Soil Pb Concentrations Research Articles

Lower Contents of Soil Organic Matter, Macro-Nutrients, and Trace Metal Elements in the Longleaf Pine Forests Restored from the Mixed Pine and Hardwood Forests

Restoration of the longleaf pine forest ecosystem is critical for biodiversity. However, the mixed hardwood forests can grow naturally in the same area. There are limited studies comparing soil organic matter and nutrient contents for restoring longleaf pine forests from the mixed hardwood forest areas in the southeastern USA. In this study, a comparison of the contents in soil organic matter, macro-nutrients, trace metal elements, and litterfall amount, was conducted on the 16 forest stands (4 treatments including stand stages × 4 replicants) at William B. Bankhead National Forest in Alabama through the space-replace-time approach. The results indicate that longleaf pine forests have lower contents of soil organic matter, macro-nutrients, most trace metal elements, and litterfall amount than mixed hardwood forests. However, longleaf pine forests have higher soil Ca, Ba, and Pb contents than hardwood forests. Soil Fe content has more correlations with the contents of other metal elements than soil Mn. The results suggest that multiple ecosystem functions, including soil ecology, must be considered in the regional restoration of the longleaf pine ecosystem. Longleaf pine forests with a certain amount of mixed hardwood trees may be a good way to maintain soil organic matter and nutrients.

The Isolation of Lead-Tolerant PGPR from Red Clover Soil and Its Role in Promoting the Growth of Alfalfa.

Alfalfa (Medicago sativa L.) is an outstanding species used for the remediation of heavy metal-contaminated soil, and our previous research has shown that PGPR can promote plant growth under high-concentration lead stress. This discovery has forced scientists to search for PGPR strains compatible with alfalfa to develop an innovative bioremediation strategy for the remediation of lead-contaminated soil. This study used lead-tolerant rhizosphere soil of red clover as experimental material; cultured, isolated, and screened 52 excellent lead-tolerant bacteria that promote rhizosphere growth; and then inoculated them into alfalfa. Marked differences existed in the secretion of auxin, protease, and ACC deaminase among these strains. The results indicated that Pseudomonas spp. (strain Y2), Pseudomonas spp. (strain Y22), and Bacillus spp. (strain Y23) exhibited a strong growth-promoting ability in alfalfa, and there was no antagonistic reaction among the three strains, enabling their coexistence. The pot experiment manifested that strains Y2, Y22, Y23, and YH (a mixture of Y2, Y22, and Y23) could increase the plant height, root length, fresh and dry weight above ground, and fresh and dry weight below ground of alfalfa. They could all significantly raise the chlorophyll content and antioxidant enzyme activity in alfalfa (p < 0.05) and the content of malondialdehyde (MDA) in alfalfa. Furthermore, the concurrent inoculation of three distinct types of plant growth-promoting rhizobacteria (PGPR) significantly diminished lead (Pb) concentrations in rhizosphere soil, enhanced the levels of available potassium (AK) and available phosphorus (AP), and augmented the capacity of plants to absorb Pb. The results imply that PGPR can be employed to facilitate plant growth and microbial-assisted remediation of lead and other heavy metal-contaminated soil and establish a basis for further research on the growth-promoting mechanism of PGPR in plants.

Characteristics and Comprehensive Quality Assessment of Heavy Metals in Soil-crop System of High Geological Background Area

Heavy metals （HMs） pollution in agricultural soil-rice systems has attracted worldwide attention as it directly threatens regional ecological security and human health. To understand the heavy metal pollution of agriculture soil and rice in the high geological background areas, a total of 200 paddy soil and rice samples were collected in southeast Chongqing. The concentrations of arsenic （As）, cadmium （Cd）, chromium （Cr）, copper （Cu）, mercury （Hg）, nickel （Ni）, lead （Pb）, and zinc （Zn） in paddy soil and rice were analyzed. The comprehensive impact index （IICQ） was used to evaluate the quality of heavy metals in soil-rice. The results showed that the mean concentrations of As, Cd, Cr, Hg, and Pb in soil were higher than their corresponding background values of Chongqing soil and the average values of Chinese surface soil, indicating the accumulation of HMs enrichment of these metals in the paddy soils. Compared with China's soil environmental quality standard of agricultural land （GB 15618-2018）, only 20.5% of rice samples containing Cd exceeded the national food safety standard （GB 2762-2022）, though the Cd and Hg sample contamination rates of the sampling sites were 82% and 22.5%, respectively. The evaluation results of heavy metal pollution, such as Cd in soil and crops, were quite different. With the increase in soil pH value, the average content of Cd in the soil gradually increased, but the average content of Cd in rice seeds decreased by 0.245 mg·kg-1, and the excess rate of rice seeds decreased by 42.14%. The Cd content in rice seeds was significantly correlated with the Cd ion exchange state and water-soluble state in the soil. The higher the soil pH value, the lower the proportion of bioactive components in the soil, and the pH of the soil was the main factor affecting the safety of rice in the study area. The comprehensive quality evaluation results showed that moderate and severe pollution were the main pollution levels in the study area, but most of the rice seeds were in a clean state, a few were slightly polluted, and none showed mild or above pollution. The basic safety of rice was in the alkaline area with a pH&gt;7.5. In strongly acidic soil with pH&lt;5.5 and below, the excess rate of rice seeds could reach 45%. Moreover, it is recommended to apply quicklime or calcareous soil conditioner to improve soil acidification, reduce the activity of Cd bioactive components, and improve the safety of rice and other agricultural products.

Characteristics, Risk Assessment of Microplastics, and Heavy Metal Pollution in Farmland Soils in the Upper Hanjiang River

To investigate the pollution of microplastics and heavy metals from farmland soils in the upper Han River, the pollution status and distribution characteristics of pollutants were systematically analyzed. The risk level of pollutants was evaluated using methods such as the potential ecological risk index （RI）. Source apportionment was identified using correlation analysis and cluster analysis. The results showed that ① The abundance of microplastics in farmland soils in the upper Hanjiang River ranged from 360 to 6 300 n·kg-1, with an average abundance of 2 300.73 n·kg-1； the shapes were mainly films （50.00%）； and the majority of the particle sizes were less than 0.5 mm （64.31%）. Polymers of microplastics were PP, PE, PA, PET, and PS. SEM analysis revealed that the surface of microplastics was characterized as rough, porous, cracked, and torn. ② Within the ten heavy metals （V, Cr, Mn, Co, Ni, Cu, Zn, As, Cd, and Pb） that were measured, the average concentrations of heavy metals Cu, Zn, Cd, and Pb were higher than the background values by 1.28, 1.15, 1.91, and 1.34 times, respectively, while the other metals were lower than the background values, and none of the heavy metals exceeded the screening values for pollution risks in the soil environmental quality standard. ③ The study area had moderate microplastic pollution, with a risk level of Ⅱ, and low ecological risk from heavy metal pollution. The compound effect of microplastics and heavy metals needs to be assessed. ④ A significant correlation was observed between microplastics and the content of heavy metals Cr, Ni, As, Cd, and Pb in farmland soils. The sources of pollutants were agricultural-traffic sources, natural-agricultural sources, and natural-industrial sources.

Distribution characteristics and pollution assessment of heavy metals in typical black soil profiles of Haicheng city, Liaoning province, China.

In order to understand the spatial distribution, influencing factors, pollution level and sources of heavy metals in black soil profiles in Northeast China, black soil profile samples were collected from five sampling points in Haicheng City, Liaoning Province, with the deepest profile depth of 50m. The contents of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in soil at different depths were analyzed, and the distribution characteristics and influencing factors of heavy metals in black soil profiles were analyzed. The pollution level of heavy metals in soil was evaluated based on the geo-accumulation index method and enrichment factor method, and the sources of heavy metals in soil were analyzed based on principal component analysis. The results show that the content ranges of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn in the surface soil of the five profile sampling points are 7.74-16.5μg/g, 0.14-0.38μg/g, 75.4-104μg/g, 20.6-36.1μg/g, 0.031-0.20μg/g, 27.8-45.6μg/g, 28.5-45.6μg/g and 56.8-158μg/g, respectively. The Cd, Cr, Ni and Pb contents in the surface soil of the five profiles all exceeded the soil background values in Liaoning and China. Except for profile HCZK02, the contents of 8 heavy metals generally decrease with increasing depth. As the depth of profile HCZK02 increases, As, Hg and Pb show a decrease-increase-decrease change; Cd and Cr show a decrease change and Ni shows a zigzag change; Cu and Zn show a decreasing-increasing-decreasing-increasing trend. Corg, N, TC and TFe2O3 in the profile soil have a very significant impact on the vertical distribution characteristics of heavy metals. There are certain differences in the pollution degree of heavy metals in the surface soil of different profiles. Except for profile HCB01, where Cd and Hg in the surface soil are at moderate pollution levels, the heavy metals in the surface soil of the other profiles are at non-pollution to mild pollution levels. Principal component analysis results show that As, Cr, Cu and Ni belong to natural sources, Cd and Hg belong to anthropogenic sources from agricultural activities-atmospheric deposition, and Pb and Zn have both sources.

Impact of Treated Wastewater Use on Heavy Metal Accumulation in Soils and Sudan Grass Crops in the Mexicali Valley

This study investigated the impact of using treated wastewater on the accumulation of heavy metals in soils and sudan grass crops. The transfer rate of heavy metals from soil to Sudan grass was determined. The Sudan crop was established in two plots: one irrigated with fresh water from the Colorado River and the other with treated wastewater from the Las Arenitas treatment plant. Metals Pb, Cr, Cd, Ni, and Cu were evaluated at two soil depths. Results showed that the concentration of metals in the treated wastewater is higher than in freshwater but within permissible limits. At a depth of 0-30 cm, the concentrations (mg/kg) of Pb, Cr, Cd, Ni, and Cu in soils irrigated with fresh and treated wastewater were 24.59, 19.25, 0.61, 25.33, 26.70, and 31.78, 20.10, 28.31, 28.33, respectively. These values show significant differences in the concentration of Pb and Cd. Analysis of metals in the Sudan grass showed similar results for soils irrigated with both types of water, with Pb and Cd not detected. The transfer rate was less than one for all metals. These results indicate no contamination or toxicity risks when using treated wastewater in Sudan grass crops. However, continuous monitoring is necessary to prevent contamination risks. These findings provide a scientific basis for developing policies and strategies for sustainable water resource management in arid and semi-arid regions.

Analysis of Heavy Metal Content of Mn, Cu, Fe, Zn, Pb in Agricultural Irrigation Water and Soil After Tin Mining

Abstract The content of heavy metals Mn, Cu, Fe, Zn, and Pb in agricultural irrigation water and precast tin mining soil revealed that heavy metal concentration levels had exceeded the safe limit according to health standards. The concentration of these heavy metal coils affects plant growth and the quality of agricultural products. Analysis methods used include atomic absorption spectrophotometer and flame emission spectrometry. Data collection from various literature sources that discussed the content of heavy metals in the former tin mine area. The study revealed Mn, Cu, Fe, and Zn in water and agricultural rice field soil according to the quality standard, and the Pb level in irrigated water and soil was quite high, more than 0.1 mg/L, exceeding the limit set by the quality standard. High heavy metal concentrations in post-tin mining areas can endanger human health and the environment. Comprehensive recovery efforts are needed to reduce the content of heavy metals in post-tin mining farmland so that water and soil quality can be improved.

Assessing Environmental Risks of Local Contamination of Garden Urban Soils with Heavy Metals Using Ecotoxicological Tests.

Heavy metal soil contamination in urban areas poses a significant environmental hazard, particularly in regions with historical or ongoing industrial activities. These areas are often polluted with metals such as Pb, Cu, Cd, and Zn, which can be absorbed by plants and pose risks to both ecosystems and human health. This study investigates soil contamination in urban gardens in Wroclaw, Poland, where elevated levels of trace elements were detected. Standard soil analyses, including macroelement content, granulometry, and trace element concentrations, were performed alongside an ecotoxicological evaluation using an Ostracodtoxkit test. The test evaluates the impact of contaminants on organism growth. An uncontaminated urban garden soil served as a reference. This study revealed that Zn, Cu, Pb, and Cd concentrations in soils exceeded limits permitted by Polish regulations in several soil samples. Despite the high concentrations of total metals, the bioavailable forms of these metals (measured by extraction of 1 M NH4NO3 extraction) were significantly lower, highlighting that the total metal content may not fully reflect the environmental risk. Pb was identified as the primary contributor to growth inhibition of test organisms, showing a particularly strong correlation with ecotoxicity. These findings underscore the importance of using ecotoxicological tests to evaluate soil contamination risks.

Applications of geographically weighted machine learning models for predicting soil heavy metal concentrations across mining sites

The accurate prediction of soil heavy metal contamination is crucial for the effective environmental management of abandoned mining areas. However, conventional machine learning models (CMLMs) often fail to account for the spatial heterogeneity of soil contamination, which limits their predictive accuracy. This study evaluated the performance of geographically weighted machine learning models (GWMLMs) in predicting soil Cd and Pb concentrations in abandoned mines in the Republic of Korea. We compared two GWMLMs (Geographically Weighted Random Forest and Geographically Weighted Extreme Gradient Boosting) with four CMLMs (Random Forest, Gradient Boosting, Light Gradient Boosting, and extreme Gradient Boosting). The data used in this study included soil samples from six abandoned mining sites with various geographical and soil input variables. The results showed that the GWMLMs consistently outperformed the CMLMs in predicting heavy metal contamination. For Cd predictions, GWMLMs exhibited on average 0.02 lower root mean square error and mean absolute error values, with a 0.26 increase in R2 values compared to CMLMs. Similarly, for Pb predictions, the GWMLMs showed 0.18 and 0.13 lower root mean square error and mean absolute error values, respectively, and a 0.17 increase in R2 relative to the CMLMs. The findings demonstrate the usefulness of GWMLMs for predicting the spatial distribution of soil heavy metals. SHapley Additive exPlanations analysis exhibited elevation and distance from abandoned mining sites as the most influential factors in predicting both Cd and Pb concentrations. This study highlights the value of GWMLMs that incorporate spatial heterogeneity into CMLMs for enhancing prediction accuracy and providing crucial insights for environmental management in mining-impacted regions.

The Effects of Heavy Metals on Enzyme Activity and Microbial Biomass of the Soil Around the Waste Disposal Site (Case Study of Saravan - Iran)

ABSTRACT Municipal solid waste is considered an environmental threat in Iran. The study was performed on soil near the Saravan dumpsite and measured the concentrations of 8 metals (Zn, Cu, As, Hg, Pb, Cr, Cd, and Ni) in soil, by inductively coupled plasma mass spectrometry. The average content of As, Cu, Cr, Pb, Zn, Hg, Ni, and Cd in soil were 10.48, 20.22, 19.07, 24.95, 28.83, 0.13, 19.91, and 0.1 mg/kg, respectively. The mobility factors based on water-soluble and exchangeable fractions were As (8.85%), Zn (4.19%), Pb (1.85%), Cu (1.60%), and Cr (0.02%), and not detectable for Hg, Ni, and Cd. Evaluation of metals contamination by pollution index, integrated pollution index, and Nemerowʼs pollution index for each metal showed that PI for all metals except Hg was in the range of low to moderate, and for Hg, 50% in high pollution grade; the average of the IPI (1.21), indicated a moderate pollution condition; the mean value of the PINemerow (1.20), which was in slight pollution grade. The correlations between total concentrations of metals, and bioavailable fractions with microbial biomass carbon, basal respiration, microbial quotient, metabolic quotient, urease, and alkaline phosphatase activities were moderate (r = 0.4-0.6). The activity of urease was from 37.79 to 1414.31 µg N gˉ1 dm.2 hˉ1 and alkaline phosphatase from 34.66 to 698.78 µg nitrophenyl gˉ1 dm. hˉ1. Due to the rainy climate and the continuous leaching of the surface soil, we suggested performing waste separation and the treatment of leachate produced before flowing downstream.

Assessment of Selected Heavy Metals Content in Soil and Rice Grown on Farmland around Edozhigi River in Niger State, Nigeria

The global climate continues to deteriorate, resulting in excessive carbon emissions, heavy metal pollution possesses serious threats to human life and modern civilization. The concentration of Zn, Fe, Cr, Pb, Cu and Cd in soil and rice grown in two locations (A and B) AROUND Edozhigi river were determined using standard methods og analysis. Results obtained for location A, indicate high concentration of Zn 9.75±0.55, 9.61±0.54, 1.03±0.58 and 1.69±0.66 mg/kg in soil, root, stem and seed of rice plant respectively. The order of Zn concentration of Zn metal in location B is 2.07±0.55 (soil) &gt; 1.70±0.54 (root) &gt; 1.67±0.58 (stem) &gt; 1.27±0.66 (seed). Concentration of Fe (mg/kg) in soil (25.50±0.00) and root (26.32±0.00) from location B were significantly higher than those of stem (8.46±0.00 mg/kg) and seed (6.98±0.00 mg/kg) respectively. Concentration of Cu (mg/kg) in soil, root, stem and seed from location A and B were between 0.00±0.00 - 0.03±0.40 mg/kg respectively. The low concentration of these metals in soil around Edozhigi river makes the soil fit for growing crops.

Revealing the synergistic spatial effects in soil heavy metal pollution with explainable machine learning models

The identification of factors that affect changes in the heavy metal content of soil is the basis for reducing or preventing soil heavy metal pollution. In this research, 16 environmental factors were selected, and the influences of soil heavy metal spatial distribution factors and the synergy amongst space factors were evaluated using a geographic detector (GD) and the extreme gradient boosting (XGBoost)-Shapley additive explanations (SHAP) model. Three heavy metal elements, namely, Cd, Cu and Pb, in the study region were examined. The following results were obtained. (1) XGBoost demonstrated high accuracy in predicting the spatial distributions of soil heavy metals, with each heavy metal having an R2 value of over 0.6. (2) Geological type map (Geomap) and enterprise density considerably affected the concentrations of Cd, Cu and Pb in soil in the GD and XGBoost-SHAP models. In addition, cross-detection revealed strong explanatory power when natural and human factors were combined. (3) Under the same geological background, the different trends of gross domestic product effects on heavy metals indicated that pollution control measures were effective in economically developed areas, and the economy and the environment could be balanced. Meanwhile, the interaction between the normalised difference vegetation index and enterprise density showed that vegetation could alleviate heavy metal pollution in the region. This study supports strategic decision-making, serving as a reference for the global management of soil heavy metal contamination, sustainable ecological development and assurance of people’s health and well-being.

Research on heavy metal enrichment and transportation in tea plant-soil systems of different varieties.

This study aimed to investigate heavy metal enrichment in different tea plant varieties and their distribution within different plant parts and to clarify the behavioral characteristics of heavy metals in the tea tree-soil system and their influencing factors. In this study, soil samples were collected from the root zones of 13 tea tree varieties in Guizhou, which had been planted for 10years. The aim was to compare the physicochemical properties of tea plantation soils under soil-forming matrixes and consistent management. Additionally, the study investigated the enrichment and transportation patterns of Cd, Cr, Cu, Pb, Zn, and Ni in the tea tree-soil systems of different tea tree varieties. The results showed that the planting of tea trees decreased the soil pH by 0.5; soil nutrients decreased; soil Pb, Cr, Ni, Cu, and Zn contents in the root zone increased; and Cd content decreased. Heavy metals were mainly enriched in the roots, and Zn, Cu, Ni, and other elements related to the protein and enzyme synthesis of tea trees could be mostly transported to the stems and leaves. There were significant differences in the enrichment and transportation of heavy metals among the different tea tree varieties. Under consistent soil-forming parent material, soil pH, organic matter, nutrients, and other indices only had a significant effect on heavy metal enrichment in the tea tree roots. Therefore, in areas with high background soil heavy metal contents, the construction of tea plantations should be based on regional soil environmental conditions to choose tea tree varieties with low heavy metal enrichment capacities to avoid the risk of high background soil heavy metals on the safe production of tea for consumers.

Environmental effects of acid mine drainage and rehabilitation options at closed mine site: a case study.

Irregular waste storage at closed mine sites poses severe environmental problems. This study evaluates the concentrations and effects of trace elements released into the environment by mining activity by analyzing soil, water, and sediment samples taken from a copper mining site. According to the data, acidic mine drainage was the main cause of the high concentrations of trace elements in the soil and sediments, including arsenic (As), cadmium (Cd), lead (Pb), and copper (Cu). The concentrations of As, Cd, Pb, and Cu in soil and sediments were 2734-times, 1189-times, 157-times and 32 times higher, respectively, in comparison to the background values of averaged concentrations of these elements in the upper crust. Geological and statistical studies indicate that the primary constituents of these pollutants are chalcopyrite and pyrite derivatives present in the primary rock structure. Using water analysis data from 2011 to 2020, the release of essential trace element into water was investigated to monitor the environmental effects of acidic mine drainage (AMD) from the closed Kuvarshan copper mine in the Artvin region of Turkey. This study demonstrates that trace elements concentrations may change according to local and seasonal factors and highlights the importance of conducting routine environmental monitoring studies.

Interactions between blood lead (Pb) concentration, oxidative stress, cellular immune response and reproductive status in livestock from a mining area

Chronic exposure to lead (Pb) in livestock grazing in abandoned mining areas affects animal welfare and productivity, as well as represents a significant food safety risk. Here, we evaluate the physiological effects of Pb exposure in goats maintained under extensive farming conditions in a non-remediated mining area. We monitored blood, fecal, and milk Pb levels in two groups of goats, pregnant (n = 17) and lactating (n = 24), kept in different enclosures with high soil Pb concentrations (geometric means of 270 and 143 μg/g, respectively) in Sierra Madrona mining district (Spain). We also studied the influence of Pb exposure on the ability to mount a cellular immune response, and on oxidative stress and biochemical biomarkers measured in blood. Blood Pb concentration was higher in pregnant than in lactating goats, but this difference was not observed in fecal Pb concentration. Pb levels in feces and milk concentrations were correlated with those measured in blood, with 11% of milk samples showing Pb concentrations above the maximum level (ML) for Pb in raw milk established by the EU (0.02 μg/g wet weight). Animals with increased blood Pb levels showed reduced concentrations of retinol in plasma, but these Pb levels did not affect the cellular immune response. The stimulation of the cellular immune response in lactating goats was associated with an increase in blood Pb and calcium levels. The reproductive status and age of goats significantly affected several oxidative stress, antioxidants and plasma biochemistry variables. Goats grazing on soils contaminated by past Pb mining activities may be susceptible to detrimental health effects mediated by retinol deficiency. In view of the detected transfer of Pb through milk, special attention should be paid to the food safety of derived products (i.e. cheese).

Contamination and health risk assessment of potentially toxic elements in rice (Oryza sativa) and soil from Ashanti Region.

Anthropogenic activities release potentially toxic elements into the environment, which contaminate the food chain. The main objective of this research was to analyze the concentrations of As, Cd, Cr, Hg, and Pb in rice grains and soils, establish their correlation and transfer factors between soil and rice grains as well as evaluate their human health risk from consumption of rice cultivated in the Asante Akim area. The levels of As, Cd, Cr, Hg, and Pb in soil and rice samples were assayed using an Agilent 7700 Series inductively coupled plasma-mass spectrophotometer. The mean heavy metal content in soil was 7.5, 0.52, 0.47, 1.30, and 8.69mg/kg for As, Cd, Cr, Hg, and Pb, respectively. Mean levels of the potentially toxic elements in rice were 0.082, 0.27, 0.48, 0.028, and 0.14mg/kg for As, Cd, Cr, Hg, and Pb, respectively. Soil pollution indices showed that the soils were unpolluted with the potentially toxic elements studied. The concentrations of the potentially toxic elements in rice were below the maximum allowable concentration (MAC) recommended by the Codex Alimentary Commission except Cd which was marginally higher than the MAC. Dietary exposure to the elements to consumers was assessed by comparing the estimated daily intake (EDI) to the provisional tolerable daily intake (PTDI). The estimated daily intake values for As, Cd, Cr, Hg, and Pb were 1.45 × 10-4, 4.8 × 10-4, 8.5 × 10-4, 4.95 × 10-5, and 2.4 × 10-4, respectively. The HQ for all the potentially toxic elements was less than the permissible value of 1, suggesting that the consumption of rice from the study area constitutes no potential non-carcinogenic health risk to the population. This study is unique because the risk is evaluated from rice that is directly consumed, and this gives a clearer picture of the risk to humans. Regular monitoring studies should be conducted to ascertain the levels of heavy metals in rice cultivated in the area since heavy metals can accumulate and the concentrations could increase to toxic levels with time.

Assessment of Heavy Metals in Tea Plantation Soil and Their Uptake by Tieguanyin Tea Leaves and Potential Health Risk Assessment in Anxi County in Southeast China

Evaluating heavy metal pollution in tea plantation soil and conducting potential health risk assessments are crucial for ensuring the safety of tea consumers. However, soil heavy metal pollution levels and dietary exposure risk remain poorly understood, and there is no consensus on how soil physicochemical properties affect heavy metal concentrations. In this study, seventy-three soil samples and corresponding tea leaves from main tea-producing regions in Anxi County were analyzed for arsenic (As), chromium (Cr), lead (Pb) and copper (Cu) concentrations. The results showed that mean concentrations of As, Cr, Cu and Pb in the soil did not exceed respective risk screening values in China (GB 15618-2018). The concentrations of As, Cr, Cu and Pb in the tea leaves were within limiting values of the Chinese National Food Safety Standard, and the bioaccumulation factor of heavy metals in descending order was Cu &gt; Pb &gt; As &gt; Cr. The hazard index values of heavy metals indicated no potential human health risk. Soil pH, EAl, EA and AP were the main controlling factors for heavy metal in soil and tea leaves. Cu and Pb concentrations in tea leaves were positively correlated with soil Cu and Pb concentrations. These results provide a scientific basis for effective monitoring and management in tea plantations and for controlling potential risks in tea leaves.

Machine learning-assisted risk evaluation of heavy metals in the Hainan gold mining region, China.

This study employed machine learning (ML) to thoroughly investigate the impact of informal mining activities on the distribution and pollution status of heavy metals in soils near private gold mines in Hainan Province, southern China, a region known for its ecological sensitivity and economic importance. By systematically collecting surface soil samples and samples at depths of 0.5-1m from 175 drilling sites, a comprehensive quantitative analysis was conducted on major heavy metal elements, including lead (Pb), copper (Cu), cadmium (Cd), nickel (Ni), mercury (Hg), chromium (Cr), arsenic (As), and zinc (Zn). Combined with evaluation methods such as the Pollution Load Index (PLI), Normalized Pollution Index (NIPI), and Ecological Risk Index (ERI), the study revealed a high level of soil pollution at informal mining sites. The findings indicated that the average concentrations of Pb, Cd, Hg, As, and Zn in surface soils significantly exceeded the background values for soils in China, with a pronounced positive correlation observed between these heavy metal elements in both surface and deep soil profiles (r > 0.5). Furthermore, leveraging the heavy metal content in surface soils and the constructed environmental indicators, the predictive accuracy for metal content in deep soils was found to range from R2 = 0.27 to 0.68, suggesting that informal mining activities have led to substantial variations in metal content across different soil profiles. Through the application of a random forest model for predictive analysis of the PLI, NIPI, and ERI, high prediction accuracy was achieved (R2 = 0.78, 0.86, and 0.60, respectively). The study demonstrates that informal mining activities not only elevate the risk of soil pollution but also alter the distribution patterns of heavy metals. Also, this study provides a crucial foundation for the scientific assessment of soil quality and potential environmental hazards, while also affirming the efficacy of ML techniques in forecasting soil quality parameters.

Risk assessment for soil contamination from artisanal lead-glazed pottery production in Maragogipinho, Bahia, Brazil

Pollution risk analyses are essential for the management of contaminated sites. In the village of Maragogipinho, Bahia, Brazil, artisans have been producing decorative and utilitarian pottery for almost 300 years. A lead-glaze is used on some of the products causing health concerns. An estimation of indexes for pollution and ecological and human health risks in the region around the pottery workshops was performed. The soil Pb content data from a recent study was used to evaluate the ecological and health risk indicators. These showed high values close to the pottery workshops. The risk for disease through Pb soil contamination is very high for children and high for adults close to the pottery workshops. It is estimated that about 1270 people are at risk in this region.

The Marine-Origin Exopolysaccharide-Producing Bacteria Micrococcus Antarcticus HZ Inhibits Pb Uptake in Pakchoi (Brassica chinensis L.) and Affects Rhizosphere Microbial Communities.

Exopolysaccharides (EPSs) produced by microorganisms play an important role in biotolerance and reducing heavy metal (HM) contamination by limiting the migration of HMs into plants. However, research on the application of EPS-producing marine bacteria for soil heavy metal remediation remains limited, particularly regarding their mechanisms of HM immobilization in soil and impact on plant growth. In this study, the EPS-producing marine bacterium Micrococcus antarcticus HZ was investigated for its ability to immobilize Pb and produce EPSs in soil filtrate. The effects on the growth quality and biomass of pakchoi (Brassica chinensis L.), as well as bacterial communities in inter-root soil contaminated with Pb, were also investigated. The results indicated that HZ could reduce the Pb concentration in the soil filtrate, achieving a removal rate of 43.25-63.5%. The EPS content and pH levels increased in the presence of Pb. Pot experiments showed that adding HZ significantly increased the biomass of pakchoi (9.45-14.69%), vitamin C (Vc) (9.69-12.92%), and soluble protein content (22.58-49.7%). HZ reduced the Pb content in the roots (17.52-47.48%) and leaves (edible tissues) (43.82-52.83%) of pakchoi. HZ increased soil enzyme activities (alkaline phosphatase, dehydrogenase, and urease), and the contents of ammonium nitrogen and nitrate nitrogen. Additionally, HZ also increased the relative abundance of beneficial bacteria (e.g., Proteobacteria, Cyanobacteria, and Chlorobacteria) in the inter-root soil, which have prophylactic and heavy-metal fixation functions. In summary, HZ reduces effective Pb content in edible tissues, roots, and inter-root soil by regulating inter-root soil microbial community structure, increasing soil pH, nitrogen content, and soil enzyme activity, and altering dominant phylum abundance.