The Content and Sources of Potentially Toxic Elements in the Road Dust of Surgut (Russia)

The chemical and particle size composition of road dust in Surgut, which is a rapidly developing city in Western Siberia, was studied for the first time. Contents of major and trace elements were determined using ICP-MS and ICP-AES, respectively. It was found that the road dust had an alkaline pH (from 7.54 to 9.38) and that the particle size composition was dominated by the 100–250-μm fraction. The contamination assessment based on calculations of the enrichment factor (EF) showed that the road dust was significantly enriched in Sb and Cu and moderately enriched in Zn, Pb, Mo, Ni and W. The sources of these elements are probably associated with the abrasion of car tires and brake pads. Based on calculations of global pollution index (PIr) and total enrichment factor (Ze), the road dust of Surgut was characterized by a generally low level of potential ecological risk, except for stretches of road subject to regular traffic jams, where a moderate ecological risk level was identified. In comparison to the other Russian cities (Moscow, Chelyabinsk, Tyumen, etc.) where studies of road dust composition have been carried out, Surgut had similar contents of Cr and Cu and relatively lower contents of Sb, Cd, As and Pb.

Digital mapping of soil texture in ecoforest polygons in Quebec, Canada

Texture strongly influences the soil’s fundamental functions in forest ecosystems. In response to the growing demand for information on soil properties for environmental modeling, more and more studies have been conducted over the past decade to assess the spatial variability of soil properties on a regional to global scale. These investigations rely on the acquisition and compilation of numerous soil field records and on the development of statistical methods and technology. Here, we used random forest machine learning algorithms to model and map particle size composition in ecoforest polygons for the entire area of managed forests in the province of Quebec, Canada. We compiled archived laboratory analyses of 29,570 mineral soil samples (17,901 sites) and a set of 33 covariates, including 22 variables related to climate, five related to soil characteristics, three to spatial position or spatial context, two to relief and topography, and one to vegetation. After five repeats of 5-fold cross-validation, results show that models that include two functionally independent values regarding particle size composition explain 60%, 34%, and 78% of the variance in sand, silt and clay fractions, respectively, with mean absolute errors ranging from 4.0% for the clay fraction to 9.5% for the sand fraction. The most important model variables are those observed in the field and those interpreted from aerial photography regarding soil characteristics, followed by those regarding elevation and climate. Our results compare favorably with those of previous soil texture mapping studies for the same territory, in which particle size composition was modeled mainly from rasterized climatic and topographic covariates. The map we provide should meet the needs of provincial forest managers, as it is compatible with the ecoforest map that constitutes the basis of information for forest management in Quebec, Canada.

Redistribution of particle-size fractions in ordinary chernozem affected by long-term irrigation and chemical melioration with phosphogypsum

The article reveals the issue of redistribution of particle-size fractions in ordinary low-humus leached chernozem on loamy loess in the condition of Northern Steppe of Ukraine affected by the irrigation with II class water and chemical melioration with phosphogypsum. Rather long use of water for irrigation from the reservoir on the Samara River in the Dniprovskyi district of the Dnipropetrovsk region deteriorated the soil properties due to salinization development in it, which led to the use of phosphogypsum. The calculated application rates of phosphogypsum 1,4 t/ha, 3 t/ha and 6 t/ha were applied along with irrigation and without it. The effect of chemical melioration and irrigation on the ecological and ameliorative condition of soil that resulted in the change of its particle-size composition, bulk density and structure was studied. It is established that irrigation of the soil with an average irrigation rate of 1500 m3/ha reduces the content of physical clay by 0,12-0,06% compared to the options without irrigation. When applying phosphogypsum along with irrigation there are minor changes in the redistribution of particle-size fractions: an increase in the fractions of physical sand and a decrease in the fractions of physical clay. It was determined that the particle-size composition of soil is more resistant to the effect of phosphogypsum rather than to the effect of irrigation. In non-irrigated variants when applying chemical melioration with phosphogypsum, the content of physical sand increases by 0,54-0,91% compared to the reference variant and the content of physical clay decreases by 0,87-1,13%. With increasing the rate of phosphogypsum, the content of physical sand also increases. The effect of improving the structure and loosening of the soil is observed in the variants where phosphogypsum at the rate of 6 t/ha was applied under the main tillage and at the rate of 3 t/ha under spring cultivation.

The formation of the soil section by morphological characteristics in technosol of Semenivsko-Holovkivske lignite open-cut

Analysis of morphological descriptions of technosol sections indicates the following features of soil formation in technosol under common pine plantations. The particle-size composition in all variants depends above all on the composition of rocks, which form technosol. There is a color change in the upper layer of lithosol section, where the initial stage of humus formation and humus accumulation processes take place. The humus layer, which indicates the speed of these processes, is present only in the upper and lower third of the slope in 20-year-old common pine plantations and ranges from 7 cm in the upper to 10 cm in the lower third of the slope, which may be the result of flat erosion on the slope. There is no humus horizon in valley bottom, as spring water stagnation occurs there, which caused the death of most of the plantings, which were the main source of organic matter entering the soil. The inhibition in the processes of humus formation under the plantations that develop on the upland occurs due to the low content of the dusty fraction. The formation of the soil structure was not observed in technosols formed from rocks with light particle-size composition (sandy loam and sand); on loamy variants, it passes intensively in the upper 10–15 cm layer, which contains most plant roots, worms and insects. The presence of a plate structure has a industry-related origin and is formed when heavy machinery passes through rocks with a high moisture content. An important indicator of the initial processes of soil formation is the decompression of technosols and the speed of this process. This process is the most quick under 23-year-old plantations on a upland, cultivated on rocks with light particle-size composition (the loose horizon is 80 cm), on a slope in a 20-year-old plantation on heavier rocks, this process is much slower (the loose horizon is about 7–10 cm). Brown coal, inclusions of carbonaceous clays, rippled and kaolin clays can be found among the inclusions. The number and composition of the inclusions depends on the nature of the rocks, which form tehnosol. The new growths of biological origin should be mentioned, among which there are biological capillaries, represented by root passages with a diameter of 4–7 mm, filled with soil material enriched with organic substances and ones with the diameter of 2–3 mm to 1 cm, filled with coprolites and soil mass. Thus, changes in technosols identified by morphological features depend on open-pit rocks which form the edaphotope, their composition and properties, on the quality of the technical stage of reclamation and on the terrain of the formed territory.