The objectives of this study were to investigate the response of cadmium (Cd) distribution and stability in soil aggregates as affected by applying different amendments and to understand the relationship between changes in soil aggregates and alleviation of Cd phytotoxicity to rice after amendment application. In the present study, rice (Oryza sativa L.) was cultivated on a Cd-polluted soil. Five soil amendments were applied, which are as follows: rice husk biochar (BC), Fe-added rice husk biochar (Fe-BC), attapulgite-based mixture (AM), zeolite-based mixture (ZM), and cow manure-based mixture (MM). The effect on Cd redistribution in soil and Cd accumulation in rice plant was evaluated. The results showed that the five amendments applied at the rate of 3% (w/w) significantly increased soil pH and decreased Cd mobility in soil and Cd accumulation in rice plants. The reduction rate of Cd content in rice grains ranged from 41 to 62% after amendment application. The remediation efficiency of the different amendments for decreasing Cd accumulation in rice tissues followed the order of Fe-BC > MM > BC > ZM > AM. Adding amendments promoted the formation of large aggregates (0.2–2.0 mm) with more mass loading of Cd and enhanced aggregate stability. Comparatively, Fe-BC was more effective than others for remediation of acid Cd-polluted paddy soil, as a significantly decreased Cd concentration in rice grain after its application was observed. Structural equation modeling (SEM) analysis revealed that DTPA-extractable Cd in small aggregates was the main factor affecting Cd accumulation in rice grain; soil pH directly affected aggregate stability; and aggregate stability was closely related to Cd availability in different size soil particles. These results indicated that the applied amendments were effective in reducing Cd bioavailability, most likely through raising the soil pH, improving aggregate stability, and re-distributing Cd from smaller soil aggregates to larger ones.

Mercury (Hg) is a complex and multifaceted global pollutant. Artisanal and small-scale gold mining activities are largely responsible for Hg contamination in developing countries, in many cases impacting areas of high biodiversity such as the Amazon. The aim of the study was to establish Hg exposure in indigenous citizens from the Tarapaca village, Cotuhe and Putumayo Rivers, at the Colombian Amazon. Total Hg (T-Hg) concentrations were measured employing a DMA-80 Hg analyzer. For that purpose, 190 hair samples were taken from volunteers living in different communities of Tarapaca. The overall mean T-Hg level for all samples was 10.6 ± 0.4 μg/g, with values ranging from 0.61 to 31.1 μg/g. The mean T-Hg level decreased in the order Puerto Huila > Puerto Ticuna > Ventura > Nueva Union > Buenos Aires > Santa Lucia > Puerto Nuevo > Caña Brava > Pupuña. Based on recommendations from the United States Environmental Protection Agency (US EPA), 99.5% of the samples exceeded the maximum level of 1.0 μg/g. Hg content in human hair was significantly associated with fish consumption (ρ = 0.253; p < 0.001). According to the health survey, at least 24.7% of the volunteers manifested some signs and symptoms of Hg poisoning. In short, these data support the extensive Hg exposure in the environment of the Colombian Amazon, a process that could be impacting the quality of life of its vulnerable indigenous groups. Immediate actions must be taken by competent authorities to protect these communities from Hg poisoning.

The environmental degradation has put serious concern among the nations at global level, yet contented measures are still lagged behind the prospective outcomes. This study is aimed at analyzing the existence of “aviation transportation Kuznets curve” together with “environmental Kuznets curve” in perspective of greenhouse gas (GHG) emissions for the SAARC region during 1980 to 2018. The panel unit root test summary applied to panel data indicates the first difference order while panel fisher cointegration shows long-run association among the considered variables. The econometric results by fully modified least square (FMOLS) validate the existence of “inverted U-shaped” Kuznets curve for environment as (EKC) and aviation transported carriage (ATC) while “U shaped” aviation transported passenger (ATP) is observed in context to greenhouse gas (GHG). In addition, the dynamic ordinary least square (DOLS) exhibits “inverted U shaped” for aviation transportation while GDP has an increasing trend of “U-shaped” curve. The pairwise Dumitrescu-Hurlin panel causality shows unidirectional association from economic growth, trade openness, and aviation sector to greenhouse gas (GHG) emissions. Therefore, it is an urgent need of the hour for the SAARC region to consider the sustainability of the environment by key sector. This analysis suggests that SAARC nations must focus on exploiting renewable energy means along with implementing fuel-saving traveler and merchandise expertise that thoroughly cuts the diesel fuel.

The rapid increase in urbanization has given rise to the need of proper waste management. Within municipal waste, the plastic waste is a growing concern which is causing severe harm to our ecosystem. If ignored, this problem will have harmful effects on both human and wildlife. Therefore, this study aims to find out the factors that influence the recycling behavior patterns of consumers regarding plastic waste. The variables from the theory of planned behavior were adopted to study the behavior of consumers toward recycling plastic waste. The data was collected from 243 residents of Karachi–metropolitan city of Pakistan. The partial least square–structural equation modelling was applied to analyze the data. The findings of the current study reveal that different consumers’ attributes and attitudes trigger different types of recycling behavior when it comes to waste disposal. Pressure from family and friends and perceived behavioral control trigger the behavior of reselling the waste plastic products while consumer’s awareness of consequences and personal attitude toward proper waste disposal leads to reuse or donating that product to someone who can use that plastic product. The understanding of these consumer attributes may help to shape the behavioral outcomes in order to manage waste disposal. This study will be beneficial for business managers looking to improve reverse logistics as well as government/municipal policy makers and academics/researchers who are interested in a solution-oriented study.

Iron (Fe) is one of the essential micronutrients for all living organisms. Despite its abundance in most of the contaminated soil, it is usually in unavailable forms. The unavailable form of Fe could be mobilized to plants by the use of microorganisms. This study was carried out to show that the Fe-contaminated field soils could be used to accumulate Fe in the plant parts using bacterial inoculation. For this, from a set of bacterial isolates, four Fe-tolerant bacteria were selected and identified based on 16S rRNA gene sequencing. The Fe-tolerant bacteria belonged to the genus Bacillus toyonensis (MG430287), Rhodococcus hoagii (MG432495), Lysinibacillus mangiferihumi (MG432492), and Lysinibacillus fusiformis (MG430290). Screening of plant growth-promoting properties of these isolates revealed that all isolates were able to produce indole acetic acid (50.0–84.0 μg/ml), siderophore, and potassium solubilization (except R. hoagii). Pot assay using Fe-contaminated ((8.07–8.35 g kg⁻¹) soils River Directorate of India) revealed that Fe-tolerant bacteria enhanced the growth of Brassica juncea and its biomass. Besides the improved plant growth, the inoculated plants also showed an overall percentage increase in the uptake of iron in root, stem, and leaf (57.91–128.31%) compared with uninoculated plants. In addition to enhanced plant growth attributes, the isolates also improved the total chlorophyll content and antioxidant properties such as total phenol, proline, and ascorbic acid oxidase. Thus, the results clearly indicated that these isolates could be used as a bioinoculant to improve the sequestration of Fe from the contaminated soils and alleviation of Fe stress in plants.

The possibility of Miscanthus×giganteus cultivation as an energy crop on the different types of mining rocks was studied. It was revealed that a loess-like loam and red-brown clay with the added black soil were the most suitable for plant growing. The yield of dry above-ground biomass ranged from 4.3 to 6.8 t DM ha⁻¹ after the first year of cultivation and from 8.9 to 9.7 t DM ha⁻¹ after the second year while using these substrates. The application of amendments stimulated the growth and development of plants and increased productivity from 50 to 140%. M.×giganteus showed sufficient tolerance and good enough growth on the geochemically active dark-gray schist clay with yield from 2 to 3 t DM ha⁻¹ after the first year of cultivation already. For plants grown on the different strata of dark-gray schist clay, the thermal decomposition of the biomass took place in four stages in the temperature range from 30 to 640 °C. The samples grown on stratum 0–20 cm showed the highest reactivity with a peak 30.6%/min at 290 °C. There were differences in the concentrations of determined heavy metals: iron, zinc, copper, and lead in the plant tissues depending on the layer depth of dark-gray schist clay from 0 to 20 cm to 40–60 cm. The relatively limited content of heavy metals in the above-ground biomass was due to the preferential accumulation in the roots.

In this investigation, performance and emission characteristics for enhancing LPG, hydrogen, and hydroxy with E20 were evaluated for the understanding of which fuel combination performs better in a gasoline engine. In the upper sequence, hydroxy-hydrogen-LPG could perform best in terms of brake thermal efficiency (BTE) and brake-specific fuel consumption (BSFC). The induction of gaseous fuel improves CO, CO₂, and HC emission but increases the NOx emission. More concisely, the enhancement of hydroxy with E20 shows the best engine performance for highest BTE while lowest BSFC as well as lowest exhaust emissions (CO, HC, except NOx).

A novel magnetic ion-imprinted polymer with high accessibility to palladium ions was synthesized via co-precipitation polymerization. Accordingly, a ternary complex composed of PdCl₂ as an imprinting ion, 8-aminoquinoline (AQ) as a ligand, and 4-vinyl pyridine (4-VP) as a complexing monomer was applied to Fe₃O₄@SiO₂ as magnetic core, followed by precipitation polymerization using 2-hydroxyethyl methacrylate (2-HEMA) as a co-monomer, ethylene glycol dimethacrylate (EGDMA) as the crosslinker, and 2,2-azobisisobutyronitrile (AIBN) as an initiator in the presence of 2-methoxyethanol as a solvent. The palladium ions were leached out by a solution containing 50% (v/v) HCl. The synthesized polymer was characterized physically and morphologically using different techniques. In order to assess the conditions required for adsorption, as well as the selectivity and reusability, batch adsorption experiments were carried out. The experiments exhibited that the maximum adsorption capacity was about 65.75 mg g⁻¹ at 25 °C, while the pH solution and the adsorbent dose were 4 and 1 g L⁻¹, respectively. Kinetic studies of experimental data demonstrated that they correspond very much to the pseudo-second-order kinetic model. The development of the Langmuir and Freundlich isothermal models on the equilibrium data proved to correspond well to the Langmuir isotherm model. Interferences studies of the magnetic polymer demonstrated higher affinity and discernment for palladium ions than other co-existing ions in the solutions. Spontaneous (ΔG < 0) and exothermic (ΔH < 0) behavior of the adsorption process is confirmed by thermodynamic studies. In addition, the affinity of the spent polymer has not been dramatically reduced over at least five regeneration cycles.

Manganese (Mn)-modified ferric oxide/nickel foam (Fe/Ni) catalysts were prepared using Ni as a carrier, Fe and Mn as active components to study NH₃–SCR of NOₓ at low temperature. The effects of different Fe loads and Mn-modified Fe/Ni catalysts on the DeNOₓ activity were investigated. Results show that when the amount of Fe is 10%, Fe/Ni catalyst has the highest NOₓ conversion. For the Mn-modified Fe/Ni catalysts, the NOₓ conversions firstly increase and then decrease with the Mn loading amount increasing. 3MnFe/Ni catalyst shows high NOₓ conversions, which reach 98.4–100% at 120–240 °C. The characterization analyses reveal that Mn-modified Fe/Ni catalysts increase the FeOₓ dispersion on Ni surface, improve significantly the valence ratio of the Fe³⁺/Fe²⁺, the content of lattice oxygen which promotes the catalyst storage and exchange oxygen capacity at low temperature, and the number of Brønsted active acid sites on the catalyst surface, and enhance the low-temperature redox capacity. These factors remarkably increase the NOₓ conversions at low temperature. Especially, 3Mn10Fe/Ni catalyst not only has excellent DeNOₓ activity but also has better water resistance. However, the anti-SO₂ poisoning performance needs to be improved. To further analyze the reason why different catalysts show different DeNOₓ performance, the reaction kinetics was also explored.

In the present study, a detailed investigation was carried out on MoO₃ alumina-supported catalysts behavior in selective catalytic reduction of SO₂ to sulfur with CH₄. At first, four different molybdenum catalysts with weight rates of 0, 5, 10, and 15 were impregnated on γ-alumina to be characterized using XRD, SEM, BET, BJH, and N₂ adsorption. Then, to find the most active catalyst, temperature dependency test was performed on all of the prepared catalysts and the result representing Al2O3-Mo10 as the best catalyst. In next step, the effects of feed gas composition, space velocity, and long-term activity, as an important industrial factor, were tested on Al₂O₃-Mo10. It was revealed instantaneously from the beginning, MoO₃ specie started to convert mainly into MoS₂ and MoO₂, and a minor part into Mo₂C, which is terminated after 750 min achieving a stable condition. Thereafter, SO₂ conversion and sulfur selectivity increased from 85.8 to 89.4% and 99.4 to 99.7%, respectively. XRD graph of the used catalyst and TPO thermogravimetric/mass-spectra proved possible happening of the proposed mechanism in long-term activity. At the end, mean activation energy was determined based on Arrhenius model in temperature range of 550 to 800 °C, with a value of 0.33 eV for Al₂O₃-Mo10.