Environmental safety of soil genetic horizons in the impact zone of Lviv city landfill (Ukraine)

Landfills cause significant technogenic pressure on the environment, being the center of depositing large volumes of hazardous materials in a relatively small area. Interacting with each other they form hazardous substances and compounds. In this study, we describe three genetic soil horizons that are within the impact zone of the landfill of a city of millions of people. It was established that the distribution of mobile forms of heavy metals according to the profile of the studied soils tended to gradual decrease with depth. When describing the genetic horizons of three profiles located in the impact zone of the landfill, it was established that the content of heavy metals in them does not exceed the MPC, except for Pb. The soil at the foot of the landfill turned out to be the most contaminated with heavy metals (profile No. 3). The activity of micromycetes in this soil was the lowest here. In general, all soils in the impact area of the landfill are impoverished in micromycete distribution. The taxonomic composition of mycelial fungi and the identified species’ ecological and biological characteristics indicate significant ecosystem pollution by household waste.


Introduction
The edaphotope has a significant influence on the development of phytocenoses.Depending on its physicochemical, mechanical, and acidic properties, vegetation in landfills develops in different ways.In the impact zone of technogenic landscapes, there is an increased radiation background and increased activity of radionuclides in edaphotops.Numerous studies of edaphotopes of technogenic landscapes are being conducted in Ukraine.According to Uzbek and Halahan, in the technogenic landscapes, the edaphotope is a man-made, spatially limited bioinert system that is in constant development under the influence of soil formation factors [1].In work [2], the contribution of the moss cover Campylopus introflexus (Hedw.)Brid. in the restoration of technogenic substrates due to the improvement of their edaphotopic properties is defined.
A carbon source of 4-6 g/L at pH 5-8 was found to enhance the heavy metal bioremediation potential of Pseudomonas aeruginosa, Enterobacter cloacae, and Klebsiella edwardsii isolated in a landfill in Lagos, Nigeria.The role of native bacteria in the remediation process can be optimized and used to standardize on-site bioremediation as well as establish biodegradation protocols.Great benefits can be provided by effective remediation of contaminated soils by improving soil condition and yield [3].
Soil microscopic fungi are very sensitive to changes in soil characteristics, so they can serve as indicators of its condition [4].Micromycetes are not only an integral component of terrestrial and aquatic biocenoses, which control a wide range of biosphere functions, but also the main group of microorganisms responsible for both the synthesis and destruction of humic substances 1254 (2023) 012117 IOP Publishing doi:10.1088/1755-1315/1254/1/012117 2 in the soil.Technogenic impact on the environment, as well as the rapid development of nanotechnology, make the problem of studying the interaction of micromycetes with organic matter of natural origin urgent.
The main feature of micromycetes is that they dominate soil microbiota.They represent the most specific group of microorganisms that participate in the mineralization of organic plant and animal residues and the formation of humus.The rate of decomposition of organic substances is determined by such factors as the chemical composition of the substrate, the efficiency of providing nitrogen to microorganisms, the composition of the microbial environment, and environmental conditions.Fungi under aerobic conditions are capable of decomposing even complex polymer compounds, for example, lignin, unlike other microorganisms, which are more conducive to the mineralization of low molecular weight organic compounds.Some soil fungi are able to decompose humus and use it as the only source of nitrogen and (or) carbon.At the same time, micromycetes participate not only in the process of destruction but also in formation of humic substances [5].
It has been established that the contribution of fungal bioaugmentation to the decontamination of soil has been clearly observed, and therefore mixed fungal organisms may serve as future bioremediation agents for contaminated areas [6].It has also been proven that the synthesized rhamnolipids can significantly increase the activity of soil enzymes to facilitate the digestion and transformation of heavy metals from the soil to the aerial part of ryegrass [7].
The study of the enzymatic activity of the soils of technogenic territories of the Nemyriv sulfur deposit is shown in the paper [8].It was established that the low activity of oxidoreductases and urease in the soils of the former development of sulfur deposits is a consequence of significant inhibition of the activity of soil microflora -the main producer of enzymes -by technogenic factors.The formation of a phytoremedial cover on the surface of devastated landscapes of coal mining is given in the article [9].The role of plant cover in the restoration of disturbed lands has been established.
It should be noted that the conditions of local growth on the landfills' surfaces negatively affect the growth and development of vegetation.Among the analyzed metals, iron reached the highest values in samples of Tanacetum vulgare L., namely, stems (103.4-6564.6 mg/kg of dry matter), roots (6563.6-33,036.6mg/kg of dry matter), leaves (535.1-11.275mg/kg of dry matter), and soil (12.389-39.381.9 mg/kg of dry matter).Cd, as well as Cr, Ni, and Zn, accumulate mainly in the leaves, while Co, Cu, Fe, Hg, Mn, and Pb accumulate mainly in the roots of T. vulgare [10].However, grass species that are tolerant to the high content of heavy metals in red mud dumps were investigated [11].Namely, based on the metal resistance index, 51.4,10.8 and 37.8% of grass species showed sensitive, moderate, and high metal resistance -Brachiaria mutica, Cynodon dactylon, Dactyloctenium aegyptium, Digitaria ischaemum, Digitaria longiflora, Eragrostis cynosuroides, Launaea asplenifolia, Parthenium hysterophorus, Sporobolus diander, Stylosanthes scabra.The research suggests a potential pathway for phytomanagement of abandoned red mud landfills through remediation using dominant metal-tolerant plant species [11].
The fact that landfills are polluting objects has been described by many scientists in their works.The impact of landfills on the human body is constantly being studied.Scientists have found that solid waste from a modern city contains more than 100 items of extremely toxic substances, including dyes, pesticides, solvents, medicines, used motor oils, phytochemicals, etc. Thermometers, fluorescent lamps, and various appliances contain mercury, an extremely dangerous substance because it is a volatile metal that can evaporate at low temperatures and, when exposed to microorganisms in landfills, turns into methylmercury, which can cause massive poisoning if ingested through water and food.
One of the world's largest landfills is the Lviv Municipal Solid Waste Landfill, which was included in the list of the 100 Greatest Environmental Disasters of Ukraine.Due to violations of the landfill's operating requirements, it has turned into a spontaneous landfill.The landfill is 3 km from the northern border of Lviv, near the village of Velyki Hrybovychi.It has been operating since 1957.Over the years, it has accumulated over 50 million cubic meters of waste.Until 1990, not only municipal solid waste, but also toxic industrial waste was stored within its boundaries.According to rough estimates, the amount of waste reached 2 million tons.In addition to garbage, more than 200 thousand tons of acidic tar, waste from the Lviv Oil Refinery, which is no longer in operation, has accumulated at the landfill.The thickness of the garbage layer in the southeastern part of the landfill reaches 50 meters, while in the northwestern part, it varies from 1-3 to 10 meters.Its total area is 33.6 hectares.
Thus, the investigation of edaphotopes of technogenic landscapes, including landfills, is relevant from the point of view of reducing their harmful effects and returning land to national economic use.

Materials and methods
Physico-chemical investigation of edaphotopes of soil horizons within the impact zone of the Lviv city landfill were carried out according to the state standards of Ukraine [12][13][14].
The surveys were conducted in July 2020, before the start of the reclamation of the Lviv landfill.
The content of mobile forms of heavy metals in edaphotops was determined: mobile forms of copper, zinc, cobalt were determined by the Rinkis method, lead, cadmium -by the atomic absorption method.They were also guided by the state standards [15].
Determination of the quantitative and qualitative composition of micromycetes of technogenic edaphotopes of landfills was carried out by sowing soil suspension from decimal dilutions on wort-agar and Chapek's agar medium.Cultivation of the studied samples was carried out at +26. . .+28 °C.Isolated cultures were studied with a microscope "MBI-6" according to the method adopted in mycological studies [16].The study of isolated micromycetes was carried out according to the generally accepted definition [5].

Results and discussion
For investigation of the influence of landfills' hazardous factors on the formation of the soil profile, the soil profile cuts were made, from which mixed soil samples were selected according to genetic horizons.Mycological and agrochemical analyzes were carried out, as well as analyzes for the content of nutritious minerals, heavy metals, and toxic elements (figure 1).
It should be noted that in the impact zone of the Lviv city landfill, we have carried out ecological monitoring of the hazardous substances distribution in edaphotopes as a result of the spillage of acid tar storage facilities, two lakes of which are stored on the southern side of the top.It has been established that hazardous substances expand to a distance of 1,500 m from the foot of the landfill.

Genetic soil horizon No. 1
The peatland (profile No. 1) is located within a radius of 2 km east of the foot of the landfill.The land belongs to the Dublyany City Council of the Lviv District (Lviv Region).In terms of peat reserves, this deposit was one of the largest in the world.After the Second World War, the local population made peat briquettes by hand to heat houses.As a result, the peatland lost a significant part of its capacity.At the moment, agricultural products are grown on peatlands, which is prohibited due to the deposition of polluting substances in peat, including leachates from landfills.The danger of landfill leachates is described in scientific works [17][18][19].Malovanyy et al [20] presents a rational scheme of the biological conveyor of an open-type installation for cleaning landfill leachate.Laboratory studies were conducted to determine the efficiency of using nozzles for the immobilization of microbiocenosis in aerated lagoons, which are used to clean landfill leachate.The interest in studying the physical and chemical properties of peat, which is When describing the deep peatland, it was found that the content of heavy metals in the surface layer T1 significantly exceeds the indicators in the genetic horizon T2 (figure 2, figure 3).
In view of the above-mentioned data, it can be stated that the content of cobalt in peatlands does not exceed the MPC, which is 5 mg/kg.The mercury content is 250 times lower than the MPC, which is 2 mg/kg.The cadmium content is twice as low as the permissible standard of 0.7 mg/kg.In general, the presence of this toxicant in the soil section with a concentration of 0.5 MPC is a negative phenomenon.The source of cadmium in landfills is waste containing varnishes and paints, fluorescent lamps, batteries, etc. Cadmium sulfide is the basis of yellow paints used in vehicle painting, textile production, and soap making.Cadmium selenide is used as a red dye.Cadmium is also used in semiconductor materials, cryogenic technology, lead-cadmium and mercury-cadmium elements of reserve batteries, and anti-corrosion metal coatings.
The distribution of the content of mobile forms of heavy metals according to the profile of the studied soils is demonstrated by their gradual decrease with depth.
The physical and chemical composition analysis of section No. 1 showed that the peatland has a significant supply of nitrogen (56.05 mg/100 g) and potassium (58.5 mg/100 g) nutrients  and a low content of humus (2.06%) and nitrogen fertilizers (0.84 mg/100 g).In terms of humus, the peatland is considered like weakly humus.
When adding peat to the soil, it is necessary to improve agrophysical properties, since peat is depleted in nutrients.Effective use of peat for the development of agricultural crops is possible when fertilizers are applied to it.
The analysis of the micromycete activity of landfills showed that the families Mucoraceae, Moniliaceae, and Tuberculariaceae are widespread in the T1 horizon of the peatland.The total number of micromycetes was determined by sowing on Chapek's acidified nutrient medium (the number of colony-forming units -CFU in g of soil).This indicator turned out to be quite low compared to the background values.In general, all soils are characterized as very poor in the degree of micromycetes distribution.
It should be noted that the presence of micromycetes of the genus Fusarium in the edaphotope indicates a significant content of mineral substances and a low content of heavy metals.This genus of micromycetes was discovered by researchers in landfill leachate during the study of a biosorption multilayer filter.Micromycetes of the genus Fusarium, along with bacteria, took an active part in the formation of the filter biofilm.
The analysis of peatland micromycetes by growth rate showed that slow-growing micromycetes have the largest share -70%, respectively, fast-growing -30%.Undoubtedly, such an indicator of the growth rate of mushrooms is negative, as it causes inhibition of the development of successional processes.The distribution by color showed that dark-colored micromycetes of the Moniliaceae family predominate and are characterized as toxic (80%), the share of light-colored ones is 10%, unclassified -10%.

Genetic soil horizon No. 2
When describing soil profile No. 2, it was found that the soil is sod, shallow, light loamy, and glazed.The profile is made on the western side of the Lviv landfill at a distance of 20 m from the road that leads to the village Zbyranka.The soil-forming and underlying rock is loess loam.Genetic horizons H(gl) and P(h)(gl) were revealed.
It was established that the mobile forms of such heavy metals as Mn, Cu, Zn, and Pb do not exceed the maximum permissible concentration (MPC) and accumulate in the upper horizon.Exceeding the MPC is observed only for lead (2 mg/kg) in the H(gl) horizon.At a depth of 30 cm or more, the concentration of these elements decreases 10 times (figure 4).Mobile forms of pollutants such as Co, Cd, and Hg accumulate, mostly, in the P(h)(gl) horizon of profile No. 2, but their content does not exceed the MPC (figure 5).
The mineral composition of the genetic horizons of soil profile No. 2 has quite high indicators, with the exception of humus, with content of 1.53-1.7%.According to this indicator, the soil belongs to low-humus, which is a disadvantage for the development of vegetation in the impact zone of the landfill.The content of NO 3 in the horizon is 20.6-30.5 mg/100 g of soil, P 2 O 5 -9.92-11.51mg/100 g of soil, K 2 O -55.8-56 mg/100 g of soil (figure 6).Thus, the soil located on the western side of the landfill did not tend to accumulate heavy metals, the concentration of which would exceed the MPC.However, the humus content in these soils is low, worsening the conditions for the syngenetic stages of succession.
The species composition of the micromycetes of the genetic horizons of the profile differs.Micromycetes of the Mucoraceae, Moniliaceae families develop in the H(gl) horizon.The P(h)(gl) horizon is inhabited by Moniliaceae, Tuberculariaceae, and Dematiaceae.
The life activity of the micromycete Rhizopus stolonifer (bread mold) in the upper horizon of the profile indicates their active participation in the syngenesis and decomposition of litter and leaf litter.These micromycetes develop on bread, fruits, and vegetables.It is well-known that microscopic fungi Rhizopus stolonifer can cause an allergic condition in humans.Micromycetes of the genus Aspergillus acquired the greatest development in this soil.These microfungi are involved in the transformation of organic matter and plant residues.In general, the micromycete species composition of the profile is extremely depleted, and the abundance of the species composition is low.
One of the most opportunistic and toxin-producing micromycetes is Aspergillus fumigatus Fries.var.sclerotiorum,discovered by us in this soil profile.This micromycete can cause mycosis and mycotoxicosis in living organisms (humans, animals).On figure 7 is shown a micromycete under a microscope.
Analysis of micromycetes by color and growth rate showed that dark-colored (78%) and slowgrowing (89%) micromycetes develop within this genetic horizon.The rates of slow growth are even higher than for the peatland, indicating the detrimental effect of the hazardous factors of the landfill on micromycetes, including heavy metals and radionuclides.The share of fast-growing micromycetes is 11%, light-colored -11%, and unclassified -11%.

Genetic soil horizon No. 3
The studies of turf soil (profile No. 3), formed in conditions of moistening of the territory, showed that it has slightly different physical and chemical parameters.The name of the soil (with mechanical composition) is the field: sod, deep, clay, medium loam (light).
It was formed on diluvial sediments.The cut is laid 100 m east of the foot of the landfill and The content of mobile forms of Mn and Cu increases with depth (from 29.4 mg/kg to 39.7 for Mn and from 0.57 mg/kg to 0.93 mg/kg for Cu), however, they do not exceed the MPC.The content of Zn in genetic horizons is 1.6-3.9mg/kg and also does not exceed the MPC.The content of Pb in the genetic horizons exceeds the MPC by 1.5 times and the concentration increases with depth starting from the level of 23 cm (figure 8).
Concentrations of mobile forms of Co, Cd, and Hg increase with depth but do not exceed the MPC.The accumulation of heavy metals in the genetic horizon P(h)(gl) indicates their leaching to the parent rock (figure 9).The humus content in the horizons decreases with depth and is only 0.5-0.71%.There is also a low content of P 2 O 5 -0.95-3.84mg/100 g of soil and a decrease in concentration with depth.The concentrations of NO 3 and K 2 O in the horizons are relatively high ranging from 41.85 to 47.4 mg/100 g of soil for the former, and from 50.5 to 67.1 mg/100 g of soil for the latter (figure 10).
Data on the content of heavy metals and the mineral composition of soil profile No. 3 make it possible to assert the negative impact of landfills on the adjacent territories and the environment.The concentrating of toxic elements with depth indicates their leaching to lower horizons and parent rock, which causes long-term technogenic pressing in the impact zone of landfills.
The species composition of micromycetes in section No. 3 is extremely depleted.A total of 10 species belonging to 3 families of the class Hyphomycetes (Deuteromycetes) were found.
The above data indicate the biological activity of micromycetes only in the upper layer of the horizon.Species (Moniliaceae) that carry out transformation reactions of complex organic compounds (solid and liquid paraffins, alcohols, diesel fuel, steroids) became the most widespread here.With depth (23-43 cm), the species composition and number of colonies decrease sharply, which indicates the contamination of the edaphotope with heavy metals, in the particular lead.At a depth of 43 cm and below, the vital activity of only one species is observed -Mycelia st.dark.
Analysis of micromycetes by color and growth rate of soil profile No. 3 showed that within this genetic horizon, dark-colored micromycetes develop the most (60%), light-colored micromycetes -30%, unclassified -10%.According to growth classification, only slowly growing micromycetes (100%) develop.The absence of any type of fast-growing micromycetes indicates strong pollution of the horizon with dangerous substances and compounds.

Conclusions
The conducted research and the results of analytical work in the laboratory showed that in the areas adjacent to the Lviv city landfill, mostly wet soils are common.The reason for their formation is insufficient drainage of the territory, which causes waterlogging in the area.Turf soils and peatlands were found.When describing the genetic horizons of three profiles that are in the impact zone of the landfill, it was established that the content of heavy metals does not exceed the MPC, except for lead.The soil at the foot of the landfill turned out to be the most contaminated with heavy metals (profile No. 3).Also, the lowest activity of micromycetes was found in this soil.
The families Mucoraceae, Moniliaceae, and Tuberculariaceae are widespread in the T1 horizon of the peatland (profile No. 1).The presence of micromycetes of the genus Fusarium in the horizon proves a significant content of mineral substances and a low content of heavy metals.The species composition of the micromycetes of the genetic horizons of profile No. 2 is significantly different.Micromycetes of the Mucoraceae, and Moniliaceae families develop in the H(gl) horizon.The P(h)(gl) horizon is inhabited by Moniliaceae, Tuberculariaceae, and Dematiaceae.The species composition of micromycetes in profile No. 3 is extremely depleted.A total of 10 species belonging to 3 families of the class Hyphomycetes (Deuteromycetes) were found.With depth (23-43 cm), the species composition and number of colonies decrease sharply, which indicates the contamination of the edaphotope with heavy metals, in the particular lead.At a depth of 43 cm and below, the vital activity of only one species is observed -Mycelia st.dark.
It was found that the mobile forms of such heavy metals as Mn, Cu, Zn, Pb do not exceed the maximum permissible concentrations (MPC) and accumulate in the upper horizon No. 2. Exceedance of the MPC is observed only for lead (2 mg/kg) in the H(gl) horizon.
All soils in the area affected by the landfill are characterized as very poor in micromycete distribution.The taxonomic composition of mycelial fungi and the ecological and biological characteristics of the identified species indicate significant pollution of the ecosystem by household waste.

Figure 1 .
Figure 1.Location of objects of research in the impact zone of the Lviv municipal landfill.

Figure 2 .
Figure 2. The content of manganese, copper, zinc, and lead in the studied horizons of section 1.

Figure 3 .
Figure 3. Content of cobalt, cadmium and mercury in the studied horizons of section 1.

Figure 4 .
Figure 4.The content of manganese, copper, zinc, and lead in the studied horizons of profile 2.

7 Figure 5 .
Figure 5. Content of cobalt, cadmium, and mercury in the studied horizons of profile 2.

Figure 6 .
Figure 6.The content of mineral elements in the horizons of profile 2.

Figure 8 .
Figure 8.The content of manganese, copper, zinc, and lead in the investigated horizons of profile 3.

Figure 9 . 10 Figure 10 .
Figure 9.The content of cobalt, cadmium, and mercury in the studied horizons of profile 3.