High Heavy Metal Research Articles

CERCETĂRI PRIVIND ACUMULAREA ŞI TRANSFERUL METALELOR GRELE DIN SOL ÎN FRUCTE DE PĂDURE (AFINE - Vaccinium myrtillus L.ȘI ZMEURĂ - Rubus idaeus)

The current study has investigated the accumulation and transfer coefficient for three heavy metals (Cu, Pb, Zn) found in the contaminated soil with three concentrations (c1=1.5%, c2=3.0%, c3=4.5%, c4=6.0%), obtained by mixing the three metals, in blueberry and raspberry fruits. The pots in which the shrubs were planted were loaded with fertile soil which was mixed and homogenized in turn with each of the three solutions of different concentrations. The highest accumulation in blueberry fruits was recorded for zinc, then copper and the lowest for lead, while for raspberries the highest results was recorded for zinc, then lead and the lowest for copper. The findings are valid for all four concentrations used. The transfer coefficient decreases as the concentration of heavy metals increases, thus for high heavy metal concentrations, the values of the transfer coefficient are very low, and for small heavy metal concentrations in the soil, the values for the transfer coefficient are higher. From the assessment of accumulation and transfer of heavy metals to berries (blueberries and raspberry) grown in the contaminated soil, it was concluded that all concentrations of the copper, lead and zinc mix have shown a low risk for human consumption.

Detection of Physiochemical and Some Heavy Metals in Potato and Corn Chips Products in Iraqi Markets with their Daily Intake

The study of heavy metals in the human diet is important due to their dual effects as either essential or toxic to the human body. In this study, we determined the concentration of selected heavy metals in common potato and corn chips brands in Iraq markets. Ten common brands were selected and analyzed for their concentrations of the studied heavy metals by ICP-MS. The results shown that the average heavy metals level in potato and corn chips in (mg kg-1±SD) were 2.68±0.67 and 2.96±3.00 for Mn, 4.64±1.99 and 5.82±5.45 for Fe, 0.29±0.33 and 1.36±0.95 for Cu and 2.84±1.26 and 6.26±1.67 for Zn respectively. Corn chips were found to contain higher heavy metals than potato chips. The daily consumption of heavy metals from potato and corn chips (20 g daily intake) is lower than the recommended level set by the World Health Organization and Food and Agriculture Organization. Also, Daily intake of these metals is lower than the oral suggested amount and the upper tolerable daily intake set by the US. The contamination risk for the Iraqi population especially children from heavy metals exposure by this study performs to be non-significant, emphasizing the need to conduct more studies and confirm examining of heavy metals in foodstuffs especially chips brands.

Cadmium Uptake From Soil by Ornamental Metallophytes: A Meta-analytical Approach.

Soil pollution by cadmium (Cd) is a serious issue worldwide affecting environmental and human health. Conventional chemical and physical methods of treating contaminated soil are costly, time-consuming, and less effective. Phytoremediation using ornamental plants is a safe and effective method for the treatment of heavy metal-polluted soil due to their rapid growth and accumulation of biomass, high heavy metal tolerance, and non-edible nature. The present study is the first attempt for the meta-analysis of existing literature on Cd accumulation and translocation by ornamental plants. The uptake and transfer capacity of ornamental plants was measured using the bio-concentration factor (BCF) and translocation factor (TF). The results indicate that ornamental plants have varying Cd-absorption capacities. Among the 49 plant species identified from 31 articles, Helianthus annuus (BCF = 5.785), Impatiens glandulifera (BCF = 4.722), and Crassocephalum crepidioides (BCF = 3.623) represented higher accumulation capacity, whereas Rorippa globosa (TF = 1.653) and Sedum spectabile Boreau (TF = 1.579) represented significantly higher translocation capacity for Cd. The contribution of various environmental factors in influencing BCF was obtained through multiple linear regression analysis. Results showed that soil pH was the major factor influencing the BCF. To further explain the influence of four main factors that are soil pH, soil organic matter (SOM), cation exchange capacity (CEC), and soil Cd concentration on the accumulation efficiency of ornamental plants, a subgroup meta-analysis was performed. Results of the subgroup meta-analysis revealed that the BCF is negatively correlated with the soil pH and SOM, while the estimated limit of soil Cd concentration for growing ornamental plants was up to 50 mg/kg. Results of this study indicate that choosing a native hyperaccumulator is not the sole key to the success of a phytoremediation design, rather the conditions of the pedosphere will determine the regulating factor for efficient removal. In order to overcome the issue of recirculation and gradual release in the rhizosphere, it is important to match the type of hyperaccumulators to the soil environment (pH, CEC, SOM, etc.) to achieve maximum translocation and desired removal. This study will help researchers to pair the right plant with environmental conditions and customize more efficient phytoremediation systems.

Occurrence and Distribution of Heavy Metals in Mining Degraded Soil and Medicinal Plants: A Case Study of Pb/Zn Sulfide Terrain Northern Areas, Pakistan

Mining activities have serious environmental impacts, thus releasing heavy metals (HMs) such as cadmium (Cd), lead (Pb), chromium (Cr), zinc (Zn) and nickel (Ni) into the surrounding environment. The current paper investigated the impacts of mining activities of Pb-Zn sulfide on soil and medicinal plants. Hence, soil samples (n = 36) and medicinal plants (n = 36) samples were collected, acid extracted and were analyzed through Inductively Coupled Plasma Mass Spectrometry (ICP-MS) for HMs quantification. Our results showed that mineralized zones showed high HMs enrichment levels as compared to non-mineralized zones. Various Indices for HMs assessment revealed that the contaminated soil of the study area had low to extreme level. The mean concentrations of HMs in mining degraded soil and medicinal plants were significantly higher (p ≤ 0.01) and were found in order of Zn > Pb > Cr > Ni > Cd and Cr > Zn > Pb > Ni > Cd respectively. Similarly, some widely consumable medicinal plants showed good metal accumulation for Cd, Cr and Pb i.e., 3.57mg kg1, 350mg kg-1 and 335mg kg-1 in C. sativa, while 5.9mg kg-1, 276.9mg kg-1 and 188.7mg kg-1 in R. hestatus respectively. Hence, the present study recommended that medicinal plants grown in mining areas should be analyzed for HMs concentration before consumption.

A Properties of Municipal Solid Waste Incineration Fly Ash (IFA) And Cement Used in The Manufacturing of New Inventive Blended Cement

Municipal solid waste incinerator fly (IFA) ash is prone to accumulate high concentration heavy metals. Due to the increasing costs to treat remaining fly ash at the landfill, a lot of research has been done to recycle IFA. This studywas focusing on the properties of IFA and cement as main raw materials in new inventive blended cement. The properties of blended cement were also being investigated. Properties of IFA and cement were examined through several test which includes density, specific gravity, X-Ray Fluorescence (XRF), Loss of Ignition (LOI) and through Toxicity Characteristic Leaching Procedure (TCLP) test. The density test and LOI test were also being done for the blended cement. From the tests for IFA and cement, it can be found that density the density of fly ash and cementthat has been used for this study were found to be 0.76 g/cm3and 3.67 g/cm3respectively. Then, the specific gravity of fly ash and cementwere 1.69 and 2.98, accordingly. XRF results shows that both materialshave highest content of aluminium, silicaand iron, as expected. LOI of fly ash and cementwere found to be 17.33 % and 12.33 %, respectively.In terms of the leaching rates of heavy metals (Mn, Ni, Cd, Cr, Cu), only Cd leached at rate 2.39 mg/L, which is above the USEPA's regulatorylevel, 1.0 mg/L. 5 %, 10 % and 15 % of IFA was mixed with cement to produced blended cement. As the density of blended cement, it was found to be 1.12 g/cm3, 1.08 g/cm3and 1.09 g/cm3for each of 5 %, 10 % and 15 % of fly ash in blendedcement.

PHYTOEXTRACTION OF HEAVY METALS BY HERBAL PLANTS ON TECHNOGENIC SOILS

The purpose of the work is to study the specifics of the natural restoration of vegetation on highly toxic embryozems (on the example of the technogenic dump from the large chemical production «Usoliekhimprom», Irkutsk region). It was shown that organo-accumulative embryozem is the first stage of soil formation and the beginning of plant colonization. The level of technogenic soils pollution with heavy metals was assessed by a set of indicators, based on them, organo-accumulative embryozems were classified as soils with an extremely dangerous level of pollution. It was found that the first pioneers on these embryozems were 9 aboriginal species of herbaceous plants: Melilotus albus Medikus., Melilotus officinalis (L.) Pall., Trifolium hybridum L., Trifolium repens L., Trifolium pratense L., Vicia cracca L., Medicago sativa L., Sonchus arvensis L., Chamerion angustifolium (L.) Scop. A number of their unique features allow them to grow in conditions of very strong soil pollution – this is a high level heavy metals accumulation in phytomass, good adaptation of mineral nutrition to hard growing conditions, an increase in biomass during the growing season, and the absence of visual signs of damage. The obtained results give every reason to recommend these herbaceous plants for use as phytoextractors of heavy metals on technogenic dumps.

Efficient removal of heavy metals by endophytic bacteria Staphylococcus succinus H3.

Heavy metal pollution is a serious and difficult environmental problem. With increasing heavy metal content in industrial wastewater, an environmentally friendly and efficient treatment method must be identified. Considering the ability of endophytic bacteria to adsorb metal ions, this paper explored the heavy metal resistance, adsorption, and adsorption mechanisms and performance of S. succinus H3, an endophytic bacterium. S. succinus H3 exhibited metal resistance at 4 mM Cu2+ and 5 mM Mg2+. The adsorption rate of Cu2+ and Mg2+ ions by the live/dead strain was approximately 70%, and the adsorption capacity was positively correlated with the metal ion concentration. The kinetics and isothermal models were used to study the process of S. succinus H3 adsorption on Cu2+. It exhibits a good correlation with the Freundlich isothermal model. The N-H group, protein C=O group, polysaccharide C-O group, O-H group and some lipids are the main functional groups in the cell wall. S. succinus H3 may bond with the amine group to adsorb Mg2+ through complexation/coordination and may form a copper complex after adsorbing Cu2+. S. succinus H3 has a live adsorption rate of 15% in eight mixed metal ion systems at a 50 mg/L concentration. The study results can lay a foundation for expanding the bacterial resource pool of pollutant treatment and improving the efficiency for sewage treatment. The high heavy metal adsorption capacity of microorganisms has a decisive role in industrial wastewater treatment by microorganisms. Such microorganisms with high metal resistance and adsorption capacity to heavy metals can thrive in industrial wastewater, remove heavy metals efficiently, and greatly improve the efficiency of wastewater treatment. The study results can lay a theoretical foundation for the use of S. succinus H3 to biologically treat heavy metal wastewater in the future.

Aeromonas sobria as a potential candidate for bioremediation of heavy metal from contaminated environments.

The uncontrolled discharge of industrial wastes causes the accumulation of high heavy metal concentrations in soil and water, leading to many health issues. In the present study, a Gram-negative Aeromonas sobria was isolated from heavily contaminated soil in the Tanjaro area, southwest of Sulaymaniyah city in the Kurdistan Region of Iraq; then, we assessed its ability to uptake heavy metals. A. sobria was molecularly identified based on the partial amplification of 16S rRNA using novel primers. The sequence was aligned with 33 strains to analyze phylogenetic relationships by maximum likelihood. Based on maximum tolerance concentration (MTC), A. sobria could withstand Zn, Cu, and Ni at concentrations of 5, 6, and 8mM, respectively. ICP-OES data confirmed that A. sobria reduced 54.89% (0.549mM) of the Cu, 62.33% (0.623mM) of the Ni, and 36.41% (0.364mM) of the Zn after 72h in the culture medium. Transmission electron microscopy (TEM) showed that A. sobria accumulated both Cu and Ni, whereas biosorption was suggested for the Zn. These findings suggest that metal-resistant A. sobria could be a promising candidate for heavy metal bioremediation in polluted areas. However, more broadly, research is required to assess the feasibility of exploiting A. sobria in situ.

Soil heavy metal contamination in the vicinity of the abandoned Zeïda mine in the Upper Moulouya Basin, Morocco. Implications for airborne dust pollution under semi-arid climatic conditions

For thirteen years, the Zeïda mine was one of Morocco's biggest lead reserves. The mining activities produced a huge volume of waste stored as tailings and subjected to meteoric agents. To better understand the impact of the past mining activity on the soil ecosystem in the vicinity of the abandoned mine, several physical and chemical analysis were done to identify the level of soil contamination. A total of 27 surface soil samples were collected from a depth of about 0–20 cm from crop areas and analysed for Pb, Zn, Cu, Co, Cd, and As total concentrations (aqua regia extraction) using the ICP-MS method. Results showed that soils have high to medium levels of metal concentrations, especially close to the tailings, compared to the non-contaminated soil sample taken as a geochemical background reference. Analysis of physicochemical parameters (pH, electrical conductivity, total calcium, phosphorus, potassium, and organic matter) has shown high alkalinity levels related to carbonates, varying organic matter content, and electrical conductivity values ranging from 4.12 to 1466 μS/cm. Most of the studied soils share the same mineralogical composition that includes: carbonates (Calcite and Dolomite), Quartz, Orthoclase, and Muscovite. Lead mineral phases (cerussite and wulfenite) have been found in 3 samples (ZAM17, ZAM18, and ZAM21). The Illite and the Kaolinite are the main clay minerals. Descriptive and multivariate statistics were carried out to investigate the distribution of the studied metals. Comparing the obtained results with International Standard Limits (ISL), soils especially those close to the mine tailings show high heavy metals content. Pb, Zn, Cu, As, and Cd contents in Zeïda soils are usually linked to anthropogenic origins. Results have shown correlation values between As, Cu, and Cd and Pb and Zn indicating that they come from the same origin and react similarly throughout transport.

Cytobacillus pseudoceanisediminis sp. nov., A Novel Facultative Methylotrophic Bacterium with High Heavy Metal Resistance Isolated from the Deep Underground Saline Spring

In this study, we present the characterization of the BNO1T bacterial strain isolated from the deep subsurface saline spring at the Baksan Neutrino Observatory INR RAS (Kabardino-Balkaria, Russia). The complete genome sequence of the strain BNO1T is 5,347,902bp, with a GC content 41 and 49%. The cell wall peptidoglycan contains meso-diaminopimelic acid. The major isoprenoid quinone is MK-7 and the polar lipids are diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine. The major fatty acids are anteiso-C15:0 (23.34%), iso-C15:0 (20.10%), C16:0 (11.96%), iso-C16:0 (10.88%), and anteiso-C17:0 (10.79%). The 16S rRNA gene sequence clearly demarcated the strain as belonging to Cytobacillus genera. Based on the phylogenetic analysis, ANI (average nucleotide identity) and dDDH (digital DNA-DNA hybridization) assessments we propose to assign the strain BNO1T and other related strains to new species and to name it Cytobacillus pseudoceanisediminis sp. nov. (The values of ANI and dDDH between BNO1T and Cytobacillus oceanisediminis CGMCC 1.10115T are 80.65% and 24.7%, respectively; values of ANI and dDDH between BNO1T and Cytobacillus firmus NCTC 10335T are 89% and 38%, respectively). Genomic analysis of strain BNO1T revealed pathways for C1 compounds oxidation and two pathways for C1 compounds assimilation: serine and ribulose monophosphate pathways. In addition, strain BNO1T contains a plasmid (342,541bp) coding multiple genes involved in heavy metal ion balance. Moreover, heavy metal toxicity testing confirmed the high potential of the strain BNO1T as a source of metal resistance genes and enzymes. The type strain is BNO1T (= BIM B-1921T = VKM B-3664T).

Potential utilization of mussel meals as an alternative fish feed raw material for aquaculture

Increasing the target of aquaculture production will increase the need for feed which an increase will follow in the need for fish meal. The constraint in aquaculture fish feed dependence on a fish meal import is known. In efforts to find local raw materials to reduce dependence on fish meals, one source of quality animal protein from marine resources as raw material for feed that needs to be studied and developed is mollusks or mussels. This review summarizes the use of mussel meal in aquaculture feed and is expected to provide a comprehensive overview of the existing studies’ potential on mussels meal used as a feed ingredient in fish feed. Many species of mussel have been tested for raw material in fish feed such as blue mussel (Mytilus galloprovincialis), Freshwater mussels (Anodonta anatina & Unio mancus), Mytilus edulis L and Green mussel (Perna viridis). Mussels contain high levels of nutrients and bio-actives which were utilized in the form of mussel meals for feed ingredients. The constraint mussels have high heavy metals such as Pb, Hg and Pb. The utilization of mussel meals as a source of protein feed could increase the growth of several types of cultured fish. One alternative used organic acid as a feed additive to reduce toxicity of heavy metals in fish. The conclusion is that mussel meals have the potential as raw material and an alternative protein source to reduce dependence on a fish meal in aquaculture fish feed.

Zero additional maintenance stormwater biofilters: from laboratory testing to field implementation

Abstract Stormwater biofilters are one of the most widely used nature-based solutions for urban water management. In the last 20 years, biofilters have been extensively studied for their pollutant removal performance; however, their application in the field is limited by high maintenance requirements. In this work, we propose the concept of zero additional maintenance (ZAM) biofilters as a solution to this challenge. To understand the design and operation of ZAM biofilters, a three-stage research programme was conducted to (i) examine filter media configurations that could protect against surface clogging, (ii) test the pollutant removal performance of a variety of lawn grasses, and (iii) validate the laboratory findings through field monitoring. The results showed that a protective filter media layer delayed the onset of clogging. Five lawn grasses – Kenda Kikuyu, Empire Zoysia, Santa Ana Couch, Village Green Kikuyu and Palmetto Soft Leaf Buffalo – were found to effectively reduce nitrogen concentrations and meet other local pollution reduction requirements. Monitoring of three field-scale ZAM biofilters confirmed their high nutrient and heavy metal removal performance. Overall, the findings of these three studies confirm the potential for well-designed ZAM biofilters to achieve stormwater management requirements with no additional maintenance compared with standard street landscaping.

Preparation of CMAS, LZS glass-ceramics and study of the glass ceramics anti-corrosion properties in liquid leadbismuth eutectic at 500°C

Liquid lead-bismuth eutectic (LBE) was an important candidate material for the fourth generation reactor coolant. Its high temperature and heavy metal corrosion conditions put forward higher requirements for the corrosion resistance of reactor structural materials. As a new kind of special material, glass-ceramic material, which possesses the excellent properties of glass and ceramics, has good mechanical property, wear-resisting property and corrosion resistance. The LBE corrosion behavior of glass-ceramics at typical operating temperatures of nuclear reactors was investigated. The lead bismuth corrosion test was carried out under the condition of oxygen saturation at 500°C for 500h. The lead bismuth corrosion resistance of the two glass ceramic samples in static LBE was analyzed by means of scanning electron microscope (SEM) and X-ray diffraction (XRD). After 500 h corrosion in oxygen saturated liquid LBE at 500°C, there was no obvious corrosion on the surface of CMAS glass ceramics. Its dense microstructure and stable phase composition effectively prevented the penetration of Pb and Bi elements, and had good resistance to corrosion; The surface of LZS glass ceramics was covered with a layer of loose and porous compounds, and the thickness of the corrosion zone was 10 μm, which occurred a certain degree of lead-bismuth corrosion, and its corrosion resistance was poor. The results showed that under the same corrosion conditions, no lead bismuth corrosion behavior was found on the surface of CaO-MgO-Al2O3-SiO2 (CMAS) glass-ceramic, while there was a corrosion layer with a thickness of about 10 μm on the surface of Li2O-ZnO-SiO2 (LZS) glass-ceramic, indicating that the lead bismuth corrosion resistance of CMAS glass ceramics was significantly better than that of LZS glass ceramics.

Pyrolytic synthesis of graphene-encapsulated zero-valent iron nanoparticles supported on biochar for heavy metal removal

Biochar (BC)-supported graphene-encapsulated zero-valent iron nanoparticle composites (BC-G@Fe0) are promising engineering nanocomposites that can be used to scavenge heavy metal from wastewater. However, the production of BC-G@Fe0 through carbothermal reduction using biomass as a carbon source remains challenging because of biomass pyrolysis complications. Here, we examined two carbothermal reduction routes for preparing BC-G@Fe0 using bamboo as the carbon source. The first route impregnated Fe ions (Fe2+/3+) into unpyrolyzed bamboo particles initially, followed by carbonization at 600–1000 °C. This process produced BC-G@Fe0 dominated by iron carbide (Fe3C), which led to low heavy metal removal efficiency (i.e., Cu2+ capacity of < 0.3 mmol g−1). In the second route, bamboo particles were pyrolyzed (600 °C) to biochar first, followed by impregnating this biochar with Fe ions, and then carbonized at 600–1000 °C. This route produces zero-valent iron nanoparticles, which resulted in high heavy metal removal capacities (i.e., 0.30, 1.58, and 1.91 mmol g−1 for Pb2+, Cu2+, and Ag+, respectively). The effects of carbonization temperature (600–1000 °C), iron source (i.e., iron nitrates, iron sulfate, ferrous chloride, and ferric chloride), and iron loading (5–40%) on the morphology, structure, and heavy metal ion aqueous uptake performance of BC-G@Fe0 were also investigated. This study revealed the formation mechanisms of BC-G@Fe0 through biomass carbothermal reduction, which could guide the application-oriented design of multifunctional iron-BC composites for water remediation.Graphical

Microbiome enrichment from contaminated marine sediments unveils novel bacterial strains for petroleum hydrocarbon and heavy metal bioremediation

Petroleum hydrocarbons and heavy metals are some of the most widespread contaminants affecting marine ecosystems, urgently needing effective and sustainable remediation solutions. Microbial-based bioremediation is gaining increasing interest as an effective, economically and environmentally sustainable strategy. Here, we hypothesized that the heavily polluted coastal area facing the Sarno River mouth, which discharges >3 tons of polycyclic aromatic hydrocarbons (PAHs) and ∼15 tons of heavy metals (HMs) into the sea annually, hosts unique microbiomes including marine bacteria useful for PAHs and HMs bioremediation. We thus enriched the microbiome of marine sediments, contextually selecting for HM-resistant bacteria. The enriched mixed bacterial culture was subjected to whole-DNA sequencing, metagenome-assembled-genomes (MAGs) annotation, and further sub-culturing to obtain the major bacterial species as pure strains. We obtained two novel isolates corresponding to the two most abundant MAGs (Alcanivorax xenomutans strain-SRM1 and Halomonas alkaliantarctica strain-SRM2), and tested their ability to degrade PAHs and remove HMs. Both strains exhibited high PAHs degradation (60–100%) and HMs removal (21–100%) yield, and we described in detail >60 genes in their MAGs to unveil the possible genetic basis for such abilities. Most promising yields (∼100%) were obtained towards naphthalene, pyrene and lead. We propose these novel bacterial strains and related genetic repertoire to be further exploited for effective bioremediation of marine environments contaminated with both PAHs and HMs.

Toxic effects and primary source of the aged micro-sized artificial turf fragments and rubber particles: Comparative studies on laboratory photoaging and actual field sampling

Numerous micro-sized artificial turf fragments (MATF) and rubber particles (MRP) are generated and accumulated during the use of the artificial playing field. However, attention has rarely been paid to the potential toxic effects of MATF and MRP on sportsmen. In this study, the active components and chemical composition of aged MATF and MRP derived from laboratory photoaging and actual field sampling were detected, and their effects on cytotoxicity were examined correspondingly. Laboratory photoaging significantly increased environmental persistent free radicals (EPFRs), reactive oxygen species (ROS) abundances and oxidative potential (OP) levels on MATF and MRP, but they have limited cytotoxicity. Unfortunately, in the actual field, aged MATF and MRP with higher heavy metals and polycyclic aromatic hydrocarbons (PAHs) contents exhibited markedly higher cytotoxicity with the survival rate of cells of 78 % and 26 % (p < 0.05), although they had lower EPFRs and ROS yields. Correlation analysis revealed that the cell viability was closely linked to heavy metals of MATF (p < 0.05), and to organic hydroperoxide (OHP), PAHs and heavy metals of MRP (p < 0.05). By systematically considering the above results, heavy metals and PAHs enriched on MATF and MRP from the surrounding environment played the important role in the cytotoxicity, which was different from conventional perspectives. Our findings demonstrate that MATF and MRP associated with an artificial turf field contain potent mixtures of pollutants and can, therefore, be relevant yet underestimated factors contributing to the health risks.

Bentonite as a Functional Material Enhancing Phytostabilization of Post-Industrial Contaminated Soils with Heavy Metals.

Growing awareness of the risks posed by pollution of the soil environment is leading to the development of new remediation strategies. The technique of aided phytostabilization, which involves the evaluation of new heavy-metal (HM)-immobilizing amendments, together with appropriately selected plant species, is a challenge for environmental protection and remediation of the soil environment, and seems to be promising. In this study, the suitability of bentonite for the technique of aided phytostabilization of soils contaminated with high HM concentrations was determined, using a mixture of two grass species. The HM contents in the tested plants and in the soil were determined by flame atomic absorption spectrometry. The application of bentonite had a positive effect on the biomass of the tested plants, and resulted in an increase in soil pH. The concentrations of copper, nickel, cadmium, lead and chromium were higher in the roots than in the above-ground parts of the plants, especially when bentonite was applied to the soil. The addition of the analyzed soil additive contributed significantly to a decrease in the levels of zinc, copper, cadmium and nickel in the soil at the end of the experiment. In view of the above, it can be concluded that the use of bentonite in the aided phytostabilization of soils polluted with HMs, is appropriate.

Spatial Distribution and Ecological Risk Assessment of Heavy Metals in the Sediment of a Tropical Mangrove Wetland on Hainan Island, China

Mangroves have a high ecological service value and play an important role in achieving carbon neutrality. However, mangrove wetland soil quality is constantly being affected, and the ecological services provided are gradually declining due to the threat of various pollutants, especially heavy metal pollution. Exploring the sources and ecological risks of heavy metals in mangrove sediments will be helpful in improving mangrove protection. In 2020, sediments were collected from terrestrial and aquatic areas of Dongzhai Harbor mangrove wetland in Hainan, China, and were analyzed for the concentrations of nine heavy metals (As, Cd, Cr, Cu, Hg, Pb, Ni, Zn, Co). The results showed that there were obvious spatial distributions of heavy metals in sediments. The high concentrations of heavy metals occurred largely in terrestrial areas and in 0–20 cm of the sediment surface layer. Correlation analysis and cluster analysis indicated that As mainly originated from ships and aquaculture in the harbor waters, Cd and Hg from agriculture, Cr, Cu, Ni, Zn and Co from the weathering of parent rocks, and Pb from soot emitted from metal smelters and automobile exhaust. The individual potential ecological risk index (Eir) indicated that contaminating elements were mainly Cd and Hg. The potential ecological risk index (RI) and multiple probable effect concentrations quality (mPECQs) indicated that the areas with high heavy metal concentration and the 0–20 cm range of sediment surface layer were more susceptible to heavy metal contamination. Although there were no obvious ecological risks in the area, these results could facilitate the understanding of the distribution of heavy metal pollution in mangroves and provide information to achieve sustainable development of mangroves.

Bibliometrics-Based: Trends in Phytoremediation of Potentially Toxic Elements in Soil

Land purity is of central importance to crop production. The accumulation of toxic elements in soil seriously affects crop safety. Phytoremediation is a widely used technology to clean soil pollution because of its low cost, simple implementation, and lack of secondary pollution. This investigation includes data from 4787 articles on phytoremediation of heavy metals in soil from the period between 2008 and 2021, acquired from Web of Science databases. VOSviewer was utilized to conduct statistical analysis of countries (regions), institutions, journals, cited literature, and keywords. According to the statistical data, the use of phytoremediation for cleaning soil with heavy metals has matured in recent years, showing a trend of rapid growth. There were also few collaborative studies on this subject between institutions, and China has the most extensive research in this field and, therefore, has the highest number of publications, followed by India and the United States. Publications from Pakistan are very in-depth and have the highest average number of citations. It was discovered that many researchers are now publishing articles on Environmental Science and Pollution Research. Chemosphere was revealed as the most influential journal, whereas The Journal of Hazardous Materials was the most cited. In-depth research on keywords such as metal enrichment, super-enrichment plants, phytoremediation, Cd, Pb, etc. have been conducted by many scientists; however, the research content for different countries was different. The review analysis revealed that in the future it will be possible to breed trees with high heavy metal accumulation, or to use transgenic plants and ornamental plants with high tolerance to prevent and control heavy metal pollution in soil. This paper aims to provide references for scholars in this field and to allow them quick access to summarized knowledge on this topic.

Genome-wide annotation of cuticular protein genes in non-biting midge Propsilocerus akamusi and transcriptome analysis of their response to heavy metal pollution

The insect cuticle is a sophisticated chitin-protein extracellular structure for mutable functions. The cuticles varied their structures and properties in different species, and the same species but in different regions or at different stages, to fill the requirements of different functions. The alteration of cuticle structures may also be induced due to challenges by some environmental crises, such as pollution exposures. The physical properties of the cuticle were determined by the cuticle proteins (CPs) they contain. The cuticle proteins are large protein groups in all insects, which are commonly divided into different families according to their conserved protein sequence motifs. Although Chironomidae is an abundant and universal insect in global aquatic ecosystems and a popular model for aquatic toxicology, no systematic annotation of CPs was done for any species in Chironomidae before. In this work, we annotated the CP genes of Propsilocerus akamusi, the most abundant Chironomidae species in Asia. A total of 160 CP genes were identified, and 97 of them could be well classified into eight CP families: 76 CPR genes can be subdivided into three groups (further divided into three subgroups: 36 RR1 genes, 37 RR2 genes, and 3 RR3 genes), 2 CPF genes, 3 CPLCA genes, 1 CPLCG gene, 8 CPAP genes, and 3 Tweedle genes. Additionally, we analyzed the response of P. akamusi CP genes at expression level to Cu exposure, which is related to the high heavy metal tolerance and the earlier onset of pupariation in heavy metal polluted water.