Urbanization Affects Soil Microbiome Profile Distribution in the Russian Arctic Region

Urbanization in the Arctic results in considerable and still poorly known environmental consequences. The effect of urbanization on soil microbiome—an ecosystem component highly sensitive to anthropogenic disturbance—remains overlooked for the Arctic region. The research compared chemical and microbial properties of the natural Podzol soils and urban soils of Murmansk—the largest Arctic city. Particular attention was given to the profile distribution, which is almost completely ignored by most microbial studies. Soil microbiome was investigated by the quantitative indicators based on fluorescence microscopy (microbial biomass) and PCR real-time methods (amount of rRNA genes copies of archaea, bacteria, and fungi). The principal changes in urban soils’ properties compared to the natural references included a shift in pH and an increase in C and nutrients’ contents, especially remarkable for the subsoil. The numbers of rRNA genes copies of archaea, bacteria, and fungi in urban topsoils (106–1010, 109–1010, and 107–109, respectively) were lower than in Podzol; however, the opposite pattern was shown for the subsoil. Similarly, the total microbial biomass in urban topsoils (0.55–0.75 mg g−1) was lower compared to the 1.02 mg g−1 in Podzols, while urban subsoil microbial biomass was 2–2.5 times higher than in the natural conditions. Both for urban and natural soils and throughout the profiles, fungi were dominated by mycelium forms; however, the ratios of mycelium–spores were lower, and the amount of thin mycelium was higher in urban soils than in natural Podzols. Urbanization in the Arctic altered soil morphological and chemical properties and created a new niche for microbial development in urban subsoils; its contribution to biodiversity and nutrient cycling promises to become increasingly important under projected climate change.

Presence of the Potential Toxic Metals (PTMs) in the urban and peri-urban topsoils

The occurrence of the PTEs contamination in the environment resulting from the point or diffuse sources increases with globalization and population growth. Anyway the benefits of home gardening for the physiological and physical well-being, as well as uncertainties regarding food supply chain in the case of Covid-19, the desire to use home-grown (local) food is increasing more and more. There is no information available on the PTE pollution of urban soils used for the food production in Slovenia. Therefore, the main goal of present study is the characterization of urban gardens and agricultural areas affected by flooded sediments. The total concentrations of PTEs in soil and sediment samples were ICP-MS. The concentrations of PTEs (As, Cd, Cr, Cu, Ni, Pb and Zn) exceeded the permissible limit values defined in Slovenian Official Gazette. To define the natural or artificial origin of PTEs, the mineralogical composition of the selected soils and sediments was determined. The results obtained in present study were correlated with the national background values measured in the upper soil horizon and showed elevated concentrations. In addition to the environmental issues, the social aspect of potential impacts of PTEs on human health and safety was investigated. The results show that despite the numerous local, national and international plans and measures, greater awareness of the general public is needed to understand the hazardous effects of PTEs and the need for appropriate management of contaminated soil in the case contaminated areas.

Human health risk assessment of potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs) in urban topsoils of Tyumen city, Russia

<p>Cities are the key centers of technogenesis, which leads to environmental pollution. The state of the soil cover reflects the long-term anthropogenic impact as a result of urbanization processes. In the urban environment, the priority pollutants are potentially toxic elements (PTEs) and polycyclic aromatic hydrocarbons (PAHs), since they are not only an environmental hazard, but also a risk factor for the public health. Tyumen city, with a population of 807,300 people, is a large transport and trade center in Western Siberia, Russia, with a developed service sector, construction and manufacturing industries. The aim of the study is to evaluate possible carcinogenic and noncarcinogenic risks related to PTEs and PAHs in urban topsoils of Tyumen, as representative of urban environment in Western Siberia.</p><p>Topsoil samples (0-10 cm) were collected according to the regular grid at 241 sampling points. The total content of V, Cr, Co, Ni, Cu, Zn, As, Sr, and Pb was determined using X-Ray fluorescence spectrometry. Content of twelve priority PAHs was measured using high-performance liquid chromatograph Agilent 1260 Infinity. Human health risk assessment was based on the US EPA model (1989). The noncarcinogenic risk for different age groups of the population, expressed as a hazard quotient (HQ), was evaluated by comparing the average daily dose of pollutant (ADD) with a reference dose (RfD). Carcinogenic risk (CR) reflects the probability of developing cancer in an individual throughout their life, taking into account the lifetime average daily dose of a pollutant (LADD) and carcinogen slope factor (SF). Values of RfD and SF were based on toxicological data (U. S. EPA 1997, 2004, 2020; ATSDR 2020; OEHHA 2020). The combined effects were assessed using the total hazard index (THI) and the total carcinogenic risk (TCR).</p><p>Noncarcinogenic risks were more likely caused by intake of V, Co, As, Pb, Ni and Cu. For both children and adults, the risk associated with the oral intake of pollutants was the greatest. For children, significant risks arose from exposure to V, Co, As and Pb (HQ> 1). The THI values for children varied from 0.78 to 7.25, on average 2.72, for adults - from 0.08 to 0.79, on average 0.27. Most of the territory was characterized by a medium non-carcinogenic risk for children and a low risk for adults.</p><p>Significant CR was associated with long-term exposure to Co, As, Pb and benzo[a]pyrene. The TCR values under the combined effect of PTEs and PAHs ranged from 1.2 × 10<sup>-5</sup> to 2.2 × 10<sup>-4</sup>, on average 6.9 × 10<sup>-5</sup>. In general, the level of carcinogenic risk in the city was assessed as low. Medium carcinogenic risk was established in the soils of impact zones of enterprises for the production and disposal of batteries, CHPP-1 and some large transport hubs. An extensive zone of increased carcinogenic risk was established in the residential area of the central part of the city.</p><p>The research was funded by RFBR and Tyumen Region, project no. 20-45-720003, and by Ministry of Science and Higher Education of the Russian Federation, no. 0852-2020-0029.</p>