Elements In Agricultural Soils Research Articles

Geochemical Signature and Risk Assessment of Potential Toxic Elements in Intensively Cultivated Soils of South-West Punjab, India

Soil contamination with potentially toxic elements (PTEs) in the Malwa region belt of Punjab, India, can be a serious concern as a result of intensive agricultural practices and overuse of agrochemicals. The main objectives of the present study were to evaluate the spatial distribution, geochemical signature, and contamination level/health risk of PTEs in 76 soil samples (0–10 cm) collected from the three districts viz. Muktar, Faridkot, and Moga of Punjab, India. The result shows that PTEs concentrations vary widely in the region, with Fe and Mn distribution patterns being mostly coherent with each other. When compared to the Indian natural soil background values, the average concentration of Pb and Zn were higher than the limit, only Pb exceeded the average values of the world background and upper continental crust (UCC). Spatial autocorrelation plotted with a local indicator of spatial association (LISA) in GeoDa software version 1.18 was used to identify hotspots. A positive spatial autocorrelation (>0.2) was indicated with Moran’s I values for Pb, V, Mn, Cu, and Cr, being highest for Pb. A principal component analysis (PCA) identified the major geo-chemical patterns of Fe-Al-V-Cr and TOC-Mn-Zn-HCO3−, which were positively loaded on PC1. This indicates that Fe/Al-oxyhydroxides and organic matter play a dominant role in controlling metal mobility in soils. This can be further substantiated with the Spearman’s rank correlation values. The contamination factor (CF) indicates that only Pb and Zn (15.7% and 3.9% samples, respectively) were under high risk. This could be due to the excessive application of chemical fertilizers. The large range of degree of contamination (Cdeg) values suggests that there are variations in the degree of soil pollution due to PTEs. A little over 3.9% of samples had significant contamination, compared to 72.3% of samples with low contamination and 23.6% of samples with moderate contamination. Human non-carcinogenic and carcinogenic risk levels were investigated. The hazard index (HI) values for adult ranged from 0.00 to 0.2, and values for children ranged from 0.009 to 1.2. These findings suggest that both children and adults are not at potential risk, except in a few locations. Overall, the results of this study provide the current baseline status of toxic elements in agricultural soil. This would be helpful for developing strategies for sustainable management of the soil resources in the region, as well as for future monitoring programs of the soil quality in the Malwa region as a whole, to track any changes in the contamination levels over time.

Fate, source apportionment and fractionation of potentially toxic elements in agricultural soil around a densely populated, semiarid urban center of India: baseline study and ecological risk assessment.

This study is on the outskirts of the rapidly growing city of Jaipur, located in the semiarid region of India and gateway to the 'Great Indian Thar' desert, and focused on potentially toxic elements (PTE) pollution in the farmlands around the city. Concentrations of PTE, along with associated soil parameters such as pH, available nitrogen, organic carbon, phosphorus, and potassium, were estimated in agricultural soil samples near an industrial region on the outskirts of the capital city of the largest state of India. The PTE concentrations in the soil were in the following order: Mn > Pb > Ni > Cr > Cu > Cd. Soil pollution indices, such as the geochemical accumulation index (Igeo), contamination factor (CF), and ecological risk index (ERI), indicated that the soil was moderately to highly polluted. The result of BCR extraction techniques showed Cd is found mainly in the exchangeable and residual fractions, Pb, Mn were found in the reducible as well as residual fractions, while other PTE were mostly bound to residual fraction. All other PTEs are primarily found in the residual fraction, tightly linked with the silicate lattice of soil minerals. Multivariate analysis and the Pearson correlation matrix indicate a common source apportionment for Pb and Cd. Cd, and Pb concentrations in agricultural soil indicate ecological harm that warrants immediate attention and policy-level intervention.

Geochemical behavior of rare earth elements in agricultural soils along the Syr Darya River within the Aral Sea Basin.

The widespread use of rare earth elements (REEs) across various industries makes them a new type of pollutant. Additionally, REEs are powerful indicators of geochemical processes. As one of the two main rivers in the Aral Sea, identifying the geochemical behavior of REEs in agricultural soils of the Syr Darya River is of great significance for subsequent indicative studies. In this study, the geochemical characteristics, influencing factors, and potential application significance of REEs in agricultural soils from three sampling areas along the Syr Darya River were analyzed using soil geography and elemental geochemical analyses. The results showed that the highest total concentration of REEs in the agricultural soil was in Area I, with a mean value of 142.49μg/g, followed by Area III with a mean value of 124.56μg/g, and the lowest concentration was in Area II with a mean value of 122.48μg/g. The agricultural soils in the three regions were enriched in light rare earth elements (LREEs), with mean L/H values of 10.54, 10.13, and 10.24, respectively. The differentiation between light and heavy rare earth elements (HREEs) was also high. The concentration of REEs in agricultural soil along the Syr Darya River was primarily influenced by minerals such as monazite and zircon, rather than human activities (the pollution index of all REEs was less than 1.5). The relationship between Sm and Gd can differentiate soils impacted by agricultural activities from natural background soils. The results of this study can serve as a basis for indicative studies of REEs in Central Asia.

Concentrations, source identification and environmental risk assessment of potentially hazardous elements in agricultural soils of Hamedan, west of Iran

ABSTRACT In the current study, a total of 40 agricultural surface soil samples were collected from 40 sites in Hamedan, Iran and the contents of As, Cd, Cr, Cu, Ni, Pb, and Zn were determined by ICP-OES. The average contents of all the analysed elements except Pb were found to be greater than those in the background contents reported for Iran, which could presumably show the anthropogenic sources of these elements. The average EF and PI values decreased in the order of As > Cr > Cu > Cd > Zn > Ni > Pb, while, the rank order of the mean I-geo values followed the order of As > Cr > Cu > Zn > Cd > Ni > Pb. Additionally, the cumulative mean values of RI with 175, demonstrated ‘moderate ecological risk’ across the investigated area. The results of PCC, PCA, and HCA showed that the traffic and agricultural activities could be regarded as the most important anthropogenic factors that affected the content of PTEs in the agricultural soils. In conclusion, an accurate investigation on the probability of the environmental risks due to the agricultural soil pollution by other PTEs and persistent organic pollutants (POPs) is recommended for future works.

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 and health risk assessment of potentially toxic elements in agricultural soil of the Al-Ahsa Oasis, Saudi Arabia using health indices and GIS

The current work aimed to assess contamination and human health risk of potentially toxic elements (PTEs) in agricultural soil of the Al-Ahsa Oasis, Saudi Arabia. For the purpose of evaluating the potential risks to human health associated with ingestion, skin contact, and inhalation, the chronic daily intake (CDI), hazard quotient (HQ), hazard index (HI), cancer risk (CR), and total lifetime cancer risk (LCR) were calculated in 30 soil samples. The spatial distribution and possible sources of HMs were investigated using GIS and multivariate analysis. The descending order of PTE averages (dw, µg/g) was Fe (11790) > Mn (176.43) > Zn (54.43) > Cr (28.67) > Ni (14.53) > V (12.33) > Cu (10.83) > Pb (5.23) > Co (2.87) > As (2.27). The average CDI for all PTEs from ingestion pathway in children indicates an increase of approximated 9 times compared to adults. The HI values varied from 1.969 × 10-4 to 2.318 × 10-2 for Adults, and from 1.835 × 10-3 to 2.158 × 10-1 for children, suggesting there is no significant non-carcinogenic risk to the people inhabiting the Al-Ahsa Oasis. The CRs and LCR for Cr, As, and Pb in children was found to be significantly greater than that of adults. LCR values for As, Pb, and Cr varied from lower than 1 × 10-6 to 1 × 10-4, indicating no significant health hazards to acceptable carcinogenic risk.

Spatial analysis and risk assessment of potentially toxic elements in agricultural soil downstream of the tungsten mining area in Dayu, China

ABSTRACT Located in the southwest of Jiangxi Province, Dayu County has the most abundant tungsten resources in China. In this paper, 2969 agricultural soil samples were collected downstream of the tungsten mining area in Dayu, and all samples were tested for the contents of potentially toxic elements (PTEs) such as Cd, Pb, Zn, Cr, Cu, Ni, Hg, as well as the mining-related elements W, Sn, Mo and pH. In addition, 135 soil samples were measured for chemical morphology of Cd. The results show that the distribution patterns of Cd, Pb, Zn, Cu and W, Sn, Mo are relatively consistent, which are considered to be affected by upstream mining activities. Hg is possibly overlaying the effects of human production and living activities. Cr and Ni are considered as a natural source. From the perspective of total concentration, the ecological risk of PTEs in the study area was low, with over 80% of the samples being evaluated as safe. However, based on chemical fraction of Cd, more than 75% of the samples were assessed as moderately or severely contaminated. The serious acidification of soil in the study area is the main reason for the increase activity of Cd and its ecological risk.

Determination of geochemical baselines and evaluation of potentially toxic elements in agricultural soils of Ramhormoz Plain, Iran

ABSTRACT The present study was conducted to investigate the heavy metal pollution status of the agricultural soils in Ramhormoz Plain, Khuzestan province, Iran. A total of 54 samples from the depths (0–20 cm) of the soil were collected from the selected areas in (March) 2021. According to the obtained results, the concentrations of As, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Zn, Al in soil samples were 1.3, 0.68, 60, 10.6, 0.01, 218, 23, 3.65, 14 and 0.58 mg/kg, respectively, in which As showed significant soil contamination and Cu, Hg, Mn, Ni, Pb, Zn and Al moderate contamination according to the calculation of contamination factor (CF). PCA analysis revealed that both anthropogenic and natural sources of pollution like agricultural and transport activities contributed to the enrichment of study area. Investigation of ecological risk indicated that Ramhormoz Plain was categorized as a high risk area.

Reveal molecular mechanism on the effects of silver nanoparticles on nitrogen transformation and related functional microorganisms in an agricultural soil

Silver nanoparticles (AgNPs) are widely present in aquatic and soil environment, raising significant concerns about their impacts on creatures in ecosystem. While the toxicity of AgNPs on microorganisms has been reported, their effects on biogeochemical processes and specific functional microorganisms remain relatively unexplored. In this study, a 28-day microcosmic experiment was conducted to investigate the dose-dependent effects of AgNPs (10 mg and 100 mg Ag kg−1 soil) on nitrogen transformation and functional microorganisms in agricultural soils. The molecular mechanisms were uncovered by examining change in functional microorganisms and metabolic pathways. To enable comparison, the toxicity of positive control with an equivalent Ag+ dose from CH3COOAg was also included. The results indicated that both AgNPs and CH3COOAg enhanced nitrogen fixation and nitrification, corresponding to increased relative abundances of associated functional genes. However, they inhibited denitrification via downregulating nirS, nirK, and nosZ genes as well as reducing nitrate and nitrite reductase activities. In contrast to high dose of AgNPs, low levels increased bacterial diversity. AgNPs and CH3COOAg altered the activities of associated metabolic pathways, resulting in the enrichment of specific taxa that demonstrated tolerance to Ag. At genus level, AgNPs increased the relative abundances of nitrogen-fixing Microvirga and Bacillus by 0.02 %–629.39 % and 14.44 %–30.10 %, respectively, compared with control group (CK). The abundances of denitrifying bacteria, such as Rhodoplanes, Pseudomonas, and Micromonospora, decreased by 19.03 % to 32.55 %, 24.73 % to 50.05 %, and 15.66 % to 76.06 %, respectively, compared to CK. CH3COOAg reduced bacterial network complexity, diminished the symbiosis mode compared to AgNPs. The prediction of genes involved in metabolic pathways related to membrane transporter and cell motility showed sensitive to AgNPs exposure in the soil. Further studies involving metabolomics are necessary to reveal the essential effects of AgNPs and CH3COOAg on biogeochemical cycle of elements in agricultural soil.

Risk assessment of potentially toxic elements in agricultural soils and bioconcentration in rice grains from Faridkot District, India

Potentially toxic elements (PTEs) in soil pose significant risks to both ecology and human health. Therefore, to understand the effect of PTEs in agricultural soils of Faridkot District, Punjab, India, 36 soil samples were analyzed for physicochemical properties, contents of PTEs (aluminum, arsenic, nickel, boron, uranium, barium, chromium, cadmium, copper, iron, lead, cobalt, manganese, selenium, and zinc), possible ecological and human health risks and bioconcentration in rice grains. Soils showed high mean contents (mg/kg) of potassium (906.65), sodium (760.78), and chlorides (247.13) with cadmium, copper, zinc, arsenic, and selenium contents (mg/kg) in 55.56%, 33.33%, 25.00%, 16.67%, and 13.89% of samples exceeding their safe limits (0.06, 20.00, 50.00, 20.00, and 0.20, respectively). Individual and multi-element indices suggested extremely high-soil enrichment of arsenic, cadmium, and selenium and low to moderate ecological risk. Multivariate analyses revealed the contribution of both geogenic and anthropogenic activities to soil contamination. Mean bioconcentration factors of chromium (4.48), boron (1.24), and copper (2.69) were >1.00 in rice. Residents had higher cancer risk (TCR) due to arsenic (3.64E-05) and chromium (4.04E-06) in soil, mainly through ingestion and dermal contact. This work could serve as baseline database for further research and designing the strategy to alleviate soil contamination.

Influencing Factors of Elevated Levels of Potentially Toxic Elements in Agricultural Soils from Typical Karst Regions of China

Agricultural soils originating from carbonate rocks within karst regions exhibit inherent high concentrations of potentially toxic elements (PTEs) due to geogenic processes. However, the influencing factors of the elevated levels of PTEs in the naturally contaminated karst regions remain inadequately comprehended. This research investigates the chemical compositions of 278 soils derived from carbonate rocks. Descriptive statistics, stepwise multiple regression, and the random forest (RF) method were applied to screen the significant factors that affect the distribution, migration, and enrichment of the PTEs in soils. Cadmium (Cd) and arsenic (As) are the most highly contaminated PTEs in the soils of the study area, and the average contents of Cd and As in soils are 11.5 and 2.92 times the national soil background value, respectively. The pollution risk ranking of PTEs is Cd > As > Cr > Zn > Pb > Cu > Ni > Hg, using the proportion exceeding the risk screening thresholds of agricultural land as the standard. Soil Fe2O3 and Mn contents, soil pH and total organic carbon (TOC) values, and weathering intensity (characterized using the chemical index of alternation, CIA) are the most important factors influencing the PTE levels in agricultural soils.

Estimation of key potentially toxic elements in arid agricultural soils using Vis-NIR spectroscopy with variable selection and PLSR algorithms

Potentially toxic elements (PTEs) pose a significant threat to soil and the environment. Therefore, the fast quantification of PTEs is crucial for better management of contaminated sites. Versatile technique such as Visible near-infrared spectroscopy (Vis–NIRS) (350–2,500 nm) has attracted tremendous attention for assessing PTEs and has achieved promising results combined with successful multivariate analysis. This research investigated the potential of Vis–NIRS combined with partial least squares regression (PLSR) and variable selection methods to assess key PTEs (Cd, Co, Cu, Cr, Pb, and Zn) in agricultural soils under arid conditions. The soil samples (80) were collected from a polluted area around Al-Moheet drainage, Minya Governorate–upper Egypt. The samples were scanned using an ASD FieldSpec-4 spectroradiometer. Simulated annealing (SA) and uninformative variable elimination (UVE) were used to select the effective wavelengths in predicting PTEs. PLSR was used to develop the spectral models using the full range (FR-PLS) and feature-selected spectra techniques SA (SA-PLS) and UVE (UVE-PLS). The results indicated that UVE-PLS models performed better than FR-PLS and SA-PLS models in predicting the key PTEs. The obtained coefficient of determination (R2) and the ratio of performance to deviation (RPD) were 0.74 and 2.48 (Cr), 0.72 and 2.03 (Pb), 0.62 and 1.86 (Cd), 0.59 and 1.78 (Cu), 0.52 and 1.68 (Co), and 0.46 and 1.41 (Zn), respectively. The results suggested that the UVE-PLS spectral model is promising for predicting Cr, Pb, and Cd, and can be improved for predicting Cu, Co, and Zn elements in agricultural soils.

Human health risks in Ferozepur District, Punjab, India due to potentially toxic elements in agricultural soils

In the present study, soil contamination by arsenic, cadmium, chromium, cobalt, copper, iron, lead, manganese, nickel, uranium and zinc; and associated human health risks were assessed at 30 agricultural sites in Ferozepur District, Punjab. Above 90% soil samples had high content of chloride, sodium and potassium. Cadmium, arsenic, zinc and lead in 100%, 76.67%, 76.67% and 66.67% samples exceeded their safe limits (mg/kg; 0.06, 20, 50 and 10, respectively). Individual/multi-elemental indices indicated high PTEs contamination in soils posing low to considerable ecological risk. Principal components PCI and PCII contributed 44.748% and 30.476% variance in data, respectively. PTEs in soils were classified in two categories using cluster analysis (I: Cd, U, Co, Pb, Ni, Cr, As, Cu, Zn and Mn; II: Fe), indicating both geogenic and anthropogenic origins. Health risks due to PTE exposure via dermal contact, inhalation and ingestion were also assessed. Children were found to be highly prone to non-cancer health risk (mean hazard index = 1.30) by As exposure, mainly via ingestion pathway. High total cancer risk was posed to residents via As (7.52E-05) and Cr (9.17E-06) exposure, primarily through ingestion. Bioremediation and efficient disposal of solid and liquid wastes may reduce soil contamination in the study area.

Spatiotemporal distribution characteristics of potentially toxic elements in agricultural soils across China and associated health risks and driving mechanism

Comprehensive analysis of spatiotemporal distribution characteristics of potentially toxic elements (PTEs) in soils of China, and associated driving mechanism and health risks is crucial for soil pollution prevention and risk control. In this study, a total of 8 PTEs in agricultural soils of 236 city case data from 31 provinces of China were collected from literatures published between 2000 and 2022. The pollution level, dominant drivers and probabilistic health risks of PTEs were analyzed using geo-accumulation index (Igeo), geo-detector model, and Monte Carlo simulation, respectively. The results indicated a notably accumulation of Cd and Hg, with Igeo of 1.13 and 0.63, respectively. Cd, Hg and Pb showed strong spatial heterogeneity, whereas As, Cr, Cu, Ni, and Zn has no significant differentiation. PM10 was the dominant driver for accumulation of Cd (0.248), Cu (0.141), Pb (0.108), and Zn (0.232), and PM2.5 has a significant effect on accumulation of Hg (0.245); however, soil parent material was primary driver for accumulation of As (0.066), Cr (0.113), and Ni (0.149). PM10 ∩ wind speed accounted for 72.6 % of Cd accumulation, and mining industry ∩ soil parent materials for 54.7 % of As accumulation. Approximately 38.53 %, 23.90 %, and 12.08 % of the hazard index values exceeded 1 for the minors aged 3- < 6, 6- < 12, and 12- < 18 years, respectively; whereas approximately 0.22 %, 0.21 %, 0.20 %, 0.54 % and 0.42 % of the carcinogenic risk values were greater than 1E-04 for individuals aged 3- < 6, 6- < 12, 12- < 18, 18- < 44, and 44- < 70 years, respectively. As and Cd were considered as priority elements for soil pollution prevention and risk control in China. Moreover, the hotspots of PTE pollution and associated health risks were mainly observed in southern, southwestern and central China. The results of this study provided a scientific basis for developing strategies for pollution prevention and risk control of soil PTEs in China.

Evaluation of Environmental Contamination by Toxic Elements in Agricultural Soils and Their Health Risks in the City of Arequipa, Peru

This study evaluated the concentration of toxic elements in soil samples from agricultural fields in the districts of Sachaca, Socabaya, Hunter, Quequeña, Yarabamba, Characato and Tiabaya in the city of Arequipa, Peru. The ecological risk, enrichment factor (EF), geo-accumulation index (Igeo) and integrated ecological risk index (RI) were estimated, while the health risk was determined with hazard coefficient (HQ) and hazard index (HI) values. Seven soil samples were collected in July 2019 and 17 toxic elements were analyzed in an accredited laboratory using the inductively coupled plasma-mass spectrometry (ICP-MS) methodology. The results were compared with environmental samples where no element exceeded what is established in the standard. The enrichment factor (EF), according to the background of Wedepohl, indicated that As (12.26 ± 3.66) presented a severe enrichment (high) in agricultural soils, while Cd (6.87 ± 3.25) presented moderate values. As, Cd, Pb, Cu and Zn (2.85 ± 0.85; 3.53 ± 1.67; 2.71 ± 1.25; 3.83 ± 0.81; 2.55 ± 0.79) presented low to moderate enrichment in agricultural soils, while Cr did not present enrichment in soils. The Igeo for As in Sachaca, Socabaya, Quequeña and Characato showed moderate contamination, Cu also showed moderate contamination in all the districts evaluated, and Cd showed the same contamination in the districts of Sachaca, Hunter, Quequeña and Tiabaya. The ecological risk in the districts evaluated showed a low degree of risk due to contamination by toxic elements. Finally, the health hazard index for toxic elements present in agricultural soils was evaluated, where the HQ values were negligible and the HI was less than 0.1 (H1 &lt; 0.1) for children and adults.

Investigation of Pollution Level of Traces Metals Elements in Agricultural Soil of Oubritenga Province of Burkina Faso

The purpose of this study was to investigate the pollution level of trace metals As, Cd, Co, Cr, Cu, Hg, Mn, Ni, Pb, Sb, Se and Zn in agricultural soil around the water reservoir. A total of 36 soil samples were collected both during off-season agriculture and pluvial agriculture from April to October 2022. The samples were analyzed for trace metals according to the standard methods of the US EPA 2007 with a microwave plasma atomic emission spectrometer (MP-AES), Agilent Model 4210. The pollution level was assessed using contamination factor (Cf) and modified contamination degree (mCd). During the off-season, the concentration of trace metals followed in descending order as Mn > Cr > Cu > Pb > Zn. As, Cd, Co, Hg, Ni, Sb and Se were below the detectable limits. In pluvial season, the concentration of traces of metal follows the order Mn > Cr > Zn > Cu > Ni > Pb > Hg > As. Cd, Co, Sb and Se remain below the detectable limits. The concentrations of Cr, Mn and Zn were lower in the off-season agriculture than in pluvial agriculture. For Cu and Pb, the concentrations were higher in the off-season than in pluvial agriculture. The Cf ranges from 0.24 to 11.70 depending on the considered trace metal. The Cf values of As, Ni, Pb, Zn and Mn indicated that the agricultural study soil was lowery contaminated by these trace metals. The agricultural study soil was moderately contaminated by Cr and Cu, and highly contaminated by Hg. Globally the agricultural study soil presents a moderate degree of contamination (mCd 2.25) by the eight trace metals studied. This result provides information on understanding the risks of trace metal contamination of agricultural soil. It is important to anticipate the control of soil contamination through regular monitoring of toxic metals in agricultural soils, control the quality of chemicals used in agriculture and regulate their use.

Risk Assessment of Potentially Toxic Elements in Agricultural Soils of Al-Ahsa Oasis, Saudi Arabia

Contamination of soil with potentially toxic elements (PTEs) is receiving great attention worldwide due to its apparent toxicity and hazards to local residents. The assessments of soil PTE distribution, sources, and environmental risks are, therefore, the first steps of high-efficiency pollutant degradation and sustainable utilization. The current study used a variety of contamination indicators and multivariate methods to evaluate the environmental risk of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in Al-Ahsa soils in eastern Saudi Arabia. For analysis, 30 surface soil samples were collected from palm fields irrigated with groundwater and treated sewage water. Landsat images of Al-Ahsa indicated an increase in the total vegetative area and the residential area, and a decrease in the bare land area from 1985 to 2021. The average concentrations of PTEs (mg/kg−1) were lower than the maximum admissible concentrations and had the following decreasing order: Zn (54.43) &gt; Cr (28.67) &gt; Ni (14.53) &gt; Cu (10.83) &gt; Pb (5.23) &gt; As (2.27) &gt; Hg (0.35) &gt; Cd (0.26). The enrichment factor (EF) findings confirmed that the Al-Ahsa soil is significantly enriched with Hg, moderately to severely enriched with As, and moderately enriched with Cd. The potential ecological risk index (RI) demonstrates a moderate ecological risk, with only certain parts presenting a high risk. The different PTE levels in agricultural soils may be caused partly by the various qualities of groundwater that originate from various aquifers and sewage-treated water. The results of a multivariate analysis showed that most of the anthropogenic sources of Hg, As, and Cd may come from using a lot of fertilizers and insecticides. Levels of the remaining PTEs indicated natural sources from earth crust materials.

Effects of anthropogenic and natural environmental factors on the spatial distribution of trace elements in agricultural soils

The concentrations of trace elements in agricultural soils directly affect the ecological security and quality of agricultural products. A comprehensive study aimed at quantitatively analyze the effects of anthropogenic and natural environmental factors on the spatial distribution of heavy metals (HMs) and selenium (Se) in agricultural soils in a typical grain producing area of China. Factors considered in this study were parent rock, soil physicochemical properties, topography, precipitation, mine activity, and vegetation. Results showed that the median values of Zn, Cd, Cr, and Cu of 111 topsoil samples exceeded the background values of Guangxi province but were lower than the relevant national soil quality standards, and 85% of soil samples were classified as having rich Se levels (0.40 −3.0 mg kg−1). The potential ecological risk index of soil heavy metals as a whole was low, with Cd in 9% of the samples posing moderate ecological risk. The concentrations of heavy metals and Se were relatively high in soils from shale rock. Soil properties, mainly Fe2O3 and Mn played a dominant role on soil HMs and Se concentrations. Based on GeoDetector, we found that the interaction effects of two factors on the spatial differentiation of soil HMs and Se were greater than their sum effect. Among the factors, Mn enhanced the explanatory power of the model the most when interacting with other factors for soil Zn; the greatest interactive effect was between distance from mining area and Mn for Cd (q = 0.70); Fe2O3 significantly promoted the spatial differentiation of soil Cr, Cu and Se when interacting with other factors (q > 0.50). These findings contribute to a better understanding of the factors that drive the distribution of HMs and Se in agricultural soils.

Prediction of the concentration of antimony in agricultural soil using data fusion, terrain attributes combined with regression kriging

Potentially toxic elements in agricultural soils are primarily derived from anthropogenic and geogenic sources. This study aims to predict and map antimony (Sb) concentration in soil using multiple regression kriging in two distinct modeling approaches, namely Sb prediction using data fusion coupled with regression kriging (scenario 1) and Sb prediction using data fusion, terrain attributes, and regression kriging (scenario 2). Cubist regression kriging (cubist_RK), conditional inference forest regression kriging (CIF_RK), extreme gradient boosting regression kriging (EGB_RK) and random forest regression kriging (RF_RK) were the modeling techniques used in the estimation of Sb concentration in agricultural soil. The validation results suggested that in scenario 1, EGB_RK was the optimal modeling approach for Sb prediction in agricultural soil with root mean square error (RMSE) = 1.31 and mean absolute error (MAE) = 0.61, bias = 0.37, and high coefficient of determination R2 = 0.81. Similarly, the EGB_RK was also the optimal modeling approach in scenario 2, with the highest R2 = 0.76, RMSE = 0.90, bias = 0.06, and MAE = 0.48 values than the other regression kriging modeling approaches. The cumulative assessment suggested that the EGB_RK in scenario 2 yielded optimal results compared to the respective modeling approach in scenario 1. The uncertainty propagated by the modeling approaches in both scenarios indicated that the degree of uncertainty during the modeling process was distributed across the study area from a low to a moderate uncertainty level. However, cubist_RK in scenario 2 exhibited some elevated spots of uncertainty levels. As a result, the combination of data fusion, terrain attributes, and regression kriging modeling approaches produces optimal results with a high R2 value, minimal errors as well as bias. Furthermore, combining terrain attributes with data fusion is promising for reducing model error, bias and yielding high-accuracy predictions.

Dominant roles of torrential floods and atmospheric deposition revealed by quantitative source apportionment of potentially toxic elements in agricultural soils around a historical mercury mine, Southwest China

Hg pollution in soils surrounding the Wanshan mercury mine (WMM), once the largest Hg-producing center in China, has been confirmed, neglecting other potential toxic elements (PTEs). Better understanding of the sources and transport pathways of soil PTEs remains insufficient. To response these limitations, eight soil PTEs (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) at two typical agricultural sites, namely AZ and WW that are located near and far from the WMM, respectively, were systemically investigated. The results showed that AZ exhibited significantly higher concentrations of all the PTEs in the surface soil than WW (p < 0.01). Hg and Cd were recognized as the priority control PTEs, with their average concentrations of 21.54 and 1.21 mg kg–1 at AZ, and 15.79 and 0.48 mg kg–1 at WW. Those affected PTEs tended to enrich in near-river areas. Atmospheric deposition contributed more to soil Hg than did regular irrigation, but these two sources could not explain the considerable soil Hg accumulation. Three sources, including natural sources, hydraulic transport (torrential floods and regular irrigation) and atmospheric deposition, were identified and quantified based on the positive matrix factorization model, statistical methods and various auxiliary information. Hydraulic transport (mainly torrential floods) dominated the soil Hg input, which could explain 83.8% and 69.8% of the soil Hg input at AZ and WW, respectively. Atmospheric deposition dominated the soil Cd input, explaining 44.3% and 59.9% of the soil Cd input at AZ and WW, respectively. More attention should be given to the safe utilization of agricultural land and long-term monitoring of atmospheric deposition of Hg and Cd. This study could provide insights to prevent PTE diffusion along the above dominant transportation pathways while developing similar mine regions.