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Iron-nanoparticles (Fe-NPs) are increasingly been utilized in environmental applications due to their efficacy and strong catalytic activities. The novelty of nanoparticle science had attracted many researchers and especially for their green synthesis, which can effectively reuse biological resources during the polymerization reactions. Thus, the synthesis of Fe-NPs utilizing plant extracts could be considered as the eco-friendly, simple, rapid, energy-efficient, sustainable, and cost-effective. The green synthesis route can be recognized as a practical, valuable, and economically effective alternative for large-scale production. During the production process, some biomolecules present in the extracts undergo metal salts reduction, which can serve as both a capping and reducing mechanism, enhancing the reactivity and stability of green-synthesized Fe-NPs. The diversity of species provided a wide range of potential sources for green synthesis of Fe-NPs. With improved understanding of the specific biomolecules involved in the bioreduction and stabilization processes, it will become easier to identify and utilize new, potential plant materials for Fe-NPs synthesis. Newly synthesized Fe-NPs require different characterization techniques such as transmission electron microscope, ultraviolet-visible spectrophotometry, and X-ray absorption fine structure, etc, for the determination of size, composition, and structure. This review described and assessed the recent advancements in understanding green-synthesized Fe-NPs derived from plant-based material. Detailed information on various plant materials suitable of yielding valuable biomolecules with potential diverse applications in environmental safety. Additionally, this review examined the characterization techniques employed to analyze Fe-NPs, their stability, accumulation, mobility, and fate in the environment. Holistically, the review assessed the applications of Fe-NPs in remediating wastewaters, organic residues, and inorganic contaminants. The toxicity of Fe-NPs was also addressed; emphasizing the need to refine the synthesis of green Fe-NPs to ensure safety and environmental friendliness. Moving forward, the future challenges and opportunities associated with the green synthesis of Fe-NPs would motivate novel research about nanoparticles in new directions.

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Chemical data compiled from field and laboratory studies were analysed on drinking water sources from a mountain area (Gutai Mountains) in Romania. Six physico-chemical indicators, nine anions, and twenty-one metals were determined and analysed. The results of this study showed that waters are generally rich in NH4+ and NO2-, exceeding the recommended limit of 0.5 mg NH4+/L, while some waters are rich in As, Cd, Mn and Pb, but with concentrations below the limits concerning the use of waters with drinking purposes. The applied heavy metal pollution indices (scores: 0.56-47.9) indicate that more than 50% of samples are characterized by medium pollution degrees. Based on the results obtained, it was determined that geological and human activities were influential in enriching the studied waters with the chemicals considered. Emphasizing this aspect related to pollution sources and the importance of a clean chemical status that must characterize waters used for drinking purposes, a human health risk assessment for heavy metals was implemented. The results indicated that even though the studied waters are rich in heavy metals, scores related to the risk assessment of heavy metals indicated a lack of non-carcinogenic risks for As, Mn, Cd and Cu. Nevertheless, this study and the results obtained are significant at national and international levels by offering a perspective on determining the potential pollution and associated human health risks at heavy metals in drinking water sources from a mountain area.

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Mangrove areas are considered the most retention zone for heavy metal pollution as it work as an edge that aggregates land and sea sediments. This study aims to examine if the heavy metals' existence in the mangrove sediment is related to contamination or natural resources. In addition, it gives an interpretation of the origin of these metals along the Egyptian Red Sea coast. Twenty-two samples of mangrove sediments were collected and then, analyzed for metals (Mn, Ni, Cu, Fe, Cd, Ag, and Pb) using inductively coupled plasma mass spectroscopy (ICP-MS). Integration between the in-situ data, contamination indices, and remote sensing and geographical information science (GIS), and multivariate statistical analysis techniques (PCA) were analyzed to assess and clarify the spatial origin of heavy metals in sediment at a regional scale. The average concentration of heavy metals from mangrove sediments were shown to be substantially lower than the referenced value, ranging from moderate to significant except the levels of Ag were very high. The heavy metals concentrations were expected to be naturally origin rather than anthropogenic and that be confirmed by mapping of Red Sea alteration zones spots. These alteration zones are parallel to mangrove sites and rich by several mineralization types including heavy metals that are carried by flooding to the coastline. Remote sensing and GIS techniques successfully contributed to interpreting the pattern of the origin of heavy metals and discharging systems that control the heavy metals concentration along the Red Sea coast.

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The present study aimed to assess the ecological and health risks of the Pouma rock samples. Twenty-three (23) trace element concentrations were evaluated. The concentrations of these trace elements were compared with those of quartzite from other countries and with global reported values. When compared with the world values, the concentrations of trace metals were below the world average values except that of Barium. The ecological risk assessment was carried out using the geo-accumulation index, contamination factors and the potential ecological risk index. The geo-accumulation index and contamination factors showed that the quartzite of Pouma subdivision are not polluted and not contaminated by the investigated metal except for Barium and Mercury. The health risk assessment using the USEPA (United States Environmental Protection Agency) method showed that there is a possible non-carcinogenic risk from Al2O3 (for children and adults) and from Cr for Children. However, there is a tolerable and high carcinogenic risk due to Cr for adults and children, respectively. It was found independently for non-carcinogenic and carcinogenic risk that the exposure via the ingestion route is the most dangerous for adults and children.

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Due to rising populations and human activities, heavy metals (HM) toxicity has become a serious problem for all life forms. The present study deals with isolating and identifying lead-resistant bacteria from contaminated wastewater of tanneries effluents. Two isolated strains were identified as Bacillus cereus (ID1), and Bacillus sp. (ID3), and both strains resisted a 25 mM concentration of Lead nitrate (Pb (NO3)2). After four days of treatment, Bacillus cereus (ID1) showed 80% lead uptake, and Bacillus sp. (ID3) showed 88%. Lead uptake was confirmed by Energy dispersive X-Ray (EDX) analysis. Fourier transform infrared spectroscopy (FTIR) showed that structural alterations had occurred in functional groups of the treated samples compared to the controls. Our research indicates that these Bacillus strains may be useful in bioremediating heavy metals from polluted environments. Further investigation into the processes involved in the uptake and homeostasis of heavy metals by these strains is required, as is the identification of the genes and enzymes responsible for Pb-bioremediation.

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Heavy metal pollution of soils in industrial agglomeration areas is an increasing concern worldwide. In this study, we traced the sources of heavy metal emissions using a positive matrix factorization (PMF) model. Accordingly, we proposed a novel static-dynamic risk interaction model incorporating multiple risk-related factors to quantify the spatial interaction of emission sources and the probability of accumulation of heavy metals on a large scale. This model was further classified using the Jenks optimization technique to predict the spatial distribution of high-risk hotspots. Our results determined four primary emission sources of heavy metals: industrial (35.01 %), natural (28.61 %), agricultural (26.07 %), and traffic (10.31 %) sources. Five levels were classified by the integrated risk coefficient (IRC), namely, from extremely high to extremely low risk. The extremely high- and high-risk hotspots constituting 41.52 % of the total area of the Zhenhai District, with IRC values ranging from 0.221 to 0.413, were mainly generated by multiple sources linked to PMF-based factors. This quantitative evaluation framework can generate a high-resolution spatially distributed pollution risk map at the grid scale (1 km), which can provide a relatively precise basis for policymaking for point-to-point soil pollution management.

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Heavy metals are one of the most serious pollutants in aquatic ecosystems, and their accumulation in fish products causes harmful effects on human health. In this context, we set out to determine the concentrations of heavy metals in the muscle of two fish species of commercial interest, Chelon auratus and Chelon saliens on the south coast of the Caspian Sea. We aimed to assess the degree of environment contamination in this area and to estimate the potential risk to human health derived from the consumption of fish. The mean concentrations of the different metals analysed were very varied in both species. In fact, some concentrations exceeded the permissible limits for the protection of human health for Cd and Pb, and some values of As were above those referenced by other authors in same species in the Caspian Sea. None of the estimated daily intake values exceeded the tolerable intake based on the consumption under consideration. Nonetheless, the accumulative hazard values evidenced a potential risk to human health, Pb and Hg being those giving a higher target hazard quotient. The cancer risk from exposure to As from fish consumption in children was above the "acceptable" risk to life. Thus, in view of the accumulative nature of heavy metals, a moderate and non-abusive fish consumption in this area, particularly in children, would be recommendable.

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The health risk of soil heavy metals pollution has been gaining increasing public concern. However, many countries have not set their own health risk assessment (HRA) framework and most of the existing studies directly referred to the USEPA risk assessment model and parameters. For those countries that do not propose an original HRA framework, the experience of developed countries is crucial for advancing their own HRA system. This study systematically reviewed the development of HRA framework in some representative developed countries. The theoretical basis, conceptual model, progress, and challenges of HRA researches concerning soil heavy metals pollution were summarized. By recalling and comparing the health risk-related laws and guidance in the USA, UK, and Japan, results showed that the construction of HRA framework varied between these countries, but HRA has become the main method for deriving their soil environmental criteria. We further summarized the evaluation scales, land use types, exposure pathways, and sensitive receptors of HRA studies, and highlighted the key parameters affecting health risk outputs. There has been a shift toward the incorporation of probabilistic modeling, metals bioavailability, and sources emission characteristics into recent HRA studies. Nonetheless, challenges remained on how to minimize the uncertainty of generating probability distribution and detecting metal bioavailability. To facilitate the development of HRA framework, it was advised that developing countries should strengthen the theoretical researches of health risk and localization researches of exposure factors. Future directions are suggested to tend to: 1) promote sensitive analysis to quantify the impact of distribution assumptions on health risk outputs, 2) derive reasonable risk threshold and consistent evaluation protocol for bioavailability-based health risk assessment method, and 3) strive to explore the combined health effect of exposure to heavy metals in soil through source-media-receptor integrated studies.

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Blesbokspruit wetland is one of the least conserved ecosystems in the Southern Africa region with active and latent threats of anthropogenic contamination stretching over decades of mining wastewater discharge, agricultural run-off, and a consistent influx of untreated sewage. This study provides an insight into the present-day spatial distribution of heavy metal contamination and the role of localised macrophytes in their phytoremediation. With exception of the first sampling point, the concentration of heavy metals in water samples throughout the wetland was within limits however findings from sediment samples were the inverse. The concentrations of Chromium and Nickel significantly exceeded both effect range low (ERL) and effect range medium (ERM) limits (250-430 mg/Kg and 73-151 mg/Kg respectively) as set out by international sediment quality guidelines. Emergent- Phragmites australis, Typha capensis, and free-flowing-Eichhornia crassipes macrophytes, which are naturally localised to the wetland were found to have varying bioaccumulation potential for different heavy metals; Bioconcentration of heavy metals in emergent macrophytes was relatively low especially for Nickel and Chromium compared to free-flowing macrophytes. E. crassipes accumulated significant amounts of the heavy metals with root concentrations of up to 17.23, 116.6, 330.5, and 342.9 mg/Kg for Arsenic, Lead, Nickel, and Chromium respectively. The emergent macrophytes were however found to bioconcentrate Arsenic up to 1.15 L/Kg (T. capensis) and 9.9 L/Kg (P. Australis) at sites 4 and 5 respectively.   Findings with regards to bioconcentration especially of the E. crassipes, validate recommendations for the utilization of hyperaccumulating macrophytes for the natural recovery of these heavy metals towards alleviating the anthropogenic stress on this valuable ecosystem.

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Over the last decades, the concern about air pollution has increased significantly, especially in urban areas. Active sampling of air pollutants requires specific instrumentation not always available in all the laboratories. Passive sampling has a lower cost than active alternatives but still requires efforts to cover extensive areas. The use of biological systems as passive samplers might be a solution that provides information about air pollution to assist decision-makers in environmental health and urban planning. This study aims to employ subaerial biofilms (SABs) growing naturally on façades of historical and recent constructions as natural passive biomonitors of atmospheric heavy metals pollution. Concretely, SABs spontaneously growing on constructions located in a tropical climate, like the one of the city of Barranquilla (Colombia), have been used to develop the methodological approach here presented as an alternative to SABS grown under laboratory conditions. After a proper identification of the biocolonizers in the SAB through taxonomic and morphological observations, the study of the particulate matter accumulated on the SABs of five constructions was conducted under a multi-analytical approach based mainly on elemental imaging studies by micro Energy Dispersive X-ray fluorescence spectrometry (µ-EDXRF) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray spectrometry (SEM-EDS) techniques, trying to reduce the time needed and associated costs. This methodology allowed to discriminate metals that are part of the original structure of the SABs, from those coming from the anthropogenic emissions. The whole methodology applied assisted the identification of the main metallic particles that could be associated with nearby anthropogenic sources of emission such as Zn, Fe, Mn, Ni and Ti by SEM-EDS and by µ-EDXRF Ba, Sb, Sn, Cl and Br apart others; revealing that it could be used as a good alternative for a rapid screening of the atmospheric heavy metals pollution.

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The cascade hydropower development in the Lancang River has significantly modified the hydrologic regime and is consequently responsible for many local environmental changes. The influence of the altered hydrological regime on heavy metals accumulation in the soils of the riparian zone was evaluated for the Xiaowan Reservoir (XWR). Specifically, this study focused on investigating the trace metals As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn and their concentrations in the riparian soils. Furthermore, this research aimed to examine the contamination levels of heavy metals by employing the geoaccumulation index (Igeo) and the ecological risk index (RI), respectively. Additionally, the relationship between heavy metals and water level fluctuations as caused by the dam operation was explored. The results showed that heavy metals deposits occurred in relatively low levels in the riparian soils of XWR, even though several of these metals were revealed to occur in higher concentrations than the local background value. The Igeo assessment indicated that the riparian soils exhibited slight pollution by Hg at the Zhujie wharf (ZJW) and Cr at the transect of the Heihui River (HHR), and moderate contamination by As at ZJW. Moreover, the RI revealed that As in riparian soils is moderately hazardous while Hg poses a high risk at ZJW. The polluted water and sediments from upstream and upland of the riparian zone may be contributing to the changed concentrations of heavy metal in the riparian soils. The present study inferred that the WLFs due to reservoir impoundment play a vital role in the accumulation of trace metals in the riparian zone. However, more exhaustive investigations are necessary for verification.

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Soil heavy metal pollution is widespread around the world. Compared with hyperaccumulation plants, non-hyperaccumulator plant communities have many advantages in the remediation of heavy metals pollution in soil. The application of nitrogen (N) and phosphorus (P) is inexpensive and convenient, which can promote the growth of plant. N and P fertilizer might increase plant community remediation of heavy metal polluted soils. In our study, the effects of N and P fertilizer on remediation of soil Cd, Cu, Pb pollution by plant community were studied through a greenhouse experiment. Our results indicated that addition of N, P and N + P fertilizer increased plant community aboveground biomass. Simultaneously, addition of N and P fertilizer increased the accumulation of heavy metals in aboveground of the plant community and accelerated plants absorption soil heavy metals. Among them, N fertilizer had the best effect. Our results provide an inexpensive method for remediation heavy metal pollution of contaminated farmland, abandoned land and mine tailings, etc.

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This study aimed to assess the spatial distribution, contamination levels, pollution degree and ecological risks of eight heavy metals (Cd, Cr, Co, Cu, Mn, Ni, Pb and Zn) in topsoils of UMaT, Brahabobom, A'koon, Boboobo and Bogoso Junction (areas in Tarkwa, a mining town in Ghana). Eighty soil samples were collected, and metal concentrations were determined using atomic absorption spectroscopy (AAS). The results revealed that Cu, Ni, Pb and Zn concentrations exceeded the WHO/FAO (2001) standard in some areas. The geoaccumulation index (Igeo) value of metals in soils under study revealed extreme contamination by Pb and Mn; however, Mn was in abundance due to the presence of Mn minerals in the study area. The study area was also moderately contaminated by Cd, Cu and Zn. Cd and Pb posed a considerable and very high potential ecological risk to the study area, respectively, especially at Bogoso Junction. The two metals were mainly from vehicular traffic and the activities of auto mechanics at Bogoso Junction. Nemerow's pollution index also revealed that about 20% of the study area was polluted, mainly from Cu and Pb concentrations.

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The golden snub-nosed monkey is one of the most endangered animal species endemic to China. In order to explore the characteristics and health risks of golden snub-nosed monkeys exposed to heavy metals, we collected the plant food sources, soil, and water samples from the golden snub-nosed monkey habitat in the Shennongjia Mountains; examined the contents of seven heavy metals (Cu, Zn, Pb, Cd, Cr, Ni, and As); and adopted the comprehensive pollution index, potential ecological risk index, and Nemerow index to evaluate pollutants in the water, soil, and food plants. At the same time, the Target Hazard Quotient method was used to assess heavy metals in the food plants. The results showed that the heavy metal concentration of the habitat water was 0.004-1.220 µg·L-1. The water comprehensive pollution index showed that the habitat water was safe. In addition, the ω(Cd)(0.162-0.822 mg·kg-1) in the soil was 2.71 times the background value of the soil in Hubei province, indicating a moderate risk of ecological harm. The over-standard rates of Pb, Cd, Cr, and Ni in food plants were 29%, 29%, 18%, and 35%, respectively; the pollution indexes of lichen and bark were 6.038 and 7.709, which were at a heavy pollution level; and the pollution indexes of Abies fragesii and Vicia cracca were 2.716 and 2.034, which indicated a moderately polluted level. The rest of the plants were at a safe level. Our health risk analysis showed that the risk of lichen and bark were higher than that of leaves, followed by fruits. Among the seven metals, As most threatened the health of the golden snub-nosed monkeys (THQ>1). In general, heavy metals had polluted the habitats of the golden snub-nosed monkeys in the Shennongjia Mountains, and we are certain that the heavy metal pollution was associated with human activities. Thus, human activities in the Shennongjia Mountains should be reasonably restricted in the future. Our results can provide scientific support for the population conservation of golden snub-nosed monkeys in China and provide research samples in the health risk valuation of heavy metals in endangered animals through food plants.

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Soil archaeal communities play an essential role in the biogeochemical cycles of agricultural ecosystems. However, the response and mechanisms of soil archaeal community structure and assembly processes to heavy metal pollution remain poorly understood. This study examined the archaeal community composition and assembly process and their relationships with environmental factors in arable soils around high geological background areas, metal enterprises, and mining areas, based on high-throughput sequencing. The arable soils within the study area exhibited high spatial heterogeneity of heavy metal content, as well as severe cadmium pollution. The ecological risk levels were high in some soil samples from mining areas, but low to moderate in other soil samples. Crenarchaeota (62.7%-98.3%) was the dominant phyla in all soil samples, followed by Halobacterota (1.1%-23.2%). The pH, organic matter, arsenic, and lead contents of the soil were significantly correlated with the archaeal community (P<0.05), making them the main driving factors of archaeal community structure. The null-model analysis showed that the assembly process of the archaeal community was mainly influenced by heterogeneous processes, including heterogeneous selection (deterministic process) and dispersal limitation (stochastic process). Heterogeneous selection played a vital role in our study areas, while homogeneous selection only occurred in samples around the metal enterprises. Therefore, environmental selection was the ultimate driver of the archaeal community assembly process in this study, and its relative importance varied according to habitat type. Environmental heterogeneity increased the contribution of heterogeneous selection to community assembly, thus enhancing the community's resistance to environmental stress, and contributing to the stability and sustainability of the agricultural ecosystem.

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The systematic and scientific assessments on heavy metal pollutions and water quality characteristics are greatly important to protecting the river and coastal eco-environment. In this paper, sediment size, organic matter, total nitrogen, total phosphorus, and heavy metal contents were analyzed by collecting surface sediments and surface water in the reservoir control reach of the middle Han River. Besides, sediment enrichment factor and sediment pollution index were used to evaluate the heavy metal pollution, and enrichment analysis and redundancy analysis were applied to analyze the sources of heavy metals in sediments. The results show a low heavy metal content in the surface water, and the water quality is graded as a Good level. The average enrichment factor of Cd in surface sediments reached 4.63. Zn and Cu also showed significant enrichment in the tributary sediments, whose content far exceeded the background value of soil elements. Thus, the potential ecological risk of heavy metals was at a medium level. Statistical analysis and enrichment factors showed that the accumulation of heavy metals in sediments was affected by pollutant input and reservoir regulation, and it was urgent to conduct an integrated regulation of the heavy metals in river sediment. This study provided an insight into the understanding of feasible assessment for heavy metal contaminated sediment.

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Spatiotemporal distributions of heavy metals (HMs) and their contamination status linked with the sedimentary environment were investigated in 2 monitoring years (MY-I and MY-II) along the Pakistan coast. The concentrations of HMs in sediments were analyzed through an atomic absorption spectrometer and presented the following order: Fe > Zn > Cu > Pb ≈ Cr > Ni > Co > Cd in MY-I and Fe > Cr > Zn > Ni > Cu > Pb > Co > Cd in MY-II. In the coastal sediments, all HMs surpassed the edges of shale values and sediment quality guidelines, excluding Fe. The burial flux (FB), mass inventory (MI), and deposition flux (FD) of HMs were evaluated and compared to explore the potential of sediments to adsorb and desorb the metals into the marine environment during the last decade. Metal-specific pollution indices (Igeo, EF, Cf, and Er) presented moderate contamination of Cu, Zn, Cr, Ni, and Co but considerable contamination of Pb and Cd in sediments. However, site-specific geoindicators (CD, RI, and PLI) signified the Sandspit as the highest polluted site along the coastal vicinity. Multivariate analyses via principal component analysis (PCA) and cluster analysis (CA) also highlighted the significant interactions between geochemical properties. The current study concluded the high pollution state toward the HMs and rendered the knowledge for policymaking and conserving the coastal and estuarine environment of Pakistan bordering the Northern Arabian Sea.

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In analytical chemistry, biomonitoring is known as the methodology, which consider the use of living organisms to monitor and assess the impact of different contaminants in a known area. This type of monitoring is a relatively inexpensive method and easy to implement, being a viable alternative to be developed in sites where there is no infrastructure/instruments for a convenctional air quality monitoring. These organisms, having the capability to monitor the pollution, are also known as passive biomonitors (PBs), since they are able to identify possible contamination sources without the need of any additional tool. In this work, a multianalytical methodology was applied to verify the usefulness of naturally growing Grimmia genus mosses as PBs of atmospheric heavy metals pollution. Once mosses were identified according to their morphology and taxonomy, thei ability to accumulate particulate matter (PM) was determined by SEM. EDS coupled to SEM also allowed to identify the main metallic particles deposited and finally, an acid digestion of the mosses and a subsequent ICP-MS study define more precisely the levels of metals accumulated on each collected moss. The study was focused on six sampling locations from the Bilbao Metropolitan area (Biscay, Basque Country, north of Spain). The experimental evidences obtained allowed to propose naturally growing Grimmia genus as PB of atmospheric heavy metals pollution and to identify the anthropogenic sources that contribute to the emission of the airborne particulate matter rich in metals, evaluating in this sense the atmospheric heavy metals pollution of the selected locations.

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Heavy metal pollution is widespread, and has an increasing trend in some countries and regions. It can be easily accumulated in plants, leading to plant species loss and affecting plant community composition. Artificial restoration can conserve plant diversity in contaminated soils and accelerate the recovery of polluted ecosystems. The application of nitrogen (N) and phosphorus (P) is inexpensive and convenient, which can increase the resistance of plants to adversity and promote the growth of plants in heavy metal polluted soils. In order to examine the effect of N and P nutrition on the conservation of plant community, we conducted a comparison experiment in greenhouse using soil with low N and P concentration, and set five treatments: C (soil with no heavy metals and fertilizer addition), H (soil with heavy metals addition but with no fertilizer), HN (soil with heavy metals and N addition), HP treatment(soil with heavy metals and P addition), HNP treatment (soil with heavy metals, N and P addition). Our results showed that heavy metal pollution reduced plant species by 300%, and significantly decreased plant diversity (P < 0.05). N addition increased the richness of plant species and increased the dominance of Euphorbia peplus, but had no significant effect on plant diversity and community structure, while reduced the evenness of plant species. P addition of HP and HNP treatments restored plant species richness and increased plant diversity under heavy metal pollution. The plant community structures of these two treatments were more similar to that of group C. Compared with N addition, P addition had a better performance to restoring the species composition and relative dominance of plant communities. Our results provided a guidance for the restoration of plant communities and the conservation of plant species in low N and P concentration soils with the context of heavy metal pollution.

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Hydrocalumite (Ca-Al-LDHs) is a new type of layered composite metal hydroxide that has a large specific surface area, high anion exchange performance, and high stability. This study focuses on the application of hydrocalumite to remediate different Cd-contaminated farmland soils. These were collected from the Lanping County in the Yunnan Province (highly polluted), Kunshan City in the Jiangsu Province (medium polluted), and Nanjing City in the Jiangsu Province (lowly polluted). Changes in the available Cd, Pb, Zn, and the morphological transformations of these heavy metals in the three soils were investigated through a passivation experiment; moreover, the immobilization mechanism of hydrocalumite was explored by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results showed that hydrocalumite could increase the soil pH and reduce the content of available Cd, Pb, and Zn:the maximum reduction in the available Cd reached 97.7%, 96.3%, and 91.8% in each of the three polluted soils, respectively. The easily exchangeable heavy metals were converted into carbonates, as well as into Fe-Mn oxide organic and residual forms following the addition of hydrocalumite:the passivation effect was more evident in the highly Cd-polluted soil than in the low and medium Cd-polluted soils. Since hydrocalumite possess several adsorption sites, the presence of carbonate impurities and reactive groups (e.g., hydroxyl and carboxyl groups) easily coordinated with Cd, Pb, and Zn can lead to a considerable reduction of heavy metal availability in the soils. Therefore, we conclude that hydrocalumite can be effectively applied to the remediation of farmland soils characterized by different Cd pollution levels.