Method of determining loosely bound compounds of heavy metals in the soil

Method of determination of heavy metals loosely bound compounds in the soil was developed using three separate extractions. The group of loosely bound compounds of metals includes exchangeable, complexed, and specifically adsorbed forms. This method is available, rapid and not expensive. Extraction takes less than 24 h. Sample procedure preparation is simple, and the analysis consists of only three steps, which can be performed simultaneously. The parallel extraction gives reliable and reproducible results and provides a relatively complete idea of the metals mobility in the soil, their availability to plants, migratory capacity, and transformation. • Method is suitable for a wide range of heavy metals and soil types. From the obtained data, the content of loosely bound compounds of heavy metals and the coefficients of metals mobility in the soil can be calculated. • Method is suitable for estimation the microelement supply of uncontaminated soils. The content of elements in the 1 N CH3COONH4 extract characterizes the actual pool of elements, and their content in the 1 N HCl extract defines their potential pool in the soil. • The coefficient of mobility (Km) is calculated to assess the contamination of soil with heavy metals. Estimation criteria of Km for Haplic Chernozem were developed. Method name: Method of determination of loosely bound metals compounds in the soil, Keywords: soil samples, mobile forms of heavy metals, exchangeable form, complex form, specifically adsorbed form, parallel extraction, ammonium acetate buffer, ethylenediaminetetraacetic acid, hydrochloric aci

Assessing Growth-Promoting Activity of Bacteria Isolated from Municipal Waste Compost on <i>Solanum lycopersicum</i> L.

Rapid urbanization and population growth are stressing the present agricultural systems and could threaten food security in the near future. Sustainable development in agriculture is a way out to such enormously growing food demand. Plant growth-promoting bacteria (PGPB) are considered pivotal to providing adequate nutrition and health to plants and maintaining soil microbial dynamics. In the present study, municipal solid waste composts (MSWC) were studied for the presence of PGPB and their growth-promoting characteristics such as ammonium production, siderophores production, phosphorus solubilization and potassium solubilization, IAA (indole acetic acid), and HCN production. Four promising isolates were chosen and identified through 16S rRNA sequencing as Bacillus sp. strain L5-1, Bacillus pumilus strain EE107-P5, Bacillus sp. strain LSRBMoFPIKRGCFTRI6 and Bacillus sp. strain LPOC3. The potential of isolates is validated using Solanum lycopersicum (tomato) and was found to improve its growth significantly. The findings indicated the presence of potential Bacillus strains in MSWCs, and these composts can be utilized as biofertilizers for urban agricultural practices. However, studies concerning their impact on other crops’ growth and health are still underdeveloped. Since MSWCs might carry hazardous metals or chemicals, their evaluation for the safe application on the crops should also be assessed

Method for hydrophytic plant sample preparation for light and electron microscopy (studies on Phragmites australis Cav.)

Nowadays there are no well-established, standard methods in electron microscopy despite its 50-year history. An excessive variety of research objects prompt researchers to modify and improve methodological approaches to sample preparation. One of the difficult objects to study by electron microscopy is hydrophytic plants, for example, Phragmites australis Cav. Traditional approaches to fixation and sample preparation do not give satisfactory results due to the peculiarities in structure and physiology of hydrophytic plants. The purpose of present research is modification description of the widespread method developed for double fixation of hydrophytic plant tissue for transmission electron microscopy. Suggested approach takes into account the features of hydrophyte plants. • The developed method allows improving the quality of plant samples by additional fixatives imbibition and removing of air bubbles from aerenchyma tissue using a vacuum. • The new step of sample preparation consisting in the layer-by-layer sample mixing in a special inclined mixer is applied for the embedding media penetrate sufficiently into the sample tissue. • The process of samples inclusion in polymeric resins is carried out in the flat-bottom capsules. Compare to standard conical capsules, flat-bottom capsules allow strictly defined orientation sample pieces, that is permit to produce a semi-thin and ultra-thin slices of perpendicular to the longitudinal structures of the plant. This is especially important to conduct an adequate comparative analysis of dimensions, shape, and electron density of fragments and parts of the studying samples. Method name: Method for hydrophytic plant sample preparation for light and electron microscopy, Keywords: Method of plant preparation, Transmission electron microscopy, Ultrastructural analysis, Contamination with heavy meta

Effect of Platinum Nanoparticles (PtNPs) Pollution on the Biological Properties of Haplic Cambisols Eutric of the Caucasus Forests

Pollution by platinum (Pt) is an emerging threat to forest soil health. The widespread use of Pt nanoparticles (NPs) in gas neutralizers for automobile exhaust has sharply increased the amount of PtNP pollution in the environment, including forest ecosystems. Recently, territories with Pt concentrations greater than 0.3 mg/kg in soil have been discovered. This concentration is 750 times greater than the background content in the earth’s crust. Cambisols, the most prevalent forest soil type in boreal forests that determines the functioning of the entire forest ecosystem, occupy a significant share of the Earth’s soil cover, which is about 1.5 billion hectares worldwide, or 12% of the entire continental land area. This shows the importance of studying the effect of pollution on this type of soil. In this study, laboratory simulations of PtNP contamination of the Haplic Cambisols Eutric at concentrations of 0.01, 0.1, 1, 10, and 100 mg/kg were carried out. The effect of PtNPs on soil properties was assessed using the most sensitive and informative biological indicators. The total number of bacteria was studied by the methods of luminescent microscopy, catalase activity (gasometrically), dehydrogenases activity (spectrophotometrically), germination, and length of roots by the method of seedlings. It was found that at the concentrations of 0.01, 0.1, and 1 mg/kg of PtNPs, there was either no effect or a slight, statistically insignificant decrease in the biological state of Haplic Cambisols Eutric. Concentrations of 10 and 100 mg/kg of PtNPs had a toxic effect on all the studied parameters. No statistically significant stimulating effect (hormesis) of PtNPs on the biological properties of Haplic Cambisols Eutric was observed, which indicates the high toxicity of PtNPs and the importance of studying the consequences of soil and ecosystem contamination with PtNPs. However, when the content of Pt in the soil was 1 mg/kg, there was a tendency to stimulate germination, the length of radish roots, and the total number of bacteria. The toxicity of PtNPs measured by biochemical indicators (activity of catalase and dehydrogenases) starts at a concentration of 100 mg/kg for phytotoxic effects (germination and root length of radish) and 10 mg/kg for microbiological effects (total number of bacteria)

Assessment of soil properties and trace element accumulation in arid regions: A case study of Kalmykia's central dry steppe zone, Russia

Soil plays a pivotal role in ecosystem health and agricultural productivity. This study focuses on a critical region for soil research, Kalmykia's central dry steppe zone in southern Russia, characterized by arid conditions and unique challenges. Our investigation aimed to evaluate the current state of soil properties and assess trace element accumulation within this environment. The region's distinctive characteristics, including being home to Europe's first desert, present a complex scenario for soil conservation and management. A thorough analysis of key physicochemical properties, including organic matter content, soil texture, pH levels, and the concentrations of trace elements (V, Cr, Co, Ni, Cu, Zn, Sr, and Pb) using established methodologies, was conducted. Our findings revealed several crucial insights into the soil conditions of this arid region. Soil samples predominantly consisted of Haplic Kastanozems Sodic, characterized by low organic carbon content (0.3-1.9%). Soil texture analysis indicated a predominantly light and medium loamy granulometric composition with a prevalence of sandy fractions. Soil pH values ranged from neutral (pH = 7.6-7.9) to slightly alkaline (pH = 8.0-8.4). Furthermore, the study provided the first assessment of soil conditions in residential areas of the Caspian Lowland's arid region. Notably, trace element analysis showed elevated concentrations of several metals, with Sr having the highest levels. Co, Cr, and Zn concentrations did not significantly increase compared to the background values. The results of this soil fertility evaluation hold significance for soil restoration and conservation efforts in this unique and fragile ecosystem. In conclusion, this study underscores the urgent need for soil monitoring and management practices to address soil degradation and desertification driven by overgrazing and erosion. Understanding the physicochemical properties and trace element dynamics in arid regions is essential for developing strategies to restore and conserve these valuable soils

Nanobionics in Crop Production: An Emerging Approach to Modulate Plant Functionalities

The “Zero Hunger” goal is one of the key Sustainable Development Goals (SDGs) of the United Nations. Therefore, improvements in crop production have always been a prime objective to meet the demands of an ever-growing population. In the last decade, studies have acknowledged the role of photosynthesis augmentation and enhancing nutrient use efficiency (NUE) in improving crop production. Recently, the applications of nanobionics in crop production have given hope with their lucrative properties to interact with the biological system. Nanobionics have significantly been effective in modulating the photosynthesis capacity of plants. It is documented that nanobionics could assist plants by acting as an artificial photosynthetic system to improve photosynthetic capacity, electron transfer in the photosystems, and pigment content, and enhance the absorption of light across the UV-visible spectrum. Smart nanocarriers, such as nanobionics, are capable of delivering the active ingredient nanocarrier upon receiving external stimuli. This can markedly improve NUE, reduce wastage, and improve cost effectiveness. Thus, this review emphasizes the application of nanobionics for improving crop yield by the two above-mentioned approaches. Major concerns and future prospects associated with the use of nanobionics are also deliberated concisely

Assessment of Heavy Metal Distribution and Health Risk of Vegetable Crops Grown on Soils Amended with Municipal Solid Waste Compost for Sustainable Urban Agriculture

Rapid urbanization is one of the key factors that leads to defragmentation and the shrinking of agricultural land. It further leads to the generation of an ample amount of municipal waste. Several technologies have emerged in the past for its utilization, and in this regard, composting is one of the conventional approaches gaining popularity in modern agriculture. To overcome the possible criticality of intense urbanization, the concept of urban agriculture is taking shape. Municipal solid waste compost (MSWC) has been popularly explored for the soil amendments and nutritional requirements of crops. With this, the assessment of soil pollution (due to the heavy metals presently found in MSWC) is a required step for its safe application in agriculture. The present study aims at assessing the utilization of MSWC (in different ratios) to amend the soil and its impact on the growth and yield of brinjal (Solanum melongena), tomato (Solanum lycopersicum), and okra (Abelmoschus esculentus). The study also explored the uptake of heavy metals by plants and their risk to human consumption. The findings suggested that MSWC amendments upgraded the physio-chemical properties of soil, including organic matter (OM) and micronutrients, and increased the heavy metal concentrations in soil. Heavy metal analysis underlined the presence of several heavy metals both in soil and crops. Total metal concentration in soil increased with increased MSWC dosage. Concerning metal uptake by crop plants, 25% of MSWC was found to impart metal concentrations within permissible values in edible parts of crops. On the contrary, 50%, 75%, and 100% compost showed higher metal concentrations in the crops. A Health Risk Index (HRI) of less than 1 was found to be associated with soil amended with 25% MSWC. Our study implies that MSWC significantly improved the growth and yield of crops, and it can be considered an alternative to chemical fertilizer but only in a safer ratio (≤25%). However, further studies are required, especially on field conditions to validate the findings regarding metal accumulation

Microplastic Pollution: An Emerging Threat to Terrestrial Plants and Insights into Its Remediation Strategies

Microplastics (MPs) are ubiquitous and constitute a global hazard to the environment because of their robustness, resilience, and long-term presence in the ecosystem. For now, the majority of research has primarily focused on marine and freshwater ecosystems, with just a small amount of attention towards the terrestrial ecosystems. Although terrestrial ecosystems are recognized as the origins and routes for MPs to reach the sea, there is a paucity of knowledge about these ecological compartments, which is necessary for conducting effective ecological risk assessments. Moreover, because of their high persistence and widespread usage in agriculture, agribusiness, and allied sectors, the presence of MPs in arable soils is undoubtedly an undeniable and severe concern. Consequently, in the recent decade, the potential risk of MPs in food production, as well as their impact on plant growth and development, has received a great deal of interest. Thus, a thorough understanding of the fate and risks MPs, as well as prospective removal procedures for safe and viable agricultural operations in real-world circumstances, are urgently needed. Therefore, the current review is proposed to highlight the potential sources and interactions of MPs with agroecosystems and plants, along with their remediation strategies