High Concentrations Of Heavy Metals Research Articles

Methane oxidation coupling with heavy metal and microplastic transformations for biochar-mediated landfill cover soil

The impact of co-occurring heavy metal (HM) and microplastic (MP) pollution on methane (CH4) oxidation by methanotrophs (MOB) in landfill cover soil (LCS) and the role of biochar in mediating these collaborative transformations remains unclear. This study conducted batch-scale experiments using LCS treated with individual or combined HMs and MPs, with or without biochar amendment. Differentiation in methanotrophic activities, HM transformations, MP aging, soil properties, microbial communities, and functional genes across the groups were analyzed. Biochar proved essential in sustaining efficient CH4 oxidation under HM and MP stress, mainly by diversifying MOB, and enhancing polysaccharide secretion to mitigate environmental stress. While low levels of HMs slightly inhibited CH4 oxidation, high HM concentration enhanced methanotrophic activities by promoting electron transfer process. MPs consistently stimulated CH4 oxidation, exerting a stronger influence than HMs. Notably, the simultaneous presence of low levels of HMs and MPs synergistically boosted CH4 oxidation, linked to distinct microbial evolution and adaptation. Methanotrophic activities were demonstrated to affect the fate of HMs and MPs. Complete passivation of Cu was readily achieved, whereas Zn stabilization was negatively influenced by biochar and MPs. The aging of MPs was also partially suppressed by biochar and HM adsorption.

Exploring mercury detoxification in fish: The role of selenium from tuna byproduct diets for sustainable aquaculture

Exposure to mercury (Hg) through fish consumption poses significant environmental and public health risks, given its status as one of the top ten hazardous chemicals. Aquaculture is expanding, driving a surge in demand for sustainable aquafeeds. Tuna byproducts, which are rich in protein, offer potential for aquafeed production, yet their use is challenged by the high content of heavy metals, particularly Hg. However, these byproducts also contain elevated levels of selenium (Se), which may counteract Hg adverse effects. This study examines the fate of dietary Hg and Se in an aquaculture model fish. Biomolecular speciation analyses through hyphenated analytical approaches were conducted on the water-soluble protein fraction of key organs of juvenile rainbow trout (Oncorhynchus mykiss) exposed to various combinations of Hg and Se species, including diets containing tuna byproducts, over a six-month period. The findings shed light on the dynamics of Hg and Se compounds in fish revealing potential Hg detoxification mechanisms through complexation with Hg-biomolecules, such as cysteine, glutathione, and metallothionein. Furthermore, the trophic transfer of selenoneine is demonstrated, revealing novel opportunities for sustainable aquafeed production. Understanding the interactions between Hg and Se in aquaculture systems is crucial for optimizing feed formulations and mitigating environmental risks. This research contributes to the broader goal of advancing sustainable practices in aquaculture while addressing food security challenges.

Sequential carbonization of pig manure biogas residue into engineered biochar for diethyl phthalate removal toward environmental sustainability

Manure biogas residue has attracted increasing attention in waste recycling but faces substantial challenges because of its low carbon content, high ash content, and high heavy metal content. A novel sequential carbonization approach was proposed for recycling biogas residue; this approach consisted of pre-pyrolysis, activation with Ca(OH)2, and then activation with KOH. Pig manure-derived biogas residue was upcycled into engineered biochar (EB) with a high yield (26 %) and showed excellent performance in removing a typical plasticizer, diethyl phthalate (DEP). The proportion of carbon content greatly increased from 18 % (biogas residue) to 67 % (EB); however, the ash content decreased from 50 % (biogas residue) to 24 % (EB). The concentration of heavy metals decreased, and Zn had the largest decrease from 713 mg kg−1 to 61 mg kg−1 (p < 0.001). The sorption of DEP onto EB was rapid and reached equilibrium within 20 h. The developed specific surface area of EB was 1247 m2/g and provided abundant sorption sites for DEP; additionally, the sorption quantity reached 309 mg/g. The sorption capacity was dominated by surface adsorption. The oxygen-containing functional groups, graphene structure, porous structure, and hydrophobicity of EB contributed to the pore filling, hydrogen bonding, π–π stacking, and partitioning processes. Furthermore, the EB showed excellent practical application potential and great cycling stability. A sequential carbonization strategy was proposed to upcycle manure biogas residue into the EB for DEP removal; moreover, this strategy can aid in the attainment of environmental sustainability, including sustainable waste management and environmental pollution mitigation.

Investigation of mercury contamination in lipstick sold in the Saudi market and the potential health risk

Background: Environmental contamination is a significant global health issue, with cosmetics and pharmaceuticals being major polluters. High concentrations of heavy metals, such as Hg, have been found to have toxic effects and may pose a threat to human health. This study aimed to determine the concentration of mercury (Hg) in lipsticks available in the Saudi Arabia market. Methods: In this study, 12 lipstick samples from three colors were analyzed using inductively coupled plasma optical emission spectrometry (ICP-OES) to measure the content of Hg. Results: The concentration range of Hg was 0.004–0.296 ppm. Moreover, the systemic exposure dosage of mercury in the lipstick samples examined in this study ranged from 5.01 × 10−8 to 1.43 × 10−6 μg/kg bw/day, while the range of the margin of safety was from 7.3 × 109 to 2.2 × 108. Discussion: The Hg concentration in all analyzed samples was less than 0.50 and 1 ppm, which indicated that the Hg level was within acceptable limits according to Saudi Standards, Metrology and Quality Organisation (SASO) and the United States Food and Drug Administration (US FDA), respectively. On the other hand, the calculated margin of safety values for mercury exceeded the safe standard established by the WHO. The results derived from using hazard quotient (HQ) indices depict the potential carcinogenic health risk posed to consumers who employ red-colored lipsticks.

The involvement of cyclotides in the heavy metal tolerance of Viola spp.

The Violaceae family is rich in metal-tolerant species and species producing cyclic peptides (cyclotides) that are linked to the resistance to biotic factors. Plants that inhabit areas polluted with heavy metals have developed various mechanisms of tolerance. To test the role of cyclotides in protection against abiotic factors, including heavy metals, cell suspension cultures of Viola species/genotypes (V. lutea ssp. westfalica, V. tricolor, V. arvensis, and V. uliginosa), representing different levels of tolerance to heavy metals (from the most tolerant-MET to the least tolerant populations/species-NMET), were used. The relative abundances of the cyclotides in the control, untreated cell suspensions of all the selected species/genotypes, and cells treated with Zn or Pb (200 µM or 2000 µM) for 24 h or 72 h were determined via MALDI-MS. Transmission electron microscopy with X-ray microanalysis was used to detect putative co-localization of the cyclotides with Zn or Pb in the cells of V. tricolor treated with the highest concentration of heavy metals for 72 h. Cyclotide biosynthesis was dependent on the type of heavy metal and its concentration, time of treatment, plant species, and population type (MET vs. NMET). It was positively correlated with the level of tolerance of particular Viola species. The increased production of cyclotides was observed in the cells of metallophyte species, mostly in Zn-treated cells. The nonmetallophyte—V. uliginosa presented a decrease in the production of cyclotides independent of the dose and duration of the metal treatment. Cyclotides co-localized with Pb more evidently than with Zn, suggesting that cyclotides have heavy metal affinity. V. lutea ssp. westfalica transcriptome mining yielded 100 cyclotide sequences, 16 known and 84 novel named viwe 1–84. These findings support the hypothesis that cyclotides are involved in certain mechanisms of plant tolerance to heavy metals.

Research Progress on the Physiological Mechanism by Which Selenium Alleviates Heavy Metal Stress in Plants: A Review

Human activities, such as mining, industrialization, industrial waste emissions, and agricultural practices, have caused heavy metals to become widespread and excessively accumulated in soil. The high concentrations of heavy metals in soil can be toxic to plants, severely affecting crop yield and quality. Moreover, these heavy metals can also enter the food chain, affecting animals and humans and leading to various serious illnesses. Selenium (Se) is not only an essential element for animals and humans but is also beneficial for plants, as it promotes their ability to respond actively to biotic and abiotic stresses. The global issue of Se deficiency in diets has made plants the primary source for human Se supplementation. This paper comprehensively reviews the effects of heavy metal stress on plant growth and development, physiological responses of plants to such stress, and the intracellular transport processes of heavy metals within plants. It particularly focuses on the mechanisms by which Se alleviates heavy metal stress in plants. Additionally, the study delves into how Se significantly enhances plant tolerance mechanisms against typical heavy metals, such as cadmium (Cd), lead (Pb), and mercury (Hg). This integrative research not only expands the boundaries of research in the field of plant heavy metal stress and Se application but also provides new perspectives and solutions for understanding and addressing complex environmental heavy metal pollution issues. By integrating these aspects, this paper not only fills existing gaps in the literature but also offers comprehensive scientific basis and strategic recommendations for environmental protection and sustainable agriculture development.

Staged separation and recovery of As, Pb, Bi, and Zn from lead smelting dusts

The lead smelting dust is extensively produced in the lead smelting process. It poses a huge threat to environmental safety if not properly disposed, because of its high contents of heavy metals. Wherever, from another point of view, it is a high-valued resource for heavy metals. This study proposed an efficient approach to gradually separate and recycle As, Pb, Bi, and Zn from it. FeS2 was firstly used as a reductant for the As separation and recovery, via which As2O5, BiAsO4, and Pb3(AsO4)2 from the dust were reduced to volatile As2O3&As2S3 and then separated. Moreover, Pb3(AsO4)2 and PbSO4 could be sulfurized to PbS, decreasing the formation of PbO·PbSO4 and then the sintering of the residue. The As volatilization was accelerated and achieved 95.4 %. Pb, Zn, and Bi retained in the residue in the sulfur compounds of PbS, PbSO4, ZnS, and Bi2S3. In the followed smelting reduction, Na2CO3 was used as an additive to promote these sulfur compounds conversion, reduction and recycle. The recovery rates of Pb, Bi, and Zn achieved up to 96.5 %, 95.9 %, and 94.3 % respectively. While, with an excess Na2CO3 in the presence of 7.50 % coke, a sodium matte named Na-Pb-Bi-S was formed, decreasing the metals reduction and recycling. This study provided an efficient method to separate and recover As, Pb, Zn, and Bi gradually from solid wastes.

Heavy Metal Exposure-Mediated Dysregulation of Sphingolipid Metabolism.

Exposure to heavy metals (HMs) is often associated with inflammation and cell death, exacerbating respiratory diseases including asthma. Most inhaled particulate HM exposures result in the deposition of HM-bound fine particulate matter, PM2.5, in pulmonary cell populations. While localized high concentrations of HMs may be a causative factor, existing studies have mostly evaluated the effects of systemic or low-dose chronic HM exposures. This report investigates the impact of local high concentrations of specific HMs (NaAsO2, MnCl2, and CdCl2) on sphingolipid homeostasis and oxidative stress, as both play a role in mediating responses to HM exposure and have been implicated in asthma. Utilizing an in vitro model system and three-dimensional ex vivo human tissue models, we evaluated the expression of enzymatic regulators of the salvage, recycling, and de novo synthesis pathways of sphingolipid metabolism, and observed differential modulation in these enzymes between HM exposures. Sphingolipidomic analyses of specific HM-exposed cells showed increased levels of anti-apoptotic sphingolipids and reduced pro-apoptotic sphingolipids, suggesting activation of the salvage and de novo synthesis pathways. Differential sphingolipid regulation was observed within HM-exposed lung tissues, with CdCl2 exposure and NaAsO2 exposure activating the salvage and de novo synthesis pathway, respectively. Additionally, using spatial transcriptomics and quantitative real-time PCR, we identified HM exposure-induced transcriptomic signatures of oxidative stress in epithelial cells and human lung tissues.

Newly Identified Melanistic and Rostrate form of Monetaria caputdraconis from Easter Island

A newly discovered population of Monetaria caputdraconis has been identified on Easter Island. This new population has a high occurrence of specimens expressing morphologythat appear both melanistic and rostrate, and is named herein Monetaria caputdraconis formdarkini. It is suggested that the geology of the island, which comprises Roiho basalt containing olivine tholeiite with relatively high concentrations of heavy metals, may contribute to this unique morphology

The impact of different types of wastewaters on electrode passivation in electrical coagulation systems

Water is a crucial part of the production process when the company uses reaction or cooling water to create customized goods. It is therefore expected that some of the chemical components from the boats will be present in the water. Ensuring the safety of discharged water into rivers for human consumption is vital, as water supplies are limited and subject to cycles. Industrial wastewater sometimes includes higher concentrations of heavy metals like copper, lead, and other pollutants, whereas domestic wastewater usually has higher amounts of nitrogen and phosphate. Our previous strategy to dealing with these components involved adding chemicals and filtering them, but this method introduced additional compounds into the water sample. Science and technology have advanced alongside sewage treatment techniques. In this paper, we investigated the effects of electrical coagulation on water treatment in a rapidly industrializing environment. The effectiveness of electrical coagulation has been extensively studied, but less is known about how it impacts aquatic habitats and machinery. This work addresses the issue of equipment passivation in a number of potential methods that are related to an improvement in water quality.

Ladle slag–based binder for the solidification/stabilization of heavy-metal-rich industrial waste

Heavy metal pollution from industrial sources is a major environmental and health hazard on a global scale. This study introduces a solidification/stabilization method of industrial waste using a waste-based, ettringite-rich solid binder from ladle slag and gypsum for the immobilization of an industrial waste material with extremely high contents of several heavy metals. The importance of sulfate and water content on the immobilization efficiency and the use of citric acid to increase the processing time of the binder were studied. The leaching of Pb, Hg, Se, As, Cd, Cu, and Ni was measured, and X-ray powder diffraction, field-emission scanning electron microscopy, and field-emission electron probe microanalysis combined with wavelength-dispersive X-ray spectroscopy were used to analyze the structure of the hardened binder and the location of the heavy metals within. The study shows that the ladle slag/gypsum binder is suitable for the solidification/stabilization of heavy-metal-rich solid industrial waste. Hg, As, Cd, Cu, and Ni were fully immobilized in all scenarios covered in the study, whereas Pb and Se showed more complicated behaviors. The main immobilization method was encapsulation, and partial Se incorporation into ettringite was observed. The presence of citric acid increased the processing time of the binder without harming the immobilization, unless combined with low sulfate content.

Glacier mice as a temporary sink for fallout radionuclides and heavy metals on the Norwegian glacier Austerdalsbreen

Glacier mice are peculiar rolling or stationary moss balls found on the surface of some glaciers. They may harbour an ecological habitat for cold-adapted invertebrates and microorganisms, but little is known about their potential to accumulate and disseminate harmful elements and substances. In this study, we investigate the presence of fallout radionuclides (137Cs, 238Pu, 239Pu, 240Pu, 210Pb) and heavy metals (Pb, As, Hg, Cd) in glacier mice and compare the results to bryophytes from adjacent glacier ecosystems. Samples were collected at Austerdalsbreen, a Norwegian outlet glacier from Jostedalsbreen ice cap.Maximum activity concentrations for bryophytes are 552 ± 12 Bq kg−1 for 137Cs, 3485 ± 138 Bq kg−1 for 210Pb, 0.0223 ± 0.065 Bq kg−1 for 238Pu and 4.34 ± 0.43 Bq kg−1 for 239+240Pu while maximum heavy metals concentrations are 70.5 mg kg−1 for Pb, 1.0 mg kg−1 for As, 1.6 mg kg−1 for Hg and 0.13 mg kg−1 for Cd. Maximum activity concentrations in cryconite are 1973.4 ± 5.0 Bq kg−1 for 137Cs, 3632 ± 593 Bq kg−1 for 210Pb, 0.51 ± 0.11 Bq kg−1 for 238Pu and 13.1 ± 1.4 Bq kg−1 for 239+240Pu and maximum heavy metal concentrations are 50.4 mg kg−1 for Pb, 3.4 mg kg−1 for As, 1.5 mg kg−1 for Hg and 0.082 mg kg−1 for Cd. We find that glacier mice show lower activity concentrations of radionuclides compared to cryoconite. The major source of plutonium isotopes is related to global fallout, whereas detected radio-cesium may be additionally affected by post-Chernobyl fallout to an unknown extent. Comparison between glacier surface and adjacent glacial habitats shows higher concentrations of heavy metals in glacier mice on the glacier ice surface and medial moraines compared to bryophytes in the glacier forefield. Glacier mice exported from a receding glacier may affect the cycling of radioactive and metal pollutants in developing proglacial ecosystems.

Ecotoxicological and Microbiological Risk Assessment of Groundwater from Dimba Cave, Democratic Republic of the Congo.

Dimba Cave is a large array of natural galleries in limestone mountains of the Democratic Republic of the Congo that contains highly valued pre-historic archaeological artifacts. The cave attracts a high number of tourists every year and is used by local populations as a water supply source. The main objective of the research undertaken in Dimba Cave consisted of assessing the quality of water and sediments from Dimba Cave ponds through evaluating contamination by heavy metals (15 elements analyzed, including As, Cd, Pb, and Hg) and by microbial populations (including Escherichia coli and total coliforms) in order to estimate the ecotoxicological risk to humans and to non-human biota. All water samples collected in the cave ponds showed very high metal concentrations exceeding the internationally recommended limits for drinking water, particularly for Cr, Mn, As, Pb, and Hg. Most sediment samples from cave ponds also displayed high heavy metal concentrations. The calculated pollution parameters, such as the enrichment factor (EF), and ecological risk parameters, such as the ecological risk index (Eri), indicated that the sediment may be toxic to aquatic biota. Furthermore, the microbiological analysis of pond waters indicated a widespread contamination with bacteria such as Escherichia coli, Enterococcus spp., total coliforms, and Pseudomonas spp., probably from anthropogenic and/or animal sources. Therefore, the consumption of Dimba Cave water as a drinking water represents a threat to public health. Urgent management measures should be enforced to protect public health and the cave ecosystem.

Hydrothermal carbonisation of manure-derived digestates: Chemical properties and heavy metals distribution in end-products

Hydrothermal carbonisation (HTC) presents a promising method for converting high-moisture biomass into hydrochars, which can serve as valuable sources of carbon and nutrients for soil applications. However, there is a lack of comprehensive understanding regarding the characterisation and potential environmental risks of hydrochars with respect to different feedstock types and operating conditions especially when compared to those obtained from dry pyrolysis. This research aims to investigate the chemical properties and re-partitioning of Ni, Cd, Cr and Pb in the HTC-treated mono-and co-digestates derived from the anaerobic digestion of pig manure and ensiled maize. Hydrochars were produced from homogeneous digestate slurries, where manure was derived from a unique source separation facility, and maize was collected from a contaminated land, both containing potentially higher concentrations of heavy metals (HMs) compared to typical feedstock. The hypothesis states that HTC would further reduce the potential availability of these metals, enhancing the quality of the end-products as bio-based fertilisers or soil improvers. The derived hydrochars were analysed for their composition and HMs extractability. Higher yields were observed for both digestates at lower temperatures and shorter residence times, whereas the total nitrogen and carbon content showed an opposite trend. The composition of the digestates and the HTC operating parameters influenced the enrichment of nutrients and release of the HMs from the hydrochars, enabling their classification as potential solid organic fertilisers according to the Fertilising Products Regulation (EU) 2019/1009. Notably, the HTC treatment at 200–220 °C for 4 h resulted in the highest immobilization of Ni, Cd, Cr, and Pb in both digestates. This treatment strategy effectively reduced the ecological risk index of these products, thereby mitigating potential environmental impacts associated with the HMs contamination.

Geopolymer Materials from Fly Ash-A Sustainable Approach to Hazardous Waste Management.

This study explores the utilisation challenges of fly ash from municipal waste incineration, specifically focusing on ash from a dry desulphurisation plant (DDS), which is categorised as hazardous due to its high heavy metal content. The ash's low silicon and calcium contents restrict its standalone utility. Laboratory investigations initially revealed that geopolymers derived solely from fly ash after flue gas treatment (FGT), in combination with coal combustion fly ash, exhibited low compressive strength (below 0.6 MPa). However, the study demonstrated significant improvements by modifying the FGT ash through water leaching. This process enhanced its performance when mixed with high-silica and -aluminium fly ash, resulting in geopolymers achieving compressive strengths of up to 18 MPa. Comparable strength outcomes were observed when the modified ash was blended with commercial cement. Leachability tests conducted for heavy metals (HMs) such as copper, zinc, lead, cadmium, and nickel indicated that their concentrations fell below the regulatory limits for landfill disposal: 2, 4, 0.5, 0.04, and 0.4 mg/kg, respectively. These results underscore the effectiveness of water-washing FGT ash in conjunction with other materials for producing geopolymers, contributing to sustainable waste management practices.

Multi-biomarker approach reveals the effects of heavy metal bioaccumulation in the foundation species Prosopis laevigata (Fabaceae).

Mining is a major economic activity in many developing countries. However, it disturbs the environment, producing enormous quantities of waste, known as mine tailings, which can have deleterious environmental impact, due to their high heavy metals (HM) content. Often, foundation species that establish on mine tailings are good candidates to study the effects of HM bioaccumulation at different levels of biological organization. Prosopis laevigata is considered a HM hyperaccumulator which presents attributes of a foundation species (FS) and establishes naturally on mine tailings. We evaluated the bioaccumulation of Cu, Pb, and Zn in P. laevigata foliar tissue, the leaf micro- and macro-morphological characters, DNA damage, and population genetic effects. In total, 80 P. laevigata individuals (20/site) belonging to four populations: The individuals from both sites (exposed and reference) bioaccumulated HMs (Pb > Cu > Zn). However, in the exposed individuals, Pb and Cu bioaccumulation was significantly higher. Also, a significant effect of macro- and micro-morphological characters was registered, showing significantly lower values in individuals from the exposed sites. In addition, we found significant differences in genotoxic damage in P. laevigata individuals, between the exposed and reference sites. In contrast, for the micro-morphological characters, none of the analyzed metals had any influence. P. laevigata did not show significant differences in the genetic structure and diversity between exposed and reference populations. However, four haplotypes and four private alleles were found in the exposed populations. Since P. laevigata is a species that establishes naturally in polluted sites and bioaccumulates HM in its foliar tissues, the resulting genetic, individual and population effects have not been severe enough to show detrimental effects; hence, P. laevigata can be a useful tool in phytoremediation strategies for soils polluted with Pb and Cu, maintaining its important ecological functions.

Determination of Heavy Metals Concentrations in Local and Imported Chicken Meat Found in Hilla Province Markets

This study was carried out in Hilla province, the chicken samples were collected of both local and imported chicken, the concentration of eight heavy metals (iron, copper, zinc, nickel, manganese, cadmium, lead and chromium) were measured in all samples in order to find if the concentrations of these metals were within or exceeded the permissible limit, The samples were analysis by used the Atomic Absorption spectrophotometer. The result show that for iron, copper, Zinc, nickel, manganese, cadmium, lead and chromium the concentrations were ranged from 70.66 - 81.33 ppm, 0.34 - 0.71 ppm, 6.06 - 8.21 ppm , 6.13 - 8.02 ppm, 0.213- 0.51ppm, 0.276 - 0.833 ppm, 0.733 -1.39 ppm and 0.37 - 0.716 ppm respictively . Generally, the highest heavy metal concentration was recorded in Iraqi house breading chicken. While the lowest concentrations of almost all measured heavy metal in Iraqi Farm breed in chickens.

Preparation and Screening of SRB Gel Particles Used for Deep Purification of Acid Mine Drainage.

The progressive decline of the coal industry necessitates the development of effective treatment solutions for acid mine drainage (AMD), which is characterized by high acidity and elevated concentrations of heavy metals. This study proposes an innovative approach leveraging sulfate-reducing bacteria (SRB) acclimated to contaminated anaerobic environments. The research focused on elucidating the physiological characteristics and optimal growth conditions of SRB, particularly in relation to the pH level and temperature. The experimental findings reveal that the SRB exhibited a sulfate removal rate of 88.86% at an optimal temperature of 30 °C. Additionally, SRB gel particles were formulated using sodium alginate (SA) and carboxymethyl cellulose (CMC), and their performance was assessed under specific conditions (pH = 6, C/S = 1.5, T = 30 °C, CMC = 4.5%, BSNa = 0.4 mol/L, and cross-linking time = 9 h). Under these conditions, the SRB gel particles demonstrated an enhanced sulfate removal efficiency of 91.6%. Thermal analysis via differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) provided further insights into the stability and properties of the SRB gel spheres. The findings underscore the potential of SRB-based bioremediation as a sustainable and efficient method for AMD treatment, offering a novel and environmentally friendly solution to mitigating the adverse effects of environmental contamination.

The influence of the pre-addition of semi-dry and dry slaked lime during the purification of flue gas on the subsequent chelation and solidification treatment of MSWI fly ash

Incineration is a main way to dispose the municipal solid waste (MSW) in China, but municipal solid waste incineration (MSWI) fly ash will negatively impact the environment and human health as containing high content of heavy metals. This study aimed to investigate the influence of the pre-addition of dry/semi-dry slaked lime during the purification of flue gas on the subsequent chelation and solidification treatment of fly ash. This study has found that semi-dry slaked lime had more effect on the solidification rate of heavy metals in MSWI fly ash compared to the pre-addition of the dry slaked lime. As the dosage of semi-dry slaked lime increased, the solidification rate of Zn and Ba increased to 100 %, while the solidification rate of Cr decreased to as low as 0 %. However, the effect of the dosage of semi-dry slaked lime on the other heavy metals (Cu, Pb, Cd, Ni) showed a complex trend. This study underscores the importance of the pre-addition of slaked lime during the purification of flue gas in influencing subsequent chelation and solidification treatment of MSWI fly ash. It provides valuable insights into optimizing lime dosage to enhance heavy metal stabilization, contributing to more effective and sustainable waste management practices.

Use of Forest Trees in the Treatment of Polluted Soil by Heavy Metals: A Mini Review

Human activities lead to a large accumulation of heavy metals in the soil which comes from industrial activities such as mining smelting refining manufacturing processes and waste resulting from excessive use of chemical fertilizer and vehicle exhausts. So, soil pollutants especially with heavy metals can be treated using different types of plants; such as forest trees and grasses. These plants can tolerate soil pollutants at high concentrations in their biological tissue, and treat pollutants by absorbing and accumulating heavy metals in their living tissues. Therefore, in this article, we reviewed several forest tree species, that showed high resistance in the absorption and accumulation of heavy metals, such as genus Eucalyptus, Acacia, Salix, Populus, Tamarix, Melia, Dalbergia, Leucaena, Acer, Fraxinus, and Thuja. It has been noted that planting forest trees with high biomass that resist high concentrations of heavy metals in soil, works to rid the soil of these pollutants. This is the latest and best technology for treating soil pollution. In particular, it is unique from its counterparts in its environmental friendliness, economic benefits, and other returns resulting from plant cultivation. Therefore, applying phytoremediation techniques that benefit is the best and safest for the environment and living organisms.