Soil Cadmium Concentration Research Articles

Assessment of Cadmium, Chromium, and Lead Concentrations in Water, Bank Soil, Sediment, Plants, and Fish in Bagega Lake, Zamfara State, Northwest-Nigeria

Assessment of Cadmium, Chromium, and Lead Concentrations in Water, Bank Soil, Sediment, Plants, and Fish in Bagega Lake, Zamfara State, Northwest-Nigeria

Impact of compost and biochar from agricultural waste on reducing cadmium concentration and mancozeb residue in soil

The negative impact of excessive exposure to agrochemicals in shallot cultivation causes environmental pollution and human health. Biochar has the potential to absorb agrochemical contamination. This research aimed to investigate the effect of providing compost and biochar from agricultural waste on land quality, reducing the concentration of heavy metal cadmium (Cd) and mancozeb pesticide residues in soil and products in shallot. The experiment was carried out in shallot fields in Ngurensiti Village, Pati Regency, Central Java Province. Four different treatments, including combinations of biochar and compost, were applied, along with conventional controls. Data were analyzed using the F test (ANOVA) and Tukey's test using the Minitab statistical program version 16.0. The research showed that using biochar made from sugarcane bagasse, rice husk, corncob, and compost helped more soil bacteria grow and lowered Cd and mancozeb concentrations. In addition, treatment with biochar from sugarcane bagasse waste showed a decrease in Cd and mancozeb concentrations and a more significant increase in bacterial populations compared to other treatments (rice husk biochar and corncob biochar). Although there was a slight increase in Cd concentration in shallot leaves post-treatment, Cd levels in shallot bulbs remained within safe limits. This study shows that using biochar and compost from agricultural waste effectively improves soil quality, reduces heavy metal pollution, and lowers pesticide levels to support sustainable agriculture and protect people's health.

Perfluoroalkyl compounds in groundwater alter the spatial pattern of health risk in an arsenic‑cadmium contaminated region

Integrated health risk assessment strategies for emerging organic pollutants and heavy metals that coexist in water/soil media are lacking. Contents of perfluoroalkyl compounds and potentially toxic elements in multiple media were determined by investigating a county where a landfill and a tungsten mine coexist. The spatial characteristics and sources of contaminants were predicted by Geostatistics-based and multivariate statistical analysis, and their comprehensive health risks were assessed. The average contents of perfluorooctane acid, perfluorooctanesulfonic acid, arsenic, and cadmium in groundwater were 3.21, 0.77, 1.69, and 0.14 μg L−1, respectively; the maximum content of cadmium in soils and rice highly reached 2.12 and 1.52 mg kg−1, respectively. In soils, the contribution of mine lag to cadmium was 99 %, and fertilizer and pesticide to arsenic was 59.4 %. While in groundwater, arsenic, cadmium and perfluoroalkyl compounds near the landfill mainly came from leachate leakage. Significant correlations were found between arsenic in groundwater and arsenic and cadmium in soils, as well as perfluoroalkyl compounds in groundwater and pH and sulfate. Based on these correlations, the geographically optimal similarity model predicted high-level arsenic in groundwater near the tungsten mine and cadmium/perfluoroalkyl compounds around the landfill. The combination of analytic network process, entropy weighting method and game theory-based trade-off method with risk assessment model can assess the comprehensive risks of multiple pollutants. Using this approach, a high health-risk zone located around the landfill, which was mainly attributed to the presence of arsenic, cadmium and perfluorooctanesulfonic acid, was found. Overall, perfluoroalkyl compounds in groundwater altered the spatial pattern of health risks in an arsenic‑cadmium contaminated area.

Long-term straw removal and double-cropping system reduce soil cadmium content and uptake in rice: A four-year field analysis

Several studies have demonstrated that reintroducing crop straw to fields may intensify cadmium (Cd) contamination in agricultural soils. However, the specific effects of long-term straw management practices on Cd concentration and its bioavailability in soil-rice ecosystems remain unclear. In this context, to explore the influence of straw return (SR) and straw removal (NSR) on Cd accumulation in both soil and rice within a double-cropping system, we conducted a four-year field study. Our research study unveiled that NSR consistently decreased soil Cd concentration and its bioavailability by approximately 16.93%–27.30% and 8.23%–21.05% respectively across both study sites. Conversely, SR resulted in a substantial increase in soil Cd bioavailability, ranging from 38.64%–53.95%. Notably, compared to NSR, SR significantly increased total soil Cd by 5.47%–36.58% and increased Cd content in brown rice by 8.00%–100.24%. Remarkably, after four consecutive years of NSR, brown rice Cd concentration at the Changfeng site compiled with national safety standards (GB 2762–2022). Additionally, returning early rice straw significantly raised soil Cd bioavailability for the subsequent crop, more so than late rice straw did for the early rice the following year. The findings suggest that traditional double-cropping cultivation with straw removal can effectively mitigate Cd contamination risks in crops and farmland in Hunan Province.

Prevention of Cadmium Contamination by Microbial Inoculant and Its Potential Mechanism

Cadmium is the main heavy metal contaminant of food in the world. The extent of cadmium pollution in peanut in China remains unclear. To determine the cadmium pollution level in peanut, samples from the main producing regions in China were assessed. The findings revealed that the cadmium pollution level in Chinese peanuts was relatively low. Moreover, the Aflatoxin Rhizobia Couple B. amyloliquefaciens, B. laterosporu, B. mucilaginosus, E. ludwiggi (ARC-BBBE) microbial inoculants on cadmium contamination in peanut were evaluated. The fertilization methods were categorized into conventional fertilization and conventional fertilization supplemented with 60 kg/hectare of microbial inoculant ARC-BBBE as the base fertilizer. The cadmium contents in the soil and peanut plant parts were detected and analyzed. The results demonstrated that the microbial inoculant ARC-BBBE significantly reduced the total cadmium content in peanut, as well as the available cadmium and exchangeable cadmium in soil. Furthermore, the pH and urease and alkaline phosphatase activities in soil were significantly enhanced, suggesting that the microbial inoculant ARC-BBBE decreased cadmium content in soil and reduced the cadmium uptake by plants through a combination of the action of the bacteria itself and the secretion of extracellular substances. This ultimately achieves the goal of reducing the cadmium content in peanut seeds.

Functional Hydrogels Promote Vegetable Growth in Cadmium-Contaminated Soil.

Over the years, the concentration of cadmium in soil has increased due to industrialization. Cadmium in the soil enters the human body through plant accumulation, seriously endangering human health. In the current study, two types of hydrogels were successfully synthesized using a free radical polymerization method: an ion-type hydrogel referred to as DMAPAA (N-(3-(Dimethyl amino) propyl) acrylamide)/DMAPAAQ (N,N-Dimethyl amino propyl acrylamide, methyl chloride quaternary) and a non-ion-type hydrogel known as DMAA (N,N-Dimethylacrylamide). In the experiment carried out in this study, the ion-type hydrogel DMAPAA/DMAPAAQ was introduced to cadmium-contaminated soil for vegetable cultivation. The study found that at cadmium levels of 0 and 2 mg/kg in soil, when exposed to a pH 2 solution, cadmium wasn't detected in the filtrate using ICP. As the amount of cadmium increased to 500 mg/kg, hydrogel addition gradually reduced the filtrate cadmium concentration. Notably, the use of the 4% hydrogel resulted in 0 mg/L of cadmium. For the 0% hydrogel, vegetable cadmium absorption was determined to be 0.07 mg/g, contrasting with 0.03 mg/g for the 4% hydrogel. The DMAPAA/DMAPAAQ hydrogel significantly boosts vegetable growth by efficiently absorbing nitrate ions through ion exchange, releasing them for plant uptake. In contrast, the DMAA hydrogel, used as a control, does not enhance plant growth despite its water absorption properties. In summary, the composite hydrogel shows great potential for enhancing vegetable yield and immobilizing heavy metals in soil.

Lead and cadmium content in soil, oil palm fiber, and palm kernel in the oil palm plantation with mulch application

Solid waste in palm oil mills is waste that has the potential to have a negative impact on the environment if not used properly. One of the solid wastes from palm oil mills is empty fruit bunche (EFB) which can be used as mulch on oil palm land. The mulch and inorganic fertilizer used can contain heavy metals, such as Pb and Cd. This study was aimed to assess the heavy metal content of Pb and Cd in the soil, fibers and kernels of oil palm fruit. This study evaluated the Pb and Cd content in the soil at depths of 0 – 20 cm and 20 – 40 cm, palm fiber and palm kernel. The results showed of the study showed that the Pb and Cd content of soil on land applied with inorganic fertilizer was greater than the Pb and Cd content of soil on land applied with mulch, where on land applied with mulch the level of Pb contamination was in the very slightly contaminated category, while Cd was in the quite polluted category, and inorganic fertilizer land is heavily polluted. On land where mulch was applied, the Pb and Cd content of fiber and kernel was smaller than the Pb and Cd content of fiber and kernel on land where inorganic fertilizer was applied.

Risk assessment of four toxic heavy metals in terrestrial and aquatic ecosystems around BSCIC tannery industrial estate of Savar, Dhaka,Bangladesh.

The shifting of tannery industries from Hazaribagh to Savar adjacent to Dhaleshwari River might have inevitable adverse impacts, especially the heavy metal contamination of both terrestrial and aquatic ecosystems. The study was carried out to investigate the concentrations of four heavy metals in the soil, water, and plant samples collected from around Dhaleshwari River adjacent to the Bangladesh Small & Cottage Industries Corporation Tannery Industrial Estate, Dhaka. This study revealed that average concentrations of cadmium and chromium in soil exceeded the maximum permissible limit of World Health Organization (1996) and average concentrations of lead, cadmium, and chromium in water exceeded the maximum permissible limit of World Health Organization (2011) and Environmental Conservation Rules (1997). The average concentrations of lead, cadmium, and chromium in the roots and shoots of both Eichhornia crassipes and Cynodon dactylon exceeded the maximum permissible limit of Food and Agriculture Organization/ World Health Organization (2016). Ecological risk assessment using indices model for soil pollution indicated that soil is mostly contaminated with cadmium and chromium which can pose strong ecological risk Health risk assessment using indices model for water pollution revealed the high degree of contamination and unacceptable non-carcinogenic risk and carcinogenic risk for adults as well as children through ingestion of water. Average bioconcentration factor and bioaccumulation factor were higher in Eichhornia crassipes than Cynodon dactylon for lead, cadmium, and chromium. Average translocation factor was also higher in Eichhornia crassipes for all the metals except cadmium. It is suggested remedial and mitigation measures be instituted to control environmental degradation of the newly established Tannery Industrial Estate.

Estimation of Cadmium Content in Lactuca sativa L. Leaves Using Visible–Near-Infrared Spectroscopy Technology

In order to monitor cadmium contamination in lettuce quickly, non-invasively, and accurately, and to understand the growth status of lettuce under cadmium pollution, lettuce was used as the test material to detect and analyze the visible–near-infrared reflectance spectra and leaf cadmium content under different concentrations of cadmium stress. A model for estimating lettuce leaf cadmium content was established. For model establishment, firstly, the original spectra were preprocessed using smoothing (Savitzky–Golay, SG), SG combined with multiplicative scatter correction (MSC), SG combined with standard normal variable transformation (SNV), SG combined with mean normalization (MN), SG combined with the first derivative (FD), SG combined with the second derivative (SD), SG combined with the baseline offset (B), and SG combined with de-trending (D). Then, the principal component analysis (PCA) was applied to perform dimensionality reduction on the data. Finally, the reduced dataset was divided into training and testing sets in a 2:1 ratio, and separate models for estimating the lettuce leaf cadmium content were built using partial least squares regression (PLSR), the backpropagation neural network (BP-NN), and support vector regression (SVR) in combination. The results showed that the accumulated cadmium content in lettuce leaves increased with an increase in the soil cadmium concentration. In the visible light range, the spectral reflectance of lettuce leaves increased with an increase in the cadmium concentration. In the near-infrared range, the spectral reflectance of the lettuce leaves under 10 mg/kg and 20 mg/kg cadmium stress was lower than that of the control group. The PLSR models established using the SG + MSC and SG + SNV preprocessing methods exhibited the strongest estimation capability for lettuce leaf cadmium content, with Rp2 and RMSEp values of 0.92 and 1.53 mg/kg, respectively, for the testing dataset. This study demonstrated that visible–near-infrared spectroscopy has great potential in monitoring cadmium contamination in lettuce.

Effects of lime and organic manure on cadmium content in soil and maize crop

Effects of lime and organic manure on cadmium content in soil and maize crop

Hyperaccumulator Solanum nigrum L. Intercropping Reduced Rice Cadmium Uptake under a High-Bed and Low-Ditch Planting System

Anthropogenic activities have raised cadmium (Cd) concentrations in agricultural soil, emerging as a primary catalyst for the decline in crop yield. Intercropping of two or several plants is one technique among many Cd phytoremediation techniques that has gained enormous attention recently. However, the impact of cultivation modes on Cd movement in rice plants when intercropped with heavy metal (HM) hyperaccumulator plants remains unclear. Thus, this study was designed to explore the effects of cultivation modes and the intercropping of rice with Solanum nigrum L. on rice growth and Cd uptake in Cd-contaminated soil. The experimental design encompassed five treatments: dry cultivation of monocultured rice, monocultured Solanum nigrum L., and intercropped rice–Solanum nigrum L.; flood cultivation of monocultured rice; and intercropped rice–Solanum nigrum L. in a high-bed and low-ditch planting system. The results revealed a significant increase in rice growth when intercropped with Solanum nigrum L., with a notable increase of 18.32 g∙plant−1 observed in rice biomass in dry cultivation under the intercropping system. In contrast, a more modest increase of 3.67 g∙plant−1 was observed in the high-bed and low-ditch intercropped rice–Solanum nigrum L. mode. The soil total Cd was higher in dry cultivation of monocultured rice and Solanum nigrum L. compared to intercropped rice/Solanum nigrum L.-cultivated soil, with lower values recorded for intercropped rice/Solanum nigrum L. under the high-bed and low-ditch planting system. In contrast, no significant effect was noted on soil exchangeable Cd content based on the planting pattern and cultivation mode. Intercropping with Solanum nigrum L. demonstrated a significant reduction of Cd content in various rice tissues, particularly in roots at the maturity stage, while Cd content was reduced across all rice tissues under the high-bed and low-ditch planting system. The Cd content in the stem, leaves, and bran of monocropped rice was higher compared to intercropped rice. This study suggests that the rice–Solanum nigrum L. intercropping system effectively reduces rice Cd uptake, particularly under the high-bed and low-ditch planting system.

Lung cancer mortality and soil content of arsenic and cadmium: an ecological study in 26 EU countries

Abstract Background Environmental risk factors, such as exposure to air pollution, are linked with lung cancer. However, potential health impacts of exposure to carcinogenic pollutants in soil are less defined. In this ecological study, we evaluated at a regional scale potential associations between lung cancer mortality and the soil content of two carcinogens: arsenic and cadmium. Methods Data on deaths from lung cancer were from EUROSTAT. Soil content of arsenic and cadmium were from the Land use/cover area frame (LUCAS) 2009 survey. Analysis covered 26 EU countries and 21,035 sampling points. Three socioeconomic indicators and seven lung cancer risk factors were included. Data were linked at the NUTS2 level (n = 219) and analysed by negative binomial regression. Results After inclusion of significant predictors, the ratio of lung cancer mortality rates in the population resident in the regions within the highest quantile of arsenic concentration in soil, compared to the rest of the dataset, was 1.062 for females (95% CI 1.024 - 1.101) and 1.037 for males (95% CI 1.020 - 1.074). In the regions within the highest quantile of cadmium in soil, compared to the lower quantiles, the ratio of the mortality rates was 1.062 for females (95% CI 1.019 - 1.101) and 1.075 for males (95% CI 1.033 - 1.117). When data were stratified by land cover, significant (p < 0.05) positive associations in males were only shown for cadmium sampled from agricultural land (cropland and grassland) but not from the non-agricultural land. Conclusions Higher rates of lung cancer mortality were reported in regions with high concentration of arsenic or cadmium in soil, relative to regions with lower concentration. Due to the ecological design, this study cannot prove causality but is in agreement with other reports linking exposure to arsenic or cadmium and lung cancer. This warrants future investigations at a finer geographical scale, focused on regions with high soil levels of arsenic and cadmium. Key messages • Higher lung cancer mortality rates were reported in regions with high concentration of arsenic or cadmium in soil, relative to regions with their lower concentration. • There was an association between cadmium in soil and lung cancer mortality in males for the subset of sampling points from the agricultural land but not for the non-agricultural land.

The Effect of EDTA on the Ability to Absorb Different Concentrations of Nickel, Cadmium, and Lead in Soil by Corn Plants

Background & Aims: The use of resistant and widely used species such as corn in agriculture and industry can be an effective solution for the bioremediation of soil pollutants, including heavy elements. The current research aimed to investigate the effect of EDTA on the ability to absorb different concentrations of heavy metals in the soil of corn plants in 2019. Materials and Methods: This research was conducted as a three-factor pilot design at concentrations of 0, 50, and 100 mg/kg in the greenhouse. The samples were analyzed using an atomic absorption device. The laboratory pilot design was based on Taguchi’s algorithm. Finally, transfer factor (TF), bioconcentration factor (BCF), and bioaccumulation coefficient (BAC) were calculated. Results: The results showed that different organs (root, stem, and leaf) show different levels of bioaccumulation under the influence of variable factors in different concentrations of heavy elements (nickel, cadmium, and lead). Also, there is a significant difference between the measured amounts of heavy elements in different organs of the corn plant (P≤0.05). The average TF levels for elements at concentrations of 50 and 100 mg/kg were 0.79 and 1.66 for nickel, 0.82 and 0.78 for cadmium and 1.361, 1.378, and 1.387 for lead. Based on the results, with the increase in nickel concentration, the absorption level increased, and with the increase in cadmium concentration, the absorption level decreased. Conclusion: The results of this research showed that it is possible to use EDTA to increase the efficiency of corn plants in absorbing heavy elements of nickel, cadmium, and lead.

Trans-Global Biogeochemistry of Soil to Grain Transport of Arsenic and Cadmium

Previous studies have shown that arsenic and cadmium can accumulate in rice grain to levels that cause health concerns. Furthermore, geographical survey has shown that there is considerable variation (~ 100-fold) in accumulation of these carcinogens in rice grain. This variance must be due to heterogeneity in soil biogeochemistry and contrasting rice management regimens. Here we present the first systematic global study to investigate the impact of soil biogeochemistry on accumulation of these elements in rice grain. Matched grain, shoot, root and soil samples were collected across a latitudinal gradient from East Africa to Europe and soil, shoot, grain chemistry and soil microbial community (prokaryotes and fungi) assessed within the context of arsenic and cadmium biogeochemistry. European and Vietnamese grain sum of arsenic species (inorganic arsenic plus dimethylarsonic acid) concentration medians, ~ 0.1 mg/kg, were found to be around ten-fold higher compared to those in East Africa and Sri Lanka. Arsenic concentrations were linked to higher levels of soil arsenic, and to higher abundance of soil sulphur-oxidising and sulphate reducing bacteria and methanogenic archaea. For cadmium, Sri Lanka showed highest (median 0.0156 mg/kg) and Europe lowest (median of 0.001 mg/kg) levels in grain, with the other regions showing intermediate values. Interestingly, grain cadmium was unrelated to soil cadmium concentrations, with Europe having the highest levels of cadmium in soil. Instead, grain cadmium correlated with higher oxidation/reduction potential, lower -log[hydrogen ion], lower soil calcium, and to a higher abundance of aerobic bacteria and fungi (lowest abundance of these organisms in European soils).

Feasibility of using Vis-NIR spectroscopy and PXRF spectrometry to estimate regional soil cadmium concentration

Conventionally, soil cadmium (Cd) measurements in the laboratory are expensive and time-consuming, involving complex processes of sample preparation and chemical analysis. This study aimed to identify the feasibility of using sensor data of visible near-infrared reflectance (Vis-NIR) spectroscopy and portable X-ray fluorescence spectrometry (PXRF) to estimate regional soil Cd concentration in a time- and cost-saving manner. The sensor data of Vis-NIR and PXRF, and Cd concentrations of 128 surface soils from Yunnan Province, China, were measured. Outer-product analysis (OPA) was used for synthesizing the sensor data and Granger-Ramanathan averaging (GRA) was applied to fuse the model results. Artificial neural network (ANN) models were built using Vis-NIR data, PXRF data, and OPA data, respectively. Results showed that: (1) ANN model based on PXRF data performed better than that based on Vis-NIR data for soil Cd estimation; (2) Fusion methods of both OPA and GRA had higher predictive power (R2) = 0.89, ratios of performance to interquartile range (RPIQ) = 4.14, and lower root mean squared error (RMSE) = 0.06, in ANN model based on OPA fusion; R2 = 0.88, RMSE = 0.06, and RPIQ = 3.53 in GRA model) than those based on either Vis-NIR data or PXRF data. In conclusion, there exists a great potential for the combination of OPA fusion and ANN to estimate soil Cd concentration rapidly and accurately.

Genotypical response of barley to increased cadmium content in soil

The results of a comparative evaluation of spring barley (Hordeum vulgare L.) varieties obtained by different methods on control and provocative soil background for cadmium are presented. A total of 10 varieties were studied: Rodnik Prikamya, Novichok, Dina, Zazersky 85, Triumph, Tallon (hybridization and selection); Forward, Bionic, Vitrum (cell selection); In memory of Dudin (mutagenesis). The studies were carried out in 2021 under the climatic conditions of the Kirov region. Seeds of the plants of each variety were sown in vegetation containers filled with soddy-podzolic soil. Cadmium provocative background (6.4 ± 0.5 mg/kg) was created by adding cadmium acetate to the soil. The average yield of barley varieties in the control (soil background without cadmium) was 279 g/m2; against a provocative background – 216 g/m2. Under the conditions of cadmium stress, the yield of hybrids decreased compared to the control by 12.2 %, regenerants – by 29.6 %, mutant – by 42.4 %. Among the studied varieties, the Bionic variety, which has a regenerated origin, showed a consistently high yield both on the control (334 g/m2) and cadmium background (263 g/m2). Productive bushiness of hybrid barley varieties against the control background varied from 2.8 to 4.1; in regenerants – from 3.4 to 4.8; mutant varieties – 4.3 pieces. Under the conditions of cadmium stress, productive bushiness decreased by an average of 2.7 – in hybrids; for 3.4 – for regenerants, for 2.6 pieces – a mutant. Bionic, regardless of the soil background, compared with other varieties, had the highest productive bushiness. Significant differences in the content of polyphenols in the grain of the studied varieties on the control and provocation soil background for cadmium were not revealed. Under the conditions of cadmium stress, a decrease in the content of flavonoids in grain was noted, as well as the accumulation of cadmium (0.29–0.92 mg/kg). Varieties of hybrid origin showed the ability to accumulate cadmium in grain to a greater extent.

Ensemble learning-based applied research on heavy metals prediction in a soil-rice system

Accurate prediction of heavy metal accumulation in soil ecosystems is crucial for maintaining healthy soil environments and ensuring high-quality agricultural products, as well as a challenging scientific task. In this study, we constructed a dataset containing 490 sets of multidimensional environmental covariate data and proposed prediction models for heavy metal concentrations (HMC) in a soil–rice system, EL-HMC (including RF-HMC and GBM-HMC), based on Random Forest (RF) and Gradient Boosting Machine (GBM) ensemble learning (EL) techniques. To reasonably evaluate the effectiveness of each model, Multiple linear and Bayesian regressions were selected as benchmark models (BM), and mean absolute error (MAE), root mean square error (RMSE), and determination coefficient R2 were selected as evaluation indicators. In addition, sensitivity and spatial autocorrelation (SAC) analyses were used to examine the robustness of the model. The results showed that the R2 values of RF-HMC and GBM-HMC for modeling available cadmium (Cd) concentrations in soil were 0.654 and 0.690, respectively, with an average increase of 48.0 % compared to the BMs. The R2 values of RF-HMC and GBM-HMC for predicting Cd, lead (Pb), chromium (Cr), and mercury (Hg) concentrations in rice ranged from 0.618 to 0.824 and 0.645 to 0.850, respectively, with an average increase of 58.2 % compared with the BMs. The corresponding MAEs and RMSEs of RF-HMC and GBM-HMC had low error levels. Sensitivity analysis of the input features and the SAC of the prediction bias showed that the EL-HMC models have excellent robustness. Therefore, the EL technology-based prediction models for HMCs proposed herein are practical and feasible, demonstrating better accuracy and stability than the traditional model. This study verifies the application potential of EL technology in pollution ecology and provides a new perspective and solution for sustainable management and precise prevention of heavy metal pollution in farmland soil at the regional scale.

Исследование характера загрязнения почвы цинком и кадмием вдоль автомобильных дорог города Волжского

The character of zinc and cadmium pollution of the roadside soil of the city of Volzhsky is analyzed. Exceedings of approximately permissible concentrations of total forms of zinc and cadmium in the soil were not found. The concentration of zinc in the soil near the highways of the city of Volzhsky does not correlate with the concentration of cadmium. The influence of the intensity and structure of the traffic flow, the level of landscaping and the age of development on the spatial dynamics of the concentrations of zinc and cadmium in the soil was studied. Near highways with heavy traffic, the concentration of zinc in the soil is greater than on less busy roads. The concentration of cadmium in the soil is higher along the roads, where the role of trucks and buses in the structure of the traffic flow is high. Roadside areas with a higher level of greenery are characterized by lower concentrations of zinc in the soil. There was no statistically significant relationship between the concentration of cadmium in the soil and the level of landscaping of roadside areas. No relationship was found between the age of development and the concentrations of zinc and cadmium in the roadside soil. The concentration of heavy metals in soil near highways seems to depend on many factors. The influence of some factors overlaps with the influence of others, which complicates the identification of clear relationships.

Increased soil cadmium concentrations enhanced poplar defence against a leaf pathogenic fungus infection

AbstractSince heavy metals are toxic to herbivores and pathogens, the Elemental defence hypothesis suggested that metals accumulated in plants might serve as defence against herbivores and pathogen attacks. However, several studies have tested this hypothesis with regard to pathogen resistance are limited. Most existing studies used herbaceous species as study model while studies on tree species are still lacking. In this study, we used poplar as a study model, to investigate whether soil treatment with five different cadmium (Cd) concentrations can protect plants from artificial infection of a leaf pathogenic fungus. The results showed that the Cd concentrations accumulated in plant leaves were positively correlated with increasing Cd concentrations amended in the soil while negatively correlated with the disease severity index (DSI) of plants after pathogen infection. Additional partial correlation analysis indicated that the plant DSI was only significantly correlated with Cd concentration accumulated in plant leaves while plant growth parameters and other leaf substances showed no clear correlations. The in vitro toxicity test of fungal mycelium grown on a series of Cd concentrations amended in the artificial medium further showed that the mycelium growth decreased with increasing Cd concentrations contained in the medium, which confirmed the biological toxicity of Cd on this fungus independently of other organic defensive substances present in poplar leaves. In conclusion, our study supported the Elemental defence hypothesis and proved that even a lower accumulation of Cd in poplar plants can provide sufficient protection against leaf pathogen infection.

The distribution of cadmium in soil and cacao beans in Peru

Peru is the eighth largest producer of cacao beans globally, but high cadmium contents are constraining access to international markets which have set upper thresholds for permitted concentrations in chocolate and derivatives. Preliminary data have suggested that high cadmium concentrations in cacao beans are restricted to specific regions in the country, but to date no reliable maps exist of expected cadmium concentrations in soils and cacao beans. Drawing on >2000 representative samples of cacao beans and soils we developed multiple national and regional random forest models to develop predictive maps of cadmium in soil and cacao beans across the area suitable for cacao cultivation. Our model projections show that elevated concentrations of cadmium in cacao soils and beans are largely restricted to the northern parts of the country in the departments of Tumbes, Piura, Amazonas and Loreto, as well as some very localized pockets in the central departments of Huánuco and San Martin. Unsurprisingly, soil cadmium was the by far most important predictor of bean cadmium. Aside from the south-eastern to north-western spatial trend of increasing cadmium values in soils and beans, the most important predictors of both variables in nation-wide models were geology, rainfall seasonality, soil pH and rainfall. At regional level, alluvial deposits and mining operations were also associated with higher cadmium levels in cacao beans. Based on our predictive map of cadmium in cacao beans we estimate that while at a national level <20 % of cacao farming households might be impacted by the cadmium regulations, in the most affected department of Piura this could be as high as 89 %.