Search

The amelioration and remediation technology was developed on the basis of research of phosphogypsum and utilization in the Haplic Chernozem of South-European facies (Rostov Region). Phosphogypsum was utilized via dispersed application into a soil layer of 20–45 cm with intrasoil milling of this layer. The phosphogypsum utilization doses were 0, 10, 20, and 40 t ha–1. The Pb analytical content in soil solution was studied in the model experiment. The soil solution Pb thermodynamic forms were calculated. The mathematical chemical–thermodynamic model ION-2 was developed to calculate the real soil solution (water extract) calcium-carbonate equilibrium (CCE) ion forms, considering the ion pair association. The associated ion pairs CaCO30, CaSO40, MgCO30, MgSO40, CaHCO3+, MgHCO3+, NaCO3–, NaSO4–, CaOH+, and MgOH+ were accounted for in soil solution equilibrium macroion form calculation. The procedure for the microelement ion [including heavy metals (HMs)] equilibrium concentration in the soil solution coefficient kas calculation was proposed to account for the real soil solution CCE, macroions, and HM (including Pb) association. The Pb2+ ion in soil solution was mostly bound to associates PbOH+, Pb(OH)20, PbCO30, Pb(CO3)22–, and PbHCO3+. The calculation of CCE and ion association in soil solution revealed 14.5–21.5 times HM passivation compared to HM water-soluble values. The calculated HM activity in the soil solution in the example of the Pb2+ ion was less than 4% after phosphogypsum application in the target amelioration layer of 20–45 cm. The studied phosphogypsum doses were substantiated as environmentally safe. This was because the real soil solution CCE provided HM ion form association and consequent passivation. The dry steppe soil remediation after phosphogypsum application was justified as highly probable. The intrasoil milling chemical soil-biological engineering technology was developed for simultaneous soil amelioration and remediation on the basis of the biogeosystem technique (BGT*) transcendental methodology. The BGT*-based technology was tested in the long-term field experiments and is capable of ensuring the priority geophysical micro- and macroaggregate structure via intrasoil milling and mixing of soil illuvial and transitional horizons. This helps synthesize soil multilevel architecture, providing intrasoil-dispersed environmentally safe recycling of wastes of different origin. Addressing the environment safety concerns, a new decision of the intrasoil milling device was proposed for phosphogypsum and other substance application to soil.

Biochar is considered as a potential substitute for soil organic matter (SOM). Considering the importance of biochar, the present review is based on the different benefits and potential risks of the application of biochar to the soil. Biochar addition to low organic carbon soils can act as a feasible solution to keep soil biologically active for the cycling of different nutrients. The application of biochar could improve soil fertility, increase crop yield, enhance plant growth and microbial abundance, and immobilize different contaminants in the soil. It could also be helpful in carbon sequestration and the return of carbon stock back to the soil in partially combusted form. Due to the large surface area of biochar, which generally depends upon the types of feedstock and pyrolysis conditions, it helps to reduce the leaching of fertilizers from the soil and supplies additional nutrients to growing crops. However, biochar may have some adverse effects due to emissions during the pyrolysis process, but it exerts a positive priming effect (a phenomenon in which subjection to one stimulus positively influences subsequent stimulus) on SOM decomposition, depletion of nutrients (macro- and micro-) via strong adsorption, and impact on soil physicochemical properties. In view of the above importance and limitations, all possible issues related to biochar application should be considered. The review presents extensive detailed information on the sustainable approach for the environmental use of biochar and its limitations.

This review outlines the use of phosphogypsum, a by-product from the phosphate fertilizer industry, in Russia including its ameliorative roles for Na-affected and compacted soils; its value as a multi-nutrient fertilizer; in composting with various organic wastes to produce organo-mineral fertilizers; and in remediation of oil-contaminated soil.

The combustion of solid fuel at power plants pollutes adjacent areas with potentially toxic elements (PTEs), which increases risks to public health in the vicinity of these facilities. With an installed electric capacity of 2258 MW, the Novocherkassk Power Plant (NPP) is the top electric energy producer in Southern Russia. This facility is located in the vicinity of one of the largest cities in the Rostov Region, Novocherkassk, with a population of 168,035 people. Among the major cities in the region, Novocherkassk is characterized by the maximum level of atmospheric pollution. The study was conducted at 12 monitoring sites laid along the radii emanating from the NPP chimneys. The sites were located in the near-source influence zone (up to 3 km) in various directions and at greater distances (from 3 to 20 km) downwind. In this study, various indicators of environmental quality (geoaccumulation index (Igeo), pollution index (PI), and Nemerow pollution index (NPI)) as well as human health risk model (US EPA 1989) were applied to identify spatial distribution and to evaluate risks of seven PTEs (Cr, Mn, Ni, Cu, Zn, Cd, and Pb) in soils. The results demonstrate the relationship between the features of atmospheric circulation and PTE content in soils within the NPP impact zone. The main pattern in spatial distribution of soil pollution is a decrease in the concentrations of PTEs with distance from the source. The influence of NPP can be traced out to approximately 7 km downwind. The total content of PTEs in the soils slightly exceed the Clarke values for the upper continental crust, as well as the world average concentrations of these elements in soils (up to two times). Moderate to high pollution by Cd and Pb, according to the Igeo, is characteristic of the soils at a distance of up to 3 km to the NPP. The PI also demonstrates higher pollution estimates relative to distance from the source; soils in impact zone of NPP are characterized by low or no pollution by Cr, Mn, Ni, Cu, and Zn, and moderate pollution by Cd and Pb. Soils located in the leeward zone are moderately polluted with Ni and Zn and very strongly to strongly polluted with Cd and Pb. According to the NPI values, pollution decreases from heavy in the area immediately downwind of the source to slight for most of the territory under consideration. The risks of noncarcinogenic effects on children are assessed as low, their occurrence is attributed to the intake of Mn, Ni, and Pb, while for adults there was no significant general toxic risk associated with the intake. The total carcinogenic risk to human health slightly exceeds the permissible standard for soils in close vicinity of the enterprise due to the potential intake of Ni, Cd, and Pb.The reported study was funded by RFBR, project number 19-05-50097 and Grant of President of Russian Federation, no. МК-6137.2021.1.5.

Amelioration and remediation technology was developed comprises dispersed application and mixing of the phosphogypsum into the soil layer 20–45 cm with the intra-soil milling. The phosphogypsum doses 0, 10, 20, and 40 t ha−1 were studied in the model experiment focusing on the intra-soil passivation of Cd contained in phosphogypsum, environmental remediation, and amelioration of the Haplic Chernozem of South-European facies (Russia). The soil total and water-soluble Cd form content depend on geographical location, the ionic composition of soil solution, and soil genesis. The mean total Cd content in soils of South Russia is about 1 mg kg−1 SDW. The mobility of Cd in the soil solution, as well as its penetration into the plants, depends on the content of carbonates, pH, ionic composition of the soil solution. The mathematical chemical-thermodynamic model and program ION–3 developed for the quantitative characterization of Cd thermodynamic forms in soil solution. The forms of ion in soil solution were calculated accounting the soil solution calcium-carbonate equilibrium, ionic strength, and association of ion pairs СаСО30; CaSO40, MgCO30, MgSO40, CaHCO3+, MgHCO3+, NaCO3−, NaSO4−, CaOH+, MgOH+. The coefficient of microelement association kas was proposed for the calculation of the equilibrium concentration of microelement ion or heavy metal (HM) in soil solution. According to calculations, a Cd2+ ion mostly bounded to associates CdOH+, partly to associates CdCO30 and CdHCO3+. The Cd kas was 1.24 units in the control option and decreased to 0.95 units at a phosphogypsum dose 40 t ha−1. The calculated ratio of “active [Cd2+] to total Cd” reduced from 33.5% in control option to 28.0% in the option of a phosphogypsum dose 40 t ha−1. According to calculation, the biogeochemical barrier for penetration of HMs from soil to plant roots was high after application of phosphogypsum. The standard soil environmental limitations for the content of Cd in soil overestimate the real toxicity of Cd. Re-evaluation of the current TENORM and other environmental limitations become possible. The new decision for intra-soil milling and simultaneous application of phosphogypsum was developed the chemical soil engineering technology to decide simultaneously the tasks of soil contamination decrease, soil amelioration and soil remediation. The technology based on the transcendental Biogeosystem Technique (BGT*) methodology provides environmentally safe phosphogypsum application to soil. The BGT* management of ecosphere provides health and productivity. Indirect transcendental nature-similarity of technology provides the new niche of developing capabilities addressing environmental safety concerns of ecosphere management. The technology ensures geophysical, chemical, physicochemical structural and architectural prerequisites for the stable soil evolution, environmentally safe waste recycling, the healthy soil microbiome and phytopathogen suppression, high-quality soil biological production, and human health.The research was financially supported by the RFBR, project no. 18-29-25071, and the Ministry of Science and Higher Education of Russia, project no. 0852-2020-0029.

Current land-use policy needs for innovative soil processing technologies. We carried out a long-term field experiment on the Kastanozem in following options: moldboard plowing to a depth of 22 cm; chiselling to a depth of 35 cm; three-tier PTN–40 plowing to a depth of 40–45 cm; PMS–70 intra-soil milling of the 20–45 cm layer. Moldboard, chisel and three-tier plowing does not improve soil aggregate system. 20–45 cm soil layer milling by PMS–70 provides the formation of the 1–3 mm aggregates. 30–40 years after PMS–70 processing, the soil profile structure remained fine aggregate. Soil organic matter and dissolved organic matter content, as well as the soil productivity, were higher after PMS–70. New intra-soil milling machine PMS–260 was developed. The moldboard plowing did not change the natural soil profile vertical morphological differentiation. The soil loosening effect was short-term after soil chiselling. After the three-tier PTN-40 plowing, a large part of humus horizon material strews down the soil profile between the chaotically spread large structural blocks of illuvial and transitional horizons. After PMS–70 processing, the content of 1–3 mm size aggregate particle fraction in the illuvial horizon was triple compared to the three-tier PTN–40 plowing. The soil desalination was intensive after PMS–70. The absorbed Na+ content in solonetz was about 18–20% of soil cation exchange capacity (CEC) in the moldboard option. The same was after the chiselling. The CEC Na+ content was of 14–16% after the PTN–40. The CEC Na+ content was of 10–12% after the PMS–70. The SOM content in the 0­–20 cm soil layer was 2.0%, in the 20-40 cm layer of 1.3%; the DOM content was 0.03% and 0.02% respectively in moldboard plowing option. The SOM and DOM content increased slightly in a period 3–4 years after chiselling. The SOM content was 2.2% in the 0­–20 cm, and 1.4% in the 20–40 cm; the DOM content was 0.04% and 0.03% respectively after the PTN–40. The SOM content increased to 3.3% in the 0–20 cm soil layer, and to 2.1% in the 20–40 cm layer; the DOM content increase was 0.05% and 0.04% respectively after the PMS–70. In the moldboard option, the rhizosphere developed only in the upper soil layer of 0–20 cm. The rhizosphere spreads through the soil crevices after chilling. The conditions of rhizosphere development were better in the local comfort zones of the soil profile after three-tier PTN–40 plowing. The rhizosphere developed well and uniformly both in the upper 0–20 cm and in the 20-45 cm layer after intra-soil milling by PMS–70. Improved plant growing conditions provide higher plant resistivity to pathogens. The technology life cycle profitability: moldboard 21.5%, chiseling 6.9%, three-tier 15.6%, intra-soil milling 45.6%. The new design of intra-soil milling machine provides five times less traction resistance; 80% increased reliability, halving energy costs. Intra-soil milling provides long-term land-use prospects.The research was supported by the RFBR, project no. 18-29-25071, and by the President of the Russian Federation, no. MK-2244.2020.5.

The Kastanozem complex in the dry steppe of southern Russia underlies an artificially-constructed forest strips. Deep ploughing to a depth of 45 cm was used to process the soil prior to planting. Between 20 and 40 cm depth, soil density was high, 1.57 t m−3. Soil hardness was also high, 440 psi. Soil aggregates greater than 5 cm in size were impermeable to tree roots. The content of such aggregates was high, comprising 35%. The number of tree roots with diameters greater than 0.5 cm that cross the soil profile was as low as 0.15 to 0.3 pcs cm−2. The soil matric potential signifying water availability was low in the vegetation period −0.9 MPa to a depth of 1.0 m. According to modelling experiments, the main salt components in the soil solution drive the transfer of soil organic matter (SOM) and heavy metals (HM). The composition of the soil solution determined by the calcium carbonate equilibrium (CCE) and the association and complexation of ions. ION-3 software was used to calculate the ion equilibrium in the soil solution. Macro-ions Cа2+, Mg2+, SO42−, and CO32− partly bonded as ion pairs. Oversaturation of the soil solution with CaCO3 was calculated according to the analytical content of macro-ion, which was high up to 1000 units, and its value decreased in response to ionic strength, activity, association, complexation, and thermodynamic equilibrium of macro-ions in the soil solution. Oversaturation calculated for Salic Solonetz and Gleyic Solonetz soil solutions was small considering the SOM content. Calculations indicate the profile and lateral loss of C from the soil to the vadose zone. The content of Pb in the soil solution was calculated sirca 75%–80%. The calculated coefficient of Pb2+ association was as high as 52.0. The probability of Pb passivation by SOM in the Kastanozem complex was significant. The probability of uncontrolled transfer and accumulation of HM in the soil and vadose zone was high. Biogeosystem Technique (BGT*) transcendental methodology, an innovative methodology created for stable geomorphological system formation to achieve sustainable agriculture and silviculture, was applied. The BGT* elements were: intra-soil milling of the 30–60 cm soil layer for geophysical conditioning; intra-soil continuously-discrete pulse watering for plants and trees to improve the hydrologic regime. The BGT* methodology reduced HM mobility, controlled biodegradation, enriched nutrient biogeochemical cycling, increased C content, increased soil productivity, and reversible carbon sequester in biological form.

The long-term field experiment on the Kastanozem showed that the standard moldboard plowing to a depth of 22 cm (control), chiseling to a depth of 35 cm, and three-tier plowing (machine type PTN–40) to a depth of 45 cm was incapable of providing a stable soil structure and aggregate system. The transcendental Biogeosystem Technique (BGT*) methodology for intra-soil milling of the 20–45 cm layer and the intra-soil milling PMS–70 machine were developed. The PMS–70 soil processing provided the content of 1–3 mm sized aggregate particle fraction in the illuvial horizon of about 50 to 60%, which was 3-fold higher compared to standard plowing systems. Soil bulk density reduced in the layer 20–40 cm to 1.35 t m−3 compared to 1.51 t m−3 in the control option. In the control, the rhizosphere developed only in the soil upper layer. There were 1.3 roots per cm−2 in 0–20 cm, and 0.2 roots per cm−2 in 20–40 cm. The rhizosphere spreads only through the soil crevices after chilling. After three-tier plowing (PTN–40), the rhizosphere developed better in the local comfort zones of the soil profile between soil blocks impermeable for roots. After intra-soil milling PMS–70, the rhizosphere developed uniformly in the whole soil profile: 2.2 roots per cm−2 in 0–20 cm, 1.7 roots per cm−2 in 20–40 cm. Matric water potential was higher, soil salinization was lower, and the pH was close to neutral. Soil organic matter (SOM) content increased to 3.3% in 0–20 cm and 2.1% in 20–40 cm compared to the control (2.0% in the 0–20 cm soil layer and 1.3% in the 20–40 cm layer). The spring barley yield was 53% higher compared to the control. The technology life cycle profitability was moldboard 21.5%, chiseling 6.9%, three-tier 15.6%, and intra-soil milling 45.6%. The new design of the intra-soil milling machine provides five times less traction resistance and 80% increased reliability, halving energy costs.

In the conditions of the adjacent location of agricultural land with industrial land, there is a continuous soil contamination of the territories adjacent to the emission sources. There is a threat of hazardous ecotoxicants migration, including heavy metals and benzo[a]pyrene, one of the main persistent compound, the marker of soil PAHs pollution, along trophic chains, which can be dangerous for a public health. In this study, the technology of biochar manufacturing from sunflower husks tested for improving the territories adjacent to technogenic emissions sources of heavy metals and PAHs. Using scanning electron microscopy showed that the resulting sorbent has a high specific surface area. With the help of phyto-testing, the optimal dose of the sorbent introduction into the combined contaminated soil was determined in the level of the 1% and 2%. The use of a sorbent in an amount of 1% significantly increased the root length of the test culture by 3.5 times as compared to the variant without adding the sorbent. The biochar applying into the contaminated soil contributed to an increase in the length of the barley root that confirms the effectively of the developed sorbent remediation of the co-contaminated soils.