Soil Pb Concentrations Research Articles

New sustainable strategy for rehabilitating phosphate mining sites using phosphate industry by-products and sludge integrating Argan, Carob, and Olive trees

In semi-arid context, the development of anthroposol from phosphate industry by-products and sewage sludge could be a new approach for sustainable phosphate mining soils. The objective of this 2 years field study carried out at Benguerir phosphate mine, was to evaluate nutrients and heavy metals dynamics in the soil-plant system of three species planted on anthroposol consisting of a mixture of 65% phosphogypsum (PG), 30% phosphate sludge (PS), and 5% sewage sludge (SS). The experimental layout was a randomized complete block design with six replicates and three species: argan, olive, and carob. No fertilizer was applied to the different plots. Heights and diameters of the different species were measured. Species were pruned, and leaves and stems were separated. The nutrients (N, P, K, Ca, and Mg) and heavy metals (Cd, Cu, Cr, Pb, Ni and Zn) contents in both soil and plant part were determined. The results of the Pearson correlation showed significant correlations between height and diameter of the different species. The strongest correlation was observed for the argan tree. Furthermore, nutrient contents in the rhizosphere of species were significantly reduced, excepted Ca. Also, nutrient contents in leaves were significantly higher than those in the stems. In addition, the concentration of heavy metals in argan, olive and carob leaves, were below international standards. In semi-arid contexts, argan tree could be the best candidate for revegetating mining sites and this anthroposol (65% PG – 30% PS – 5% SS) could be a new approach to rehabilitate mining site on large scale.

Biochar and Azolla Effects on Soil Chemical Properties, Lead Content and Growth of Paddy

The objective of the study was to determine the influences of biochar amendments and Azolla sp application on soil chemical value, lead (Pb) content, and growth of paddy. The research was conducted in Growth Centre LLDIKTI I, Medan, Sumatera Utara, Indonesia, from April to July 2014. The research design used a factorial randomized block design with three replications. The first factor was Azolla sp application: without Azolla (A0); Azolla pinnata (A1); Azolla mikropilla (A2)] and the second factor was biochar amendment without biochar (B0); RSB-Rice straw biochar (B1), RHB-Rice husk biochar (B2), CPB-coconut peat biochar (B3), OPB-Oil Palm Empty Bunch biochar (B4)]. The result showed that the biochar amendment treatments had significant differences (P<0.05) in all soil chemical values and growth parameters of paddy. The Azolla application showed significant differences (P<0.05) in plant height, number of tillers, shoot dry weight, root dry weight, and Pb content in the root. The interaction among the Azolla sp and the biochar amendments showed significant differences (P<0.05) in a number of the tillers. It was concluded that the application of rice husk biochar and Azolla microphylla was able to increase soil chemical properties, increase the growth of paddy, and also increase the Pb content in soil, leaves, and roots.

Effect of Secondary Paper Sludge on Physiological Traits of Lactuca sativa L. under Heavy-Metal Stress.

To eliminate the negative effect of soil contamination with heavy metals on plant growth and crop yield, different methods and techniques are the subject of discussion and study. In this study, we aimed to evaluate the effect of secondary pulp and paper-mill sludge application to soil on the response of the main physiological processes such as the growth, photosynthesis, and respiration of lettuce (Lactuca sativa L.) plants to soil contamination with Pb. For the pot experiment, Pb was added to sandy loam soil at concentrations of 0, 50, and 250 mg Pb(NO3)2 per kg of the soil, and secondary sludge was added to a 0, 20, or 40% sludge solution during each plant watering. The Pb-mediated change in plant biomass allocation, decrease in the photosynthetic rate, increase in leaf respiration rate, and the degree of light inhibition of respiration were closely associated with increases in both root and shoot Pb content. For the Pb-free soil condition, secondary sludge application contributed to the allocation of plant biomass towards a greater accumulation in the shoots than in the roots. Although stomatal opening was not affected by either Pb or sludge, sludge application increased photosynthetic CO2 assimilation regardless of soil Pb content, which was associated with an increase in the electron-transport rate and carboxylase activity of Rubisco. Soil contamination with Pb significantly increased the ratio of respiration to photosynthesis, reflecting a shift in the carbon balance toward carbon losses in the leaves, but sludge application modified the coupling between the processes with a decrease in the proportion of respiratory carbon losses. The sludge-mediated recovery of the physiological processes of L. sativa reflected an increase in plant tolerance to soil contamination with heavy metals, the formation of which is associated with plant and soil adjustments initiated by secondary sludge application.

Organic Materials Promote Rhododendron simsii Growth and Rhizosphere Soil Properties in a Lead-Zinc Mining Wasteland.

The mining of metal minerals generates considerable mining wasteland areas, which are characterized by poor soil properties that hinder plant growth. In this study, a field plot experiment was carried out in the mining wasteland of the Lanping lead-zinc mine in Yunnan Province to study the effects of applying three organic materials-biochar (B), organic fertilizer (OF), and sludge (S)-at concentrations of 1% (mass fraction), on promoting the soil of mining wasteland and the growth of two plant varieties (Huolieniao and Yingshanhong). The results showed that the amount of available nutrients in the surface soil of a mining wasteland could be considerably increased by S and OF compared to the control check (CK). In the rhizosphere soils of two Rhododendron simsii varieties, the application of S increased the available phosphorus (P) content by 66.4% to 108.8% and the alkali-hydrolyzed nitrogen (N) content by 61.7% to 295.5%. However, the contents of available cadmium (Cd) and available lead (Pb) were reduced by 17.1% to 32.0% and 14.8% to 19.0%, respectively. Moreover, three organic materials increased the photosynthetic rate and biomass of two R. simsii varieties. Specifically, OF and S were found to significantly increase the biomass of R. simsii. Organic materials have direct impacts on the increased plant height and biomass of R. simsii. Additionally, organic materials indirectly contribute to the growth of R. simsii by reducing the content of available Cd and available Pb in rhizosphere soil while increasing the content of available nutrients according to the structural equation model (SEM). Overall, S can stabilize Cd and Pb, increase soil nutrient contents, and promote the growth of R. simsii effectively, and has great potential in the vegetation reconstruction of mining wasteland.

Distribution Characteristics, Source Analysis and Ecological Risk Assessment of Heavy Metals in the Typical Industry Reclaimed Soil

To further explore the characteristics of heavy metal pollution and the ecological risk of typical industries in reclaimed soil, based on data from 315 different depth profiles of soil samples collected from 49 plots in Jiading District, Shanghai, the geo-accumulation index and potential ecological risk index were used to evaluate the contents and potential ecological risk of seven heavy metals, namely Cd, Pb, Cu, Zn, Ni, Hg, and As. The APCS-MLR receptor model and PMF positive matrix factorization model were employed to analyze the pollution sources. The results showed that:① except for As, the contents of other heavy metals in the soil of the study area exceeded the Shanghai soil background values to varying degrees. The contents of Cd, Pb, Cu, Zn, Ni, and Hg in the surface soil were 3.54, 2.34, 2.91, 1.20, 3.75, and 4.40 times the background values, respectively. The contents of heavy metals in the soil decreased with the increase in depth, and heavy metals were enriched to a certain extent in the surface soil, indicating that human activities had an impact on the distribution of heavy metals in the soil. ② The APCS-MLR and PMF receptor models identified four main sources of soil heavy metals in the study area. Source 1 (Cu, Zn, and Pb) was a mixture of metal products and automobile manufacturing, source 2 (Ni and Cd) was electroplating enterprises, source 3 (Hg) was mainly from chemical enterprises, and source 4 (As) was natural. The combined use of the two receptor models further improved the accuracy and credibility of source identification. ③ The geo-accumulation index in descending order was Hg(1.54)>Ni(1.32)>Cd(1.21)>Cu(0.96)>Pb(0.64)>Zn(-0.33)>As(-1.02). The potential ecological risk index showed that the comprehensive potential ecological risk index RI value in the study area ranged from 32.50 to 4 910.97, with a mean of 321.40, indicating a strong potential ecological risk. The pollution values of heavy metals Hg, Ni, and Cd in industrial site soil deserve further attention for re-development and utilization purposes.

WITHDRAWN: Trace metals translocation from soil to plants: Health risk assessment via consumption of vegetables in the urban sprawl of a developing country

The study was conducted at 15 locations around the thermal power plant of Patuakhali district at the coastal area of Bangladesh to determine trace elements in vegetable and assess risk of toxicity. Eight vegetables, namely, tomato (Solanum lycopersicum L.), radish (Raphanus raphanistrum L.), bean (Phaseolus vulgaris L.), brinjal (Solanum melongena L.), bottle gourd (Lagenaria siceraria L.), red amaranth (Amaranthus cruentus L.), arum (Arum maculatum L.) and lady's finger (Abelmoschus esculentus L.) were analyzed for nine trace metals (Cr, Ni, Cu, As, Cd, Pb, Fe, Mn and Zn) to assess contamination load of trace elements in agricultural soil, and health risks posed from vegetable consumption. The mean concentrations of Cr, Cr, Ni, Cu, As, Cd, Pb, Fe, Mn, and Zn in soil were 16.6, 14.8, 5.8, 1.3, 0.72, 9.7, 55261, 456.1, and 105.8 mg/kg, respectively. Average concentrations of As, Cd, and Pb in vegetable species were higher than the maximum allowable concentration (MAC), indicating vegetables species were contaminated by these elements and may pose potential risk to human. Fe, Mn, Zn, Cr, Cu, Pb, and As in soil and vegetables of the study area may arise from anthropogenic activities. The present study suggests that surface soil used for vegetables production should be continuously monitored to check the transfer of toxic metals into the vegetables to minimize the adverse health impacts on consumers and potential threats to food safety.

Contamination of urban soils in a historical mining town of northern Chile

In northern Chile, economic activities related to mining and thermoelectric energy have existed in the city of Tocopilla since the early 1900s and metal concentrations in soils have likely been altered by historic anthropogenic activities. To assess the concentrations of Cu, Zn, Pb, Ni, Co, and Cr in urban soils of Tocopilla, a total of 70 superficial (2 cm) and 70 deep (20 cm) soil samples were collected in 2014. Furthermore, to analyze concentration changes in soils over time, 18 superficial (5 cm) samples were collected in 2020–2021. A numerical evaluation (geoaccumulation index, and enrichment factor), principal component analysis, and spatial distribution approach were applied to infer geogenic and anthropogenic influence on the concentrations of these elements. The main conclusions of this research indicate that urban soils of Tocopilla contain geogenic Cu, Zn, Pb, Ni, Co and Cr. However, elevated concentrations of Cu, Zn, and Pb cannot be attributed to a geogenic origin alone, as a proportion of their enrichment is considered to be anthropogenically sourced. The contamination of anthropogenic elements has been found to be related to historic copper mining and thermoelectric energy production. Furthermore, when compared to other sites globally, median concentrations of Cu (945 mg/kg in 2014 and 823 mg/kg in 2020) and Zn (305 mg/kg in 2014 and 196 mg/kg in 2020) in superficial urban soils are among the highest worldwide. Regarding 2020–2021 sampling, Zn and Pb concentrations have increased, while Cu, Cr, Co, and Ni have remained similar to the 2014 samples.

Impact of coconut-fiber biochar on lead translocation, accumulation, and detoxification mechanisms in a soil–rice system under elevated lead stress

Biochar, an environmentally friendly material, was found to passivate lead (Pb) in contaminated soil effectively. This study utilized spectroscopic investigations and partial least squares path modeling (PLS-PM) analysis to examine the impact of coconut-fiber biochar (CFB) on the translocation, accumulation, and detoxification mechanisms of Pb in soil-rice systems. The results demonstrated a significant decrease (p < 0.05) in bioavailable Pb concentration in paddy soils with CFB amendment, as well as reduced Pb concentrations in rice roots, shoots, and brown rice. Synchrotron-based micro X-ray fluorescence analyses revealed that CFB application inhibited the migration of Pb to the rhizospheric soil region, leading to reduced Pb uptake by rice roots. Additionally, the CFB treatment decreased Pb concentrations in the cellular protoplasm of both roots and shoots, and enhanced the activity of antioxidant enzymes in rice plants, improving their Pb stress tolerance. PLS-PM analyses quantified the effects of CFB on the accumulation and detoxification pathways of Pb in the soil–rice system. Understanding how biochar influences the immobilization and detoxification of Pb in soil–rice systems could provide valuable insights for strategically using biochar to address hazardous elements in complex agricultural settings.

Lead (Pb) Pollution in Soil: A Systematic Review and Meta-Analysis of Contamination Grade and Health Risk in Mexico

Lead (Pb) is a toxic metal associated with several health disorders. The mining and Pb battery industry are related to Pb increase in air, water, and soil. Mexico is an important worldwide Pb producer; however, reviews on environmental Pb contamination in Mexico are insufficient. Since Pb remains stable in soil and its concentration is an indicator of Pb exposure, this systematic review focused on reports of Pb concentrations in soil from Mexico published in 2010–2023. The retrieved reports were ordered, and contamination grade and health risk were estimated for location. From 36 retrieved reports, 24 were associated with mining Pb pollution, while a unique report mentioned the battery industry. The publications evaluated mining (13), agricultural (11), and residential (16) soils. Pb concentrations in soil were higher than the allowed limits in more than half of the reports. According to the Pb concentrations in soil, the locations evaluated in Mexico presented a contamination grade from heavily contaminated to extremely contaminated and health risks results suggested severe hazards, particularly for children. This work can guide other researchers to identify potentially contaminated but understudied Mexican locations.

Combined Remediation Effects of Sewage Sludge and Phosphate Fertilizer on Pb-Polluted Soil from a Pb-Acid Battery Plant.

Pb soil pollution poses a serious health risk to both the environment and humans. Immobilization is the most common strategy for remediation of heavy metal polluted soil. In this study, municipal sewage sludge was used as an amendment for rehabilitation of Pb-contaminated soils, for agricultural use, near a lead-acid battery factory. The passivation effect was further improved by the addition of phosphate fertilizer. It was found that the leachable Pb content in soils was decreased from 49.6 mg kg-1 to 16.1-36.6 mg kg-1 after remediation of sludge for 45 d at applied dosage of municipal sewage sludge of 4-16 wt%, and further decreased to 14.3-34.3 mg kg-1 upon extension of the remediation period to 180 d. The addition of phosphate fertilizer greatly enhanced the Pb immobilization, with leachable Pb content decreased to 2.0-23.6 mg kg-1 with increasing dosage of phosphate fertilizer in range of 0.8-16 wt% after 180 d remediation. Plant assays showed that the bioavailability of Pb was significantly reduced by the soil remediation, with the content of absorbed Pb in mung bean roots decreased by as much as 87.0%. The decrease in mobility and biotoxicity of the soil Pb is mainly attributed to the speciation transformation of carbonate, Fe-Mn oxides and organic matter bound Pb to residue Pb under the synergism of reduction effect of sludge and acid dissolution and precipitation effect of phosphate fertilizer. This study suggests a new method for remediation of Pb-contaminated soil and utilization of municipal sewage sludge resources.

Risk Assessment and Attribution Analysis of Potentially Toxic Elements in Soil of Dongdagou, Baiyin, Gansu Province, China

Analyzing the cause is crucial for recognizing the risks associated with potentially harmful substances found in soil, such as toxic elements. These substances can have adverse effects on both the ecological environment and human health, as they can migrate and transform within food chain networks. Therefore, it is imperative to address and prioritize the risks associated with these elements. Dongdagou, Baiyin City, Gansu Province, is a typical area of potentially toxic element pollution in farmland soil, which has attracted much attention and urgently needs to be controlled. Therefore, the main objective of this investigation is to analyze the concentrations of As, Cd, Pb, Hg, Cu, and Zn in the agricultural soil found in Dongdagou. Using statistical analysis, ecological and human health risk, principal component analysis, and the PMF model, we found that (1) there are varying degrees of accumulation in the soil in the study area, with Cu being the main component. (2) The soil in the study area has high and extremely high concentrations of Cd, posing significant risks. On the other hand, Hg presents mild and medium risks. However, there are no risks associated with As, Pb, Cu, and Zn. Overall, the ecological risks in the study area’s soil due to potentially toxic elements are predominantly extremely high (49.65%) and high (38.25%). A small proportion of the soil exhibits low risks (2.76%) and medium risks (9.33%). (3) As has a moderate acceptable carcinogenic risk for local residents, Cd has a moderate acceptable carcinogenic risk for local children, and other potentially toxic elements do not have carcinogenic or non-carcinogenic risks. (4) The source analysis shows that Cd in the soil in the study area mainly comes from agricultural activities and sewage irrigation, As mainly comes from industrial production, and Zn, Cu, Pb, and Hg are multiple sources. We recommend adopting targeted and differentiated safety utilization and control measures based on the pollution level and potential risks of potentially toxic elements in the research area, combined with the sources of potentially toxic elements.

Biogenic calcium improved Cd2+ and Pb2+ immobilization in soil using the ureolytic bacteria Bacillus pasteurii

Bioremediation based on microbial-induced carbonate precipitation (MICP) was conducted in cadmium and lead contaminated soil to investigate the effects of MICP on Cd and Pb in soil. In this study, soil indigenous nitrogen was shown to induce MICP to stabilize heavy metals without inputting exogenous urea. The results showed that applying Bacillus pasteurii coupled with CaCl2 reduced Cd and Pb bioavailability, which could be clarified through the proportion of exchangeable Cd and Pb in soil decreasing by 23.65 % and 12.76 %, respectively. Moreover, B. pasteurii was combined separately with hydroxyapatite (HAP), eggshells (ES), and oyster shells (OS) to investigate their effects on soil heavy metals' chemical fractions, toxicity characteristic leaching procedure (TCLP)-extractable Cd and Pb as well as enzymatic activity. Results showed that applying B. pasteurii in soil significantly decreased the heavy metals in the exchangeable fraction and increased them in the carbonate phase fraction. When B. pasteurii was combined with ES and OS, the content of carbonate-bound Cd increased by 114.72 % and 118.81 %, respectively, significantly higher than when B. pasteurii was combined with HAP, wherein the fraction of carbonate-bound Cd increased by 86 %. The combination of B. pasteurii and biogenic calcium effectively reduced the leached contents of Cd and Pb in soil, and the TCLP-extractable Cd and Pb fractions decreased by 43.88 % and 30.66 %, respectively, in the BP + ES group and by 52.60 % and 41.77 %, respectively, in the BP + OS group. This proved that MICP reduced heavy metal bioavailability in the soil. Meanwhile, applying B. pasteurii and calcium materials significantly increased the soil urease enzyme activity. The microstructure and chemical composition of the soil samples were studied, and the results from scanning electron microscope, Fourier transform infra-red spectroscopy, and X-ray diffraction demonstrated the MICP process and identified the formation of CaCO3, Ca0.67Cd0.33CO3, and PbCO3 in heavy metal-contaminated soil.

Spatial Distribution, Risk Assessment and Sources of Heavy Metals in Roadside Soils Exposed to the Zhengzhou-Kaifeng Intercity Railway in Huanghuai Plain, China

ABSTRACT Heavy metal accumulation in soil can seriously harm human health, and it is necessary to identify the accumulation status and access the potential risks for local pollution control and sustainable economic development. This study evaluated the pollution level, spatial distribution, potential risk and sources of soil heavy metals along the Zhengzhou-Kaifeng intercity railway and compared pollution characteristics in north side soils with south side soils of the railway. A total of 260 soil samples were collected from a section along the railway. In practice, only the average Zn and Pb contents in soils were slightly higher than their corresponding risk screening values. The heavy metal enrichment in the north side soils was marginally lower than that in the south side soils. The spatial distribution of soil heavy metals except Pb could be mainly influenced by the different land use types. The geoaccumulation index and potential ecological risk of a single heavy metal indicated that Cd was the major contaminant with moderate pollution and high ecological risks in the south side soils and none to moderate pollution and moderate ecological risks in the north side soils. However, the mean multimetal potential ecological risk values suggested that the north side soils were at low ecological risks and the south side soils were at moderate ecological risks. The comprehensive non-carcinogenic risks and total carcinogenic risks for adults were low and acceptable, respectively. Pearson correlation analysis, PCA, and APCS-MLR analyses identified that the contributions of natural sources, mixed sources of industrial and traffic activities, agricultural activities, and other sources were 57.49%, 21.44%, 12.67% and 8.40%, respectively, and the major soil pollution Cd was mainly related to mixed sources of industrial and traffic activities. Therefore, continuous soil heavy metal monitoring is essential to elucidate the long-term railway operation effect on soil heavy metal accumulation.

Determination of Cu, Pb, and Zn Contents of Soils Formed on Different Parent Materials (Çanakkale, Türkiye)

This study was carried out to determine the heavy metal (Cu, Pb, and Zn) contents and their differences in soils formed on three different parent materials (basalt, clastic and carbonate rocks and granite) in the Ezine district of Çanakkale province. For this purpose, surface sampling was conducted in soils formed under natural conditions on different geological materials. Heavy metal contents of the soil samples were determined using flame atomic absorption spectrometry using the wet digestion Aqua regia method. Analysis of variance (ANOVA) was used to determine the elemental differences in soil samples. Pearson correlation analysis was applied to reveal the relationship between heavy metals and the physicochemical properties of soils taken from different parent materials. As a result of the evaluation, the mean Cu concentrations in the samples ranged from soils formed on basalt (40.8 ± 3.8 μg/g)&gt; soils formed on clastic and carbonate rocks (24.8 ± 1.5 μg/g)&gt; soils formed on granite (22.5 ± 2. 8 μg/g); mean Pb concentrations followed the order of soils formed on granite (37.50 ± 3.30 μg/g)&gt; soils formed on clastic and carbonate rocks (35.67 ± 2.74 μg/g)&gt; soils formed on basalt (21.6 ± 6.7 μg/g). The mean Zn concentrations of the soil samples were as follows: soils formed on basalt (80.9 ± 8.7 μg/g)&gt; soils formed on clastic and carbonate rocks (44.1 ± 3.7 μg/g)&gt; soils formed on granite (37.0 ± 9.4 μg/g). Pb concentrations of all soil samples were found to be higher than the average of the earth's crust.

Farmers' Bussiness as Usual Increase Lead (Pb) Level in the Soil: a Case Study Horticulture Land in Batu, Indonesia

Lead (Pb) is a toxic heavy metal for humans. Agrochemical applications contribute to Pb contamination and accumulation in plants which is harmful to humans. This study aims to investigate the habits of horticultural farmers in applying inorganic fertilizers and pesticides intensively on Pb concentration in the soil and cultivated plants, and its effect on plant growth. The measured parameters consisted of soil and plant Pb content, soil pH, organic C, total N, available P, and exchangeable K. This study used a randomized block design consisting of 4 treatments (Control (KT); (PR); (TN); and (TP)). The results showed that horticultural farmers' dosage of inorganic fertilizers exceeded Indonesia Ministry of Agriculture recommendation. The application of inorganic fertilizers and pesticides by farmers (business as usual) increased Pb content in plants up to 31.46 mg/kg. Besides the application of inorganic fertilizers increases fertilizer residues in the soil by up to 65%, which increases environmental pollution even though the application of inorganic fertilizers increases plant growth and production (shoot length, the number of leaves, and plant dry weight). Thus, wisely applying agrochemicals is required in order to support plant growth and production without further environmental problems.

Cadmium and lead accumulation in important food crops due to wastewater irrigation: Pollution index and health risks assessment

The contamination of farm soils with heavy metals (HMs) has raised significant concerns due to the increased bioavailability and accumulation of HMs in agricultural food crops. To address this issue, a survey experiment was conducted in the suburbs of Multan and Faisalabad to investigate the spatial distribution, bioaccumulation, translocation, and health risks of cadmium (Cd) and lead (Pb) in agricultural crops. The results show a considerable concentration of Cd and Pb in soils irrigated with wastewater, even though these levels were below the permissible limits in water and soil matrices. The pollution index for Cd was mostly greater than 1 at the selected sites, indicating its accumulation in soil over time due to wastewater irrigation. Conversely, the pollution index for Pb was below 1 at all sites. Among the plants, Zea mays accumulated the highest concentration of Cd and Pb. The translocation factor from soil to root was highest for Brassica olearecea (7.037 for Cd) and Zea mays (6.383 for Pb). The target hazard quotient (THQ) value of Cd exceeded the non-carcinogenic limit for most vegetables. The highest value was found in Allium cepa (5.256) and the lowest in Allium sativum (0.040). In contrast, the THQ level of Pb was below the non-carcinogenic limit for most vegetables, except for Allium cepa (1.479), Solanum lycopersicum (1.367), and Solanum tuberosum (1.326). The study highlights that Allium cepa poses the highest health risk for humans, while Medicago sativa poses the highest risk for animals due to Cd and Pb contamination. These results underscore the urgent need for effective measures to mitigate the health risks associated with HM contamination in crops and soils.

Pitfalls of distinguishing anthropogenic and geogenic reasons for risk elements in soils around coal-fired power plants: from a case study in the Northwestern Czech Republic to general recommendations

PurposeMany historical industrial activities, including coal mining and burning, have started near geogenic anomalies. It resulted in spatial overlap of anthropogenic and natural causes of elevated soil risk element contents. Here, distinguishing between anthropogenic and geogenic contributions cannot be achieved by conventional geochemical soil mapping, in particular, when only pseudo-total contents of risk elements were obtained, soil depth profiles were not acquired, and geological maps were not implemented.MethodsThe local geology, topography and anthropogenic activities were taken into account when planning the soil sampling. Soil profiles were obtained using an auger sampler. Total contents of risk and lithogenic elements were obtained by X-ray fluorescence. Aqua regia extraction and inductively coupled plasma mass spectrometry (ICP-MS) were also used for analyses.ResultsCoal use in the study area increased the soil contents of Cd, Hg, and Zn in 7 km circle east of the major power plant, typically to 2 × local background in topsoils. In the profiles closest to that plant, Cd emissions have already been translocated to soils below ploughed horizons that weaken the contamination signal in topsoils. The highest As and Pb contents in the Most Basin soils originated from a local geogenic anomaly and not coal burning.ConclusionCommon soil mapping projects and data mining routines cannot decipher anthropogenic contribution to the soil risk elements unequivocally, as it is demonstrated in this paper. When working in geogenically anomalous areas, a fundamental knowledge of the mechanisms controlling the content of risk elements in soils is required.

Risk assessment and source identification of soil heavy metals: a case study of farmland soil along a river in the southeast of a mining area in Southwest China.

To investigate the heavy metals (HMs) contamination of surface farmland soil along the river in the southeast of a mining area in southwest China and identify the contamination sources, 54 topsoil samples were collected and the concentrations of seven elements (Zn, Ni, Pb, Cu, Hg, Cr, and Co) were determined by inductively coupled plasma optical emission spectrometry (ICP-OES) and atomic fluorescence spectrometry (AFS). The geo-accumulation index ([Formula: see text]) and comprehensive potential ecological risk index ([Formula: see text]) were used for analysis to determine the pollution degree of HMs and the risk level of the study area. Meanwhile, the Positive Matrix Factorization (PMF) model was combined with a variety of statistical methods to determine the sources of HMs. To explore the influence of the river flowing through the mining area on the concentrations of HMs in the farmland soil, 15 water samples were collected and the concentrations of the above seven elements were determined. The results showed that the concentrations of Pb, Cu, and Zn in soil all exceeded the risk screening value, and Pb in soil of some sampling sites exceeded control value of "Agricultural Land Soil Pollution Risk Control Standard".[Formula: see text] showed that Pb was heavily contaminated, while Cu and Zn were moderately contaminated. RI showed that the study area was at moderate risk. PMF and various statistical methods showed that the main source of HMs was the industrial source. In the short term, the river flowing through the mine has no significant influence on the concentration of HMs in the soil. The results provide a reference for the local government to control contamination and identify the sources of HMs.

Prediction of Spatial Distribution of Heavy Metals in Cultivated Soil Based on Multi-source Auxiliary Variables and Random Forest Model

Spatial prediction of the concentrations of soil heavy metals (HMs) in cultivated land is critical for monitoring cultivated land contamination and ensuring sustainable eco-agriculture. In this study, 32 environmental variables from terrain, climate, soil attributes, remote-sensing information, vegetation indices, and anthropogenic activities were used as auxiliary variables, and random forest (RF), regression Kriging (RK), ordinary Kriging (OK), and multiple linear regression (MLR) models were proposed to predict the concentrations of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in cultivated soils. In comparison to those of RK, OK, and MLR, the RF model had the best prediction performance for As, Cd, Cr, Hg, Pb, and Zn, whereas the OK and RK models had highest prediction performance for Cu and Ni, respectively, showing that R2 was the highest, and mean absolute error (MAE) and root mean square error (RMSE) were the lowest. The prediction performance of the spatial distribution of soil HMs under different prediction methods was basically consistent. The high value areas of eight HMs concentrations were all distributed in the southern plain area. However, the RF model depicted the details of spatial prediction more prominently. Moreover, the importance ranking of influencing factors derived from the RF model indicated that the spatial variation in concentrations of the eight HMs in Lanxi City were mainly affected by the combined effects of Se, TN, pH, elevation, annual average temperature, annual average rainfall, distance from rivers, and distance from factories. Given the above, random forest models could be used as an effective method for the spatial prediction of soil heavy metals, providing scientific reference for regional soil pollution investigation, assessment, and management.

Phytoremediation of Toxic Lead from Contaminated Soil Using Neyraudia reynaudiana: Soil of Xuzhou as a Case Study

Lead (Pb), as one of the main pollution elements, has resulted in large-scale soil pollution around the world. Even if phytoremediation can solve this problem, the selection of restoration potential plants has always been a scientific problem. As a multifunctional repair plant, Neyraudia reynaudiana can rehabilitate both polluted soils and slopes. N. reynaudiana has been widely used in terrain restoration in southern China before. This study was the first to study the growth and Pb absorption and enrichment capacity of N. reynaudiana in Xuzhou, north of the Yangtze River. In this study, N. reynaudiana was planted in soils with different lead concentrations, and the change of lead content in roots, shoots, and soils, as well as the redox enzyme, was tested and analyzed during each growth stage. The results showed that the roots could absorb Pb and transfer 79.45% to the shoots at most. With the growth of the plant, the ability to accumulate and transfer gradually increased. Moreover, when the soil Pb concentration was above 800 mg kg−1, the ability to accumulate by N. reynaudiana was significantly restrained. Furthermore, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and peroxidase (POD) first acted on the redox response in the initial phase, while increasing the pollutant concentration or the growth of N. reynaudiana in the later stage, and the glutathione reductase (GR) redox system continued to feed back on the lead stress. This study proved that N. reynaudiana is a kind remediation plant for lead pollution soil and could repair soil with a lead pollution concentration lower than 800 mg kg−1. The results provide a theoretical reference for clarifying the action mechanism and threshold value of N. reynaudiana in rehabilitating soil lead pollution and provide practical guidance for the planting proportion of N. reynaudiana.