High Concentrations Of Heavy Metals Research Articles

A metallurgical approach for separation and recovery of Cu, Cr, and Ni from electroplating sludge

Electroplating sludge is extensively produced in chemical precipitation–based treatment of electroplating wastewater. It poses a huge threat to environmental safety if not properly disposed, ascribed to its high contents of heavy metals. An innovative metallurgical approach was proposed a to recycle Cu, Cr, and Ni from it. Ammonia leaching was firstly performed to selectively leach Cu from Cr, in which the Cu oxide and sulfide were leached into the leachate while the Cr oxide and Ni carbide (NiCx) retained in the residue. (NH4)2SO4 increased the Cu leaching rate via increasing the dissolved oxygen amount in the ammonia leachate and converting CuS to Cu2+. Under the optimal conditions, the leaching efficiency of Cu achieved 96.5 % while that of Cr was only 0.1 %. In the followed aluminothermic reduction, C in the leaching residue could be effectively removed via a thermal oxidation, which in turn decreased the formation of a C-containing compound of high melting point and benefited the Cr and Ni recovery. Cr and Ni from the residue were reduced and recovered in a Cr-Ni alloy, and the reductant of Al first changed to a refractory Al2O3 and then transformed to a low melting point 12CaO·7Al2O3 with the additive of CaO. This transformation increased the molten slag fluidity and promoted the separation of Cr-Ni alloy from slag. Moreover, the excessive Al increased the Cr and Ni yields and concentrated all of them to be together. Partial Al was used as reductant, and the other Al transferred into Cr-Ni alloy to decrease its melting point. Cr and Ni contents in the smelting slag could be decreased to 0.11 wt% and 0.12 wt% respectively, showing an efficient recovery. This work provided a high efficiency method to recover Cu, Cr, and Ni from waste electroplating sludge.

Arsenic biomineralization and selenium nanoparticles biosynthesis by Halomonas boliviensis strain H-10 isolated from the high-altitude Salar de Huasco salt flat (Chile)

High-altitude Andean wetlands of the Atacama Desert (Chile), including the Salar de Huasco salt flat, are unusual environments characterized by a great variability of physical-chemical conditions, often combined with a high concentration of heavy metals, including arsenic (As) and semimetals, such as selenium (Se). Microorganisms present in these environments evolved adaptative strategies to cope with environmental stresses, with biotechnological potentials. The present work investigated the natural bacterial community composition in sediments collected from the Salar de Huasco salt flat, by high-throughput Illumina sequencing, and to isolate bacterial strains able to remove As and biosynthesize Se nanoparticles (SeNPs). Dominant taxonomic groups (abundance ≥1%) were affiliated to Proteobacteria (mainly consisting in Delta- and Alfa- Gamma-proteobacteria) Bacteriodetes, Firmicutes, Acidobacteria, Spirochaetes, Deinococcus-Thermus, Gemmatimonadetes and Verrucomicrobia. Halomonas boliviensis strain H-10 was able to both biomineralize As and biosynthesise SeNPs; therefore, the characteristics of H. boliviensis strain H-10 could be used for biotechnological purposes, including As bioremediation from water and bioproduction of SeNPs.

Heavy metal contamination through wastewater irrigation on the soil and vegetables: Impact on the nutrient content and health risks ​

The use of wastewater irrigation may contribute to the metal accumulation, and reduction of nutrient level of vegetables, which would then have an adverse effect on human health. Therefore, in the present study we investigated heavy metals contamination and its impact on nutrient quality of vegetables and health risk. The study was conducted from the agricultural fields of Varanasi distinct during the period from March 2022 to June 2023 and all the laboratory work was carried in the department of Botany, Banaras Hindu University. Heavy metal concentrations in water, soil, and vegetable samples were measured using an atomic absorption spectrophotometer. The physiochemical property (pH), daily intake of metal, metal pollution index and health quotient were also calculated according to the published protocols. All heavy metal were found in higher concentrations in the wastewater irrigated soil that control site. The Lohta site had the highest concentration of heavy metals in the vegetables, followed by Dinapur, and least at control site (BHU). The highest concentration of metals (Cu, Zn, and Pb) were found in the leafy vegetables (S. oleracea and A. esculentus) whereas lowest in fruity vegetables (P. vulgaris). The rise in the Metal Pollution Index (MPI) also provided evidence for the greater metal content of these vegetables. The S. oleracea was found to have the highest DIM (0.061 g/g) while P. vulgaris had the lowest (0.007 g/g). HQ values of these metals were found greater than one ( greater than 1) for both children and adults on the ingestion of the vegetables of wastewater irrigated sites. Further, nutrient contents (Na, Mg, Ca) were also declined in the vegetables of wastewater irrigated site when compared to control site. These findings suggest that the consumption of such vegetables leads to compromised health and might be associated with severe health risk in the human.

Integrated water quality dynamics in Wadi Hanifah: Physical, chemical, and biological perspectives.

The Wadi Hanifah, a crucial aquatic ecosystem, has unfavorable consequences from natural occurrences and human activities. Recognizing the critical need for sustainable water management, this study provides an in-depth evaluation of wadi water quality. A comprehensive assessment was conducted, analyzing physical properties (temperature, pH, electrical conductivity, turbidity, color, and odor), chemical constituents (nitrogen compounds, ion concentrations, heavy metals), and bacterial diversity. The study found significant temperature fluctuations, particularly in sun-exposed or stagnant water areas. The water exhibited slight alkalinity and variable electrical conductivity and turbidity, indicating differing pollution levels. High ammonia and heavy metal concentrations suggested organic and industrial contamination, respectively. In addition, the prevalent fecal-indicator bacteria pointed to possible sewage or agricultural runoff. The research highlights the complex interplay of natural and anthropogenic factors affecting Wadi Hanifah's water quality. It emphasizes the need for location-specific environmental management strategies focusing on pollution control and conservation to safeguard the wadi's ecological health. This study provides vital insights for effective water resource management in Wadi Hanifah, serving as a model for similar ecosystems.

Isolation and identification of metallotolerant bacteria with a potential biotechnological application

Mining has led to severe environmental pollution in countries with exhaustive mining production and inadequate industrial waste regulation. Microorganisms in contaminated sites, like mine tailings, have adapted to high concentrations of heavy metals, developing the capacity of reducing or removing them from these environments. Therefore, it is essential to thoroughly characterize bacteria present in these sites to find different ways of bioremediation. In this regard, in this study, an enrichment and isolation procedure were performed to isolate bacteria with lower nutritional requirements and high tolerance to Cu(II) and Fe(II) from two Sonoran River basin mining tails. Two Staphylococcus species and a Microbacterium ginsengisoli strain were isolated and identified from the San Felipe de Jesús mining tail. Also, three strains were isolated from the Nacozari de García mining tail: Burkholderia cenocepacia, Sphingomonas sp. and Staphylococcus warneri. Significant microbiological differences were found between the two sites. All these species exhibited tolerance up to 300 mg/L for Cu (II)–Fe (II) solutions, indicating their capacity to grow in these conditions. Moreover, a consortium of isolated bacteria was immobilized in two different biocomposites and the biocomposite with larger pore size achieved greater bacterial immobilization showcasing the potential of these bacteria in biotechnological applications.

The Hypersaline Soils of the Odiel Saltmarshes Natural Area as a Source for Uncovering a New Taxon: Pseudidiomarina terrestris sp. nov.

The hypersaline soils of the Odiel Saltmarshes Natural Area are an extreme environment with high levels of some heavy metals; however, it is a relevant source of prokaryotic diversity that we aim to explore. In this study, six strains related to the halophilic genus Pseudidiomarina were isolated from this habitat. The phylogenetic study based on the 16S rRNA gene sequence and the fingerprinting analysis suggested that they constituted a single new species within the genus Pseudidiomarina. Comparative genomic analysis based on the OGRIs indices and the phylogeny inferred from the core genome were performed considering all the members of the family Idiomarinaceae. Additionally, a completed phenotypic characterization, as well as the fatty acid profile, were also carried out. Due to the characteristics of the habitat, genomic functions related to salinity and high heavy metal concentrations were studied, along with the global metabolism of the six isolates. Last, the ecological distribution of the isolates was studied in different hypersaline environments by genome recruitment. To sum up, the six strains constitute a new species within the genus Pseudidiomarina, for which the name Pseudidiomarina terrestris sp. nov. is proposed. The low abundance in all the studied hypersaline habitats indicates that it belongs to the rare biosphere in these habitats. In silico genome functional analysis suggests the presence of heavy metal transporters and pathways for nitrate reduction and nitrogen assimilation in low availability, among other metabolic traits.

Environmental surveillances of River Ogio in Edo State, Nigeria

AbstractThe study assessed the quality of water obtained from River Ogio in Etsako West Local Government Area of Edo State, Nigeria. Using standard procedures, the water samples obtained from three points of the river were analyzed for physicochemical parameters, Total heterotrophic bacteria count and Total coliform count. With exception of upstream samples, the temperature of midstream and downstream samples was lower than the range specified by the World Health Organization (WHO). The Cadmium and Arsenic levels, Total heterotrophic bacteria count and Total coliform count were above the WHO recommended limits. A total of four genera of bacteria were isolated from the water samples. Correlational analysis revealed no significant (p > 0.05) relationship between the physicochemical parameters and bacteriological properties of water obtained from River Ogio. The water obtained from River Ogio is considered unsafe for domestic consumption due to its high heavy metal content and bacteria load.

Heavy metal accumulation and health risk assessment in S. alterniflora Loisel. and native plant Suaeda salsa (L.) Pall. in Dongtai Tiaozini wetland

Coastal wetlands play an irreplaceable role in the global ecosystem, and both human activities and natural factors may lead to the contamination of Tiaozini coastal wetland with heavy metals. The study was conducted to determine the contents of eight heavy metals, Hg, Cd, Cr, As, Pb, Cu, Ni, and Zn, in the above-ground and below-ground parts of the plants and in the rhizosphere sediment, using the invasive species S. alterniflora and the native plant S. glauca, calculating the geoaccumulation index (Igeo), bioaccumulation factor, transfer factor, total target risk quotient (TTHQ), and carcinogenicity risk (CR), to analyze the transfer characteristics and potential health risks to human beings of the heavy metals in plants. This study aims to investigate the enrichment characteristics of the dominant plant, S. alterniflora Loisel. (S. alterniflora) and Suaeda salsa (L.) Pall. (S. glauca). Regarding heavy metals, eight common heavy metal elements were selected, including Hg, Cd, Cr, As, Pb, Cu, Ni, and Zn, and examined their content in surface sediments and different parts of the two plants. The transfer characteristics of heavy metals in the plant body and their potential health risks to humans were also analyzed. These findings suggest that both plants accumulate higher concentrations of heavy metals in their below-ground parts. Cr, Cu, and Zn had the highest average concentrations in both plants. Geoaccumulation index (Igeo) indicated that the Tiaozini Wetland is not yet contaminated. S. alterniflora had transfer factors less than 1 for all heavy metals, while S. glauca had transfer factors greater than 1. Both plants had a certain purifying effect on heavy metal pollution in wetlands, including Cr, Cd, Cu, and Zn. However, Cr and As in the below-ground part of S. alterniflora and Cr in the above-ground part of S. glauca had a target hazard quotient (THQ) greater than 1, indicating a potential health risk to humans, but the carcinogenic risk is low. For other heavy metals, THQ was less than 1, indicating no health risk. The total target hazard quotient (TTHQ) of different parts of both plants was greater than 1, which must be taken into account when considering their suitability as edible resources.

Assessment of the influence of the toxic effect of municipal solid waste on the ecological state of the soil

Introduction. Тhe municipal solid waste of pollution negatively affects on the state of the environment, since during their storage on the territory of landfills and the adjacent territory, accumulation of heavy metals (HM) can change the biological indicators of soil conditions: microbiological, biochemical, and phytotoxic.
 The aim of the study was to assess the influence of the toxic effect of the municipal waste landfill “Azov” in the Rostov region on the ecological state of the soil. 
 Materials and methods. It was explored the influence of municipal solid waste landfill “Azov” of the Rostov region on the ecological condition of the ordinary chernozem in the landfill and adjacent territory (140, 260, 380, and 540 m). The content of heavy metals in the soil, such as chromium (Cr), strontium (Sr), zinc (Zn), vanadium (V), copper (Cu), nickel (Ni), cobalt (Co), lead (Pb), and arsenic (As) were defined. The ecological state is assessed by sensitive and informative-biological indicators of soil pollution: the abundance of bacteria of the genus Azotobacter, the total prevalence of soil bacteria, the activity of catalase, dehydrogenases. 
 Results. Soils were found to contaminate with arsenic by MAC / TAC (exceeding the MAC by 7 times at the landfill and exceeding the MAC by 4 to 6 times in the territory). Pollution with heavy metals according to German MACs with chromium exceeded by 1.4 times). The highest concentration of heavy metals prevailed in the body of the landfill. Depending on distance from the landfill the concentration of heavy metals in the soil decreased. HM contamination leads to negative consequences for the ecological state of ordinary chernozem: the total number of bacteria decreases (until to 95% of the control), the number of the genus Azotobacter decreases (up to 95% of the control), the activity of catalase (up to 25% of the control) and dehydrogenase decreases (up to 30% of control) and increased soil phytotoxicity (up to 60% of control). It can be concluded that the exploitation of the landfill leads to a deterioration of the environmental situation on the territory of the landfill and beyond.
 Limitations. The ecotoxic effect of HMs on soils less buffered to pollution will be higher than on the chernozems studied in the article.
 Conclusion. The Landfill “Azov” was found to impact on the microbiological, biochemical, and phytotoxic parameters of the soil negatively. This problem connects with influence of heavy metals which get into the soil of during the operation of the landfill. The most sensitive and informative biological indicators are total number of bacteria and length of radish roots.

Applying machine learning random forest (RF) method in predicting the cement products with a co-processing of input materials: Optimizing the hyperparameters

Co-processing recycled waste during cement production, i.e., using alternative materials such as secondary raw materials or secondary raw fuels, is widely practiced in developed countries. Alternative raw materials or fuels contain high concentrations of heavy metals and other hazardous chemicals, which might lead to the potential for dangerous heavy metals and hazardous chemicals to be transferred to clinker or cement products, resulting in exposure and emissions to people or the environment. Managing input materials and predicting which inputs affect the final concentration is essential to prevent potential hazards. We used the data of six heavy metals by input raw materials and input fuels of cement manufacturers in 2016–2017. The concentrations of Pb and Cu in cement were about 10–200 times and 4 to 200 times higher than other heavy metals (Cr, As, Cd, Hg), respectively.We profiled the influence of heavy metal concentration of each input material using the principal component analysis (PCA), which analyzed the leading causes of each heavy metal. The Random Forest (RF) ensemble model predicted cement heavy metal concentrations according to input materials. In the case of Cu, Cd, and Cr, the training performance showed R square values of 0.71, 0.71, and 0.92, respectively, as a result of predicting the cement heavy metal concentration according to the heavy metal concentration of each cement input material using the RF model, which is a machine learning model. The results of this study show that the RF model can be used to predict the amount and concentration of alternative raw materials and alternative fuels by controlling the concentration of heavy metals in cement through the concentration of heavy metals in the input materials.

Genetic variability of New Caledonian Boeckella De Guerne & Richard, 1889 (Copepoda: Calanoida), with the description of a new species

Abstract Thirteen new freshwater populations of the copepod genus BoeckellaDe Guerne & Richard, 1889 were found during three expeditions to New Caledonia (‘La Planète Revisitée,’ 2016-2018). The 12 populations from the Plaine des Lacs, which show remarkable genetic diversity among themselves, were identified as B. spinogibbaDefaye, 1998, the only species of its genus known from New Caledonia until now. The sole exception, the population from Mont-Dore 22 km further east, appeared genetically and morphologically distinct from the others and is described herein as a new species. The two species are distinguished from each other by the shapes of the male and female P5, female Th5, and body colour. A previously published key is amended to separate the species. Our concatenated COI+28S phylogeny places the two New Caledonia species as a new branch within Boeckella, distinct from the branches consisting of South American, Antarctic and Australasian species. All 13 Boeckella populations inhabit the extreme south of New Caledonia, an area known for endemism and high heavy metal concentrations in the soil. Extensive mining activity in this metal-rich area, begun in 1873, is now leading to conflict with conservation goals. By using aerial photographs to trace the fate of the pond that is the type locality of B. spinogibba, we confirmed that it disappeared between 2007 and 2014 as a result of the expansion of the Goro nickel mine.

Assessment of soil contamination by heavy metals in the vicinity of the Sahiwal coal power plant, Pakistan, employing an innovative statistical analysis approach

ABSTRACT Pollution from heavy metals has become a major issue globally. Human activities could result in lower environmental quality and higher concentration of heavy metals in the soil. The establishment of coal power plants causes a significant threat to the Environment, soil and people who consume the food crops cultivated in that area. In this study, the concentration of some heavy metals like Calcium (Ca), Cadmium (Cd), Cobalt (Co), Chromium (Cr), Lead (Pb), and Magnesium (Mg) has been determined by utilising an Atomic Absorption Spectroscopy (AAS) and 10 soil samples were collected in nearby agricultural soil in the vicinity of coal power plant in Sahiwal, Pakistan during 2021–22 for this purpose. The samples for AAS were prepared via the Wet Digestion Method (WDM). The concentrations of Ca, Co, Cd, Cr, Pb and Mg that have been found are 1.7096 ± 1.4623 mg/kg, 0.0141 ± 0.0664 mg/kg, 0.1413 ± 0.3328 mg/kg, 0.2057 ± 0.3214 mg/kg, 0.1114 ± 0.07316 mg/kg and 0.8951 ± 0.4672 mg/kg, respectively. The results indicate that none of the metals were detected to be above the authorised limits, making the soil appropriate for agricultural purposes. It has been concluded that there are no detectable adverse effects due to the operation of coal power plants in terms of the analysed concentration of heavy metals. Moreover, a statistical Neutrosophic approach has been applied to the specific problem to check the reliability and variation in the concentration of heavy metals. The results come up with extensive and clear information about the particular issue. This study delivers a scientific basis for taking proper measures and managing soil pollution in incoming future in the areas near coal power plants.

Tepidibacter aestuarii sp. nov., isolated from the Bach Dang Estuary, Haiphong, Vietnam.

A mesophilic, anaerobic, endospore-forming, fermentative bacterium designated strain 8C15bT was isolated from bank sediment of the Bach Dang Estuary, Haiphong, Vietnam. The Bach Dang Estuary, where Haiphong harbour is located, is subject to strong anthropogenic influence, resulting in high concentrations of black carbon and heavy metals. Strain 8C15bT grew optimally at 30 °C, pH 7.5 and with 2.5 % (w/v) NaCl. The main cellular fatty acids consisted of iso-C15 : 0 (51 %), iso-C15:1 ω7c (32 %) and iso-C13 : 0 (5 %). Genomic considerations of strain 8C15bT and comparisons with the phylogenetically closest strains of the genus Tepidibacter provide evidence that Tepidibacter thalassicus SC562T (=DSM 15285T), Tepidibacter formicigenes DV1184T (=DSM 15518T), Tepidibacter mesophilus B1T (=JCM 16806T) and strain 8C15bT could be differentiated at the species level. We propose the name Tepidibacter aestuarii sp. nov. for the type strain 8C15bT (=JCM 35983T=KCTC 25692T). Finally, the nickel-tolerance properties of strain 8C15bT are highlighted in this study.

Adsorption Performance and Mechanism of Fe(II) Adsorption in Abandoned Mine Water of Nonstick Coal

Aiming at the problem of the low reuse rate of mine water due to the high content of heavy metals in mine water, in this research, the microcharacterization means of EDX, XRD, BET, SEM, and FT-IR were used to characterize the nonstick coal in a mine in western China. The effects of solid–liquid ratio, solution pH, solution temperature, adsorption time, and initial concentration of the solution on the adsorption of Fe(II) by the nonstick coal were analyzed. The adsorption performance of nonstick coal on adsorbed Fe(II) was analyzed under different influencing factors. The results showed that the adsorption capacity and unit removal rate of the coal samples gradually decreased with the increase in the solid–liquid ratio; the adsorption amount increased with the increase in pH in an “S” shape, and the adsorption effect was better in the range of pH = 5~7; and the adsorption amount increased linearly with the temperature. The quasi-secondary kinetic model and Langmuir model could fit the adsorption kinetic curve and isothermal adsorption curve better, which indicated that the adsorption of Fe(II) by the nonstick coal was dominated by the chemical adsorption of the monomolecular layer. The quantitative analysis of the FT-IR results showed that the adsorption of Fe(II) was mainly by complexation with -OH detached from the coal samples to produce precipitation.

Health Risk Assessment of Heavy and Trace Metals in Personal Care Products in Nigeria

Heavy metal poisoning is linked to disorders like cancer, endocrine disruption, and kidney dysfunction due to prolonged exposure to environmental pollutants. This study assesses heavy and trace metal levels in cosmetic products sold in Nigeria, including eye shadow, face powder, foundation, henna, eyeliner, and lipsticks. Using Atomic Absorption Spectrophotometry (AAS), concentrations of heavy metals (mercury, arsenic, cadmium, lead, nickel) and trace metals (iron, chromium, zinc) were determined. A health risk assessment based on the Margin of Safety (MoS), calculated from systemic exposure dosage (SED) and No Observed Adverse Effect Level (NOAEL), was conducted. Face powders and eyeliners showed concerning iron and lead levels, with MoS values indicating potential health risks from prolonged use. The highest heavy metal concentration (262.850 ppm of iron) was found in henna, while the lowest (0.001 ppm) was observed in various products. The findings highlight the need for stricter regulatory oversight to mitigate these risks.

Contaminated Water Effects on Human Health: A Case of Pakistan

It is vital to have clean water for a healthy lifestyle. Drinking polluted and dirty water causes millions of people to perish. This study's goal was to investigate the effects of tainted water on Rahim Yar Khan's population's health. Rahim Yar Khan's water management and monitoring are subpar, and the city's subsurface water is unfit for drinking because high concentrations of calcium, magnesium, chloride, hardness, and heavy metal are present. The data's empirical component was gathered from hundred replyers in Rahim Yar Khan. The interview schedule was the tool utilized in this study's with the help of purposive sampling for data collection. Descriptive and inferential statistical methods were applied to the data analysis. This study examined public perceptions of the negative health effects after consuming contaminated water and the results shows that high level of diseases are increasing in that selected area just because of drinking contaminated water, some people seemed concerned because of poor hygiene measures for drinking water. The results of this study shows high level of health risk in that selected area for human health.

Assessment of the health risk of some heavy metals in cabbage grown on dumpsite at Hanwa in Zaria, Kaduna State, Nigeria

Pollution of soil with heavy metals can lead to high concentration of the metals in plants, consequently in animals and human body. Cadmium, Copper and Lead concentrations were determined in soil samples and cabbage (Brassica oleracea) grown on a dumpsite at Hanwa in Zaria, Nigeria. Both the soil and plant samples were digested using a mixture of Nitric acid and Perchloric acid (ratio 3:1). The metals concentrations in the samples were determined using Atomic Absorption Spectroscopy (AAS). Soil parameters like Particle Size, pH, Moisture Content, and Organic Matter were also evaluated using standard methods. The results indicated much higher concentrations of heavy metals in the soil than roots, stems and leaves of the analyzed cabbage sample. The Cd level in the plant samples ranged from 1.20 to 1.70mg/kg (site) and 0.80 to 1.00mg/kg (control). Concentration of Cu in the samples ranged from 15.50 to 35.90mg/kg (site) and 7.30 to 13.90mg/kg (control) and Pb: 19.40 to 42.70mg/kg (site) and 5.80 to 26.40mg/kg (control)were above the recommended limit by joint FAO/WHO. The Transfer Factor (TF) of the studied metals from soil to cabbage leaves were in the order of Cd (0.92) > Pb (0.58) > Cu (0.44).In this study, the Health Risk Index (HRI) for Pb (3.421) was found to be greater than 1, which indicates significant potential health risks. The high level of these heavy metals places the consumers of cabbages grown within the dumpsite area at health risk. Cultivation of vegetables on metal dumpsites should be discouraged as the soils are polluted with heavy metals.

Intercropping of Pteris vittata and maize on multimetal contaminated soil can achieve remediation and safe agricultural production

Soil contamination by multimetals is widespread. Hyperaccumulator–crop intercropping has been confirmed to be an effective method for arsenic (As)- or cadmium (Cd)-contaminated soil that can achieve soil cleanup and agricultural production. However, the influencing factors and response of hyperaccumulator–crop intercropping to multimetal-contaminated soil are still unclear. In this study, intercropping of the As hyperaccumulator Pteris vittata and maize was conducted on two typical types of multimetal-contaminated soil, namely, Soil A contaminated by As, Cd, and lead (Pb) and Soil B contaminated by As, Cd, and chromium (Cr). Intercropping reduced As, Cd, and Pb in the maize grains by 60 %, 66.7 %, and 20.4 %, respectively. The concentrations of As, Cd, Pb, and Cr in P. vittata increased by 314 %, 300 %, 447.3 %, and 232.6 %, respectively, relative to their concentrations in the monoculture plants. Two soils with different levels of contamination showed that higher heavy metal content might diminish the ability of intercropping to reduce soil heavy metal risk. No notable difference in soil microbial diversity was found between the intercropped and monocultured plants. The composition of microbial communities of intercropping groups were more similar to those of monoculture P. vittata on two different soils (Soils A and B). An imbalance between the amount of As taken up by the plants and the reduction in As in the soil was observed, and this imbalance may be related to watering, As leaching, and heterogeneity of soil As distribution. Reducing the risk resulting from As leaching and enhancing the efficiency of phytoextraction should be emphasized in remediation practices.

Modulatory Role of Biochar Properties and Environmental Risk of Heavy Metals by Co-Pyrolysis of Fenton Sludge and Biochemical Sludge.

Recent studies have reported that Fenton sludge and biochemical sludge contain high concentrations of toxic substances and heavy metals (HMs), whereas improper treatment can pose serious threats to environmental safety. Pyrolysis is considered an efficient technology to replace conventional sludge treatment. This study investigated the pyrolysis and kinetic processes of Fenton sludge and biochemical sludge, revealed the physicochemical properties of sludge biochar, and highlighted the role of co-pyrolysis in sludge immobilization of HMs and environmental risks. Results showed that Fenton sludge and biochemical sludge underwent three stages of weight loss during individual pyrolysis and co-pyrolysis, especially co-pyrolysis, which increased the rate of sludge pyrolysis and reduced the decomposition temperature. The kinetic reaction indicated that the activation energies of Fenton sludge, biochemical sludge, and mixed sludge were 11.59 kJ/mol, 8.50 kJ/mol, and 7.11 kJ/mol, respectively. Notably, co-pyrolysis reduced the activation energy of reactions and changed the specific surface area and functional group properties of the biochar produced from sludge. Meanwhile, co-pyrolysis effectively immobilized Cu, Pb, and Zn, increased the proportion of metals in oxidizable and residual states, and mitigated the environmental risks of HMs in sludge. This study provided new insights into the co-pyrolysis properties of sludge biochar and the risk assessment of HMs.

Dynamic adaptation of the extremophilic red microalga Cyanidioschyzon merolae to high nickel stress

The order of Cyanidiales comprises seven acido-thermophilic red microalgal species thriving in hot springs of volcanic origin characterized by extremely low pH, moderately high temperatures and the presence of high concentrations of sulphites and heavy metals that are prohibitive for most other organisms. Little is known about the physiological processes underlying the long-term adaptation of these extremophiles to such hostile environments. Here, we investigated the long-term adaptive responses of a red microalga Cyanidioschyzon merolae, a representative of Cyanidiales, to extremely high nickel concentrations. By the comprehensive physiological, microscopic and elemental analyses we dissected the key physiological processes underlying the long-term adaptation of this model extremophile to high Ni exposure. These include: (i) prevention of significant Ni accumulation inside the cells; (ii) activation of the photoprotective response of non-photochemical quenching; (iii) significant changes of the chloroplast ultrastructure associated with the formation of prolamellar bodies and plastoglobuli together with loosening of the thylakoid membranes; (iv) activation of ROS amelioration machinery; and (v) maintaining the efficient respiratory chain functionality. The dynamically regulated processes identified in this study are discussed in the context of the mechanisms driving the remarkable adaptability of C. merolae to extremely high Ni levels exceeding by several orders of magnitude those found in the natural environment of the microalga. The processes identified in this study provide a solid basis for the future investigation of the specific molecular components and pathways involved in the adaptation of Cyanidiales to the extremely high Ni concentrations.