Cd In Agricultural Soils Research Articles

Bioavailability of Cd in Agricultural Soils Evaluated by DGT Measurements and the DIFS Model in Relation to Uptake by Rice and Tea Plants

The elevated accumulation of cadmium (Cd) in rice (Oryza sativa L.) and tea (Camellia sinensis L.) grown in agricultural soils may lead to a variety of adverse health effects. This study collected and analyzed crop samples along with paired rhizosphere soil samples from 61 sites in Cd-contaminated regions in Anhui Province, China. The findings revealed that both the diffusive gradients in thin-films (DGT) and soil solution were capable of effectively predicting Cd contents in crops. Conventional chemical extraction methods were inappropriate to evaluate the bioavailability of Cd. However, the effective concentrations (CE) corrected by the DGT-induced fluxes in soils (DIFS) model exhibited the strongest correlation with crop Cd contents. Except for CE, various measurement methods yielded better results for predicting Cd bioavailability in tea compared to rice. Pearson’s correlation analysis and the random forest (RF) model identified the key influencing factors controlling Cd uptake by rice and tea, including pH, soil texture, and contents of zinc (Zn) and selenium (Se) in soils, which antagonize Cd. To reduce the potential health risk from rice and tea, the application of soil liming and/or Se-oxidizing bacteria was expected to be an effective management strategy.

Accumulation Characteristics and Probabilistic Risk Assessment of Cd in Agricultural Soils Across China

To understand cadmium (Cd) pollution status and associated health risks in agricultural soils of China, a database including Cd concentrations of 160446 soil samples from 240 cities (counties) in 31 provinces was constructed based on domestic and foreign literature. The contamination factor and geochemical accumulation index were applied to explore the pollution level of Cd, and then health risks for different population groups were evaluated with the probabilistic risk assessment method based on Monte Carlo simulation. The results indicated that soil Cd concentrations in China ranged from 0.012 to 23.33 mg·kg-1, with the geometric mean of 0.473 mg·kg-1, which was 1.58 times the risk screening value of heavy metals in the soil of agricultural land (GB 15186-2018) (6.5<pH ≤ 7.5). From the perspective of different regions, the highest concentrations of soil Cd were found in central China, followed by southwest, south, northwest, northeast, east, and north China. From the perspective of time, there was no significant difference in soil Cd in different time periods (P>0.05). Cd pollution in agricultural soils was mainly distributed in Yunnan, Hunan, Guangxi, and Gansu provinces in China, which may have been related to the mining and smelting activities. The non-carcinogenic risks for all the population groups could be negligible, whereas there were potential carcinogenic risks for adults and seniors, with 5.81% and 4.49% of carcinogenic risk values exceeding the threshold of 1E-06 set by USEPA for adults and seniors, respectively. The results of this study provided valuable information for the pollution prevention and risk control of soil Cd pollution. To improve the accuracy of health risk assessment results, the exposure ingestion route of agricultural products and bioavailability of soil Cd should be considered in the probabilistic ecological risk assessment.

Remediation of cadmium contaminated soil using K2FeO4 modified vinasse biochar

The remediation of cadmium (Cd) contaminated soil is challenging for agricultural practices. In this study, a novel vinasse biochar modified by potassium ferrate (K2FeO4) was synthesized to immobilize Cd in agricultural soil. Three biochars [i.e., vinasse biochar (BC), KMnO4 modified vinasse biochar (MnBC), and K2FeO4 modified vinasse biochar (FeBC)] were applied to compare their efficiencies of Cd immobilization. The results showed that the orders of pH, ash content, and functional groups in different biochar were the same following BC < MnBC < FeBC. Scanning electron microscope images showed that the FeBC has more micropores than MnBC and BC. X-ray diffraction identified manganese oxides and iron oxides within MnBC and FeBC, indicating that Mn and Fe were well loaded on the biochar. In the soil-based pot experiment, both MnBC and FeBC significantly reduced soil available Cd by 23–38% and 36–45% compared with the control, respectively (p < 0.05). In addition, the application of BC, MnBC, and FeBC significantly increased the yield, chlorophyll, and vitamin C of Chinese cabbage (p < 0.05), and decreased its Cd uptake compared with the control. Notably, shoot Cd significantly reduced when 2% FeBC was applied (p < 0.05). Overall, using K2FeO4 to modify vinasse biochar enriched the surface functional groups and minerals as well as reduced Cd availability in soil and its uptake by the plant. Our study showed that K2FeO4 modified vinasse biochar could be used as an ideal amendment for the remediation of Cd-contaminated soil.

Spatial Distribution, Migration, and Ecological Risk of Cd in Sediments and Soils Surrounding Sulfide Mines—A Case Study of the Dabaoshan Mine of Guangdong, China

Acid mine drainage (AMD) resulting from metal sulfide mining activities can lead to contamination by potentially toxic elements (PTEs) primarily concentrated around the mining area and gradually spreading outward. However, ecological risks do not correspond directly to PTE concentrations, making it challenging to effectively manage the mining environment and accurately prevent potential ecological impacts. In this paper, we analyzed Cd levels in sediments, soils, and corresponding rice grains sampled from four villages near Dabaoshan Mine of Guangdong, China, in 2017. Our results reveal that Cd is the most prominent pollutant element, exhibiting significant enrichment and spatial heterogeneity in both soil and sediments and higher accumulation levels in rice grains compared to other PTEs. Cd concentrations in soil decrease from the tailings pond to the river terrace, with a slight increase after Taiping River joins and flows into the alluvial plain. However, the concentrations in sediments show the opposite trend. The bioconcentration factor (BCF) for Cd in agricultural soil from the river terrace is lower than that from the alluvial plain and the degree of exceeding the maximum permit level (MPL) of Cd in rice grains increases along the river. Mineral transformation and topography are important factors in controlling the geochemical behavior of PTEs. Remediation efforts alter the physicochemical properties of the river, resulting in the release of PTEs during schwertmannite transformation followed by their adsorption by clay minerals. Furthermore, the random forest (RF) analysis highlights that the bioavailability and potential ecological risk of Cd in soils are governed by the occurrence form of Cd in different topographies, mainly controlled by TFe2O3, Mn, and CaO in the river terrace and CaO, Al2O3/SiO2, and Mn in the alluvial plain. Therefore, considering the impact of topography on mineral compositions, physicochemical properties, and occurrence form of PTEs in soil and sediments is essential for assessing ecological risk in mining areas.

Galactoglucomannan oligosaccharides alleviate cadmium toxicity by improving physiological processes in maize

Phosphate fertilisers and past mining activity are significant source of cadmium (Cd) pollution; thus, the concentration of Cd in agricultural soils has been substantially rising. Various substances have been tested for their potential to alleviate the toxicity of Cd and stimulate the accumulation of Cd in plant organs. This study brought new insight of the impact of galactoglucomannan oligosaccharides (GGMOs) on the maize plants grown under/in Cd stress. The application of GGMOs reduced concentration of Cd in the maize leaves and thus GGMOs increased their growth (by 24%), concentration of photosynthetic pigments (up to 39.4%), effective quantum yield of photosystem II (up to 29.6%), and net photosynthetic rate (up to 19.6%). The concentrations of stress markers increased in the Cd and Cd + GGMOs treatment; however, significantly lower concentration was detected in the Cd + GGMOs treatment (malondialdehyde by 21.7%, hydrogen peroxide by 13%). The concentration of auxin increased almost by two-fold in the Cd + GGMOs treatment compared to the Cd treatment. The recovered auxin level and enhanced nutrient uptake are proposed mechanisms of GGMOs’ action during stress. GGMOs are molecules with biostimulant potential that could support vitality of maize plants in Cd stress.

Prediction of the concentration of cadmium in agricultural soil in the Czech Republic using legacy data, preferential sampling, Sentinel-2, Landsat-8, and ensemble models

The current study assesses and predicts cadmium (Cd) concentration in agricultural soil using two Cd datasets, namely legacy data (LD) and preferential sampling-legacy data (PS-LD), along with four streams of auxiliary datasets extracted from Sentinel-2 (S2) and Landsat-8 (L8) bands. The study was divided into two contexts: Cd prediction in agricultural soil using LD, ensemble models, 10 and 20 m spatial resolution of S2 and L8 (context 1), and Cd prediction in agricultural soil using PS-LD, ensemble models and 10 and 20 m spatial resolution of S2 and L8 (context 2). In context 1, ensemble 1, L8 with PS-LD was the cumulative optimal approach that predicted Cd in agricultural soil with a higher R2 value of 0.76, root mean square error (RMSE) of 0.66, mean absolute error (MAE) of 0.35, and median absolute error (MdAE) of 0.13. However, with R2 = 0.78, RMSE = 0.63, MAE = 0.34, and MdAE = 0.15, ensemble 1, S2 of PS-LD was the best prediction approach in predicting Cd concentration in agricultural soil in context 2. Overall, the predictions from both contexts indicated that ensemble 1 of S2 combined with PS-LD was the most appropriate and best model for Cd prediction in agricultural soil. The modeling approaches' uncertainty in both contexts was assessed using ensemble-sequential gaussian simulation (EnSGS), which revealed that the degree of uncertainty propagated in the study area was within 5% in both contexts. The combination of the PS dataset and the LD along with ensemble models and the remote sensing dataset, produced promising results. Nonetheless, the results demonstrated that the 20 m spatial resolution band dataset used in the prediction of Cd in agricultural soil outperformed the 10 m spatial resolution. When PS is combined with LD, an appropriate modeling approach, and a well-correlated remote sensing dataset are used, good results are obtained.

Pollution Characteristics and Health Risk Assessment of Heavy Metals in Agricultural Soils over the Past Five Years in Zhejiang, Southeast China.

Heavy metal contamination in agricultural soils has attracted increasing attention in recent years. In this study, 1999 agricultural soil samples were collected from 11 cities in Zhejiang Province from 2016 to 2020, and the spatial and temporal variation characteristics of 3 of the most important heavy metals, i.e., lead (Pb), cadmium (Cd), and chromium (Cr) were analyzed. The results showed that Cd had a slightly higher sample over-standard rate of 12.06%. Spatial distribution and temporal trends showed that the Pb concentrations overall increased from 2016 to 2020 and mainly accumulated in southern Zhejiang. In addition, multiple exposure routes were evaluated for human health risks. Children are more susceptible to the adverse effects of heavy metals in agricultural soils, and oral ingestion was the major exposure route. Cr poses higher human health risks to humans than Pb and Cd in agricultural soils. Therefore, more rigid environmental monitoring and related soil remediation counter-measures for some sites with high concentrations of heavy metals are necessary to limit the potential threat to human health.

Meta-analysis of Cd input-output fluxes in agricultural soil.

Heavy metal pollution of agricultural soil, especially Cd, has become a global threat to food safety and human health. Analysis of Cd fluxes through different input/output pathways is widely used to predict the change of Cd content in agricultural soil, identify the critical pathways, and assist in developing effective management strategies to protect the environmental quality of agricultural soils. In the present study, literature recording input/output fluxes of Cd through different pathways in agricultural soils were investigated, with study areas primarily located in China, Japan, and Europe. Fluxes of Cd at the study sites were calculated, and comparative analyses were carried out. Results indicated that the dominant input pathway of Cd was strongly associated with the intensity of local industrial activities. Atmospheric deposition was the predominant input pathway of Cd for 75% of the study cases. Irrigation and livestock manure were also major pathways of Cd input in China. The main output pathways were influenced by the planting structure, precipitation, topography, etc. Crop harvesting and leaching to groundwater played important roles among all Cd output pathways in China, and crop harvesting alone could remove a significant amount of Cd from the soil, with an estimated average flux of 6.27g/ha/yr. Leaching was the dominant Cd output pathway in Europe, accounting for 77%-93% of total outflux. To mitigate the accumulation of Cd in agricultural soil, standards to regulate Cd in the atmospheric environment, irrigation water, and agricultural additives should be tightened, and regulated removal and disposal of crops harvested from the heavily contaminated field should be promoted.

Heavy metal(loid)s in agricultural soils in the world’s largest barium-mining area: Pollution characteristics, source apportionment, and health risks using PMF model and Cd isotopes

Barium (Ba) mining and smelting activities release heavy metal(loid)s (HMs) that may cause threats to agroecological systems and human health. Here, contamination features, source apportionments, and associated health risks from agricultural soils were systematically investigated. According to descriptive statistics and HM single-pollutant indices, Ba, Cd, and As are priority control pollutants. Spatial interpolation and autocorrelation results indicate that Ba, Cd, and Zn have an aggregated distribution, clustered in the northwest of the study area in Guizhou Province, SW China. Pollution sources were apportioned based on multivariate statistics and a positive matrix factorization (PMF) model. As Cd is the dominant pollutant in Ba mines, Cd isotopic fingerprints and Bayesian isotopic mixing models in R were used to characterize the sources of Cd. PMF source apportionment and Bayesian isotopic mixing modeling indicate that the predominant sources of Cd in agricultural soils in Ba mining areas are mining and smelting, followed by agricultural activities and atmospheric deposition. PMF source apportionment suggests that the primary sources of HMs are Ba mining/smelting and agriculture, followed by sewage irrigation, and atmospheric deposition. Barium, As, and Cd pose the highest non-carcinogenic and carcinogenic risks, and should be prioritized for control.

Using spectral indices and terrain attribute datasets and their combination in the prediction of cadmium content in agricultural soil

The continuous demand placed on farmland to yield optimal harvest is dependent on the continuous application of agrochemicals and fertilizers to increase soil fertility and manage diseases. Successive application of fertilizers and use of agrochemicals coupled with metal and steel industries introduce potentially toxic elements into the soil. Active agricultural activities and industrial emissions that result in atmospheric cadmium (Cd) injection and active deposition on agricultural soil (particularly from the primary metal industry, steel and iron industrial production). The concentration of cadmium in the study area exceeds the local background value. As a result, excessive cadmium soil concentration will contribute to increased toxic and carcinogenic effects, with negative implications for both environmental and human health. Therefore, determining the spatial distribution of Cd is critical for environmentally friendly agricultural production and reducing Cd emission into soils. The goals of this study are to (i) determine the variability of Cd prediction in agricultural soil using spectral indices or terrain attributes coupled with modeling algorithms, and (ii) determine whether combining spectral indices and terrain attributes coupled with modeling algorithms can improve Cd prediction efficiency in agricultural soil. The study applied three modelling scenarios, comprised prediction using terrain attributes coupled with digital soil mapping (DSM) approaches (Scenario 1), prediction using spectral indices combined with DSMs (Scenario 2), and prediction using a combination of terrain attributes, spectral indices, and DSMs (Scenario 3). Gaussian process regression (GPR), partial least square regression (PLSR), extreme gradient boosting (EGB), multivariate adaptive regression splines (MARS), Bayesian regularized neural network (BRNN), regularized random forest (RRF), Bayesian generalized linear model (BGLM), and M5 tree models were the DSMs used in the study. The M5 tree model and terrain attributes {Scenario 1 R2 = 0.77, concordance correlation coefficient (CCC) = 0.73, root mean square error (RMSE) = 0.45, mean absolute error (MAE) = 0.37 and median absolute error (MdAE) = 0.35}, EGB and spectral indices {Scenario 2, R2 = 0.83, CCC = 0.76, RMSE = 0.54, MAE = 0.33 and MdAE = 0.23} and the M5 tree model, spectral indices and terrain attributes {Scenario 3, R2 = 0.84, CCC = 0.81, RMSE = 0.39, MAE = 0.31 and MdAE = 0.24} were the overall best combinations that predicted Cd in the agricultural soil. The overall evaluation of the approaches suggested that the combination of spectral indices, terrain attributes, and the M5 tree model in Scenario 3 was the optimal technique for predicting Cd in agricultural soil. Thus, a combination of environmental covariates with a high correlation with the response variable, combined with appropriate modeling techniques predicting potentially toxic elements in agricultural soil, will produce the best results.

Prediction of soil solution concentrations and leaching losses of cadmium in agricultural soils.

Cadmium (Cd) leaching is often estimated in Cd balance models using the product of drainage water (precipitation excess) and soil solution Cd concentration. However, Cd concentrations are seldom available but rather predicted using empirical models. Despite the availability of empirical models that estimate soil solution Cd concentrations, they have limitations for use in New Zealand where total Cd in agricultural soils is low and organic matter (OM) high. This study derived a Freundlich-type model from desorption data and a soil-liquid partitioning coefficient (KD ) model based on sorption data to predict soil solution Cd concentrations from commonly measured soil parameters that could be used to calculate Cd leaching fluxes. Independent soil solution Cd concentrations and Cd fluxes measured in drainage water from field trials were used to validate the predictive capacity of the models. It was found that soil pH and OM content were the most important factors controlling soil solution Cd, along with total Cd. Both models explained 83% of the variation in measured soil solution Cd concentrations in an independent dataset. Comparisons between Cd fluxes predicted using the Freundlich-type model and measured fluxes were within 25% of each other at 6 of 19 field sites studied. However, physical and chemical nonequilibrium conditions in soils and uncertainty in measured values likely contributed to differences between predicted and measured Cd fluxes at other sites. To unravel the impact of nonequilibrium and soil physical conditions on Cd concentrations in drainage water, more data are required on Cd concentrations collected under field conditions. This will allow better validation of the approach used in Cd balance models to calculate Cd leaching from soils.

Information on the Distribution of Cadmium in Agricultural Land in the Middle of the Serayu Watershed

&#x0D; &#x0D; &#x0D; Cadmium (Cd) is a heavy metal that is prohibited in food products. In the long term, consumption of food containing Cd can cause cancer (it is a direct carcinogen in humans). Poor management of the Serayu watershed has resulted in pollution of the surrounding land. Meanwhile, trust in management must be built within the framework of trade in the Industrial Era 4.0, which is developing continuously in world trade relations. This study aimed to obtain information on the distribution of Cd in agricultural soils in the middle of the Serayu watershed in March-August 2017. A total of 220 soil samples were taken using the GRID method, and the analysis of Cd concentration was determined by atomic absorption spectrofotometry (AAS). The results showed that Cd was detected in 142 soil samples in the range of 1.0-&lt;1.5 mg kg−1 and detected in the range of 0.5-&lt;1.0 mg kg−1 in 78 soil samples. The results were non-normally distributed with a clustered distribution pattern. The average value of the distribution of Cd in agricultural land in the middle of Serayu watershed was 1.21 mg kg−1, and the highest Cd concentration was 2.18 mg kg−1. The Cd concentration in the middle of the Serayu watershed is classified within the safe category because the concentration is still below the critical Cd threshold value of 3-8 mg kg−1.&#x0D; &#x0D; &#x0D; &#x0D; Keywords: agricultural land, cadmium, distribution, the middle of Serayu watershed&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D;

Long-term stabilization of Cd in agricultural soil using mercapto-functionalized nano-silica (MPTS/nano-silica): A three-year field study.

Cadmium (Cd) contamination in agricultural soil is a worldwide environmental problem. In situ stabilization has been considered an effective approach for the remediation of Cd-contaminated agricultural soil. However, information about the long-term effects of amendment on soil properties and stabilization efficiency remains limited. In the present study, mercapto-functionalized nano-silica (MPTS/nano-silica) was used to stabilize Cd in contaminated agricultural soil under field conditions for three years (with application rates of 0%, 0.2%, 0.4%, 0.6%, 0.8% and 1.0%). The application of MPTS/nano-silica reduced the soil aggregate stability (PDA0.25) (14.8%) and available K (24.9%) and significantly increased the soil dehydrogenase (DHA) (43.4%), yield of wheat grains (33.5%) and Si content in wheat tissues (55.2% in leaf, 50.4% in stem, and 37.7% in husk) (p<0.05). More importantly, MPTS/nano-silica decreased the leachability (36.0%) and bioavailability (54.3%) of Cd in the soil and transformed Cd into a more stable fraction. The content of Cd in wheat grains decreased by 53.9%, 61.9% and 54.1% in 2017, 2018 and 2019, respectively, in comparison with the control. These results indicated that MPTS/nano-silica has long-term stabilization effects on Cd in agricultural soil and is a potential amendment for the remediation of Cd-contaminated agricultural soils.

Environmental and edaphic factors affecting soil cadmium uptake by spinach, potatoes, onion and wheat

The relative ease with which cadmium (Cd) in agricultural soils can transfer to crop plants can pose a potential health risk to consumers. However, efforts to predict and mitigate these risks are often confounded by the various factors that influence metal accumulation in the edible plant parts. The aim of this work was to identify key drivers that determine Cd concentrations in spinach leaves, potato tubers, onion bulbs and wheat grain grown in commercial horticultural operations across New Zealand (NZ). Paired soil and plant samples (n = 147) were collected from farms across different NZ growing regions. Cadmium concentrations in the edible parts were measured and four different tests were used to examine the potential bioavailability of soil Cd: pseudo-total and porewater concentrations, 0.05 M Ca(NO3)2-extraction and diffusive gradients in thin-films (DGT). Information on a range of soil and climatic variables was also collected. The methods' ability to represent Cd concentrations in the plant parts was assessed through single and multiple regression analysis that considered the different variables and the farm locations. Soil Cd concentrations determined by the different tests were positively related to plant concentrations and there were clear regional differences between these relationships. The Ca(NO3)2 extraction predicted over 76% of the variability in Cd concentrations in onion bulbs and spinach leaves, while DGT and porewater Cd provided the best estimates for potato tubers and wheat grains, respectively, once regional differences were considered, along with certain environmental and soil variables. The results show that certain soil and environmental factors can be a key influence for determining Cd accumulation in the edible parts of some plants and that regional differences are important for modulating the extent to which this occurs. These effects should be considered when trying to mitigate the potential risks arising from Cd in agricultural soils.

Chelator complexes enhanced Amaranthus hypochondriacus L. phytoremediation efficiency in Cd-contaminated soils

The use of degradable chelating agent to enhance phytoextraction is a promising and low-cost method for remediation of heavy metals-polluted soil. However, very limited information is available regarding the effect of chelating agent combinations on plant growth and its capacity to extract metals. In this study, a pot experiment was conducted to evaluate the applicability of [N, N]-bis glutamic acid (GLDA), nitrilotriacetic acid (NTA), [S, S]- ethylenediamine disuccinic acid (EDDS), and citric acid (CA) alone and in combination to enhance the phytoextraction efficiency of amaranth (Amaranthus hypochondriacus L.) in two Cd-contaminated agricultural soils (S1 soil 2.12 mg/kg and S2 soil 2.89 mg/kg; the environmental standard value of Cd in agricultural soils in China is lower than 0.8 mg/kg). The results showed that, except for EDDS, other treatments had no obvious effect on plant biomass, and even promoted biomass increase to reach 1.06 (S1), 2.07 (S2) g/pot. The increase in total Cd extraction amount by 5 mM of single chelators GLDA and NTA reached 3.87 and 2.81 (S1), and 3.28 and 2.50 (S2) times that of the control group, respectively. For complexed chelating agents, G-N (GLDA + NTA) combinations (GLDA = 3 mM, NTA = 2 mM) extracted the highest amount of Cd compared with other treatments, reaching 0.36 and 0.52 mg/pot (4.50 and 3.71 times that of the control group), respectively. The order of extraction amount was G-N > GLDA > NTA > G-E (GLDA + EDDS) > G-C (GLDA + CA) > CA (5 mM total Cd concentration). Moreover, soil enzyme activity of G-N treatment increased significantly compared to that of the control group, indicating the great application potential of a composite chelating agent relative to a single chelating agent. Therefore, degradable chelators, especially the G-N combination, can effectively increase the available Cd content and greatly enhance the ability of plants to absorb and transport Cd in soils.

Application of arc emission spectrometry and portable X-ray fluorescence spectrometry to rapid risk assessment of heavy metals in agricultural soils

Ecological risk assessment of soil is commonly performed by determining heavy metals (HMs) through conventional laboratory analysis, which is cost-, time- and labor-consuming, especially in large-scale agricultural soils. Therefore, appropriate cheaper and faster analytical methods of comparable accuracy are urgently required. In this study, rapid analyses of HMs were performed via Portable X-ray fluorescence (PXRF) spectrometry and arc emission spectrometry (AES) in agricultural soils from a representative greenhouse vegetable area on the east bank of Dianchi Lake in Kunming City, Yunnan Province, southwest of China. Here AES was specifically used as a replacement of PXRF for measuring Cd in soil because the measurement limit of PXRF for Cd is usually higher than the normal content of Cd in agricultural soils. The performances of rapid analysis and conventional laboratory analysis were compared and evaluated, and ecological risk was assessed with the Nemerow composite pollution index for classifying HM contamination grades and Kriging interpolation for mapping spatial variation. Results showed that the PXRF and AES were applicable and accurate with the relative standard deviation (RSD) and the relative percent difference (RPD) for HMs being within 20%. Significant positive correlations were found between the rapid analysis results and conventional laboratory analysis results for both certified reference materials and collected soil samples. The classification of soil HM contamination grades and their spatial patterns were similar between the rapid analysis and laboratory analysis. Overall, results of the rapid analysis were almost identical to those of conventional laboratory analysis. Therefore, rapid HM analysis using PXRF and AES is effective and economic for accurately assessing ecological risk of agricultural soils in greenhouses.

Assessment of Pb, Zn, As, Ni, Cu, Cr and Cd in Agricultural Soils around Settlements of Abandoned Lead-Zinc Mine in Mkpuma Ekwoku, South-eastern, Nigeria

This study was carried out to assess the level, distribution and the contamination status of Pb, Zn, As, Ni, Cu, Cr and Cd in agricultural soils around the settlements of Abandoned Lead-Zinc Mine in Nkpuma Ekwoku, Southeastern, Nigeria. The mean concentrations of the heavy metals, Pb, Zn, As, Ni, Cu, Cr and Cd are 109.55, 210, 1.83, 2.34, 8.24, 12.66 and 8.57 mg/kg respectively. The values obtained were compared with the established soil sediment standard by Canadian Council of Ministers of Environment (CCME). Generally most samples around the abandoned Pb/Zn mine show higher concentration of Pb, Zn, Cd, and Cr compare to individual Effect Range Low (ERL) values of the elements while Cu, and Ni were below both Effect Range Low (ERL) and Effect Range Medium values. However, Cd and Cr exceed the Effect Range Medium of the elements. Pollution Load Index (PLI) was found to be generally low in all the locations whereas the contamination factor (CF) values for metals like Pb, Zn and Cd are >1 while CF values of As, Cu, Cr and Ni are <1. The contamination is most probably resulted from the mineralized veins and mining of the ores. Keywords : heavy metals; soil contamination; lead-zinc; Mkpuma-Ekwoku

Oil Extraction in the Amazon Basin and Levels of Metals among Indigenous Populations

Between May and August 2016 the Peruvian Ministry of Health conducted a cross-sectional study to assess levels of exposure to metals in the local population and stablish risk factors in Corrientes, Pastaza, Mara&amp;#241;&amp;#243;n and Tigre river basins (Peru). 1168 people from 39 indigenous communities participated in the study. Information on socio-demographic variables and environmental exposures was collected in questionnaires. Blood and urine samples were collected from each study participant, and environmental samples were collected from each community to measure levels of metals and hydrocarbons. We used atomic absorption spectrophotometry to measure metals concentrations (Pb, As, Ba, Cd and Hg) in biological and environmental samples. We used multilevel mixed-effects linear regression models with a random effect for community and river basin, adjusted for potential confounders to study the association between socio-demographic variables and environmental exposures and levels of metals in biological samples. We used linear regression models to study the association between median concentration of metals on environmental samples and on biological samples at the community level.57% of the study population had blood lead levels above 5 µg/dL and 28%, 13%, 9% and 26% of the study population had urinary levels of As, Ba, Cd and Hg, respectively, higher than those recommended by the Peruvian Ministry of Health (20 µg Cd/g As, 6 µg Ba/g creatinine, 2 µg Cd/g creatinine and 5 µg Hg/g creatinine). There were differences in levels of metals in environmental samples according to river basin. Inhabitants of communities with higher levels of Cd in agricultural soil presented higher levels Cd urinary levels than inhabitants from other communities. The analysis of risk factors at the individual level did not yield clear results. Differences in level of exposure to metals were generally explained by ethnic group, which might reflect geographical differences in levels of exposure.

Distribution of Cadmium in Sweet Corn Grown on a Peat Soil and Its Implication on Food Safety

Cadmium (Cd) is a heavy metal that can contaminate agricultural soils, in which one of the sources of Cd in agricultural soils is the use of phosphate fertilizers. Some plant species are known to have the ability to accumulate large amounts of Cd in their organs despite the Cd content in soil is relatively small. Cadmium distribution in various organs of plants also shows a diverse variation. Maize is able to accumulate Cd in its organs, either in roots, leaves or grains. This study aims to determine the distribution of Cd in sweet corn plants grown on a peat soil. Samples of maize plants were taken from nine maize fields in the village of Rasau Jaya 1, Rasau Jaya subdistrict, Kubu Raya district, West Kalimantan. The cultivars of sweet corn planted were Zea mays saccharata cultivar Bonanza and Zea mays saccharata cultivar Secada. Samples for roots, leaves, stems and panicles were taken at the stage of early grain filling. Grain samples were taken at the phase of fresh pod consumption. The Cd contents in the plant organ tissues were determined using dry ashing method. The results showed that the distribution of Cd in plant organs of sweet corn cultivars Secada and Bonanza follows the pattern of Cd in leaves &gt; roots &gt; grains &gt; panicles &gt; stems. The leaves contain the highest concentration of Cd, while the stems contain the lowest amount of Cd. The Cd concentration in leaves is about 3.5 times higher than that in grains, and 1.5 times higher than that in roots. The average Cd content in grains of sweet corn is 0.037 mg kg-1, which is still below the safe limit of Cd content in grains allowed by the Standar Nasional Indonesia, i.e. 0.2 mg kg-1.

Fate of Cd in Agricultural Soils: A Stable Isotope Approach to Anthropogenic Impact, Soil Formation, and Soil-Plant Cycling.

The application of mineral phosphate (P) fertilizers leads to an unintended Cd input into agricultural systems, which might affect soil fertility and quality of crops. The Cd fluxes at three arable sites in Switzerland were determined by a detailed analysis of all inputs (atmospheric deposition, mineral P fertilizers, manure, and weathering) and outputs (seepage water, wheat and barley harvest) during one hydrological year. The most important inputs were mineral P fertilizers (0.49 to 0.57 g Cd ha-1 yr-1) and manure (0.20 to 0.91 g Cd ha-1 yr-1). Mass balances revealed net Cd losses for cultivation of wheat (-0.01 to -0.49 g Cd ha-1 yr-1) but net accumulations for that of barley (+0.18 to +0.71 g Cd ha-1 yr-1). To trace Cd sources and redistribution processes in the soils, we used natural variations in the Cd stable isotope compositions. Cadmium in seepage water (δ114/110Cd = 0.39 to 0.79‰) and plant harvest (0.27 to 0.94‰) was isotopically heavier than in soil (-0.21 to 0.14‰). Consequently, parent material weathering shifted bulk soil isotope compositions to lighter signals following a Rayleigh fractionation process (ε ≈ 0.16). Furthermore, soil-plant cycling extracted isotopically heavy Cd from the subsoil and moved it to the topsoil. These long-term processes and not anthropogenic inputs determined the Cd distribution in our soils.