Soil Heavy Metal Pollution Research Articles

Assessment of Soil Heavy Metal Pollution and the Ecological Risk in an Agricultural Area from Sánchez Ramírez Province, Dominican Republic

Heavy metal pollution in agricultural soils is one of the main problems in agricultural production worldwide, which threatens human health and the environment. To evaluate the pollution levels of heavy metals and the ecological risks in an agricultural area from Sánchez Ramírez Province, Dominican Republic, the concentration levels of heavy metals (Fe, Mn, Cr, Ni, Cu, Zn, Pb, and As) were measured using energy-dispersive X-ray fluorescence spectroscopy (EDXRF). Several pollution indices, including the geo-accumulation index (Igeo), enrichment factor (EF), and single pollution index (PI), were used to investigate the pollution status. The spatial distribution of different heavy metals in the studied soils was also determined. The mean concentrations of Fe, Mn, Cr, Ni, Cu, Zn, Pb, and As were 73735, 1616, 426; 34; 20; 200; 43; and 5 mg kg−1, respectively. These results indicated that the mean concentration of Cr, Cu, Zn, and Pb exceeded FAO-recommended levels for healthy agricultural soils. However, the potential ecological risks assessment indicated a low-risk status. The results obtained could help improve soil–rice–environment management practices and prevent heavy metal pollution in this type of production system, protecting the health of the local population and the environment.

Assessment of Heavy Metal Contamination and Ecological Risk in Soil within the Zheng–Bian–Luo Urban Agglomeration

As urbanization accelerates, the contamination of urban soil and the consequent health implications stemming from urban expansion are increasingly salient. In recent years, a plethora of cities and regions nationwide have embarked on rigorous soil geological surveys with a focus on environmental quality, yielding invaluable foundational data. This research aims to develop scientifically robust and rational land-use planning strategies while assessing the levels of heavy metal pollution and associated risks. The urban agglomeration encompassing Zhengzhou, Luoyang, and Kaifeng (referred to as Zheng–Bian–Luo Urban Agglomeration) in Henan Province was designated as the study area. Leveraging the Nemerow comprehensive index method alongside the Hakanson potential ecological risk assessment method, this study delved into the pollution levels and potential ecological ramifications of nine heavy metals, namely Cr, Mn, Ni, Cu, Zn, As, Cd, Pb, and Co. Research indicates that the hierarchy of individual potential ecological risks ranges from most to least significant as follows: Cd > Pb > Cr > Ni > Cu > Zn > As > Mn > Co. The concentrations of Cd in both Zhengzhou and Kaifeng surpassed the established background levels. Furthermore, the mean single-factor pollution index values for the heavy metals Cd and Zn exceeded 1, signifying a state of minor pollution. The Nemerow comprehensive index P of Cd and Zn is between 1 < Pcomp ≤ 2, which is considered mild pollution. The comprehensive P values of the other seven metal elements are all less than 0.7, reaching a clean (alert) level. Predominantly, the primary potential risk factor in the superficial soil of the Zheng–Bian–Luo urban agglomeration is Cd, while the ecological risk implications associated with other heavy metal elements are comparatively minimal. The soil environmental quality within the designated study area remains secure, although certain localized areas pose potential risks of heavy metal pollution. A comprehensive assessment of the current state of soil heavy metal pollution is essential to establish a theoretical foundation and provide technical support for soil environmental protection, pollution mitigation, and sustainable utilization.

Different behavior of two strains of the arbuscular mycorrhizal fungus Rhizophagus intraradices on Senecio bonariensis Hook. & Arn. against heavy metal soil pollution: a pilot-scale test

Arbuscular mycorrhizal fungi (AMF) have different biological mechanisms to alleviate stressful conditions in heavy metals (HMs) polluted soil. These mechanisms were widely assessed under controlled/greenhouse conditions, but scarcely studied at pilot or territory scale. The aim of this study was to evaluate the response of two Rhizophagus intraradices strains isolated from soils with different histories of pollution, in association with Senecio bonariensis plants, growing in an engineering vegetal depuration module filled with artificially HMs polluted substrate. Plants inoculated with GC3 strain uptook low amounts of HMs and translocated them to shoot biomass. Heavy metals (Mg, Zn, Mn, Cr, Cu and Ni) and macronutrients (Ca, K, S and P) were accumulated in roots of S. bonariensis when inoculated with GB8 strain, limiting their translocation to the shoot. Uninoculated plants showed high translocation of all studied elements to shoot tissues. Concluding, tested R. intraradices strains have exhibited different phytoprotection mechanisms under extremely toxic concentrations of HMs. Moreover, the development of the assay at such a high Technological Readiness Level represents a novel contribution in this field of study.

Spatial variability and source analysis of soil heavy metals: A case study of the key planting area of special agricultural products in Cangxi County, China.

Heavy metal pollution in farmland soil represents a considerable risk to ecosystems and human health, constituting a global concern. Focusing on a key area for the cultivation of special agricultural products in Cangxi County, we collected 228 surface soil samples. We analyzed the concentration, spatial distribution, and pollution levels of six heavy metals (Cr, Cu, Pb, Ni, Zn, and Hg) in the soil. Moreover, we investigated the sources and contribution rates of these heavy metals using Principal Component Analysis/Absolute Principal Component Scores (PCA/APCS) and Positive Matrix Factorization (PMF) models. Our findings indicate that none of the six metals exceeded the pollution thresholds for farmland soils. However, the mean concentrations of Cr and Ni surpassed the background levels of Sichuan Province. A moderate spatial correlation existed between Pb and Ni, attributable to both natural and anthropogenic factors, whereas Zn, Cu, Hg, and Cr displayed a strong spatial correlation, mainly due to natural factors. The spatial patterns of Cr, Cu, Zn, Pb, and Ni were similar, with higher concentrations in the northern and eastern regions and lower concentrations centrally. Hg's spatial distribution differed, exhibiting a broader range of lower values. The single pollution index evaluation showed that Cr and Ni were low pollution, and the other elements were no pollution. The average value of comprehensive pollution index is 0.994, and the degree of pollution is close to light pollution. Predominantly, higher pollution levels in the northern and eastern regions, lower around reservoirs. The PCA/APCS model identified two main pollution sources: agricultural traffic mixed source (65.2%) and natural parent source (17.2%). The PMF model delineated three sources: agricultural activities (32.59%), transportation (30.64%), and natural parent sources (36.77%). Comparatively, the PMF model proved more accurate and reliable, yielding findings more aligned with the study area's actual conditions.

Modeling risk assessment of soil heavy metal pollution using partial least squares and fuzzy logic: A case study of a gully type coal-based solid waste dumpsite

Continuous release and migration of heavy metals from coal-based solid waste (CSW) dumpsites often results in significant encroachment on ecological lands and pollution of natural environments. As a result, there is an urgent need for long-term and rapid monitoring, analysis, and assessment to control environmental risks associated with large CSW dumpsites. We constructed a new composite model (PLS-FL) that uses partial least squares regression (PLSR) and fuzzy logic inference (FLI) to accurately predict heavy metal concentrations in soils and assess pollution risk levels. The potential application of the PLS-FL was tested through a gully type CSW case study. We compared 20 modeling strategies using the PLS-FL: five types heavy metals (Cd, Zn, Pb, Cr and As) * four spectral transformation methods (first derivative (FD), second derivative (SD), reverse logarithm (RL), and continuum removal (CR)) * one variable selection method (competitive adaptive reweighted sampling (CARS)). The results showed that the combination of derivative transformation and CARS was recommended for estimation, with R2C > 0.80 and R2P > 0.50. When comparing the PLSR model with four traditional machine learning methods (Support Vector Machines (SVM), Random Forests (RF), Extreme Learning Machines (ELM), and KNN), the PLSR model demonstrated the highest average prediction accuracy. Additionally, the FLI process no longer relies on human perception and expert opinion, enhancing the model's objectivity and reliability. The evaluation results revealed that the heavy metal contamination areas of the CSW dumpsite are concentrated at the bottom of the gully, with more severe contamination in the north. Furthermore, a high-risk zone exists in the interim storage area for CSW to the east of the dump. These findings align with the initial detections at the sampling sites and highlight the need for targeted monitoring and control in these areas. The application of the model will empower regulators to quickly assess the overall situation of large-scale heavy metal pollution and provide scientific program and data support for continuous large-scale pollution risk monitoring and sustainable risk management.

Health Risk Assessment of Heavy Metals in Soils of a City in Guangdong Province Based on Source Oriented and Monte Carlo Models

Taking a city in Guangdong Province as the research area, the concentration and spatial distribution characteristics of heavy metals in the surface soil were studied to clarify the situation of soil heavy metal pollution and priority control factors, providing basic data for the prevention and control of soil heavy metal pollution in the city. The content characteristics of heavy metals in 221 soil samples in the city were analyzed, and the potential health risk assessment and source analysis were carried out through the Monte Carlo model, the potential health risk assessment (HRA) model, and the PMF receptor model. It was found that heavy metals ω(As), ω(Hg), ω(Cd), ω(Pb), ω(Cr), ω(Cu), ω(Ni), and ω(Zn) in the soil of the city were 18.16, 0.43, 1.46, 68.57, 98.34, 64.19, 26.53, and 257.32 mg·kg-1, respectively, with a moderate to high degree of variation. Except for Ni concentration, the soil concentrations of other heavy metal elements exceeded the background values of soil in Guangdong Province to a certain extent, and the concentrations of Cd and Zn exceeded the national secondary standards, resulting in severe heavy metal pollution; the main sources of heavy metals were industrial sources, and natural parent materials, lead battery manufacturing, transportation, artificial cultivation, and pesticide and fertilizer inputs also had an undeniable impact on the accumulation of heavy metals in the soil. Heavy metals in the soil had a certain degree of tolerable carcinogenic health risk for both children and adults, whereas non-carcinogenic risks could be ignored. The potential health risk of children was greater than that of adults, and the main exposure route was through oral intake. The input sources of pesticides and fertilizers and As should be the main controlling factors for the health risks of heavy metals in the city's soil, followed by mixed sources and Cr. There were differences in the spatial distribution characteristics and relative pollution levels of heavy metals, and it is necessary to deepen zoning monitoring and control, strengthen soil pollution prevention and control, and reduce human input of heavy metals in soil.

Transcriptome Analysis Revealed the Possible Reasons for the Change of Ni Resistance in Rhus typhina after Spraying Melatonin.

Melatonin (MT) plays an important role in alleviating the stress of soil heavy metal pollution on plants. However, its ability to improve the tolerance of Rhus typhina to Ni stress and its mechanism of action are still unclear. Therefore, MT (0, 50, 100, and 200 μmol·L-1) was sprayed on the leaf surface of R. typhina seedlings under Ni (0 and 250 mg·kg-1) stress to study the differences in growth, physiology, and gene expression. The results showed that exogenous MT could improve the ability of R. typhina to resist Ni stress by inhibiting the degradation of chlorophyll and carotenoid, enhancing photosynthesis, and augmenting the activity of antioxidant enzymes. Moreover, 100 μmol·L-1 MT could increase the Ni concentration in R. typhina seedlings and reduce the translocation factor. Transcriptome analysis showed that MT mainly regulated the expression of related genes in plant hormone signal transduction, starch and sucrose metabolism, and various amino acid metabolism pathways. This study combined physiological and transcriptomic analysis to reveal the molecular mechanism of MT enhancing Ni resistance in R. typhina, and provides a new direction for expanding its application in phytoremediation.

Research And Impact of Bioremediation on Soil Cadmium

There are many studies on the interaction between Cd pollution and bioremediation at home and abroad, mainly local and short-term toxicological effects, and there is a lack of systematic reviews. The purpose of this report is to provide a summary of the research on several bioremediation methods through specific experiments and mechanisms. and a summary and report on the principles and mechanisms of phytoremediation technology and animal remediation technology. In the future, bioremediation technology should focus on further exploration in the treatment cycle and final treatment of materials, avoid secondary pollution, strengthen the prevention and control of soil cadmium pollution, master more scientific soil cadmium pollution prevention and control technology, and expand more experiments and research on bioremediation If necessary, researchers can comprehensively apply and match a variety of different control technologies to enhance the control effect of soil cadmium pollution. It is also hoped that more attention will be paid to some potential future research on remediation methods for soil cadmium pollution, and that bioremediation is not only for the further exploration and discovery of cadmium and other heavy metal pollution in soil.

Impact of Heavy Metal Contamination on Soil and Crop Ecosystem with Advanced Techniques to Mitigate Them

Heavy metal pollution in soils has become widespread globally due to both natural processes and human activities. Geologic and anthropogenic activities, such as mining, industrial processes, and agricultural practices, significantly contribute to heavy metal accumulation in soil, posing threats to both plant and animal health. These metals endure in the environment and build up in organisms because they resist breakdown or metabolism. They enter the food chain via primary producers and move up as higher trophic levels consume them. This contamination adversely affects the overall human health, plant growth, performance, and yield and also impacts the soil properties. To minimize this effect of heavy metal toxicity, bioremediation emerges as a highly effective method for treating such polluted soils, often conducted in situ, making it suitable for crop establishment or reestablishment. Bioremediation encompasses various techniques like bioventing, biostimulation, air sparging, natural attenuation, phytoremediation, vermistabilization, rhizofiltration, biosorption etc. Both microorganisms and plants play crucial roles in bioremediation, with the combined approach ensuring more efficient cleanup. However, the success of this method depends significantly on the specific species involved. Traditional physical and chemical remediation methods are often costly and fail to restore soil suitability for plant growth. In contrast, bioremediation offers a more environmentally friendly and economically viable solution, leveraging natural processes to encourage plant growth on contaminated soils.

A potential slow-release fertilizer based on biogas residue biochar: Nutrient release patterns and synergistic mechanism for improving soil fertility

The large yield of anaerobic digestates and the suboptimal efficacy of nutrient slow-release severely limit its practical application. To address these issues, a new biochar based fertilizer (MAP@BRC) was developed using biogas residue biochar (BRC) to recover nitrogen and phosphorus from biogas slurry. The nutrient release patterns of MAP@BRC and mechanisms for enhancing soil fertility were studied, and it demonstrated excellent performance, with 59% total nitrogen and 50% total phosphorus nutrient release rates within 28 days. This was attributed to the coupling of the mechanism involving the dissolution of struvite skeletons and the release of biochar pores. Pot experiments showed that crop yield and water productivity were doubled in the MAP@BRC group compared with unfertilized planting. The application of MAP@BRC also improved soil nutrient levels, reduced soil acidification, increased microbial populations, and decreased soil heavy metal pollution risk. The key factors that contributed to the improvement in soil fertility by MAP@BRC were an increase in available nitrogen and the optimization of pH levels in the soil. Overall, MAP@BRC is a safe, slow-release fertilizer that exhibits biochar-fertilizer interactions and synergistic effects. This slow-release fertilizer was prepared by treating a phosphorus-rich biogas slurry with a nitrogen-rich biogas slurry, and it simultaneously addresses problems associated with livestock waste treatment and provides a promising strategy to promote zero-waste agriculture.

Multiple pathway exposure risks and driving factors of heavy metals in soil-crop system in a Pb/Zn smelting city, China

Heavy metals (HMs) in soil near metal smelting areas have attracted great interest due to their crucial threat to agricultural product safety and human health. We investigated HMs in agricultural soils and crops (wheat and maize) in a Pb/Zn smelting city, central China; analysed the exposure risk of HMs through multiple pathways in a soil-crop system through Monte Carlo simulations; and identified the key driving factors using random forest (RF) model. The results showed that most soil HMs exceeded their background level. Cd had the highest exceeding rate compared with the screening values and the highest exceeding rate (40%, in wheat) compared with the food safety limit. Additionally, Cd had the highest bioaccumulation capacity in both maize and wheat. In identifying the key driving factors of soil HMs, RF had a satisfactory prediction performance for As, Cd, and Pb, with corresponding R2 values of 0.47, 0.51, and 0.60, respectively, with the dominant factors being distance to the Pb/Zn smelter, coal washery, and road area, respectively. However, Cr and Hg exhibited lower R2 values which may be due to their limited influence from the selected anthropogenic, traffic, and industrial variables. Probabilistic health risk assessments through Monte Carlo simulations revealed that the non-carcinogenic risk was around the risk limit (HI = 1), while the carcinogenic risk for both children and adults exceeded the risk limit (TCR = 1E-04), and adults had higher carcinogenic risk than children, which was due to a longer duration of exposure and higher ingestion rate of crop grains in adults. Cd had the highest carcinogenic risk and the highest probability of exceeding the limiting risk. Briefly, levels of Cd in both soil and crops should be controlled, especially for the source of smelting emissions. The results of this study could be treated as valuable references for policymakers to formulate control strategies for soil HM pollution in agricultural areas near Pb/Zn smelting activities.

Assessment of heavy metal accumulation and its effect on phytochemical profiling in Jacobaea maritima (L.) Pelser & Meijden

Modernization and industrialization have been of great importance in the recent past, yet there are a few disadvantages, including the release of harmful effluents into the environment. The medicinal plants that are found in these heavy metal-polluted soils can have positive and negative effects as well. In this study, the plant Jacobaea maritima (L.) Pelser & Meijden, an important medicinal plant in the field of homeopathy was subjected to 3 different heavy metals: cadmium, chromium and lead at a concentration range of 50 ppm to 250 ppm. The morphological parameters show a clear effect on the growth of the plant and its development, which includes the shoot length and root length reducing by more than 50 % and 25 % in the case of shoot and root respectively. Phytochemical analysis shows significant variation, including chlorophyll. The highest protein is seen in Cr 100 ppm (7.47 mg) and the lowest was found in Cd 250 ppm (0.38 mg). Proline, which is a stress-induced compound, was found to be highest in Pb 200 ppm (1.242 mg/mL) and least in Cr 50 ppm (0.368 mg/mL). The Total Phenolic Content (TPC) was seen to be highest in Cr 250 ppm (3.229 mg/g) and least in control (0.57 mg/g) and the Total Flavonoid Content (TFC) was found to be highest in Cd 100 ppm and least in control (0.04 mg/g) plant which includes root, shoot and leaf.

Evaluation of effects of animal dung composites and Bacillus sp in amended bioremediation of Zn-polluted soil on maize seedlings growth

Heavy metal pollution of arable soils reduces their productivity, hence the need for ecofriendly techniques to ameliorate this increasing menace. In this study, cow dung, poultry wastes and their composites were applied as organic supplements, together with Bacillus sp as plant growth promoting rhizobacteria to amend bioremediation of zinc-polluted soil sample. Effects of amendments on physicochemical, mineral contents, and dehydrogenase activity of soil, as well as on corn seedlings growth rate, protein and chlorophyll contents and bioaccumulation of Zn were analyzed. Results demonstrated an increase in pH and nutrient contents including N, organic carbon, soil organic matter, K etc., of amended soil samples. Amendment with composite of two organic supplements produced highest increase in dehydrogenase activity, recording 2.35±2.04 µgTPFg-1h-1 at 33.75 mg/kg, and 2.19±0.04 µgTPFg-1h-1 at 52.55 mg/kg level of Zn pollution. Number of leaves recorded in most samples reduced with increasing Zn pollution, with seedlings grown on soil samples amended with cow dung alone outperforming others and recorded 10.3±0.5, 11.3±0.5 and 12.3±0.5 leaves at 32.75 mg/kg, 42.02 mg/kg and 52.44 mg/kg levels of Zn pollution respectively. Heights of seedlings in most of amendments also decreased with increasing Zn pollution. Also, seedlings grown on samples treated with cow dung alone were tallest, and recorded 109.0±3.4 cm, 115.8±4.3 cm and 127.3±2.6 cm at 32.75 mg/kg, 42.02 mg/kg and 52.44 mg/kg levels of Zn pollution respectively. Zn bioaccumulation different parts of corn seedlings was generally in the order; roots>leaves>stems, while it was; control samples>composite of poultry wastes and cow dung samples>only poultry wastes samples>only cow dung samples, for various treatments. This buttresses the usefulness of organic amendments, especially cow dung, in bioremediation of Zn-polluted soil used for agricultural activities.

The Hotspots and Trends of Patented Technologies for Heavy Metal-Contaminated Soil Remediation: A Systematic Review

Heavy metal soil pollution severely threatens human health and food safety. This study used PRISMA to systematically review heavy metal-contaminated soil remediation patents in the Derwent Patent Database from 2003 to 2023. A total of 1744 patents were selected. The results of the analysis show that related patent applications are growing around the world. Among them, China has the most significant number of patents, but the layout of transnational patents needs to be revised. Countries have different preferences in transnational patent technology. Technological development is generally balanced, and there is no apparent monopoly. However, the need for continuous in-depth research on inventors is an obstacle to technological development. In addition, the technology in this field is concentrated in chemistry and engineering. Currently, the mainstream technology is soil remediation agents, and thermal desorption technology has also attracted much attention. Future technologies will use new polymer materials and advanced machinery to improve efficiency and control repair costs. In addition, remediation has shifted from the total amount of heavy metals to the control of practical parts. This study summarizes the current status of heavy metal-contaminated soil remediation technology and analyzes future development trends, providing a reference for technology development.

Synergistically Effect of Heavy Metal Resistant Bacteria and Plants on Remediation of Soil Heavy Metal Pollution

Synergistically Effect of Heavy Metal Resistant Bacteria and Plants on Remediation of Soil Heavy Metal Pollution

Industrial hemp (Cannabis sativa L.) can utilize and remediate soil strongly contaminated with Cu, As, Cd, and Pb by phytoattenuation

Industrial hemp (Cannabis sativa L.) has great application potential in heavy metal-polluted soils owing to its safe non-food utilization. However, the fate of heavy metals in different varieties of hemp planted in strongly contaminated natural soils remains unknown. Here, we investigated the growth, heavy metal uptake, distribution, and transfer of nine hemp varieties in soils strongly contaminated with Cu, As, Cd, and Pb. Hemp variety and metal type were the main factors affecting the growth and heavy metal uptake in hemp. The nine hemp varieties grew well in the contaminated soils; however, differences existed among the varieties. The biomass of Z3 reached 5669.1 kg hm−1, whereas that of Yunma No. 1 was only 51.8 % of Z3. The plant height, stalk diameter, and stalk bark thickness of Z3 were greater than those of the other varieties, reaching 168 cm, 9.2 mm, and 0.56 mm, respectively. Permanova's analysis revealed that the total effects of Cu, As, Cd, and Pb on the growth of the nine hemp varieties reached 60 %, with leaf As having the greatest effect, reaching 16 %. , Even in strongly contaminated soils, the nine varieties showed poor Cu, As, Cd, and Pb uptake. Most of the Cu, As, Cd, and Pb were retained in the root, reaching 57.7–72.4, 47.6–64.7, 76.0–92.9, and 70.0–87.8 %, respectively. Overall, the Cu, As, Cd, and Pb uptake of Wanma No.1 was the highest among the nine varieties, whereas that of Guangxi Bama was the lowest. These results indicate that hemp is a viable alternative for phytoattenuation in soils contaminated with heavy metals because of its ability to tolerate and accumulate Cu, As, Cd, and Pb in its roots, and Guangxi Bama is superior to the other varieties considering the safe utilization of hemp products.

Plant Growth-Promoting Bacteria Influence Microbial Community Composition and Metabolic Function to Enhance the Efficiency of Hybrid pennisetum Remediation in Cadmium-Contaminated Soil.

The green and efficient remediation of soil cadmium (Cd) is an urgent task, and plant-microbial joint remediation has become a research hotspot due to its advantages. High-throughput sequencing and metabolomics have technical advantages in analyzing the microbiological mechanism of plant growth-promoting bacteria in improving phytoremediation of soil heavy metal pollution. In this experiment, a pot trial was conducted to investigate the effects of inoculating the plant growth-promoting bacterium Enterobacter sp. VY on the growth and Cd remediation efficiency of the energy plant Hybrid pennisetum. The test strain VY-1 was analyzed using high-throughput sequencing and metabolomics to assess its effects on microbial community composition and metabolic function. The results demonstrated that Enterobacter sp. VY-1 effectively mitigated Cd stress on Hybrid pennisetum, resulting in increased plant biomass, Cd accumulation, and translocation factor, thereby enhancing phytoremediation efficiency. Analysis of soil physical-chemical properties revealed that strain VY-1 could increase soil total nitrogen, total phosphorus, available phosphorus, and available potassium content. Principal coordinate analysis (PCoA) indicated that strain VY-1 significantly influenced bacterial community composition, with Proteobacteria, Firmicutes, Chloroflexi, among others, being the main differential taxa. Redundancy analysis (RDA) revealed that available phosphorus, available potassium, and pH were the primary factors affecting bacterial communities. Partial Least Squares Discriminant Analysis (PLS-DA) demonstrated that strain VY-1 modulated the metabolite profile of Hybrid pennisetum rhizosphere soil, with 27 differential metabolites showing significant differences, including 19 up-regulated and eight down-regulated expressions. These differentially expressed metabolites were primarily involved in metabolism and environmental information processing, encompassing pathways such as glutamine and glutamate metabolism, α-linolenic acid metabolism, pyrimidine metabolism, and purine metabolism. This study utilized 16S rRNA high-throughput sequencing and metabolomics technology to investigate the impact of the plant growth-promoting bacterium Enterobacter sp. VY-1 on the growth and Cd enrichment of Hybrid pennisetum, providing insights into the regulatory role of plant growth-promoting bacteria in microbial community structure and metabolic function, thereby improving the microbiological mechanisms of phytoremediation.

Spatial distribution characteristics and pollution evaluation of soil heavy metals in Wulongdong National Forest Park

To scrutinize the spatial distribution attributes of soil heavy metal content and discern its pollution status within the expanse of Wulongdong National Forest Park, a meticulous investigation is imperative. Three altitude gradients of 900, 1000, and 1069 m were selected on the shady and sunny slopes of Wulongdong National Forest Park, and a total of 300 soil sample points were collected. Soil samples were collected in layers, and the contents of seven soil heavy metal elements, Cr, Cd, Hg, Ni, Se, As, and Pb, were measured. With regard to the national soil element background values, the single factor index method, Nemerow index method, and pollution load index were employed to undertake a thorough assessment of soil heavy metal pollution. (1) The contents of heavy metal elements Cr, Se, As, and Pb in the 0–20 cm soil layer of Wulongdong National Forest Park are lower than the national soil element background value and the Henan soil element background value; the Cd and Hg contents exceed the national soil element background value. The value and Henan soil element background value are 2.2 times and 2.92 times the national soil element background value, and 2.75 times and 9.5 times the Henan soil element background value respectively; Ni content is lower than the Henan soil element background value, but higher than the national soil element background value. The background value is 1.03 times its content. The coefficients of variation of the contents of seven heavy metal elements are all greater than 50%, among which Hg shows extreme variation, and the remaining six are highly variable. (2) In the same soil layer, the Cr and As contents are lower on sunny slopes than on shady slopes, and the contents of Pb, Ni, and Hg are generally higher on sunny slopes than on shady slopes. On sunny slopes, the contents of As, Cd, and Hg decrease with increasing altitude, and the Se content increases with increasing altitude; while on shady slopes, the contents of Cr, Se, and As decrease with increasing altitude, and Pb and Hg content increase with the increase of altitude; the content of heavy metal element As increases with the deepening of the soil layer on shady slopes, and the Hg content decreases with the deepening of the soil layer on sunny slopes. The contents of other heavy metal elements have no obvious regularity among different slope directions, altitudes and soil layers. (3) The single factor index evaluation results show that in the 0 ~ 20c soil layer and on the sunny slope, Hg is heavily polluted, Cd is moderately polluted, Ni is lightly polluted, and Cr, Se, As, and Pb are all non-polluted; On the shady slope, Cd and Hg are moderately polluted, and the other five heavy metal elements are in a non-polluting state. (4) The Nemerow index method evaluation results show that in the 0 ~ 20 cm soil layer, the soil on sunny slopes is significantly more polluted by heavy metals than on shady slopes, and the main pollutants are Ni, Cd and Hg. (5) In the 0 ~ 20 cm soil layer of Wulongdong National Forest Park, the three heavy metal elements Ni, Cd and Hg have reached pollution levels, of which Ni is slightly polluted, Cd and Hg are moderately or above polluted; the sunny slope soil is slightly polluted. Heavy metal pollution, no heavy metal pollution on shady slopes.

The influence of nZVI composites as immobilizing agents on the bioavailability of heavy metals and plant growth in mining metal-contaminated soil

<p>Under the greenhouse scale, nano zero valent iron (nZVI) have been evaluated evaluated by formulation with carboxymethyl cellulose (CMC-nZVI), chitosan (Ch-nZVI), biochar (BC-nZVI), and smectite (SC-nZVI) at rates of 0 and 0.5 and 1% (w/w). The properties of manufactured compounds and their impact on the soil ecosystem planted with safflower (Carthamus tinctorius L.) as a phytoremediation crop for inorganic contaminants in contaminated mining soils have been measured. After 33 days, growth parameters were recorded in harvested plants and the concentrations of some HMs in plant tissues. Furthermore, pH, EC, soluble Na and available Cd, Cu, Pb and Zn concentrations in the treated soil after harvest were analyzed. Results revealed that Ch-nZVI and SC-nZVI application at 0.5% led to a narrow non-significant increase in the dry biomass and the shoot length compared to the control. On the other hand, the application of CMC-nZVI and BC-nZVI resulted in reduced plant growth. All the applied amendments increased soil pH, EC, and soluble Na contents. The soils treated with synthesized nZVI composites showed a considerable increase (non-significant) in available heavy metals in treated soils compared to control. Application of CMC-nZVI1% resulted in increased shoot copper (Cu) and zinc (Zn) (182% and 114%, respectively, compared to control), while Ch-nZVI, SC-nZVI applied at 1%, and BC-nZVI0 applied at 5% resulted in reduce Cu, Zn, and Pb concentrations in roots by 65.2%, 31.4% and 85.5% in Cu, Zn and Pb respectively as compared to control). The phytoremediation indices showed that the uptake and extraction of HMs by safflower plants weren't significant in decreasing heavy metals in polluted soil and the applied materials disabled the actions of hyperaccumulated plant used. Results showed that these materials didn’t have a significant effect on immobilize of HMs in mining soil, while the application of Ch-nZVI, SC-nZVI, and BC-nZVI resulted in disabled hyperaccumulated plant to reducing the uptake of Pb, Cu, and Zn. It could be concluded that the application of synthesized nZVI composites to mining polluted soil might be restricted, mainly due to their negative impacts on soil ecosystem besides their side effects on HMs uptake by test hyperaccumulated crop.</p>

Risk assessment of antimony-arsenic contaminated soil remediated using zero-valent iron at different pH values combined with freeze-thaw cycles.

Soil in mining wastelands is seriously polluted with heavy metals. Zero-valent iron (ZVI) is widely used for remediation of heavy metal-polluted soil because of its excellent adsorption properties; however, the remediation process is affected by complex environmental conditions, such as acid rain and freeze-thaw cycles. In this study, the effects of different pH values and freeze-thaw cycles on remediation of antimony (Sb)- and arsenic (As)-contaminated soil by ZVI were investigated in laboratory simulation experiments. The stability and potential human health risks associated with the remediated soil were evaluated. The results showed that ZVI has a significant stabilizing effect on Sb and As in both acidic and alkaline soils contaminated with dual levels of Sb and As, and the freeze-thaw process in different pH value solution systems further enhances the ability of ZVI to stabilize Sb and As, especially in acidic soils. However, it should be noted that apart from the pH=1.0 solution environment, ZVI's ability to stabilize As is attenuated under other circumstances, potentially leading to leaching of its unstable form and thereby increasing contamination risks. This indicates that the F1 (2% ZVI+pH=1 solution+freeze-thaw cycle) processing exhibits superior effectiveness. After F1 treatment, the bioavailability of Sb and As in both soils also significantly decreased during the gastric and intestinal stages (about 60.00%), the non-carcinogenic and carcinogenic risks of Sb and As in alkaline soils are eliminated for children and adults, with a decrease ranging from 60.00% to 70.00%, while in acidic soil, the non-carcinogenic and carcinogenic risks of As to adults and children is acceptable, but Sb still poses non-carcinogenic risks to children, despite reductions of about 65.00%. These findings demonstrate that soil pH is a crucial factor influencing the efficacy of ZVI in stabilizing Sb and As contaminants during freeze-thaw cycles. This provides a solid theoretical foundation for utilizing ZVI in the remediation of Sb- and As-contaminated soils, emphasizing the significance of considering both pH levels and freeze-thaw conditions to ensure effective and safe treatment.