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Blue honeysuckle (Lonicera caerulea var. kamtschatica Sevast.) is a valuable berry crop with a unique biochemical composition. It is rich in vitamins, minerals, and biologically active substances. Different species and cultivars of honeysuckle require different cultivation conditions in the field of accelerated reproduction in vitro. Taking into account the high clonal replication potential of the plant, we conducted research on the chelated-iron form’s influence on the micropropagation productivity of the blue honeysuckle “Lulia” cultivar at the multiplication, rooting, and subsequent acclimatization stages of microplants. In a preliminary study, five types of iron chelates were tested with carboxyl- and phosphorus-containing ligands: Fe(III)-EDTA, Fe(III)-DTPA, Fe(III)-EDDHA, Fe(III)-HEDP, and Fe(II)-HEDP. Each type of iron chelate was applied at four concentrations: standard, decreased by 2 times, and increased by 1.5 times and 2 times in the basic Murashige and Skoog (MS) nutrient medium. It was found that the blue honeysuckle “Lulia” had a selectivity to the type of iron chelate that was used. The nutrient-medium modifications with iron chelates, which caused the plant response, contributed to a significant improvement in the plant’s physiological status and increased its survival rate during the microplant’s acclimation to the nonsterile conditions stage. At the rooting stage, an increase in the rooting rate of up to 100% (Fe (III)-EDDHA), an increase in the number of shoots by 1.5–2 times, and an increase in the number of roots by 1.4–1.9 times were observed. The positive effect of the iron’s chelated forms was also observed at the acclimation stage. According to the results of the research, the most suitable iron forms for clonal micropropagation of blue honeysuckle were carboxyl-containing Fe(III)-EDDHA and phosphonate-containing Fe(II)-HEDP. Moreover, the effectiveness of both complexonates was confirmed in a wide concentration range: Fe(III)-EDDHA from (×1.0) to (×2.0), and Fe(II)-HEDP from (×0.5) up to (×1.5).

This text highlights the aesthetic explorations of Bulgarian cinematographers from the 1980s, specifically those aimed at people of art. The article offers, first, a brief overview of films that examine the symbolic potential of the artist, which defines the consideration of an established and meaningful tendency in the development of Bulgarian cinema. The article focuses then on the live-action film Illusion (1980, directed by Lyudmil Staykov and written by Konstantin Pavlov) and examines the figure of the artist in the piece. The presented interpretation supports the view of the film as a morally valuable expression of modern art.

Red mud is an iron-containing waste of alumina production with high alkalinity. A promising approach for its recycling is solid-phase carbothermic roasting in the presence of special additives followed by magnetic separation. The crucial factor of the separation of the obtained iron metallic particles from gangue is sufficiently large iron grains. This study focuses on the influence of Na2SO4 addition on iron grain growth during carbothermic roasting of two red mud samples with different (CaO + MgO)/(SiO2 + Al2O3) ratio of 0.46 and 1.21, respectively. Iron phase distribution in the red mud and roasted samples were investigated in detail by M&ouml, ssbauer spectroscopy method. Based on thermodynamic calculations and results of multifactorial experiments, the optimal conditions for the roasting of the red mud samples with (CaO + MgO)/(SiO2 + Al2O3) ratio of 0.46 and 1.21 were duration of 180 min with the addition of 13.65% Na2SO4 at 1150 &deg, C and 1350 &deg, C followed by magnetic separation that led to 97% and 83.91% of iron recovery, as well as 51.6% and 83.7% of iron grade, respectively. The mechanism of sodium sulfate effect on iron grain growth was proposed. The results pointed out that Na2SO4 addition is unfavorable for the red mud carbothermic roasting compared with other alkaline sulfur-free additives.

—The influence of two lead salts on the soil enzymatic activity dynamics (urease, dehydrogenase, the total hydrolase activity, acidic phosphatase, and peroxidase), with lead ion concentrations of 10, 100, 300, 500, and 1000 mg/kg, was assessed in a 21-day-long model experiment. A reliable inhibitory effect of lead nitrate applied at doses of 500 and 1 000 mg (Pb2+)/kg on the total activity of hydrolases, dehydrogenase, and peroxidase has been identified, while lead acetate mostly caused a stimulating effect. Based on the data obtained, the diagnostic indicators have been ranked by the reduction of their sensitivity to lead nitrate pollution in the following order: total activity of hydrolases > peroxidase > dehydrogenase > urease ~ acidic phosphatase.

Nowadays trace metal contamination of soils represents an important environmental hazard. Nevertheless, the use of some secondary waste products as amendments may restore the common soil functions. This paper focuses on the chemical and biological influence of wood biochar (BC), wood ash (WA) and humic substances (HS), alone and in the mixtures, on a heavily multi-contaminated sandy loam soil. The soil was amended by above-mentioned materials to follow a pH-increasing design (pHCa from 6.0 to 6.5, 7.0 and 7.5); soil samples were analyzed after 3, 30, and 60 days using a set of variables, namely the plant-available trace element concentrations (Cu, Cd, and Zn), microbial biomass carbon (Cmic), and microbial quotient (qCO2), as well as toxicity to Sinapis alba and Daphnia magna. Wood ash and WA + HS were the most efficient treatments to decrease mobile Cd and Zn concentrations in the soil, while HS, BC, and BC + HS combinations were the most effective in reducing the Cu mobility. The effect of BC and WA on the Cmic and qCO2 was mostly negative, whereas adding HS markedly increased Cmic and reduced qCO2 in soil. After amendment applications, the root elongation of mustard was significantly increased in HS and combined treatments (BC + HS, WA + HS). Additionally, BC + HS, WA + HS and WA 8.4% significantly decreased the toxicity of leachates to D. magna to the low-, or non-toxic levels. Our results suggest that the combination of amendments with HS can be a suitable remediation strategy for heavily contaminated soils.

Heavy metal contamination is a priority issue affecting millions of hectares of soil throughout the world. One of the most promising, environmentally friendly, and cost-effective approaches to restore polluted soils could be applying organic amendments. We investigated the remediation potential of three types of humic products with regard to their effect on the bioavailability of Pb and Zn, content of nutrients, and the ability to mitigate acute phytotoxicity in contaminated soil. Spodosol samples were spiked with Pb (550 mg kg−1) and Zn (880 mg kg−1). Then, two different commercial humic products (from peat and lignosulfonate) and natural humic acids (from brown oxidized coal) were added in two doses to reach an equal content of carbon: a 10% increment and a 30% increment of the initial total organic carbon in the soil. After 30 days, the content of metals and nutrients (S, K, Na, Ca, Mn, P) was determined by the sequential extraction (i−H2O, ii−NH4COOH pH 4.8, iii–CH3COOH). The effect of humic products on heavy metals bioavailability was evaluated using the calculated partition indexes. Seed germination and root elongation of Sinapis alba were also determined. Chemical and biochemical variables were aggregated by the principal component analysis. Humic products reduced the amount of bioavailable fractions of Pb and Zn in soils. The partition index, which quantitatively describes bioavailable fractions of the Zn and Pb in the soil, was 28–49% lower than in the spiked (Pb+Zn) control. The inhibition of root elongation and seed germination of mustard by Zn and Pb was significantly mitigated by humic products; in the soil test, the root length and seed germination were up to 36–87% higher than those of the Pb+Zn control and did not differ from those in the non-amended treatments. This effect may have been associated with the structural differences (H/C and O/C ratio) and content of nutrients (Na and K) in humic products. Commercial humic products used in poor multi-contaminated soils can maintain plant growth by improving nutrient status due to heavy metals immobilization and can be a promising approach to remediate the soil contaminated with heavy metals at extremely high concentrations.

Red mud is a hazardous waste obtained from bauxite ore by the Bayer method. It has a high content of iron. In this study, the iron grain growth process during solid-phase carbothermic reduction of red mud in the presence of added iron metallic particles was investigated. Carbonyl iron, cast iron shots and metallurgical mill scale were used as the additives. The influence of amount and fraction of the additives on size of reduced iron grains obtained after reduction roasting of red mud at 1250-1350°C and 60-180 min duration was studied. It is showed that the best effect on size of iron grains has the addition of carbonyl iron and mill scale. In this way, besides red mud, some other iron-containing wastes can be recycled, e.g. mill scale.

Red mud is a by-product of alumina production from bauxite ore by the Bayer method, which contains considerable amounts of valuable components such as iron, aluminum, titanium, and scandium. In this study, an approach was applied to extract iron, i.e., carbothermic reduction roasting of red mud with sodium and potassium carbonates followed by magnetic separation. The thermodynamic analysis of iron and iron-free components&rsquo, behavior during carbothermic reduction was carried out by HSC Chemistry 9.98 (Outotec, Pori, Finland) and FactSage 7.1 (Thermfact, Montreal, Canada, GTT-Technologies, Herzogenrath, Germany) software. The effects of the alkaline carbonates&rsquo, addition, as well as duration and temperature of roasting on the iron metallization degree, iron grains&rsquo, size, and magnetic separation process were investigated experimentally. The best conditions for the reduction roasting were found to be as follows: 22.01% of K2CO3 addition, 1250 &deg, C, and 180 min of duration. As a generalization of the obtained data, the mechanism of alkaline carbonates&rsquo, influence on iron grain growth was proposed.