistant to salinization due to higher nutrient content than peat. Overall, based on soil Na uptake, plant biomass, and recovery of soil microbiota, soil mixtures based on peat, loam, and carbonate sand will be the most resistant to NaCl-based de-icers and could be recommended for the creation of rain gardens in cities with permanent snow cover in winter.

The fertility of urban soils in the Arctic is limited by harsh climatic conditions and high anthropogenic pressure. In addition to the typical impacts of residential use, recreation, and transportation common in any urbanized areas, the ecosystems of Russian Arctic cities are subject to the technogenic influence of heavy industry hubs, which often serve as the foundation for these cities. Under such conditions, the soil cover of the largest cities in the Russian Arctic — Murmansk, Vorkuta, and Norilsk — has formed. An analysis of the physical and chemical properties of urban soils, an assessment of their fertility, and the limiting factors are necessary for the creation and maintenance of urban green infrastructure, which is one of the key factors in the ecological comfort of city life. This study evaluates the acidity, organic matter and total nitrogen content, availability of mobile forms of phosphorus and potassium in the topsoil of these cities and provides an integrated assessment of their fertility based on the soil-ecological index (SEI) by I.I. Karmanov, adapted within the study for application to northern soils and territories. It is shown that, based on the combination of indicators, the soils of the studied sites form the sequence Murmansk Vorkuta Norilsk, from the most fertile to the least fertile. The influence of anthropogenic factors on soil properties is noted, which can be both positive (a decrease in average soil acidity across all sites) and negative (toxic concentrations of mobile phosphorus in the soils of Murmansk). Based on the obtained SEI values, it is concluded that the soils of the studied sites have relatively high overall fertility, comparable to that of soils in the middle and southern taiga.