Heavy Metal-contaminated Environments Research Articles

Role of white rot fungi in sustainable remediation of heavy metals from the contaminated environment

ABSTRACT Heavy metal contamination has severe impacts on the natural environment. The currently existing physico-chemical methods have certain limitations, restricting their wide-scale application. The use of biological agents like bacteria, algae, and fungi can help eliminate heavy metals without adversely affecting flora and fauna. Due to their inherent ability to withstand adverse environmental conditions, nowadays, mycoremediation approaches are receiving considerable attention for heavy metal removal from contaminated sites. In this review, we emphasised the role of white rot fungi in remediation of heavy metal along with different factors influencing biosorption, effects on exposed fungi, and the mechanisms involved. Bibliometric analysis tools have been applied to literature search and trend analysis of the research on white rot fungi-mediated heavy metal removal. Annual growth rates and average citations per document are 5.08% and 35.48, respectively. Phanerochaete chrysosporium, Pleurotus ostreatus, and Trametes versicolor have been widely explored for the remediation of heavy metals. In addition to providing some prospects, the review also highlighted a few limitations, including inconsistent removal and effects of environmental factors influencing the functioning of white rot fungi. Overall, white rot fungi have been found to have immense potential to be widely utilised for sustainable remediation of heavy metal-contaminated environments.

Heavy metals biosorption in unary, binary, and ternary systems onto bacteria in a moving bed biofilm reactor

Toxic and heavy metals cause direct and indirect damage to the environment and ultimately to humans. This study involved the isolation of indigenous bacteria from heavy metal-contaminated environments that have the ability to bioabsorb heavy metals such as cadmium, nickel, and lead. The bioabsorption process was optimized by varying parameters such as temperature, metal concentration, number of bacteria, pH, and more. The bacterial isolates were investigated in terms of morphology, biochemistry, and phylogeny, with 12 strains chosen in the initial stage and one strain chosen in the final stage. It should be remembered that the metal uptake capacity of all isolates was approximately calculated. A box and reactor were designed to house these optimized microorganisms. Based on biochemical, morphological, and molecular results, the isolated strain was found to be closely related to the Bacillus genus. In the first five steps of testing, the ideal pH for removing lead alone, lead with cadmium, lead with nickel, and lead ternary (with cadmium and nickel) by Bacillus bacteria was found to be 7, 6, 5.5, and 6.5, respectively. The absorption efficiencies for single lead (unary), lead together with nickel, cadmium (binary), and ternary (lead with cadmium and nickel) were found to be 0.36, 0.25, 0.22, and 0.21 mmol/g, respectively. The ideal temperature for lead removal was around 30 °C. The adsorption isotherm for each lead metal in different states was found to be similar to the Langmuir isotherm, indicating that the surface absorption process is a single-layer process. The kinetics of the process follow the second-order kinetic model. The amount of Bacillus bacteria biomass obtained during this process was approximately 1.5 g per liter.

Effective amendment of cadmium in water and soil before and after aging of nitrogen-doped biochar: Preparation optimization, removal efficiency and mechanism

Nitrogen-doped biochar (NBC) is a green material for remediating heavy metal pollution, but it undergoes aging under natural conditions, affecting its interaction with heavy metals. The preparation conditions of NBC were optimized using response surface methodology (RSM), and NBC was subjected to five different aging treatments to analyze the removal efficiency of Cd(II) and soil remediation capability before and after aging. The results indicated that NBC achieved optimal performance with a mass ratio of 5:2.43, an immersion time of 10.66 h, and a pyrolysis temperature of 900 °C. Aging diminished NBC's adsorption capacity for Cd(II) but did not change the main removal mechanism of monolayer chemical adsorption. Freeze-thaw cycles (FT), UV aging (L), and composite aging (U) treatments increased the proportion of bioavailable-Cd, and all aging treatments facilitated the conversion of potentially bioavailable-Cd to non-bioavailable-Cd. The application of NBC and five aged NBCs reduced the proportion of bioavailable-Cd in the soil through precipitation and complexation, increasing the proportion of non-bioavailable-Cd. Aging modifies the physicochemical properties of NBC, thus influencing soil characteristics and ultimately diminishing NBC's ability to passivate Cd in the soil. This study provides reference for the long-term application of biochar in heavy metal-contaminated environments.

Role of methylglyoxal and glyoxalase in the regulation of plant response to heavy metal stress.

Methylglyoxal and glyoxalase function a significant role in plant response to heavy metal stress. We update and discuss the most recent developments of methylglyoxal and glyoxalase in regulating plant response to heavy metal stress. Methylglyoxal (MG), a by-product of several metabolic processes, is created by both enzymatic and non-enzymatic mechanisms. It plays an important role in plant growth and development, signal transduction, and response to heavy metal stress (HMS). Changes in MG content and glyoxalase (GLY) activity under HMS imply that they may be potential biomarkers of plant stress resistance. In this review, we summarize recent advances in research on the mechanisms of MG and GLY in the regulation of plant responses to HMS. It has been discovered that appropriate concentrations of MG assist plants in maintaining a balance between growth and development and survival defense, therefore shielding them from heavy metal harm. MG and GLY regulate plant physiological processes by remodeling cellular redox homeostasis, regulating stomatal movement, and crosstalking with other signaling molecules (including abscisic acid, gibberellic acid, jasmonic acid, cytokinin, salicylic acid, melatonin, ethylene, hydrogen sulfide, and nitric oxide). We also discuss the involvement of MG and GLY in the regulation of plant responses to HMS at the transcriptional, translational, and metabolic levels. Lastly, considering the current state of research, we present a perspective on the future direction of MG research to elucidate the MG anti-stress mechanism and offer a theoretical foundation and useful advice for the remediation of heavy metal-contaminated environments in the future.

Advances in mechanism for the microbial transformation of heavy metals: implications for bioremediation strategies.

Heavy metals are extensively discharged through various anthropogenic activities, resulting in an environmental risk on a global scale. In this case, microorganisms can survive in an extreme heavy metal-contaminated environment via detoxification or resistance, playing a pivotal role in the speciation, bioavailability, and mobility of heavy metals. Therefore, studies on the mechanism for the microbial transformation of heavy metals are of great importance and can provide guidance for heavy metal bioremediation. Current research studies on the microbial transformation of heavy metals mainly focus on the single oxidation, reduction and methylation pathways. However, complex microbial transformation processes and corresponding bioremediation strategies have never been clarified, which may involve the inherent physicochemical properties of heavy metals. To uncover the underlying mechanism, we reclassified heavy metals into three categories based on their biological transformation pathways, namely, metals that can be chelated, reduced or oxidized, and methylated. Firstly, we comprehensively characterized the difference in transmembrane pathways between heavy metal cations and anions. Further, biotransformation based on chelation by low-molecular-weight organic complexes is thoroughly discussed. Moreover, the progress and knowledge gaps in the microbial redox and (de)methylation mechanisms are discussed to establish a connection linking theoretical advancements with solutions to the heavy metal contamination problem. Finally, several efficient bioremediation strategies for heavy metals and the limitations of bioremediation are proposed. This review presents a solid contribution to the design of efficient microbial remediation strategies applied in the real environment.

Sinorhizobium saheli: Advancing Chromium Mitigation, Metal Adsorption, and Plant Growth Enhancement in Heavy Metal-Contaminated Environments

Sinorhizobium saheli: Advancing Chromium Mitigation, Metal Adsorption, and Plant Growth Enhancement in Heavy Metal-Contaminated Environments

Heavy-metal tolerant bacterial strains isolated from industrial sites and scrap yards in Kashmir, India.

Heavy metal pollution has posed a severe danger to environmental stability due to its high toxicity and lack of biodegradability. The present study deals with the appraisement of tolerance shown by various bacteria in varied copper and iron concentrations. Among the 20 isolates, four isolates, GN2, SC5, SC8, and SC10, exhibiting more significant iron and copper tolerance, were selected and identified by 16 S ribosomal ribonucleic acid (rRNA) gene sequence analysis as Pantoea agglomerans strain GN2, Pantoea sp. strain SC5, Bacillus sp. strain SC8 and Priestia aryabhattaistrain SC10. The minimum inhibitory concentration of molecularly identified strains revealed that P. agglomerans strain GN2 showed tolerance to iron sulfate and copper sulfate upto 600 and 400 µg/mL, whereas Bacillus sp. SC8 (OQ202165) showed tolerance of 700 and 250 µg/mL were tolerant to iron sulfate and copper sulfate up to 700 and 150 µg/mL, respectively. Pantoea sp. strain SC5 showed significant tolerance to both heavy metals. The isolates were further studied for their ability to grow at varying temperatures and pH ranges. Most of the isolates showed optimal growth at 37°C and pH 7. However, Pantoea sp. SC5 was competent to have prominent growth at 45°C and pH 8.0. Microbial remediation, which is eco-friendly, has proven the most effective method for bioremediation of heavy metal-contaminated environments. Using heavy metal-resistant bacteria for microbial remediation of iron and copper-contaminated environments could be a viable and valuable strategy. These isolates could also be used to decontaminate heavy metal-polluted agricultural soils.

Bioremediation of heavy metal-contaminated environment: developed strategies and potential use of biosurfactants as chelators

Abstract Heavy metal pollution damages the ecosystems and presents a major problem for public health. Thus, an urgent need was developed to decrease the high levels of heavy metals in the soil and aquatic environments. With this aim, numerous physicochemical strategies were developed. However, they are money-consuming, require the use of energy and chemical additives and can release secondary compounds that can pollute and cause great damage to the environment. Then, biological methods based on the investigation of bacteria, fungi and plants along with their derived secondary active metabolites became the best alternatives. Using plant capacities, different phytoremediation strategies were developed such as phytoextraction, phytovolatilization, rhizofiltration and phytostabilization. Regarding bioremediation, bacterial biosorption of heavy metals, biolixiviation and lagooning offer great potential for their environmental cleaning. Additionally, the use of secondary active metabolites, such as biosurfactants, is well-studied. Generally, they are a class of structurally very varied molecules commonly synthesized by many microorganisms with amphiphilic character. Owing to their anionic charge, they have the capacity to sequestrate heavy metals permitting their elimination. Glycolipids and lipopeptides are among the most recognized biosurfactants with interesting heavy metal chelating properties.

Removal of mercury from water by phytoremediation process with Salvinia natans(L.) All.

Mercury contamination from human activities is a severe environmental problem. The low cost of rhizofiltration of heavy metal-contaminated environments is causing an increasing interest in these technologies. The present study demonstrates the effectiveness of mercury removal from water by phytoremediation using S. natans. Plants cultured and collected from the environment were used. The study used Hoagland’s liquid medium contaminated with mercury: 0.15, 0.20, and 0.30. The bioconcentration factor obtained was 275–780. The relative growth rate was up to 0.12 g/gd and was much better for cultured plants than those collected from the environment. The removal rate of toxic metal was up to 94%. Total protein increased for cultures plants by up to 84%, while it decreased by up to 30% for those taken from the environment. Total chlorophyll for cultured plants decreased by up to 54%, which could be due to the toxic effect of the metal.

Isolation and Screening of Microorganisms from Waste Dumping Sites for Biosorption of Cadmium and Lead

Heavy metal poisoning of the environment poses a serious threat to ecosystems and human health. Landfills have been found to harbor diverse microbial communities capable of bioremediating such contaminants via biosorption. Unlike traditional methods of heavy metal remediation, which often involve costly and resource-intensive techniques, biosorption offers a promising alternative that harnesses the natural capabilities of microorganisms. The objective of this research was to identify and screen microorganisms from landfills for their ability to bio-sorb cadmium (Cd) and lead (Pb). The present study deals with the isolation and screening of the microorganisms capable of removing heavy metals from the area near Dehradun Municipal Solid Waste Management Pvt. Ltd. Among the 17 bacterial isolates and 2 fungal isolates, only 7 bacteria and one fungal strain were able to absorb the heavy metal concentration. Among the 7 bacterial strains, the percentage of microbes with the ability to absorb Pb ranged from 35% to 70%, while the percentage of microbes with the ability to absorb Cd ranged from 20% to 50%. On the other hand, the fungal strain had an absorption capacity of about 80% for both Pb and Cd. This study emphasizes the potential of microorganisms isolated from landfills as attractive candidates for Cd and Pb biosorption. These isolates show significant tolerance and efficient biosorption capacities, making them good candidates for further exploration and prospective application in the bioremediation of heavy metal-contaminated environments.

Plant Growth-Promoting Rhizobacteria (PGPR) Assisted Bioremediation of Heavy Metal Toxicity.

Due to a variety of natural and anthropogenic processes, heavy metal toxicity of soil constitutes a substantial hazard to all living beings in the environment. The heavy metals alter the soil properties, which directly or indirectly influence the agriculture systems. Thus, plant growth-promoting rhizobacteria (PGPR)-assisted bioremediation is a promising, eco-friendly, and sustainable method for eradicating heavy metals. PGPR cleans up the heavy metal-contaminated environment using various approaches including efflux systems, siderophores and chelation, biotransformation, biosorption, bioaccumulation, precipitation, ACC deaminase activity, biodegradation, and biomineralization methods. These PGPRs have been found effective to bioremediate the heavy metal-contaminated soil through increased plant tolerance to metal stress, improved nutrient availability in soil, alteration of heavy metal pathways, and by producing some chemical compounds like siderophores and chelating ions. Many heavy metals are non-degradable; hence, another remediation approach with a broader scope of contamination removal is needed. This article also briefly emphasized the role of genetically modified PGPR strains which improve the soil's degradation rate of heavy metals. In this regard, genetic engineering, a molecular approach, could improve bioremediation efficiency and be helpful. Thus, the ability of PGPRs can aid in heavy metal bioremediation and promote a sustainable agricultural soil system.

Intestinal bacteria diversity of suckermouth catfish (Pterygoplichthys pardalis) in the Cd, Hg, and Pb contaminated Ciliwung River, Indonesia

The contamination of aquatic environments with heavy metals poses a serious threat to fish, potentially leading to diseases or even death. Therefore, there is an urgent need for studies to investigate the adaptability of fish in heavy metal-contaminated environments. Several studies have explored the adaptability of suckermouth catfish (P. pardalis) to survive in the contaminated Ciliwung River. The findings obtained showed that the presence of intestinal bacteria helped these fish overcome the heavy metals in their intestines, thereby enabling the fish to survive. Analysis using the Next Generation Sequencing (NGS) technology has succeeded in identifying diversity of these bacteria in P. pardalis living in the Ciliwung River, which contaminated with Cd (0.3–1.6 ppm in the water & 0.9–1.6 ppm in the sediment), Hg (0.6–2 ppm in the water & 0.6–1.8 ppm in the sediment), and Pb (59.9–73.8 ppm in the water & 26.1–58.6 ppm in the sediment). Diversity index of intestinal bacteria in P. pardalis was relatively high, but it had a negative correlation with the presence of these contaminants. Actinobacteria, Firmicutes, and Proteobacteria were abundant in the intestines of P. pardalis from the upstream to downstream of the river, with an overall abundance range of 15–48%. Furthermore, Mycobacterium along with 6 other genera were identified as core intestinal bacteria. The presence of these bacterial communities in all the samples affected their survival in heavy metals-contaminated rivers. The fish's adaptability to live in this harsh environment indicated that it has the potential to be utilized as a bioremediator of heavy metals in river sediments.

Insights from comparative transcriptome analysis in the responses of Pb-tolerant fungi Curvularia tsudae to Pb stress

The fungus Curvularia tsudae can survive in environments that are extremely contaminated by heavy metals; however, the underlying molecular mechanisms of heavy metal tolerance are not clear. In this study, we determined the effects of lead (Pb) stress on the growth of C. tsudae and used RNA-Seq to identify significant genes and biological processes involved. The present study showed that C. tsudae had an outstanding resistant capacity to Pb stress and could survive at a concentration of 1600 mg L−1 Pb. Although an obvious inhibition on the growth was observed, the fungus exhibited tolerance as it continued to grow at a Pb concentration of 1600 mg L−1 for seven days. A total of 9997 (9020 up and 977 down) differentially expressed genes (DEGs) were detected in the mycelium of C. tsudae at Pb free (0 mg L−1) and Pb stressed samples. Pathway enrichment analysis identified several biological processes for managing Pb stress. Genes involved in carbohydrate metabolism tended to be modulated in response to Pb stress, while amino acids and the lipid metabolism would also be induced by Pb stress, and up-regulated genes involved in antioxidant substances and ABC transporters may be committed to high Pb tolerance. Our study contributes to the current literature on C. tsudae response to Pb stress and provides a useful reference for fungi as bioremediators in heavy metal-contaminated environments.

Insights into the heavy metal adsorption and immobilization mechanisms of CaFe-layered double hydroxide corn straw biochar: Synthesis and application in a combined heavy metal-contaminated environment

Biochar is an emerging eco-friendly and high-efficiency heavy metal (HM) adsorbent that exhibits satisfactory HM remediation effects in both water and soil environments. However, few studies have investigated the mechanisms and application of biochar in the remediation of combined HM-contaminated environments. Therefore, in the present study, a novel corn straw biochar-loaded calcium-iron layered double hydroxide composite (CaFe-LDH@CSB) was synthesized via the coprecipitation method and applied as a remediation adsorbent to remove HMs in both water and soil environments. The results indicated that the HM adsorption mechanism of CaFe-LDH@CSB in the aquatic phase involved a chemical endothermic adsorption process of functional group-complexed monolayers, dominated by precipitation, ion exchange, complexation and π bond interactions. The maximum adsorption capacity for Cd(II), Pb(II), Zn(II) and Cu(II) in the aqueous phase reached 24.58, 240.96, 57.57 and 39.35 mg g−1, respectively. In addition, application of CaFe-LDH@CSB in the combined HM-contaminated soil treatment helped to increase the soil pH, which increased by 5.1–17.9% in low-contamination (LC) soil and by 7.0–13.9% in high-contamination (HC) soil. Moreover, application of CaFe-LDH@CSB effectively decreased the acid-soluble fraction of HMs and increased the HM residual fraction. The immobilization mechanism of CaFe-LDH@CSB in the soil was concluded to involve pore filling, functional group action and electrostatic interactions. Overall, this study provided a novel LDH biochar composite that can be effectively applied in the remediation of combined HM-contaminated water and soil environments.

Impact of environmental factors on the ammonia-oxidizing and denitrifying microbial community and functional genes along soil profiles from different ecologically degraded areas in the Siding mine

Ammonia oxidizers (ammonia-oxidizing bacteria (AOB amoA) and ammonia-oxidizing archaea (AOA amoA)) and denitrifiers (encoded by nirS, nirK and nosZ) in the soil nitrogen cycle exist in a variety of natural ecosystems. However, little is known about the contribution of these five N-related functional genes to nitrification and denitrification in the soil profile in severely ecologically degraded areas. Therefore, in the present study, the abundance, diversity and community composition of AOA, AOB, nirS, nirK and nosZ were investigated in the soil profiles of different ecologically degraded areas in the Siding mine. The results indicated that, at the phylum level, the dominant archaea were Crenarchaeota and Thaumarchaeota and the dominant bacteria were Proteobacteria. Heavy metal contents had a great impact on AOA amoA, nirS and nirK gene abundances. AOA amoA contributed more during the ammonia oxidation process and was better adapted for survival in heavy metal-contaminated environments. In addition to heavy metals, the soil organic matter (SOM) content and C/N ratio had strong effects on the AOA and AOB community diversity and structure. In addition, variations in the net ammonification and nitrification rates were proportional to AOA amoA abundance along the soil profile. The soil C/N ratio, soil available phosphorus content and soil moisture influenced the denitrification process. Both soil available phosphorus and moisture were more strongly related to nosZ than to nirS and nirK. In addition, nosZ presented a higher correlation with the nosZ/(nirS + nirK) ratio. Moreover, nosZ/(nirS + nirK) was the key functional gene group that drove the major processes for NH4+-N and NO3−-N transformation. This study demonstrated the role and importance of soil property impacts on N-related microbes in the soil profile and provided a better understanding of the role and importance of N-related functional genes and their contribution to soil nitrification and denitrification processes in highly degraded areas in the Siding mine.

Composition and niche-specific characteristics of microbial consortia colonizing Marsberg copper mine in the Rhenish Massif

Abstract. The Kilianstollen Marsberg (Rhenish Massif, Germany) has been extensively mined for copper ores, dating from early medieval period until 1945. The exposed organic-rich alum shale rocks influenced by the diverse mine drainages at an ambient temperature of 10 ∘C could naturally enrich biogeochemically distinct heavy metal resistant microbiota. This amplicon-sequence-based study evaluates the microbially colonized subterranean rocks of the abandoned copper mine Kilianstollen to characterize the colonization patterns and biogeochemical pathways of individual microbial groups. Under the selective pressure of the heavy metal contaminated environment at illuminated sites, Chloroflexi (Ktedonobacteria) and Cyanobacteria (Oxyphotobacteria) build up whitish–greenish biofilms. In contrast, Proteobacteria, Firmicutes and Actinobacteria dominate rocks around the uncontaminated spring water streams. The additional metagenomic analysis revealed that the heavy metal resistant microbiome was evidently involved in redox cycling of transition metals (Cu, Zn, Co, Ni, Mn, Fe, Cd, Hg). No deposition of metals or minerals, though, was observed by transmission electron microscopy in Ktedonobacteria biofilms which may be indicative for the presence of different detoxification pathways. The underlying heavy metal resistance mechanisms, as revealed by analysis of metagenome-assembled genomes, were mainly attributed to transition metal efflux pumps, redox enzymes, volatilization of Hg, methylated intermediates of As3+, and reactive oxygen species detoxification pathways.

Enhanced removal of heavy metals by α-FeOOH incorporated carboxylated cellulose nanocrystal: synergistic effect and removal mechanism.

Simultaneous and highly efficient removal of heavy metal cations and oxyanions is significant for both water and soil remediation, but it remains a major challenge due to the complexity. In this work, a novel hybrid of α-FeOOH incorporated carboxylated cellulose nanocrystal (Fe/CNC) is synthesized via a hydrothermal process, which shows improved α-FeOOH dispersion and heavy metal removal capacity. In single adsorbate system, maximum adsorption capacities toward Pb(II), Cd(II), and As(V) by Fe/CNC reach 126.06, 53.07, and 15.80mgg-1, respectively, and the Fe leaching is much lower than that of α-FeOOH. In binary and ternary adsorption systems, simultaneous removal of Pb(II), Cd(II), and As(V) is proved, and the competition and synergy coexist among heavy metals. FTIR and XPS spectra have revealed the synergistic removal mechanism: Pb(II) and Cd(II) are mainly removed by surface complexation with oxygen-containing functional groups on C-CNC and α-FeOOH, and precipitation on the surface of α-FeOOH, while ligand exchange with Fe-OH is responsible for As(V) removal. The soil incubation experiments show that exchangeable and carbonate-bound Pb, Cd, and As are transformed into more stable forms in contaminated soil containing Fe/CNC composites. This work provides a novel composite material for remediation of heavy metal-contaminated environments.

Native Endomycorrhiza With Tolerance to Heavy Metal Contamination in Organic Culture Media

Endomycorrhizal fungi are spora-carrying organisms that can survive in heavy metalcontaminated environments. The goal of this study was to investigate endomycorrhizal fungi from heavy metal-affected areas and determine an effective mix of organic culture media to increase the number and diameter of endomycorrhizal spores. In Sorowako, Indonesia, endomycorrhizal fungi were isolated from the rhizosphere of: rice husk charcoal, sand, zeolite (KM1); rice husk charcoal, sand, sawdust (KM2); rice husk charcoal, sand, cocopeat (KM3); rice husk charcoal, sand, rice soil (KM4); rice husk charcoal, sand, cold magma (KM5); rice husk charcoal, sand, cold magma (KM6); and rice husk charcoal, sand (KM7). The results of the first phase of research revealed that three endomycorrhizal genera (44.44%–75.86% Acaulospora sp, 9.52%–44.44% Gigaspora sp, and 3.38%–19.05 % Glomus sp) can adapt to and resist conditions contaminated with Hg, Cd, Ni, Pb, As, Cr, Mn, Fe, Cu, Co, and Sn, namely as a carrier medium. It was concluded that a combination of organic media was recommended, but that this must decompose first.
 Keywords: Fungi, mycorrhizal, organic waste, rhizosfer

High efficiency Pb(II) removal using a green synthesized iochar/graphene-supported chlorapatite

Carbonaceous nano-chlorapatites have attracted great attention for the remediation of heavy metal-contaminated environment. Herein, a novel biochar/graphene-supported chlorapatite (BC/G-ClAP) was successfully synthesized by a green method for the purpose of removing the Pb(Ⅱ) from the water. The generated BC/G-ClAP was characterized by Scanning electron microscope (SEM) and transmission electron microscopy (TEM). It was found that biochar had the mesoporous structure with the layers of graphene on biochar surfaces and chlorapatites were distributed on the surface of biochar/graphene. BC/G-ClAP showed excellent remediation performance towards Pb(Ⅱ) contaminated water, with the Pb(Ⅱ) removing efficiency of 80.29%. The high remediation was due to the porous biochar/graphene with plenty of functional group have the strong adsorption for the Pb(Ⅱ) ions and the chlorapatites showed the cation exchange with Pb(Ⅱ) to form the stable Pb10(PO4)6Cl2. Therefore, this green synthesis method and the novel composites have a great potential for the application of remediation in the contaminanted environment.

Impacts of heavy metal pollution on the ionomes and transcriptomes of Western mosquitofish (Gambusia affinis)

Our understanding of the mechanisms mediating the resilience of organisms to environmental change remains lacking. Heavy metals negatively affect processes at all biological scales, yet organisms inhabiting contaminated environments must maintain homeostasis to survive. Tar Creek in Oklahoma, USA, contains high concentrations of heavy metals and an abundance of Western mosquitofish (Gambusia affinis), though several fish species persist at lower frequency. To test hypotheses about the mechanisms mediating the persistence and abundance of mosquitofish in Tar Creek, we integrated ionomic data from seven resident fish species and transcriptomic data from mosquitofish. We predicted that mosquitofish minimize uptake of heavy metals more than other Tar Creek fish inhabitants and induce transcriptional responses to detoxify metals that enter the body, allowing them to persist in Tar Creek at higher density than species that may lack these responses. Tar Creek populations of all seven fish species accumulated heavy metals, suggesting mosquitofish cannot block uptake more efficiently than other species. We found population-level gene expression changes between mosquitofish in Tar Creek and nearby unpolluted sites. Gene expression differences primarily occurred in the gill, where we found upregulation of genes involved with lowering transfer of metal ions from the blood into cells and mitigating free radicals. However, many differentially expressed genes were not in known metal response pathways, suggesting multifarious selective regimes and/or previously undocumented pathways could impact tolerance in mosquitofish. Our systems-level study identified well characterized and putatively new mechanisms that enable mosquitofish to inhabit heavy metal-contaminated environments.