Soil Pb Concentrations Research Articles

Distribution of cadmium and lead in soil–rice systems and their environmental driving factors at the island scale

Toxic elements, such as Cd and Pb are of primary concern for soil quality and food security owing to their high toxicity and potential for bioaccumulation. Knowledge of the spatial variability of Cd and Pb in soil–rice systems across the landscape and identification of their driving factors are prerequisites for developing appropriate management strategies to remediate or regulate these hazardous contaminants. Considering the role of rice (Oryza sativa) as a dietary staple in China, this study aimed to examine the distribution patterns and drivers of Cd and Pb in tropical soil–rice systems across Hainan Island. To achieve this goal, 229 pairs of representative paddy soil and rice samples combined with a set of environmental covariates at the island scale were systematically analyzed. Arithmetic mean values (AMs) of Cd and Pb in rice were 0.080 and 0.199 mg kg−1, and exceeded the standard limits by 27.1% and 22.7%, respectively. We found that the AMs of Cd and Pb concentrations in paddy soil were 0.294 and 43.0 mg kg−1. Additionally, Cd in 29.26% of soil samples and Pb in 11.35% of soil samples exceeded the risk screening value for toxic elements. The enrichment factor generally showed that soil Cd and Pb on Hainan Island were both moderately enriched. Results obtained from both Spearman's correlation and stepwise regression analyses suggest that the concentrations of soil Cd and Pb are significantly influenced by the soil Na and Fe concentrations. Specifically, an increment of 1 g kg−1 in soil Na caused a rise of soil Cd and Pb by 57.1 mg kg−1 and 34.4 mg kg−1, respectively, while an increase of 1 g kg−1 in soil Fe resulted in a rise by 25.0 mg kg−1 and 14.5 mg kg−1. Similarly for rice grains, an increment of 1 g kg−1 in soil Ca resulted in a rise of rice Pb by 30.8 mg kg−1, whereas an increase of 1 g kg−1 in soil Mg led to a decrease in rice Pb by 14.8 mg kg−1. However, no significant correlation between soil Se and rice Cd concentrations was found. Furthermore, the result of geographically weighted regression revealed that the impacts of soil Na, Ca, Fe, and Mg on rice Cd were more significant in the western region, whereas the effects of soil Na and Fe on rice Pb were stronger in the northeastern region. This study provides new insights for the identification of factors influencing the distribution and accumulation of Cd and Pb in tropical island agroecosystems.

Children's lead exposure in the U.S.: Application of a national-scale, probabilistic aggregate model with a focus on residential soil and dust lead (Pb) scenarios

Lead (Pb) exposures from soil and dust ingestion contribute to children's blood lead levels (BLLs) in the United States. The U.S. Environmental Protection Agency (EPA)'s Strategy to Reduce Lead Exposures and Disparities in U.S. Communities and the Federal Action Plan to Reduce Childhood Lead Exposure describe multi-pronged collaborative approaches. These include reducing multi-media lead exposures nationally using analytical tools such as EPA's Stochastic Human Exposure and Dose Simulation model for lead [SHEDS-Pb; formerly known as SHEDS-IEUBK (Integrated Exposure Uptake Biokinetic model)], which was initially developed and applied with a focus on children's drinking water exposures. In this study we applied SHEDS-Pb to determine what residential soil Pb and dust Pb concentrations (individually and their sum) can keep BLLs of potentially exposed young children in the general U.S. population below specified values, considering aggregate exposures from water, soil, dust, food, and air. We considered two age groups (1 to <2 years and 2 to <6 years), two BLL values (5 μg/dL and 3.5 μg/dL), and two population percentiles (95th and 97.5th). Sensitivity analyses were conducted using several alternative model inputs and data sets, yielding 15 scenarios summarized in the paper. Of those scenarios, we focused on ones with the most recent science and available data. Modeled soil Pb concentrations by age group, population percentile and reference BLL scenarios for the focus scenarios ranged from 70 ppm to 220 ppm; and modeled dust Pb concentrations ranged from 110 ppm to 240 ppm. These results are consistent with current soil and dust Pb concentrations in the U.S. general population and are lower than most of the current U.S. Federal standards. Estimated BLLs compared well with measured BLLs from CDC's NHANES 2009–2016 (0–27 % relative error for focus scenarios). This analysis can be used to inform EPA and other federal Pb efforts.

Deep Learning Based Spatial Distribution Estimation of Soil Pb Using Multi-Phase Multispectral Remote Sensing Images in a Mining Area

Extensive investigation and monitoring of lead (Pb) content of soil is significant for ensuring hazard-free agricultural production, protecting human health, and ecosystem security, especially in a mining area. One temporal period of a hyperspectral image is usually used to estimate the spatial distribution of Pb and other heavy metals, but hyperspectral images are usually difficult to obtain. Multispectral remote-sensing images are more accessible than hyperspectral images. In this study, a deep learning-based model using 3D convolution is proposed to estimate the Pb content from the constructed multi-phase, multispectral remote-sensing images. Multi-phase multispectral remote-sensing images were stacked to generate a data set with more spectral bands to reduce the atmospheric absorptive aerosol effect. At the same time, a neural network based on 3D convolution (3D-ConvNet) was proposed to estimate Pb content based on the constructed data set. Compared with partial least-squares regression (PLSR), random forest regression (RFR), support vector machine regression (SVMR), and gradient-boosting regression (GBR), experimental results showed the proposed 3D-ConvNet has obvious superiority and generates more accurate estimation results, with the prediction dataset coefficient of determination (R2) and the mean normalized bias (MNB) values being 0.90 and 2.63%, respectively. Therefore, it is possible to effectively estimate heavy metal content from multi-phase, multispectral remote-sensing images, and this study provides a new approach to heavy metal pollution monitoring.

Probing the effects of silicon amendment on combined stressors on rice: Lead pollution and blast fungus (Magnaporthe oryzae) infection

As agroecology deteriorates, agricultural production is threatened by the combined stressors of exposure to environmental pollutants and pathogenic microbes. Proper agronomic practices for crop growth management and fertilization require understanding plant tolerance strategies. Both rice blast and heavy metals substantially impair rice crops, while silicon (Si) is an effective amendment to alleviate the combined stressors. Herein, this study was conducted to investigate the rice physiology and pathology perspective on the mechanism of Si alleviation against both lead (Pb) toxicity and Magnaporthe oryzae infection, utilizing pot experiments with inoculation of the virulent Magnaporthe oryzae strain. Exogenous Si reduced the phyto-availability and plant absorption of Pb, resulting in a 73.5% reduction in exchangeable Pb concentration in soil and a 40.23% reduction in rice plants. Furthermore, Si addition boosted the plant antioxidant system by increasing the activities of related enzymes, as the activities of catalase, superoxide dismutase, and polyphenol oxidase were significantly improved while the activity of peroxidase in rice panicles decreased. As a result, an improvement in dry matter quantity by 19.19% was observed compared to treatments without Si application, and the panicle blast severity (PBS) was reduced by 0.4–37.52%. Notwithstanding the interaction between the combined stressors, this study revealed that the speciation of Pb formation in the rhizosphere was the primary contributor to the alleviation of abiotic stresses, whereas the regulation of oxidative stress by enzymatic antioxidants played a dominant role in alleviating Magnaporthe oryzae colonization and impairments. The regulation process may reveal the mechanism of siliceous fertilizer functioning in the paddy system. Thereby the role of exogenous Si in anti-fungal, heavy metal toxicology, and plant physiology needs further study to fully elucidate the role of Si amendment, which is proposed to be considered from the perspective of soil chemistry and plant physiology.

Rapid Estimation of Soil Pb Concentration Based on Spectral Feature Screening and Multi-Strategy Spectral Fusion.

Traditional methods for obtaining soil heavy metal content are expensive, inefficient, and limited in monitoring range. In order to meet the needs of soil environmental quality evaluation and health status assessment, visible near-infrared spectroscopy and XRF spectroscopy for monitoring heavy metal content in soil have attracted much attention, because of their rapid, nondestructive, economical, and environmentally friendly features. The use of either of these spectra alone cannot meet the accuracy requirements of traditional measurements, while the synergistic use of the two spectra can further improve the accuracy of monitoring heavy metal lead content in soil. Therefore, this study applied various spectral transformations and preprocessing to vis-NIR and XRF spectra; used the whale optimization algorithm (WOA) and competitive adaptive re-weighted sampling (CARS) algorithms to identify feature spectra; designed a combination variable model (CVM) based on multi-layer spectral data fusion, which improved the spectral preprocessing and spectral feature screening process to increase the efficiency of spectral fusion; and established a quantitative model for soil Pb concentration using partial least squares regression (PLSR). The estimation performance of three spectral fusion strategies, CVM, outer-product analysis (OPA), and Granger-Ramanathan averaging (GRA), was discussed. The results showed that the accuracy and efficiency of the CARS algorithm in the fused spectra estimation model were superior to those of the WOA algorithm, with an average coefficient of determination (R2) value of 0.9226 and an average root mean square error (RMSE) of 0.1984. The accuracy of the estimation models established, based on the different spectral types, to predict the Pb content of the soil was ranked as follows: the CVM model > the XRF spectral model > the vis-NIR spectral model. Within the CVM fusion strategy, the estimation model based on CARS and PLSR (CARS_D1+D2) performed the best, with R2 and RMSE values of 0.9546 and 0.2035, respectively. Among the three spectral fusion strategies, CVM had the highest accuracy, OPA had the smallest errors, and GRA showed a more balanced performance. This study provides technical means for on-site rapid estimation of Pb content based on multi-source spectral fusion and lays the foundation for subsequent research on dynamic, real-time, and large-scale quantitative monitoring of soil heavy metal pollution using high-spectral remote sensing images.

An investigation into the response of the soil ecological environment to tourist disturbance in Baligou.

The purpose of this study is to understand the response patterns of the soil ecological environment of the Macau Wetland Park to different levels of tourist interference and to provide a scientific basis for the rational development of the Bali Gou ecological tourism plan and the protection and management of the scenic area's ecological environment. Combine the methods of field collection and laboratory physical and chemical data analysis to analyze the impact of the strength of tourism disturbance on the soil ecological environment of Baligou. During the tourist activities in Baligou, the human factors in the process have an impact on the physical aspects of the scenic area's soil, such as soil bulk density, color tone, porosity, compactness, capacity, and leaf litter. In addition, pH value, soil enzyme activity, organic matter, and heavy metals in the soil have caused some interference. The overall data show that the dynamic of soil indicators is background area < buffer area < disturbed area,where the sample area is affected by human trampling and infrastructure construction and other disturbances leading to regular changes in the content of Pb and Cr in the sample soil, while the content of other heavy metals is lower than the national standard.The range of the most extreme values of the SRI integrated soil ecological response evaluation index was A1 disturbance area = 4.679 and C1 background area = 1.263, respectively. The larger the value of the SRI response index, the greater the impact and negative effect of the disturbance influence of tourism activities on the soil ecological environment of the scenic area, and the higher the level of response of the soil ecological environment of the scenic area to the disturbance of tourism activities. Moderate and reasonable tourism development activities play a role in promoting soil quality in scenic areas. Therefore, it is suggested to carry out reasonable ecological environment planning and take certain macro-measures to prevent the deterioration of the soil ecological environment, so as to achieve a win-win situation of ecological environmental protection while developing the tourism economy in scenic areas.

Landfill leachate has multiple negative impacts on soil health indicators in Hyrcanian forest, northern Iran

The storage of municipal solid wastes in unengineered landfills poses a severe threat to soil functions and health. Wastes seriously threaten human health and the terrestrial ecosystem, especially due to heavy metals. There is a general knowledge gap about the long-term impacts of storage wastes on the soil health indicators which are effective on soil functions. This investigation focuses on the examination of landfill leachate on soil health indicators from different years in the Hyrcanian forest region in northern Iran. For this purpose, soil sampling was done in the summer of 2012 and 2022 (from three depths of 0–10, 10–20, and 20–30 cm and on a surface of 30 cm × 30 cm). Soil samples were randomly collected from a polluted forest used as waste storage and a nearby unpolluted protected forest. In addition to the general soil physical, chemical and biological parameters, the amounts of cadmium (Cd) and lead (Pb) in the soil were also measured. Simultaneously with soil sampling, earthworms (from a depth of 0–30 cm) were collected and identified. Also, the concentration of Cd and Pb in the earthworm's biomass were measured in the laboratory. We found that unpolluted sites had maximum values of N, K, P, and Ca than the polluted sites. In addition, a decrease of soil aggregates stability, nutrient contents, microbial and enzyme activities, and also fauna and microflora abundance were found in the polluted sites in the period 2012–2022. Soil Cd and Pb contents were more in the polluted site in 2022 compared to the unpolluted site. Lumbricus rubellus and Lumbricus terrestris earthworms had significantly higher population in the polluted sites and higher accumulation of Cd and Pb in biomass. According to our results, soil health decreased in the order unpolluted site 2022 > unpolluted site 2012 > polluted site 2012 > polluted site 2022, which corresponds with the reduction of soil health during the release of landfill leachate. This investigation contributes to understand landfill pollution derived from leachate and its effects on soil physical, chemical and biological parameters to help managing landfill leachate. Therefore, the main issue is choosing a landfill system that minimizes the risk of pollution, installing a leachate collection system and constructing a landfill with engineering principles that can reduce the effects of urban waste pollution on soil health. We emphasize that landfilling is dangerous for the environment, so the government should implement sanitary landfilling to prevent further contamination of surface and underground waters, as well as soil in the precious Hyrcanian forest.

Evaluation of Soil Heavy Metal Contamination and Potential Human Health Risk inside Forests, Wildfire Forests and Urban Areas

Recently, due to rapid industrialization and urbanization, many studies have focused on the assessment of soil metal contamination. The present research aimed to investigate the concentration of potentially hazardous elements (Al, Cr, Cu, Fe, Mg, Mn, Ni, Pb, V and Zn) in three different areas (forest, wildfire forest and urban) of the Mediterranean region. Contamination levels were further assessed calculating different indices: contamination factor (CF), geo-accumulation index (GI) and ecological risk (E). The results showed high concentrations of V, Mg and Mn in forest and wildfire forest soils, as well as high concentrations of Al, Fe, Ni, Pb and Zn in urban soils. According to the contamination indices, Pb exceeded the background level in both wildfire forest and urban soils. According to human risk assessment, inhalation appeared the main route of exposure of metals in soils, especially for children. The overall cancer risk was higher than the safe level, especially for Pb. Different relationships were found between the contamination indices and the potential risk of carcinogenic effects according to the diverse metal concentrations. Particularly, wildfire soils showed human health risks mainly linked to Pb, Cu and Cr contaminations, due to human activities, and Ni, due to both anthropogenic and pedogenetic input. Instead, the urban soils showed that Zn contamination, mainly related to urban traffic, influenced the potential carcinogenetic risk in this area. The carcinogenic risk was higher than acceptable values for all the metals assessed. These findings highlighted the need to develop further management practices to protect soils from metal pollution and reduce human health risks.

Translocation, Accumulation, and Comprehensive Risk Assessment of Heavy Metals in Soil-Crop Systems in an Old Industrial City, Shizuishan, Ningxia, Northwest China

In order to explore the environmental geochemistry characteristics of heavy metals (HMs) in soil-crop systems in an old industrial city, the concentration and fraction of HMs in the paddy, wheat, and maize root soil and their seeds were detected and analyzed. Subsequently, statistical methods, risk assessment coding (RAC), the bio-enrichment coefficient factor (BCF), influence index of comprehensive quality (IICQ), and ArcGIS spatial interpolation were used to conduct the translocation, accumulation, and comprehensive risk assessment of HMs in soil-crop systems. The results showed that the average concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in root soil were ranked respectively as follows:12.56, 0.19, 63.48, 23.52, 0.038, 28.86, 21.68, and 69.47 mg·kg-1. HMs in root soil were accumulated to some extent in comparison with the soil background value in Ningxia, especially Cd and Hg, but did not exceed the soil environmental pollution screening value (GB 14618-2018). The average concentrations of the eight aforementioned elements in supporting crop seeds were 0.0149, 0.0112, 0.075, 6.7, 0.0015, 0.67, 0.0427, and 20.48 mg·kg-1 in turn. The over-limit ratio of As, Pb, and Cr in crop seeds was 4%, 3%, and 1%, respectively, relative to the national food safety standards (GB 2762-2017), whereas the other five elements were within the allowable range. In comparison to those in paddy and wheat, HMs hardly tended to translocate to maize seeds from root soil. According to the results of IICQ in soil-crop systems, the cultivated soil was in the state of slight sub-contamination regionally, and only 10% of sampling points showed slight (sub-)contamination-submoderate contamination, where we could replant maize to reduce HMs contamination risk.

Effect of Coconut Fiber Biochar and Its Nitrate Modification on Pb Passivation in Paddy Soils

The effects of coconut fiber biochar (CFB) and nitrate-modified coconut fiber biochar (NCFB) on the passivation of exogenous lead (Pb) in paddy soils and their underlying mechanisms were investigated using soil incubation experiments combined with spectroscopic techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), synchrotron radiation X-ray fluorescence (SRXRF), and Fourier transform infrared absorption spectroscopy (FTIR). The effects of NCFB and CFB on the passivation of exogenous lead (Pb) in paddy soils and its underlying mechanisms were investigated. Compared with that of CFB, the inner wall of NCFB honeycomb pores was rougher, and the amount of alcohol-phenol-ether functional groups containing the C-O structure and the amount of carboxyl groups containing the C[FY=,1]O/O[FY=,1]C-O structure on the surface of CFB was significantly decreased after nitric acid modification. Compared with that in the control (without biochar) paddy soil after 150 d of incubation, the EDTA-extracted Pb content in the paddy soil with CFB and NCFB was reduced by 39.7% and 105.4%, respectively. The carbonate-bound and Fe-Mn oxide-bound Pb contents were significantly lower, and the organic-bound and residue Pb contents were significantly higher in the NCFB-added soil. The SRXRF scans showed that the exogenous Pb was enriched in the microregions of CFB particles rich in Ca and Cu elements and relatively less so in the microregions of soil aggregates rich in the Fe, Mn, and Ti elements. In addition, the characteristic peaks of carboxylates (1384 cm-1) in A-CFBPb and A-NCFBPb were significantly enhanced in the incubation experiment in the presence of exogenous Pb compared to A-CFB and A-NCFB in the absence of exogenous Pb. The addition of CFB or NCFB was more effective in passivating exogenous Pb in paddy soils and promoted the gradual transformation of Pb from unstable to more stable forms in paddy soils to achieve the effect of passivating Pb. The greater amount of carboxyl functional groups in NCFB participated in the passivation of exogenous Pb, which made NCFB more effective than CFB in passivating Pb. NCFB was more effective than CFB in passivating exogenous Pb in paddy soils due to its rougher inner walls of honeycomb pores and abundant carboxyl functional groups. In tropical areas such as Hainan, coconut fiber biochar and its modification can be considered as an environmentally friendly candidate method for the remediation of soil Pb contamination.

Similarity in human health risk assessment using models of soil-blood lead levels (IEUBK) and non-carcinogenic condition (US EPA 2002)

Soil lead (Pb) concentrations in Sydney estuary (Australia) catchment are substantially elevated and strongly associated with traffic networks. This study compared the health risk predictions of blood Pb levels (BLL) in children using the soil IEUBK model and an independent, non-carcinogenic human health risk (NCR) assessment using the soil US EPA 2002 model. The predictions by the two models were significantly correlated (p < 0.001) and showed similar spatial distributions, but the NCR model may be more stringent in protection of human health when exposed to soil Pb in relation to adverse health effect, as the warning soil Pb concentration from the BLL was 4.6-fold higher than that from the NCR. The empirical IEUBK model considers gastric phase adsorption only and of the three exposure pathways (ingestion, inhalation and dermal) assessed by the theoretical NCR model, ingestion was the major exposure route. The reason for the similarity in outcomes of the two models is unknown, however the close correlation may be due to broadly similar formulations and, or that neurological and non-carcinogenic risks may be related to the adverse effects of Pb on bodily function. Parallel studies of human health risk based on BLL and NCR models have not been attempted previously and this opportunity to compare results from the two health risk assessments employing the same soil metal data is therefore unique.

Sepiolite, Palygorskite, and Triple Super Phosphate on the Uptake of Heavy Metals by Two Iranian Wheat Cultivars Inoculated With Piriformospora indica Fungus

Background and Purpose: Soil remediation in contaminated soils is an important factor of environmental research. This research evaluated the effect of sepiolite, palygorskite, and triple super phosphate (TSP) on decreasing the heavy metals uptake by wheat cultivars inoculated with Piriformospora indica (P. indica). Materials and Methods: Treatments included applying sepiolite, palygorskite (at the rate of 0% and 5% (W/W), and TSP (0% and 0.5% W/W) in the Pb- and Zn-polluted soil under cultivation of 2 wheat cultivars (Mihan and Pishgam cultivars) that inoculated with P. indica fungus. Plants were harvested after 90 days, and Pb and Zn concentrations in soils and plants were measured using atomic absorption spectroscopy. Furthermore, the catalase (CAT) enzyme activity was also measured. Results: With applying 5% (W/W) sepiolite and palygorskite, the plant Pb concentration was significantly reduced by 11.8%, while the plant Zn concentration increased by 13.9%. Plant Zn and Pb concentrations considerably increased and decreased following plant inoculation. However, plant cultivars showed different results. Our results showed that the Pb and Zn concentrations were lower in Mihan than in the Pishgam wheat cultivar. In addition, increasing soil Pb availability caused a significant increase in CAT enzyme activity. Soil contamination with heavy metals had a negative impact on plant root colonization. Conclusion: The interaction of plant cultivars and P. indica significantly affected plant heavy metal uptake by plants. However, environmental studies have found that applying organic amendments like nan-clays or TSP can reduce the absorption of Pb by plants.

TRANSFER OF HEAVY METALS IN SOIL IN-PLUM CULTIVATION: A FIELD STUDY IN ADAMACHI IASI, ROMANIA

Currently, global environmental concerns about heavy metal pollution are driven by rapid urbanization and industrial development. Therefore, a field study was conducted to assess the concentration of heavy metals (Pb, Co, Zn, Ni and Cu) in orchard soils and its transfer to two plum varieties (Stanley and Anna Späth) at Adamachi Farm – Iasi University of Life Sciences (IULS). In addition, heavy metal transfer (MTF), daily metals intake (DIM) and the index of health risk (HRI) were evaluated. The concentration of Pb, Co, Zn, Ni and Cu in soil and plum leaves samples were analyzed using atomic absorption spectrometry after acid digestion with a mixture of HNO3 (65%), HCl (37%) and HClO4 (60%). Metal concentration patterns occurred as follows 130.65&gt;76.6&gt;30.36&gt; 21.69&gt;13.26 mg/kg for Cu, Zn, Ni, Pb and Co in soil samples and 20.16&gt;10.00&gt; 2.10&gt;1.68 mg/kg for Zn, Cu, Ni and Pb in plum leaves, while Co residue was not detected. The maximum heavy metal concentrations were found at the soil surface (0 – 30 cm depth) due to soil organo-mineral content and antifungal treatments. The health risk index predicted (HRI) for adults as well as children was in the sequence Pb &gt; Cu &gt; Ni &gt; Zn, suggesting no health risk with values that did not exceed the safe limit (1). Therefore, it is essential to manage the causes and sources of heavy metal transfer prudently and effectively in order to prevent environmental contamination.

Change of microbial communities in heavy metals-contaminated rhizosphere soil with ectomycorrhizal fungi Suillus luteus inoculation

Ectomycorrhizal fungus Suillus luteus has been recognized to harbor the ability of improving rhizosphere soil nutrients and absorbing heavy metals (HMs), but effects of S. luteus inoculation on microbial communities in HM-contaminated rhizosphere soil remain unclear. A comprehensive study involving physicochemical analysis and comparative metagenomics was employed to determine the differences in soil properties, structure and function of microbial communities between inoculation and non-inoculation groups. Results showed that the concentrations of soil organic carbon, total carbon, and total nitrogen of rhizosphere soil in inoculation group were 2.1, 1.7, and 1.3 times as high as that in uninoculated group. Besides, concentrations of Cd, Pb, As, Cu, and Zn in inoculation soil were 79 %, 33 %, 65 %, 14 %, and 51 % lower than that in uninoculated soil. Metagenomic study indicated that S. luteus inoculation had no strong effect on diversity and richness of microbial communities in rhizosphere soil, but increased the relative abundance of certain HM-resistant microorganisms such as phylum Actinobacteria and genus Streptomyces. Metabolism-oriented functional annotation further revealed that in inoculation group the abundance of coding sequences related to nutrients metabolism (e.g., carbon, nitrogen, and sulfur metabolism) and HMs resistance (e.g., HMs transformation and efflux) distinctly differed from that in uninoculated group. In short, our findings may elucidate the potential contribution of S. luteus inoculation that affects the structure composition and metabolic functions of microbial communities to mediate the concentration variation of nutrients and HMs in rhizosphere ecosystem.

Divergent temporal changes of heavy metals in the soil induced by natural versus anthropogenic forces: A case study in the Yangtze River delta area, China

The contributions of natural versus anthropogenic forces on temporal changes of metals in the soil of the Yangtze River delta region were successfully quantified by combining repeated soil sampling, geostatistics and the modified principal component scores and multiple linear regressions approach. The findings show that the mean concentrations of Cu, Cd, As, Hg, Cr and Ni generally exhibited a decrease trend from 2010 to 2020. The decline of soil Hg was most outstanding, decreased by 20 % as a whole. The result of the modified principal component scores and multiple linear regressions approach suggests that the decrease of Hg content was predominately driven by the geochemical processes, with 48 % contribution. The mean soil Pb concentration increased by 40 % from 2010 to 2020. Approximately 76 % of the Pb change was attributed to the strengthened development of Pb-containing battery industry in the south part of the Yangtze River delta region. The Pb battery industry development also contributed 48 % of the change of Cd. The anthropogenic activities involving Cu, Zn or fossil fuel consumption contributed 32–35 % of the changes of As, Cu and Zn concentrations in the soil, and the steel industries contributed 82 % of Cr and 60 % of Ni changes, respectively.

Comparison of urban and rural soils based on speciation of heavy metals by BCR sequential extraction procedure: A case study in the historical and industrial city of Sisak, Croatia

Within the framework of the pan-European project “URban GEochemistry (URGE) in Europe – Soil, children, health”, pedological and geochemical investigations of the soils of the city of Sisak and its adjacent surroundings were carried out, and three urban and two rural soil profiles were examined. The mineralogical composition and concentration of selected potentially toxic elements (PTEs) Cr, Cu, Ni, Pb and Zn in the soil were determined. The Community Reference Bureau of Reference (BCR) sequential extraction procedure (SEP) of these PTEs was undertaken and the potential risk to human health and the environment was assessed. The concentrations of Cr and Ni are generally similar in urban and rural soil profiles, while the concentrations of Cu, Pb and Zn in soil horizons/layers are higher in urban profiles. The extracted fractions of PTEs gave the following general distribution: in urban soil profiles residual (RES) &gt; reducible (ORG) or oxidisable (FEMN) &gt; exchangeable (CARB), except for Cu where ORG &gt; RES &gt; FEMN &gt; CARB, while in rural soil profiles RES &gt; FEMN or ORG &gt; CARB, except for Pb where FEMN &gt; RES or ORG &gt; CARB. The differences between soils in urban and rural profiles depend mainly on the historical land use, i.e. on the duration and intensity of anthropogenic influences on the soil and, to a lesser extent, on the geogenic origin of the parent material and the pedogenic processes. The studied elements in the urban soil profiles are predominantly of anthropogenic origin, indicating a possible influence of the ancient settlements of Segestica and Siscia and of heavy industry in the 20th century. The anthropogenic influences on the rural profiles are low and geogenic influences dominate. Risks to the environment were assessed in the soil profiles based on PTE concentrations in the CARB fraction and the sum of the CARB, ORG and FEMN fractions from BCR SEP. All calculated risks to human health and the environment were rated as no-risk, very low risk and low risk.

Heavy Metal Concentration, Source, and Pollution Assessment in Topsoil of Chuzhou City

In order to understand the pollution level and ecological risk of heavy metals in topsoil of Chuzhou City, a total of 4360 soil samples in Chuzhou City were collected, and the concentrations of eight heavy metals including Cr, Zn, Pb, Cu, Ni, Cd, As, and Hg were measured. Correlation analysis, cluster analysis, and principal component analysis were used to analyze the sources of the heavy metals, and the enrichment factor index, single-factor pollution index, pollution load index, geo-accumulation index method, and potential ecological risk index were selected to assess the environmental risk of the eight heavy metals in the topsoil. The results showed that the average values of Cr, Zn, Pb, Cu, Ni, Cd, As, and Hg contents in the surface soil of Chuzhou City were higher than the background value of that in the soil of Yangtze-Huaihe River Basin of Anhui, and Cd, Ni, As, and Hg were significantly different in space and influenced by external disturbance. The eight types of heavy metals could be divided into four categories based on correlation analysis, cluster analysis, and principal component analysis. Cr, Zn, Cu, and Ni were from natural background sources; As and Hg mainly came from sources of industrial and agricultural pollution; Pb mainly came from the sources of transportation pollution and industrial and agricultural pollution; and Cd came from the sources of transportation pollution, natural background, and industrial and agricultural pollution. The overall pollution degree of Chuzhou City was low, and the ecological risk level was at a slight level based on the pollution load index and the potential ecological risk index; however, the ecological risk of Cd and Hg was generally serious, and these two heavy metals should be taken as the objects of priority control. The results provided a scientific basis for soil safety utilization and classification control in Chuzhou City.

ACCUMULATION OF HEAVY METALS IN CELERY PLANT APIUM GRAVEOLENS AND SOIL IRRIGATED WITH WASTEWATER WITHIN DUHOK CITY KURDISTAN OF IRAQ

Wastewater contains poisonous metals which can be moved and accumulated in plants before entering the human body through the food chain. The aim of this research was to investigate the concentrations of toxic metals such as Nickel (Ni), lead (Pb), and copper (Cu) in wastewater, celery plant and farmlands soils of Duhok city Kurdistan of, Iraq. The heavy metals accumulation in the Celery plants, soil and water samples were analyzed by using an atomic absorption spectrophotometer. The results obtained showed that the mean concentrations of Pb, Ni, and Cu in the wastewater and Celery plants samples ranged from 0.45±0.08 to 5.95±0.2, 0.18±0.01 to 1.95±0.28, 0.02± 0.01 to1.13±0.23 mg/L respectively. The pattern of metal buildup in wastewater-irrigated soil is in the order: Cu &gt; Pb &gt; Ni, and the mean concentration of Pb, Ni and Cu in soil ranged between 21.68±0.42 to 118.57±0.07, 1.27±0.47 to 5.70±0.23, 1.28±0.24 to ± 15.12 0.53 mg/kg-1, respectively. While the mean concentration of Pb, Ni and Cu in celery leaves ranged from 1.04±0.22 to 5.22±0.60, 0.52± 0.22 to 4.31± 0.12, respectively. 1.34 ±0.22 to 19.47±0.82, 1.23±0.04 to 7.29± 2.53, 1.01±0.05 to 5.76±1.32 mg/ kg-1, respectively. According to this study, roots contain more heavy metals than leaves. According to the findings, a few of the sampling sites had Pb, Ni, and Cu values that were exceeded the permissible concentration. Celery plants cannot be planted in the Duhok Valley to prevent excessive heavy metal exposure to human health through vegetables, where the main irrigated water source is sewage from the local municipalities. Celery plant irrigation with wastewater has much greater levels of heavy metals than the controls.

Metal-immobilizing Pseudomonas taiwanensis WRS8 reduces heavy metal accumulation in Coriandrum sativum by changing the metal immobilization-related bacterial population abundances.

Metal-immobilizing bacteria play a critical role in metal accumulation in vegetables. However, little is known concerning the mechanisms involved in bacteria-induced reduced metal availability and uptake in vegetables. In this study, the impacts of metal-immobilizing Pseudomonas taiwanensis WRS8 on the plant biomass, Cd and Pb availability and uptake in two coriander (Coriandrum sativum L.) cultivars, and bacterial community structure were investigated in the polluted soil. Strain WRS8 increased the biomass of two coriander cultivars by 25-48% and reduced Cd and Pb contents in the edible tissues by 40-59% and available Cd and Pb contents in the rhizosphere soils by 11.1-15.2%, compared with the controls. Strain WRS8 significantly increased the pH values and relative abundances of the dominant populations of Sphingomonas, Pseudomonas, Gaiellales, Streptomyces, Frankiales, Bradyrhizobium, and Luteimonas, while strain WRS8 significantly decreased the relative abundances of the dominant populations of Gemmatimonadaceae, Nitrospira, Haliangium, Paenibacillus, Massilia, Bryobacter, and Rokubacteriales and the rare bacterial populations of Enterorhabdus, Roseburia, Luteibacter, and Planifilum in the rhizosphere soils, compared with the controls. Significantly negative correlations were observed between the available metal concentrations and the abundances of Pseudomonas, Luteimonas, Frankiales, and Planifilum. These results implied that strain WRS8 could affect the abundances of the dominant and rare bacterial populations involved in metal immobilization, resulting in increased pH values and decreased metal availability and uptake in the vegetables in the contaminated soil.

Levels of heavy metal in soil and vegetable and associated health risk in peri-urban areas across China

Peri-urban vegetable field plays an essential role in providing vegetables for local residents. Because of its particularity, it is affected by both industrial and agricultural activities which have led to the accumulations of heavy metal in soil. So far, information on heavy metal pollution status, spatial features, and human health risks in peri-urban vegetable areas across China is still scarce. To fill this gap, we systematically compiled soil and vegetable data collected from 123 articles published between 2010 and 2022 at a national level. The pollution status of heavy metals (i.e., cadmium (Cd), mercury (Hg), arsenic (As), lead (Pb), chromium (Cr), copper (Cu), nickel (Ni), and zinc (Zn)) in peri-urban vegetable soils and vegetables were investigated. To evaluate the levels of heavy metal pollution in soil and human health risks, the geoaccumulation index (Igeo) and target hazard quotient (HQ) were calculated. The results showed that mean concentrations of Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn in peri-urban vegetable soils were 0.50, 0.53, 12.03, 41.97, 55.56, 37.69, 28.55, and 75.38 mg kg−1, respectively. The main pollutants in peri-urban vegetable soil were Cd and Hg, and 85.25% and 92.86% of the soil samples had Igeo > 1, respectively. The mean Igeo values of this regions followed the order of northwest > central > south > north > east > southwest > northeast for Cd and northeast > northwest > north > southwest > east > central > south for Hg. The mean Cd, Hg, As, Pb, Cr, Cu, Ni, and Zn concentrations in vegetables were 0.30, 0.26, 0.37, 0.54, 1.17, 6.17, 1.96, and 18.56 mg kg−1, respectively. Approximately 87.01% (Cd), 71.43% (Hg), 20% (As), 65.15% (Pb), 27.08% (Cr) of the vegetable samples exceeded the safety requirement values. The vegetables grown in central, northwest, and northern China accumulated much more heavy metals than those grown in other regions. As the HQ values for adults, 53.25% (Cd), 71.43% (Hg), 84.00% (As), and 58.33% (Cr) of the sampled vegetables were higher than 1. For children, the HQ values were higher than 1 for 66.23% (Cd), 73.81% (Hg), 86.00% (As), and 87.50% (Cr) of the sampled vegetables. The findings of this study demonstrate that the situation of heavy metal pollution in peri-urban vegetable areas across China are not optimistic and residents who consume the vegetables are at high risk of health issues. To ensure soil quality and human health, strategies should be taken to guide vegetable production and remedy soil pollution in peri-urban areas with the rapidly urbanizing China.