Effects of recreational and residential functional land use on urban soils 131Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146.DOI: 10.15201/hungeobull.73.2.2 Hungarian Geographical Bulletin 73 2024 (2) 131–146. Introduction Soil cover in cities is characterized by diver- sity and heterogeneity, featuring a combi- nation of natural, natural-anthropogenic, and anthropogenic soils. Despite significant changes in morphological, physical, and chemical properties compared to natural horizons, anthropogenic horizons play eco- logical roles by providing conditions for veg- etation growth and enhancing the quality of urban life for the population (Blume, H.P. 1989; Novák, T.J. et al. 2020). A horizons exhibit varying morphological, chemical, and physical properties depend- ing on the functional zone and the level of anthropogenic influence (Pouyat, R.V. et al. 2007; Zhevelev, H. and Kutiel, B.P. 2012; De Lucia, B. et al. 2013). For instance, soils in transportation, industrial, and residential areas tend to have high density (Zhao, D. et al. 2013; Chupina, V.I. 2020). Soil in recre- ational areas often contains elevated levels of Corg (Zhao, D. et al. 2013; Charzyński, P. et al. 2018). In residential zones, surface seal- ing and lowering of the water table lead to reduced soil moisture content (Blume, H.P. 1989; Burghardt, W. 2006; Sándor, G. et al. 2013). Urban soils become more alkaline due to dust deposits rich in calcium and magne- sium carbonates, as well as the use of deicing agents. Additionally, pH levels tend to in- 1 Federal State Budget Scientific Institution “Federal Scientific Centre of Agroecology, Complex Melioration and Protective Afforestation of the Russian Academy of Sciences”. 400062 Volgograd, Russian Federation. Corresponding author’s e-mail: oleg.gordienko.95@bk.ru, ORCID ID: https://orcid.org/0000-0001-5381-9114 Effects of recreational and residential functional land use on urban soils Oleg GORDIENKO 1 and Anastasia KULIK 1 Abstract Soils in residential areas of cities are heavily degraded, and the environmentally protective and formative functions are instead realized by the soils in recreational areas (city parks, etc.). The study aimed to analyse the influence of functional land use and the level of anthropogenic impact on the properties of anthropogenic horizons (Au and Aτ) in the city of Volgograd, Russia. In this study, we analysed 50 soil samples from the city’s recreational and residential functional areas under field and laboratory conditions. The study evaluated the morphological aspects (thickness, colour, structure, and presence of artefacts), physical properties (bulk density, texture), and chemical properties (pHwater, salt content, CaCO3, Corg, SOCstoc) of the soils. The anthro- pogenic Au horizons in residential areas exhibited a clumpy structure, numerous artefacts, and significant compaction. Conversely, the soils in recreational zones contained fewer anthropogenic artefacts, with the Aτ horizons characterized by a lumpy structure. The anthropogenic horizons’ median and mean property values in the functional zones showed significant differences. The acid-alkaline properties of the studied horizons were weakly alkaline in recreational areas and alkaline in residential areas. A common feature of all anthro- pogenic horizons was the variability in chemical, physical, and morphological properties depending on the functional zone and level of anthropogenic load. The indicators of a specific level of anthropogenic impact on urban landscapes included horizon thickness, Corg content, colour, and structure. Keywords: soils of recreational areas, residential areas, Technic, Urbic, Technosols, physical and chemical properties of soils Received February 2024, accepted May 2024. mailto:oleg.gordienko.95@bk.ru Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146.132 crease due to decreased organic matter result- ing from reduced vegetation biomass (Brevik, E.C. and Fenton, T.E. 2012; Zhevelev, H.M. et al. 2013). Some studies have observed a pH decrease attributed to precipitation acidifica- tion (Sukopp, H. et al. 1979). The use of heavy machinery in residential areas can cause soil compaction, reduced pore size, and the for- mation of a clumpy structure (Jim, C. and Ng, Y. 2018). This, in turn, slows down the infiltration of atmospheric moisture, energy transfer, plant growth, aeration, and organ- ic carbon accumulation (Scalenghe, R. and Marsan, F.A. 2009; Jim, C. and Ng, Y. 2018). Consequently, soil structure degradation and a decrease in organic carbon content occur (De Lucia, B. et al. 2013). In general, anthropogenic A horizons ex- hibit a wide range of properties across most cities worldwide. This variability has been observed in cities such as Zielona Góra in Poland (Greinert, A. 2015), Paris in France (Cambou, A. et al. 2018), Rostov-on-Don and Murmansk in Russia (Dvornikov, Y.A. et al. 2021), and Ghent in Belgium (Delbecque, N. et al. 2022). However, cities like Detroit and New York City in the USA (Howard, J. and Orlicki, K. [2015], and Huot, H. et al. [2016]), the Rostov agglomeration in Russia (Bezuglova, O.S. et al. 2018), Toruń in Poland (Charzyński, P. et al. 2018), Moscow in Russia (Prokof’eva, T. et al. 2020), Akure and Okitipupa towns in Nigeria (Adelana, A.O. et al. 2023) show similarities in certain properties of anthropogenic horizons across different functional zones, such as pH, thick- ness, and grain-size composition. The objective of the study was to analyse the morphological, chemical, and physical properties of anthropogenic soil horizons Au and Aτ in Volgograd city based on the functional land use type and the level of an- thropogenic impact. Hypothesis: The properties of anthropogenic soil horizons will exhibit distinct variations de- pending on the functional zoning of an urban area, with significant differences between resi- dential and recreational zones. We predict that soil horizons in recreational zones will demon- strate distinctive characteristics compared to those in residential areas, reflecting the specific land use practices and human activities associ- ated with each zoning type. Materials and methods Study area Volgograd, a major industrial city in the Rus- sian Federation, boasts significant industrial and residential capabilities. The town is situ- ated in an area characterized by Cambisols (Protocalcic), Cambisols (Protocalcic, Sodic), and Haplic Kastanozems of varying grain- size compositions. The soils within the city limits have undergone extensive transfor- mation, with residential and industrial ar- eas featuring Urbic Technosols and Ekranic Technosols, while recreational areas include Technosols (Mollic), Hortic Anthrosols, Cambisols (Protocalcic, Technic), and Haplic Kastanozems (Technic) (Gordienko, O. et al. 2022), classified according to the World Ref- erence Base for Soil Resources (WRB) (IUSS Working Group, 2022). The primary factor influencing soil formation is anthropogenic. In the city development plan for Volgograd, residential areas are designated for the con- struction of residential, public, and indus- trial structures, along with roads and streets, while recreational zones encompass city parks, squares, and boulevards (Figure 1). The study focused on the soils of recrea- tional areas and adjacent residential zones, specifically Druzhba Park (48°35’3.53”N, 44°26’31.27”E), Sasha Filippov Park (48°41’42.84”N, 44°29’58.67”E), and the city arboretum (48°38’37.22”N, 44°26’11.06”E). These selected research sites vary in terms of anthropogenic impact and recreational usage yet share similar geomorphological conditions. In 1943, Volgograd (at that time Stalingrad) was entirely devastated. Reconstruction ef- forts commenced promptly after the ces- sation of hostilities in February 1943. The majority of explosion craters, defensive po- sitions, and ruined structures were cleared 133Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146. through mechanical means and deposited into nearby gullies. Consequently, soil for- mation within the city is initiated simultane- ously in all zones under uniform conditions. The study focused on the anthropogenic ho- rizons designated Au and Aτ, as per FAO clas- sification, analogous to Russian urban horizons UR and RAT (FAO, 2006; Prokof’eva, T.V. et al. 2017). Despite residential and recreational soils potentially belonging to different Reference Soil Groups, they commonly feature the pres- ence of anthropogenic horizons Au and Aτ. The anthropogenic horizons were catego- rized into groups to test the hypothesis regard- ing variations in properties based on anthro- pogenic load and functional zones (Figure 2): Total sampling of A horizons (50 samples), corresponding to the number of soil genetic horizons, including: 1. Aτ (33 samples) from recreational areas, 2. Au (17 samples) from residential areas. The distinction between Au and Aτ hori- zons is based on their genesis and artefact volume (%). Au horizons (qualifier Urbic) are predominantly found in residential, in- dustrial, and transport zones, characterized by the introduction of various substrates on the surface, containing ≥ 20 percent artefacts (mainly building and household waste) and often sandy or rocky. Aτ horizons, while similar in origin to Au, contain soil material deliberately transported by humans from outside the immediate environment, with 5–10 percent artefacts, unaffected by natural recycling or movement processes. Soil properties and indicators such as ho- rizon thickness, structure, colour (based on Munsell scale), bulk density (BD), physical clay content (< 0.01 mm), pH (water), salt content, CaCO3, Corg content, and SOCstoc (soil organic carbon stock) were compared and analysed. Fig. 1. Map-scheme of research objects. I = Study areas within the boundaries of the urbanized part of the city; II = Study sites in the recreational (A, B, C), and residential (D, E, F) area. Source: Authors’ own elaboration. Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146.134 Methods Soil morphological properties Between 2022 and 2024, a total of 44 soil sections were laid out and described. Transects were established at depths ranging from 1.5 to 2.0 metres. Each transect underwent morphological description and soil sam- pling by genetic horizons. The selection of transect locations was influenced by the on-farm zoning of the area, considering factors such as paths, palisades, and inner spaces of residen- tial areas. During fieldwork, soil samples were collected, and their colours were re- corded based on the Mun- sell chart. The soil colour data obtained in the field were used to calculate the soil humus horizon index values, as per the equation: where ADI is the A hori- zon development index, HT is the horizon thick- ness in cm; V stands for value, and C stands for colour chroma accord- ing to the Munsell chart (Mazurek, R. et al. 2016). Soil classification was conducted in accordance with the international soil classification WRB 2022 (IUSS Working Group, 2022). Artefacts were de- scribed based on their abundance, size, shape, and fragment nature. The Fi g. 2 . E xa m pl es o f s oi l p ro fil es w ith a nt hr op og en ic A u an d A τ ho ri zo ns in re cr ea tio na l a nd re si de nt ia l f un ct io na l z on es . S ou rc e: A ut ho rs ’ o w n el ab or at io n. (1) 135Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146. size, abundance, and origin of artefacts were classified per FAO recommendations (FAO, 2006). Sampling was carried out from the horizon’s centre (where the expression is most pronounced). If multiple samples were collected from the same horizon, they were taken at balanced intervals. Soil chemical properties Samples were collected from each Au ho- rizon of the soil profiles. In the laboratory studies, the following soil indicators were determined: – Soil pH was measured potentio-metrically in the supernatant suspension of a 1:2.5 soil-to-liquid mixture (water) using the pH-meter-millivoltmeter pH-410 (Van Reeuwijk, L.P. 2002). – Total salt content was instrumentally deter- mined using the conductometer HI98302 DiST 2 in soil-water extracts at a ratio of 1:5 (Van Reeuwijk, L.P. 2002). – Soil organic carbon content was assessed following the Nikitin method with a col- ourimetric endpoint suggested by Orlov- Grindel (Mineev, V.G. 2001). – Soil organic carbon stock (SOCstoc) for min- eral soils was calculated using an equation: � where Corg is the soil organic carbon in percent; BD is the bulk density in g сm-3; d is the depth of the horizon in cm; CFst is the correction fac- tor for stoniness including subtraction of gravel and stones (FAO, 2017). Carbonate content was determined through the metric method, involving the decomposition with a titrated hydrochloric acid solution followed by titration of excess acid with alkali (Arinushkina, E.V. 1962). Soil physical properties The soil’s particle size distribution (% clay, % silt, % sand) was determined using the Kachinsky pipette method (Kachinsky, N.A. 1958). Bulk density was measured separately using the Cylindrical Core Method for un- disturbed samples (98.5 cm-3) (Kachinsky, N.A. 1958). Statistical processing of data The results were statistically analysed us- ing the statistical software system R 4.4.0 (Dmitriev, E. 1995). Descriptive statistics were calculated, such as minimum, maxi- mum, mean, and standard deviation. Sta- tistical methods like the Jarque–Bera test, Mann–Whitney U-criterion, and T-criterion were employed. Pearson and Spearman cor- relation coefficients were used to establish correlation relationships. The Jarque–Bera (J–B) test assessed the nor- mality of data distribution by determining skewness and kurtosis. The test was calcu- lated using a specific formula: where N is the sample volume, Sk is the skewness, K is the kurtosis. If the value of J–B > 5.991, it means that the hypothesis of normal distribution of the sample is rejected, i.e., the distribution is non-normal. After establishing the normality and non- normality of data distribution, tests were per- formed to check the equality of mean values in two samples (Au and Aτ). The T-criterion was used for the normal distribution of data according to the formula where M1 is the arithmetic mean of the first comparable population (group), M2 is the arithmetic mean of the second comparable population (group), m1 is the mean error of the first arithmetic mean, m2 is the mean error of the second arithmetic mean. In cases where data were not normally distributed, the Mann–Whitney U-criterion (2) (3) (4) Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146.136 was applied to assess differences between two independent samples. The U-criterion calculation considered sample volumes and rank sums, with lower values indicating more reliable differences in parameter values between samples: where nx and ny are sample volumes; n is the sample volume with the larger rank sum; T is the larger sum of ranks from samples X and Y. Results The histogram of the generalized data distri- bution for the thickness of all anthropogenic horizons indicated a lognormal distribution, with values predominantly falling within the range of 10–50 cm (minimum – 3; maximum – 110; median = 24 ± 3 cm). The thickness dis- tribution in recreational and residential areas was described as normal, while the overall sample showed a lognormal distribution (Figure 3). In residential areas, the average thickness was 46 ± 7 cm, whereas in recre- ational areas, it was 18 ± 2 cm. The structure of the anthropogenic hori- zons varied from clumpy to lumpy, with dif- fering ratios by zone. Of the total horizons observed, 66 percent exhibited a lumpy struc- ture, while 34 percent displayed a clumpy structure. The distribution of structure types also differed by functional zones: the clumpy structure predominated in residential areas, while the lumpy structure was more preva- lent in recreational areas. The colour of anthropogenic horizons ex- hibits a range of variations. In residential areas, the colour spans from 2.5YR to 7.5YR, with values between 4 and 6 and chroma ranging from 2 to 4. Conversely, in recre- ational zones, the colour tends to be darker, typically classified as 10YR with values of 3 to 6 and chroma between 2 and 4. The A horizon’s pHwater values exhibited a normal distribution (see Figure 3). Across all anthropogenic horizons, pH ranged from 6.6 to 8.5 (mean = 7.9 ± 0.1 cm). Specifically, the pH mean in residential areas was 8.0 ± 0.1 cm, while in recreational areas, it mea- sured 7.7 ± 0.1 cm. The distribution of salt content values in all anthropogenic horizons followed a log- normal distribution (see Figure 3). Overall, the horizons were characterized as non-sa- line, with a median of 0.12 ± 0.01 percent. Minimal differences were observed between the zones, with a median of 0.12 ± 0.02 per- cent in the recreational zone and a mean of 0.14 ± 0.02 percent in the residential zone. The distribution of CaCO3 data in the gener- al sample and recreational area was non-nor- mal, while in the residential area, it was nor- mal (see Figure 3). The minimum CaCO3 val- ues differed by 0.4 percent between residential and recreational areas and the maximum by 0.3 percent. The median CaCO3 value for the total sample was 1.3 ± 0.2 percent, while in the recreational zone it was 1.2 ± 0.3 percent. In the residential area, the mean CaCO3 content was 1.7 ± 0.3 percent. After analysing the histograms of the Corg content distribution, it was observed that the data distribution in the general sample and recreational area is non-normal (see Figure 3). The Corg content in the horizons ranged from 0.3 to 4.9 percent with a median of 1.2 ± 0.03 percent. There were notable variations in this index across zones. Specifically, the mean Corg content in the residential zone was 1 ± 0.1 per- cent, while in the recreational zone, the medi- an was 1.4 ± 0.2 percent. The highest recorded rates were 4.9 percent in the recreational zone and 1.9 percent in the residential zone. The distribution of SOCstoc data for the to- tal sample displayed leftward asymmetry, as shown in Figure 3. In the residential area, the distribution was normal. The generalized SOCstoc values ranged widely from 4 to 168 g kg-1, with a median of 39 ± 6 g kg-1. The mean in the Au horizons was 45 ± 12 g kg-1, while in the Aτ horizons, the median was 34 ± 7 g kg-1. The distribution of clay content data in all three samples of the A horizon is characterized as normal (see Figure 3). The maximum clay content was observed in the residential zone at (5) 137Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146. Fig. 3. Distribution of data in anthropogenic horizons of different functional zones. Source: Authors’ own elaboration. Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146.138 42 percent, while the minimum was 7 percent in the recreational zone. Notably, high clay content values in the residential areas were sporadic, whereas in recreational areas, the data mainly clustered around 17–25 percent, with some variation from 7 to 38 percent. The predominant clay content range in residential areas was 10–20 percent. Most Au horizons were classified as sandy loam, while Aτ hori- zons were categorized as loam, sandy loam, and loamy sand (Figure 4). The distribution of particular fractions varied across functional zones, with Aτ horizons showing dominance in coarse silt and clay along with the sandy fraction. In contrast, residential areas exhib- ited a prevalence of small and medium sand fractions. The density histogram for all studied horizons displayed a normal distribution (see Figure 3), with a mean value of 1.4 ± 0.02 g cm-3. Discussion and conclusions Correlation of anthropogenic horizons properties The greatest differences between the ho- rizons (p-value from 0 to 0.02, at p = 0.05) were found in pH, Corg, SOCstoc, and thick- ness horizons (Table 1). Consequently, these parameters are indicators of the level of an- thropogenic load on the territory. Spearman and Pearson correlation coeffi- cients were used to identify the relationship between soil properties. The non-normal data distribution causes the use of the Spearman coefficient. The result of the J–B test revealed that the distribution of data in the recrea- tional areas obeys a non-normal distribution, except for indicators such as pH, thickness, density, and clay content (see Table 1). In most cases, correlations were absent or weak due to the great heterogeneity of soil properties of all anthropogenic horizons (r < 0.5). Stronger relationships were found be- tween soil density and calcium carbonate content and Corg; between calcium carbonate content and Corg. As the calcium carbonate con- tent increased, the content of Corg and SOCstoc increased. Often, the reverse correlation was observed. For example, when soil density in- creased, Corg and SOCstoc decreased (Figure 5, A). The analysis of the relationship between anthropogenic horizons’ chemical and physi- cal properties in different functional zones Fig. 4. Texture classes anthropogenic horizons of different functional zones. Source: Authors’ own elaboration. 139Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146. revealed that the Corg in Au increased with decreasing salt content (r = 0.5) and increas- ing thickness. The content of calcium carbon- ates increased with decreasing soil density and increasing horizon thickness. A strong correlation coefficient (r = 0.9) was found be- tween SOCstoc and thickness. Therefore, the higher the Au thickness, the more SOCstoc it contains (Figure 5, B). Similarly, the Aτ horizon properties in rec- reational zones exhibit similar relationships (Figure 5, C). With increasing CaCO3 content, there was an increase in pH (r = 0.5), while Corg decreased with increasing density (r = -0.6) and with increasing CaCO3 content (r = 0.6). A correlation was also found between Corg content and SOCstoc (r = 0.7). In conclusion, the statistical analysis indi- cates that the properties of A horizons show significant variability in chemical, physical (particularly density), and morphological characteristics depending on the functional zone and, consequently, the level of anthro- pogenic load (Figure 6). Thus, the main types of impact on the res- idential area were littering and surface seal- ing. For recreational areas, the anthropogenic impact is reduced due to the special regime of the territory use. Anthropogenic impacts in green areas can include irrigation, the in- troduction of fertile reclamation mixtures, as well as cleaning the area from domestic and construction waste (Burghardt, W. 2006; Novák, T.J. et al. 2020). Changes in the morphological properties of horizons depending on the anthropogenic load level Among the morphological indicators, the highest differences were noted in the thick- ness and structure. The differences were due to the functioning regimes of the territory. In recreational areas with lower anthropogenic impact, the growth of Aτ thickness is sedi- mentologic, resulting from the slow dust ac- cumulation on the surface (Prokof’eva, T.V. et al. 2017). Conversely, in residential areas with higher anthropogenic impact, the growth of horizons is primarily due to the constant addition of new anthropogenic material. The colour of anthropogenic horizons is di- rectly related to their origin. The products of Au horizons in residential areas are mineral horizons B (Cambic) and Bk (Calcic), as well as soil-forming rocks of loess-like loams and clays (BCk and Ck). As a result, the colour of these horizons is characterized by a light and pale appearance. Conversely, in recre- ational zones, the colour of the horizons is Table 1. Variations between Au and Aτ horizons according to Mann–Whitney U-test, T-test, and Jarque–Bera test Variable Mann–Whitney U-test T-test Jarque–Bera test p-value ≤ 0.05 Aτ Au pHwater Salt content, % Bulk density, g cm-3 CaCO3, % Thickness, cm Corg, % SOCstoc, g kg-1 Clay, % Abundance of arte- facts, % Artefacts size, cm – 0.40 – 0.90 – 0.02 0.08 – 0.0110–3 0.0110–3 0.02 – 0.40 – 0.0110–3 – – 0.90 – – 4.0 11.0 5.5 7.0 2.0 10.0 30.0 1.0 13.4 21.0 2.0 5.0 0.4 5.9 3.0 1.0 2.0 2.0 6.8 10.8 Source: Authors’ own elaboration. Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146.140 Fi g. 5 . C or re la tio n co effi ci en ts : A = fo r A (S pe ar m an ); B = fo r A u (P ea rs on ); C = fo r A τ ho ri zo ns (P ea rs on ). T = Th ic kn es s, c m ; S C = S al t c on te nt , % ; B D = B ul k de ns ity , g c m -3 ; A V = A bu nd an ce o f a rt ef ac ts , % ; A S = A rt ef ac ts s iz e, c m . S ou rc e: A ut ho rs ’ o w n el ab or at io n. darker and more saturated. In the green ar- eas of Volgograd, Aτ horizons consist of the remains of the original Mollic and Cambic horizons (Kastanozems and Cambisols). The ADI index was calculated to determine the relationship of A horizon colour with other properties. The ADI is based on the horizons’ thickness and the value and saturation (chro- ma) of the wet soil colour. Au horizons are characterized by ADI values ranging from 4 to 15 (median = 6 ± 1.0). In Aτ horizons of recreational zones, the median ADI is 4 ± 0.3 (min – 1, max – 8). Thus, the lighter the hori- zons are on the Munsell scale, the higher the ADI values. This is supported by the correla- tions between ADI and SOCstoc (r = -0.67 and r = -0.73), both for the total sample and for horizons in residential and recreational ar- eas. Therefore, the colour of urban soil hori- zons can be used to assess potential organic matter reserves indirectly. The structure of the horizons is directly related to human activity. In recreational ar- eas where agronomic techniques such as ir- rigation and tillage are used, the structure of these Aτ horizons is characterized by lumpy aggregates with rounded sides. On the other hand, in residential areas, the Au horizons are consistently impacted by technogenic factors, resulting in compaction and enlarge- ment of aggregates, leading to the formation of a clumpy structure, exacerbated by mois- ture deficiency (Gordienko, O. et al. 2022). Artefacts in the Au horizons were predom- inantly identified in the form of construction, household debris fragments, and metal struc- tures. Their composition significantly varied based on the functional zone. In residential zones, their content ranged from 15 to 50 per- cent (median = 30 ± 2%), leading to the use of the Urbic qualifier, and in some cases, the addi- tional qualifier Hyperartefactic (layer contain- ing ≥ 50% of artefacts) was applied. Conversely, artefacts in recreational zones were present in smaller quantities – 5 to 10 percent (median = 7 ± 0.5%), making it challenging to classify the soils in this zone as Technosols. Therefore, the additional qualifier Technic (layer containing ≥ 10% of artefacts) was employed. The nature 141Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146. Fi g. 6 . V ar ia tio n of p ro pe rt ie s in a nt hr op og en ic h or iz on s. S ou rc e: A ut ho rs ’ o w n el ab or at io n. Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146.142 of artefacts largely depended on the functional zone. In residential areas, artefacts consisted of plastic, glass, and fragments of household and construction debris (such as bricks, concrete, and ceramics). Another significant aspect of ar- tefacts was their size. In the Au horizons, arte- fact sizes ranged from 2.5 to 12.0 cm (median = 8 ± 1 cm). Artefacts up to 5 cm comprised plas- tic, glass, and household material fragments, while those exceeding 5 cm were predominant- ly building materials (such as brick, concrete, and ceramics). In the Aτ horizons, artefact sizes ranged from 1.0 to 6.0 cm (median = 3 ± 1 cm). Changes in the chemical and physical properties of horizons depend on the anthropogenic load level The weakly alkaline reaction observed in the Aτ horizons was attributed to the absence of carbonate-containing materials inflow and the leaching process facilitated by irrigation. In residential areas where carbonate inclu- sions were prevalent, and irrigation was lacking, an increase in CaCO3 content and al- kalization was noted. The elevated pH levels in urban soils were likely caused by the re- lease of alkaline substances from calcareous materials (Jim, C. 1998). A similar scenario was observed in urban soils in Hong Kong (China) (Jim, C. 1987; Lam, K-C. et al. 2006), in Kumasi (Ghana) (Stow, D.A. et al. 2016), in Moscow and Rostov (Russia) (Kasimov, N.S. et al. [2016], and Bezuglova, O.S. et al. [2018]). The total salt content in the various Au and Aτ horizons corresponded to the values found in natural horizons of soils in the dry- steppe zone (Kastanozems and Cambisols). During the morphological description Au horizons in the residential area, it was ob- served that not only individual structural ele- ments of the soils reacted with a 10 percent HCl solution, but there was also continuous swelling of the soil fine earth. Consequently, active dissolution and redistribution of car- bonate inclusions occurred in urban soils (Prokof’eva, T.V. et al. 2017). The carbonates in the Au horizons were sourced from the dis- solving inclusions of construction debris and dust-aerosol deposition (Kasimov, N.S. et al. 2016). This hypothesis is supported by scien- tific research (Howard, J. and Orlicki, K. 2015; Khalidy, R. et al. 2022). In the anthropogenic horizons of Volgograd, no significant corre- lations between CaCO3 and the volumes and sizes of artefacts were identified. Therefore, it can be inferred that the source of carbon- ates is the material of the Au horizons. It was previously established that Au horizons in residential zones consisted of B, Bk, BCk, and Ck horizons; hence, the high carbonate values and effervescence from hydrochloric acid were attributed to their mechanical mixing. The high Corg values in the Aτ horizons can be attributed to the systematic introduc- tion of fertile mineral substrates, the optimal water-air regime of soils, and the presence of dense herbaceous, tree, and shrub vegeta- tion, whose decomposition contributes to ad- ditional soil carbon accumulation (Vasenev, V.I. and Kuzyakov, Y. 2017; O’Riordan, R. et al. 2021). In the residential area, carbon sources may include bituminous-asphalt mixtures, soot, petroleum products, and or- ganic suspended particles (Okolelova, A.A. et al. 2021). A direct correlation was observed between the CaCO3 content and the increase in Corg content (r = 0.6). Two hypotheses can explain this correlation. The first hypothesis suggests that carbonates do not directly in- fluence the increase in Corg since both dust deposition and one-time human inflow can form Au horizons. Therefore, the anthropo- genic allochthonous material already con- tains certain levels of carbonates and Corg upon arrival at the surface. According to the second hypothesis, carbonates present in dif- ferent A horizons within a single profile slow down both the accumulation of Corg (from top to bottom of the profile) and its loss to lower horizons due to their bonding proper- ties. The high Ca activity facilitates the fixa- tion of humus by the mineral component of the soil, leading to its retention in the profile through a coagulating effect on soil colloids, including organic matter, thereby inhibiting its migration through the soil profile in solu- tion form. 143Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146. Infrastructure construction in urban areas results in significant loss of SOCstoc through the removal and displacement of both natu- ral and anthropogenic topsoil and compac- tion (Elvidge, C.D. et al. 2007; Raciti, S.M. et al. 2012). In Yixing (China), a correlation between horizon compaction and an increase in SOCstoc was observed (Zhao, D. et al. 2013; Wei, Z. et al. 2014). However, in our study, the opposite relationship is observed. Greening initiatives notably positively impact SOCstoc, enhancing net primary productivity through urban trees and lawns (Zirkle, G. et al. 2011; Nowak, D.J. and Crane, D.E. 2013). Despite similar average densities, the primary factor contributing to the high SOCstoc levels is the average Corg values (Figure 7, upper) and the thickness of the horizon. The anthropogenic Au horizons are characterized by greater thickness, resulting in higher average SOCstoc levels (Figure 7, bottom). It was determined that a high CaCO3 content serves as a source of calcium, promoting mechanisms of floccu- lation and aggregation of soil particles. This enhances the cementing effect on soil aggre- gates, improves soil structure, and prolongs the preservation of SOCstoc. This relationship may explain the correlation between SOCstoc and CaCO3 (r = 0.6). Human activities have resulted in the over-compaction of soil horizons. The high-density values observed in both res- idential areas (maximum – 1.5 g cm-3) and recreational areas (maximum – 1.6 g cm-3) are primarily attributed to the significant an- thropogenic load. The over-compaction of Aτ Fig. 7. Relationship between Corg and SOCstoc (upper), and between thickness and SOCstoc (bottom). Source: Authors’ own elaboration. Gordienko, O. and Kulik, A. Hungarian Geographical Bulletin 73 (2024) (2) 131–146.144 horizons can be attributed to increased recre- ational pressure in recreational areas. These findings align with soil density values ob- served in other cities worldwide, where rec- reational areas also exhibit increased density (Lorenz, K. and Kandeler, E. 2005). On Au horizons, compaction is induced by transpor- tation activities, construction, and the use of technogenic hard materials for area sealing. The texture of the Au horizons is charac- terized as sandy loam. In recreational areas, the introduction of sand through landscap- ing and reclamation activities alters the tex- ture of Aτ horizons from the loam class to the sandy loam class. In conclusion, the individual properties such as thickness, Corg, and SOCstoc of anthro- pogenic horizons exhibit significant vari- ability in urban landscapes, challenging the definition of a typical “urban soil.” Statistical analysis of data on various properties has en- abled the identification of both general trends and distinctive characteristics. The variability of chemical, physical (especially density), and morphological properties based on functional zones and anthropogenic load levels is com- mon. Despite the diverse range of measured properties, correlations between the proper- ties of anthropogenic horizons and land use types have been established. The most sig- nificant variations in thickness, stocks, and organic matter content were observed. In res- idential zones, the thickness varies from 20 to 110 cm, while in recreational zones, it ranges from 3 to 40 cm. 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