## 3 Results and Discussion
the number of these bird species increases significantly in these habitats. New positive landforms created by artificially deposited soils attract birds of prey, who use them as roosting sites and as a place where small mammals running across the sand can be easily detected and captured. Arctic foxes and crimes are attracted by the presence of prey and are constantly present near roads. In quieter areas of embankments, these animals may also burrow, as it is easier to dig burrows in these soils than in permafrost. Therefore, soils and similar materials contribute to changes in local biodiversity in urban ecosystems. The ecological role of soils in urbanized Arctic ecosystems is underestimated. For a long time, researchers have focused on the soils of natural tundra and areas where gas and oil are produced. Urban soils in the Arctic have been neglected, yet they play a crucial role as a substrate for green spaces in cities, providing important aesthetic and recreational benefits. Furthermore, urban soils contribute to preserving and enhancing biodiversity in fragile cryolithozone ecosystems. The data on the chemical composition of the soils are provided in Figure 1.3 Since the purpose of our work was mainly to characterize the morphological transformation of soils, soil samples to determine their chemical characteristics were taken from the upper horizons in a single repetition without taking into account the spatial location of soils relative to possible sources of pollution, which will be the material for a separate article. In the case of the Longyugan and Nadym soils, the natural soils are more acidic than the urban soils. This is caused by the accumulation of cations in urban ecosystems and soils [55], as well as the disturbance or disappearance of the forest floor, which is a source of organic acids in soils. The content of organic matter in urban soils is higher than in natural soils. In some cases, this could result from urban greening practices, such as the planting of grasses in parks or residential zones, which can accelerate humus content. Conversely, some organic matter may have a technogenic origin [56]. With regard to heavy metals, there is no doubt that they are more concentrated in urban soils than in background soils in settlements. Thus, urbanized ecosystems not only undergo a transformation in the morphological organization of the soil profile, but also a significant transformation in the chemical parameters of the soil's fine earth. The soils of the Kharsaim settlement are essentially contaminated with heavy metals, both naturally occurring and urbic. This is due to intensive economic and transportation activity in the settlement itself and its vicinity. Intensive chemical impact is confirmed by the neutral and alkaline reaction of the fine earth in Kharsaim soils. The soils of Tarko-Sale and Muravlenko demonstrate the same trend as the soils of Nadym and Longyugan: urban soils are less acidic, enriched with organic matter, and accumulate heavy metals compared to natural soils. In spite of the fact that the studied settlements have existed for a shorter period in comparison with cities in European Russia, urban soils show a significant transformation of chemical state along with strong morphological changes. The low absorption capacity of sandy soils (namely, those that prevail in our study) does not contribute to a strong accumulation of pollutants. Considering that most of the soils we have studied are characterized by an acidic environment, it is not surprising that heavy metals are not fixed in the upper soil layers, as is the case in soils in large cities in the European part of Russia. In those areas, the alkalization of urban soil is more pronounced. Of course, these are the primary data of chemical analysis of soils; it is necessary to analyze a much larger number of soil samples. An important issue is the sampling strategy used for chemical analysis.