Search Results (6,688)

Mining and metallurgical activities negatively impact ecosystems due to the release of potentially toxic elements (PTEs). This study assesses PTE pollution and accumulation in native plant species that have spontaneously colonized a historical mining site (Michaly, site A) and a nearby metallurgical smelter site (Varvara, site B) on the Lavreotiki Peninsula, Attika, Greece. Soils were analyzed for As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Sb, and Zn. A total of 89 native plant taxa across 28 families were identified. The aerial parts from dominant species were analyzed for PTE concentrations, and bioconcentration factors (BCFs) were calculated. One-way ANOVA and principal component analysis (PCA) using R were used for statistical evaluation. Soils at both sites showed elevated As, Cd, Cr, Cu, Ni, Pb, Sb, and Zn; Mn was high only at site B, while Co and Fe remained at background levels. Several plant species, especially at Michaly, had elevated concentrations of As, Cd, Co, Cr, Fe, Pb, Sb, and Zn in their aerial parts. BCFs indicated general PTE exclusion from aerial parts, particularly at site B. Native vegetation on these contaminated sites shows resilience and PTE exclusion, highlighting their potential for phytoremediation, especially phytostabilization, and ecological restoration in similarly polluted Mediterranean environments. Full article

Extraction of metal ions from polluted waters and immobilization of metals in contaminated soils can be conducted using zeolites—porous aluminosilicate ion exchangers. The uptake of copper and zinc ions by the Georgian natural heulandite was studied under conditions of interaction of the zeolite with solutions (“liquid-phase” ion exchange) and powders (“solid-state” ion exchange) of the corresponding salts. The aim of the study was to compare the effect of the two procedures on the chemical composition and structure of the zeolite. It was found that the “liquid-phase” procedure provides a higher degree of uptake, particularly of zinc ions. Ion-exchange causes slight dealumination without decationization. Uptake of divalent ions occurs mainly through the leaching of sodium ions. According to X-ray data of ion-exchanged samples, the uptake of copper and zinc does not change the crystal structure of the zeolite framework, but nitrogen adsorption measurements show that ion exchange affects the mesoporous structure: solution treatment reduces the specific total pore volume and leads to the appearance of pores with a diameter of 4 nm. The “solid-state” procedure leads to an increase in specific total pore volume mainly due to an increase in the number of relatively small nanosized pores. Full article

The production of alumina produces red mud (RM), a highly alkaline solid waste. The majority of it is disposed of in landfills, which seriously pollutes the environment. It needs to be recycled and handled with care to protect the environment. RM is a promising raw material for wastewater and waste gas treatment owing to its high alkalinity and abundant metal compounds. It can efficiently remove diverse pollutants while facilitating large-scale utilization of RM resources. Reviews of the use of RM resources to create catalysts for environmental governance are, nevertheless, scarce. Therefore, this paper analyzes and summarizes the pertinent research on RM-based catalysts to remove pollutants from the environment based on journal literature related to RM resource utilization from 2015 to 2025. This study reviews the application of RM-based catalysts for degrading pollutants in wastewater and exhaust gases via advanced oxidation processes (AOPs)—including photocatalysis, Fenton-like catalysis, ozonation catalysis, and persulfate catalysis—as well as catalytic oxidation, chemical looping combustion (CLC), and selective catalytic reduction (SCR). The paper emphasizes the analysis of modification strategies and catalytic mechanisms of RM-based catalysts in environmental remediation and examines the environmental risks and corresponding mitigation measures related to their preparation from RM resources. Finally, it outlines that future research should prioritize green, low-energy modification processes; catalytic systems for the synergistic removal of multiple pollutants; and efficient, recyclable separation and recovery technologies. These directions aim to promote the sustainable application of RM in large-scale environmental remediation and to achieve the integrated advancement of resource utilization and ecological protection. Full article

As landfill mining becomes more widely applied, growing attention is being paid to the waste-to-energy conversion of landfill waste. Co-disposal of landfill waste with municipal solid waste represents one of the primary strategies for achieving energy recovery of landfill waste. In this paper, the emission characteristics of pollutants were systematically analyzed during the co-disposal of landfill waste and municipal solid waste in a full-scale municipal solid waste incineration. The study investigated the formation patterns of toxic PCDD/Fs and gaseous pollutants under different co-disposal ratios of landfill waste (0%, 15%, 25%, 35%, and 45%). In total, 136 PCDD/Fs were analyzed to investigate the influence of co-disposal ratios on PCDD/F formation in both flue gas and fly ash. The influence of varying co-disposal ratios on the phase and elemental composition of fly ash was also investigated. Co-disposal led to a significant reduction in the toxic PCDD/F concentration at the boiler outlet, mainly attributed to the higher sulfur content of LW compared to MSW. With increasing co-disposal ratios, the annual emission amounts of toxic PCDD/Fs in fly ash significantly increased. The ∑PCDD/∑PCDF ratio in both flue gas of boiler outlet and fly ash also increased, indicating an enhancement of the precursor formation pathway, while the de novo synthesis pathway was relatively suppressed. The fly ash exhibited a high proportion of highly chlorinated dioxins (degree of chlorination: 7.19–7.23), likely due to their low saturated vapor pressure. According to the Hagenmaier congener distribution, high co-disposal ratios (25–45%) suppressed the chlorination of DD/DF in fly ash but promoted the formation of gas-phase PCDFs. Different co-disposal ratios significantly influenced both the emission concentrations and removal efficiencies of air pollutants, including NOx, SO₂, and HCl. Although co-disposal did not alter the crystalline phase composition of fly ash, it led to an increased content of heavy metals such as Cu, Hg, and Pb. Full article

Nickel-based metal–organic frameworks (Ni-MOFs) have received enormous amounts of attention from the scientific community due to their excellent porosity, larger specific surface area, tunable structure, and intrinsic redox properties. In previous years, Ni-MOFs and their hybrid composite materials have been extensively explored for electrochemical sensing applications. As per the reported literature, Ni-MOF-based hybrid materials have been used in the fabrication of electrochemical sensors for the monitoring of ascorbic acid, glucose, L-tryptophan, bisphenol A, carbendazim, catechol, hydroquinone, 4-chlorophenol, uric acid, kaempferol, adenine, _L-cysteine, etc. The presence of synergistic effects in Ni-MOF-based hybrid materials plays a crucial role in the development of highly selective electrochemical sensors. Thus, Ni-MOF-based materials exhibited enhanced sensitivity and selectivity with reasonable real sample recovery, which suggested their potential for practical applications. In addition, Ni-MOF-based hybrid composites were also adopted as electrode modifiers for the development of supercapacitors. The Ni-MOF-based materials demonstrated excellent specific capacitance at low current densities with reasonable cyclic stability. This review article provides an overview of recent advancements in the utilization of Ni-MOF-based electrode modifiers with metal oxides, carbon-based materials, MXenes, polymers, and LDH, etc., for the electrochemical detection of environmental pollutants and biomolecules and for supercapacitor applications. In addition, Ni-based bimetallic and trimetallic catalysts and their composites have been reviewed for electrochemical sensing and supercapacitor applications. The key challenges, limitations, and future perspectives of Ni-MOF-based materials are discussed. We believe that the present review article may be beneficial for the scientific community working on the development of Ni-MOF-based materials for electrochemical sensing and supercapacitor applications. Full article

Marine noise pollution is a significant threat to global marine ecosystems and human activities. Most underwater sound-absorbing materials operate in the mid-to high-frequency bands (typically 1–10 kHz for mid-frequency and above 10 kHz for high-frequency), and current underwater low-frequency sound absorption performance remains unsatisfactory, with large structural sizes. To address these issues, a novel metasurface composed of a hexagonal Helmholtz resonator structure made of rubber and metal, combined with an embedded rough neck, is proposed. By introducing roughness into the neck of the Helmholtz resonator, this structure effectively provides the necessary acoustic impedance for low-frequency sound absorption without changing the overall size, thus lowering the resonance frequency. The finite element method is used for simulation, and theoretical validation is performed. The results show that the Helmholtz resonator with the rough neck achieves near-perfect acoustic absorption at a deep subwavelength scale at 81 Hz. At the absorption peak, the wavelength of the sound wave is 370 times the thickness of the resonator. By coupling seven absorption units and optimizing the parameters using a genetic algorithm, the metasurface achieves an average absorption coefficient greater than 0.9 in the 60 Hz to 260 Hz range. The complementary sound absorption coefficients of the unit cells at different frequency bands effectively broaden the absorption bandwidth. Full article

Wastewater containing heavy metals can come from a variety of sources and is extremely toxic and hard to break down. Conventional treatment methods can easily result in secondary pollution and are expensive. The research on magnetic chitosan composites, a new adsorbent in the treatment of heavy metal wastewater, is methodically reviewed in this paper. It offers a theoretical foundation for the creation of more environmentally friendly and effective wastewater treatment technology by examining its preparation and modification technology, adsorption mechanism, and application performance. This paper provides a summary of the technology used to prepare and modify magnetic chitosan composites. Both the cross-linking and co-precipitation methods are thoroughly examined. A summary of the fundamental process of heavy metal ion adsorption is provided, along with information on the chemical and physical impacts. Of these, chemical adsorption has been shown to work well with the majority of heavy metal adsorption systems. According to application research, magnetic chitosan exhibits good adaptability in real-world industrial wastewater treatment and has outstanding adsorption performance for various heavy metal ion types and multi-metal coexistence systems (including synergistic/competitive effects). Lastly, the optimization of the material preparation and modification process, the mechanism influencing the various coexisting ion types, and the improvement of regeneration ability should be the main areas of future development. Full article

Phthalic acid esters (PAEs), ubiquitously employed as a plasticizer, have been classified as priority environmental pollutants because of their persistence, bioaccumulation, and endocrine-disrupting properties. As a characterized PAE-degrading strain of marine origin, Mycolicibacterium phocaicum RL-HY01 utilizes di-(2-ethylhexyl) phthalate (DEHP) as its sole carbon and energy source. Genome sequencing and RT-qPCR analysis revealed a previously uncharacterized hydrolase gene (dehpH) in strain RL-HY01, which catalyzes ester bond cleavage in PAEs. Subsequently, recombinant expression of the cloned dehpH gene from strain RL-HY01 was established in Escherichia coli BL21(DE3). The purified recombinant DehpH exhibited optimal activity at 30 °C and pH 8.0. Its activity was enhanced by Co²⁺ and tolerant to most metal ions but strongly inhibited by EDTA, SDS, and PMSF. Organic solvents (Tween-80, Triton X-100, methanol, ethanol, isopropanol, acetone, acetonitrile, ethyl acetate, and n-hexane) showed minimal impact. Substrate specificity assay indicated that DehpH could efficiently degrade the short and long side-chain PAEs but failed to hydrolyze the cyclic side-chain PAE (DCHP). The kinetics parameters for the hydrolysis of DEHP were determined under the optimized conditions, and DehpH had a V_max of 0.047 ± 0.002 μmol/L/min, K_m of 462 ± 50 μmol/L, and k_cat of 3.07 s⁻¹. Computational prediction through structural modeling and docking identified the active site, with mutagenesis studies confirming Ser228, Asp324, and His354 as functionally indispensable residues forming the catalytic triad. The identification and characterization of DehpH provided novel insights into the mechanism of DEHP biodegradation and might promote the application of the target enzyme. Full article

Emissions from civil aviation not only degrade the environmental quality around airports but also have the significant effects on climate change. According to the flight schedules, aircraft/engine combination information and revised emission factors from the International Civil Aviation Organization (ICAO) Aircraft Engine Emission Databank (EEDB) based on meteorological data, the emissions of climate forcers (CFs: BC, CH₄, CO₂, H₂O, and N₂O), conventional air pollutants (CAPs: CO, HC, NO_X, OC, PM_2.5, and SO₂), and hazardous heavy metals (HMs: As, Cu, Ni, Se, Cr, Cd, Hg, Pb, and Zn) from flights of civil aviation of eight airports in Shandong in 2018 and 2020 are estimated in this study. Moreover, the study quantifies the impact of COVID-19 on civil aviation emissions (CFs, CAPs, and HMs) in Shandong, revealing reductions of 47.45%, 48.03%, and 47.45% in 2020 compared to 2018 due to flight cuts. By 2020, total emissions reach 9075.44 kt (CFs), 35.57 kt (CAPs), and 0.51 t (HMs), with top contributors being Qingdao Liuting International Airport (ZSQD) (39.60–40.37%), Shandong Airlines (26.56–28.92%), and B738 aircraft (42.98–46.70%). As byproducts of incomplete fuel combustion, the shares of CO (52.40%) and HC (47.76%) emissions during taxi/ground idle mode are significant. In contrast, emissions during cruise phase are the dominant contributor of other species with a share of 74.67–95.61% of the associated total emissions. The findings highlight the disproportionate role of specific airlines, aircraft, and operational phases in regional aviation pollution. By bridging gaps in localized emission inventories and flight-phase analyses, this research supports targeted mitigation strategies, such as fleet modernization and ground operation optimization, to improve air quality in Shandong. The study highlights how sudden shifts in demand, such as those caused by pandemics, can significantly alter emission profiles, providing insights for sustainable aviation planning. Full article

The interaction between microplastics (MPs) and heavy metals and their ecological risks to the soil–plant system has attracted widespread attention. This study explored the effects of polypropylene (PP) alone or combined with cadmium (Cd) pollution on wheat seed germination, plant growth, and the soil environment from multiple perspectives through seed germination experiments and pot experiments. The results of the seed germination experiment showed that the addition of 50 mg L⁻¹ PP could promote the growth of seeds. However, medium and high concentrations of PP had significant inhibitory effects on seeds. For PP + Cd co-pollution, the addition of 50 mg L⁻¹ PP could partially alleviate the stress of Cd alone. However, with the increase in PP concentration, the co-pollution showed stronger toxicity to seeds. Moreover, the synergistic effect of PP and Cd was greater than the antagonistic effect; both of them aggravated the stress on wheat. The results of the pot experiment showed that the soil microenvironment was significantly affected by PP alone or combined with Cd pollution. It was manifested as reducing soil moisture and pH, affecting soil nutrient cycling, and inhibiting the activities of soil enzymes (except for catalase). In addition, the MPs and Cd significantly affected the physiological characteristics of plants. Specifically, the addition of 50 mg L⁻¹ PP alone promoted or had no significant effect on wheat growth. However, with the increase in PP concentration, the biomass and chlorophyll content of plants decreased significantly, while carotenoids, oxidative damage, and antioxidant enzyme activities increased significantly. Moreover, PP + Cd co-pollution led to stronger phytotoxicity. Moreover, PP exposure caused an increase in plant shoot and root Cd concentrations, promoting Cd transport from roots to shoots. Correlation heat maps and RDA analysis revealed that plant Cd concentration was significantly correlated with soil environmental factors and plant physiological indicators. Finally, the results of the linear model (%) of relative importance indicated that pH and MDA content were important soil and plant variables affecting the increase in Cd concentration in plant tissues. This study is of great significance for evaluating the ecological risks of MPs-Cd composite pollution. Full article

This study examined the effect of sulfur, ethylenediaminetetraacetic acid (EDTA), olive mill wastewater (OMW), and their mixtures in remediating metal-polluted soils by implementing both leaching trials and a greenhouse experiment with sunflower (Helianthus annuus). In the leaching study, soils were subjected to five discharge volumes (V1–V5). EDTA significantly improved metal mobility of Cd (221.4) mg·kg⁻¹ in V2, Pb (340.8) mg·kg⁻¹ in V3, and Zn (1.01) mg·kg⁻¹ in V3, while OMW moderately mobilized Cd and Mn. However, sulfur mitigated leaching by buffering soil pH and metal immobilization. Mixed treatments revealed moderate leaching behavior. EDTA lowered soil pH (5.3) and raised EC (1763) µS/cm, while sulfur maintained stable chemical environments. In the greenhouse experiment, amendments significantly influenced biomass and metal uptake. Sunflower roots accumulated the highest Cd under sulfur (733.5) mg·kg⁻¹ and Mn under EDTA (743.3) mg·kg⁻¹. EDTA restricted Cd translocation (TF = 0), while OMW enhanced Cr movement to shoots (TF = 17.6). EDTA also reduced Cd bioavailability, whereas OMW raised Pb and Mn availability. Overall, EDTA improved metal solubility for potential removal and sulfur in stabilized metals, while OMW acted as a moderate mobilizer. Sunflower demonstrated selective metal uptake, indicating its potential in phytoremediation strategies tailored to specific contaminants. Full article

Urban wastewater is composed of nutrients such as nitrogen and phosphorus, organic matter, heavy metals, pathogens, and micropollutants. If untreated, these contribute to eutrophication and environmental degradation. Microalgae-based bioremediation offers a sustainable solution, showing promise for pollutant removal and high-value bioproduct generation. This study evaluates the efficacy of Galdieria sulphuraria ACUF 427 in treating urban wastewater, with a focus on nutrient removal and phycocyanin production at different optical densities (OD 2, OD 4, and OD 6). Nutrient removal rates (RRs) were analysed for ammonium nitrogen (N-NH₄⁺), ammonia nitrogen (N-NH₃), phosphate phosphorus (P-PO₄³⁻), and chemical oxygen demand (COD). The RR for N-NH₄⁺ increased with optical density, reaching 7.49 mg/L/d at an optical density of 6. Similar trends were observed for N-NH₃ and P-PO₄³⁻, with peak removal at OD 6. COD removal remained high across all ODs, though differences between OD 4 and OD 6 were not statistically significant. Significant variations (p < 0.05) in nutrient removal were noted across the ODs, except for COD between OD 4 and OD 6. Biomass growth and phycocyanin production were significantly higher in the wastewater compared to the control (Allen Medium), with the most effective performance observed at an optical density (OD) of 6. Maximum growth rates were 0.241 g/L/d at OD 6, 0.178 g/L/d at OD 4, and 0.120 g/L/d at OD 2. These results highlight the potential of G. sulphuraria as an agent for wastewater bioremediation and the production of high-value compounds, particularly at elevated cell densities, where we achieved superior nutrient removal and biomass production. Full article

In this study, we assessed soil pollutants and surveyed the bacterial communities using 16S rRNA sequencing to better understand how to improve rehabilitation strategies for nickel-laterite mines in the Philippines. Representative soil samples and rhizospheres from Saccharum spontaneum L. in three post-mining sites rehabilitated in 2015, 2017, and 2019 were collected and analyzed. X-ray diffraction (XRD) identified iron oxyhydroxides, silicates, and clays as major soil components. Based on the pollution load index and contamination degree, the 2015A and 2015B sites were classified as “pristine” and had a “low degree of pollution”, while the remaining sites (2017A, 2017B, 2019A, and 2019B) were considered “moderately contaminated” with nickel, chromium, cobalt, lead, zinc, and copper. An analysis of the bacterial community composition revealed that the phyla Proteobacteria and Actinobacteria, along with the genus Ralstonia, were the most abundant groups across both control and rehabilitated sites. Our results showed that the soil pH and organic matter contents were strongly linked to specific bacterial community composition. These taxa have potential for inoculation in nickel-laterite soils to promote the growth of hyperaccumulator plants. Our results also showed a significant correlation between the structure of the bacterial communities and nickel, chromium, and manganese soil contents, but not with rehabilitation time. Furthermore, we identified the genera Diaphorobacter as potential bioindicators because they are sensitive to nickel and chromium. This study provides valuable baseline data on heavy metal pollution and microbial diversity in a rehabilitated Ni-laterite mine site. Full article

The iron and steel industry is one of the main industrial contributors to air pollution. The aim of our study is to analyze modern studies on air pollution by the iron and steel industry, as a result of which the geography and research directions and the degree of development of current issues will be assessed, and the most cited articles and journals will be identified. A review of contemporary research (2018–2024) was conducted on the basis of articles with a digital object identifier (DOI) using machine learning methodologies (VOSviewer software version 1.6.20). The number of articles selected was 80. The heat map of study density clearly showed that the geographic distribution of studies was extremely uneven. A total of 65% of the studies were conducted in China, 9% in Nigeria, 6% in Russia, 3% in Poland, and 3% in Turkey. The remaining 14% of articles represent a series of single studies conducted in 11 countries. The revealed geographical imbalance between countries with developed production and the number of studies conducted in them shows a significant shortcoming in monitoring research. Most of the studies (20%) were devoted to the assessment of multicomponent emissions. A special place among them was occupied by the inventory of emissions using various methods. The next main directions in terms of the number of articles were aimed at studying the toxic metal emissions (19%), at the analysis of organic emissions (19%), at the modeling and forecasting of emissions (18%), and at particulate matter studies (15%). The main features of the articles for each direction are briefly noted. Citation analysis made it possible to compile a rating of articles of greatest scientific interest and the most authoritative journals. Citation network analysis revealed important insights into the structure of scientific communication in the monitoring of atmospheric pollution from the iron and steel industry. The results of our review will contribute to the consolidation of scientists, the identification of gaps in scientific knowledge, and the improvement of environmental policy and technological solutions. Full article

In petroleum production processes, the water used to maintain formation pressure often plays a key role and is pumped into injection wells to compensate for the pressure drop in the formation after oil extraction and displacement of the remaining petroleum products to the development well. The source of such water may be produced by waters extracted together with oil and previously purified from mechanical impurities and hydrocarbons. However, a significant disadvantage of using such water is the presence of pollutants such as sulphur-reducing bacteria (SRB) and a high content of hydrogen sulfide. Traditional purification methods against them show low efficiency. Hydrogen sulfide and SRB are not only a threat of environmental pollution, but they also pose a high risk to pipelines in the petroleum industry due to an increase in the rate of metal corrosion. In this paper, formation water was treated with a field deployment flow-mode plasma discharge unit. A significant decrease in the growth rate of SRB in treated water was achieved. Bacterial growth was suppressed for up to 14 days after three treatment cycles of treatment. The hydrogen sulfide content was reduced by 33% after one cycle of plasma discharge water treatment. Full article