Cd Concentrations Research Articles (Page 1)

Combining random forest and XGBoost models for source apportionment and health risk assessments of heavy metals in suburban farmland soils.

Untreated neutral metalliferous mine drainage sludge deposited without environmental protection for over a century was studied to assess its long-term stability. The lack of long-term stability data on such untreated sludge represents a critical knowledge gap in mine waste management. We characterized the sludge's mineralogy, chemistry, and metal(loid) mobility using XRD, SEM-EDS, and a suite of leaching tests (deionized water, 0.01M CaCl2, and pH-static extractions), supported by geochemical modeling. Key findings show that even after ~ 100years, the sludge's phase composition and metal(loid) content remain largely unchanged, with high concentrations of As, Cd, Pb, and Zn comparable to those in the overlying Technosol. These metal(loid)s form their own phases (e.g., cerussite, smithsonite) or are adsorbed onto goethite and clays, limiting their release under the sludge's natural pH (6.3-7.1). Leaching is primarily confined to the sludge-Technosol interface, where the Technosol's low pH (~ 4) promotes mobilization of Cd, Pb, and Zn (e.g., up to 342mgkg-1 Zn and 278mgkg-1 Pb in CaCl2 extracts from the Technosol). These findings are consistent with PHREEQC modeling. A remediation scenario involving raising the Technosol pH to ≥ 7 (e.g., by liming), combined with metal(loid)-binding amendments (amorphous Mn oxide, biochar, zeolite), could reduce metal(loid) migration from the sludge to the Technosol by ~ 99.9% (especially for Cd, Pb, and Zn) and significantly decrease their bioavailability to plants. This study provides the first field-based evidence that untreated neutral mine drainage sludge can remain geochemically stable for over a century, and suggests remediation strategies to ensure environmental safety of such historical mine residues.

Hair dyes are widely used cosmetic products that can contain trace metals and metalloids, posing potential health risks through dermal exposure. This study aimed to assess and compare the concentrations of selected metals and metalloids in six brands of commercial hair dyes sold in Brazil and Paraguay and to evaluate their average daily dermal exposure doses, hazard quotients, hazard indices, and carcinogenic risk. Concentrations of Cr, Cd, Co, Cu, Fe, Mn, Mo, Ni, As, Al, Pb, Ba, Ag, and Zn in hair dye were quantified by standardized analytical methods. The Paraguayan brand showed the highest levels for several elements, including As (4.17 mg/kg), Al (130.276 mg/kg), and Fe (30.033 mg/kg). Estimated dermal exposure doses reached up to 3.35 × 10−6 mg/kg/day for arsenic, 1.68 × 10−3 mg/kg/day for aluminum, and 8.59 × 10−8 mg/kg/day for chromium. Although all hazard indices remained below 1, suggesting low non-carcinogenic risk, the calculated carcinogenic risk for arsenic in the Paraguayan product was 1.23 × 10−5, entering the medium-risk range. These findings highlight relevant differences in raw material control and potential cumulative health risks, especially for frequent users. Continuous quality control, harmonized regulatory standards, clear labeling, and further biomonitoring studies are strongly recommended to minimize long-term exposure to toxic elements in hair dye formulations and to ensure safer consumer products.

The soil condition of Norilsk, a large industrial city located in the Arctic zone of Russia, was assessed for the first time using pollution indices calculated based on the gross content of Pb, Zn, Co, Cd, Cu, Ni, Cr, Mn, As, and petroleum products. The Nemerov Pollution Index (NPI) classifies all Norilsk soil samples as polluted. According to the PLI index, 86% of the soil samples were characterized as polluted, and according to the total pollution index (Zc), 56% of the soil samples were classified as moderately hazardous and hazardous polluted. All soil samples had a medium, high, or very high environmental risk. The high level of soil pollution in Norilsk and the crucial role of nonferrous metallurgy as the primary source of these metals are confirmed. Pollutant content in the soil varied in different districts of Norilsk, with Mn and petroleum products being significant. The maximum heavy metal pollution occurred in the soils of the enterprise protection zones and in the soil of the industrial zones. Airborne pollutants from industrial enterprises are the main cause of heavy metal soil pollution in the Norilsk agglomeration. The contribution of other sources of pollution, typical for various functional areas of the city (e.g., motor transport and waste), is not expressed. Simultaneously, the hydrocarbon content is determined by the location of areas near roads, which is typical for districts with a high population and intensive traffic. Using the example of the Central District of Norilsk, the landscaping of the territory was shown to play a role in reducing the total content of heavy metals. Based on the physicochemical properties of Norilsk’s urban soils, the following key measures are proposed to improve soil quality: increasing organic matter content; ensuring a neutral pH and a high cation exchange capacity; and reducing soil density, which will reduce the toxic load on plants and negative impact on human health.

Methylmercury (MeHg) in rice poses significant health risks to populations with rice-based diets. While cadmium (Cd) contamination of paddy soils is widespread, its role in influencing MeHg accumulation in rice remains unclear. We combined a nationwide survey of 103 rice paddies with controlled pot and incubation experiments to examine how Cd affects MeHg in soils and rice grains. Soil geochemical parameters, microbial community composition, and horizontal gene transfer (HGT) of functional genes were analyzed to disentangle biological and geochemical mechanisms. Across field sites, Cd concentrations were positively associated with rice MeHg levels, independent of total Hg. Pot and incubation experiments confirmed that Cd exposure increased MeHg levels in soils and grains. This enhancement was mediated by both microbial and geochemical pathways: Cd reshaped microbial communities, promoted HGT that conferred Cd resistance to Hg-methylating bacteria, and altered soil redox potential and dissolved organic carbon, thereby creating conditions favorable for Hg methylation. Our findings reveal Cd as a previously overlooked driver of MeHg risk in rice agroecosystems. Given the co-occurrence of Cd and Hg pollution in global rice-growing regions, integrated management of multiple metals is needed to mitigate MeHg exposure through rice consumption.

Soil heavy metal pollution is becoming increasingly severe, while traditional remediation methods are inefficient and lack long-term stability. This study innovatively combines electrokinetic remediation (EK), microbial-induced calcium carbonate precipitation (MICP), and biochar for synergistic stabilization of contaminated soil. It evaluates the combined technology by comparing it with individual EK and MICP treatments through chemical speciation analysis and the Toxicity Characteristic Leaching Procedure (TCLP). The concentration of 1 mol/L urea–CaCl2 was identified as optimal for microbial activity, achieving a microbial cell density (OD600) of 1.0, a urease activity of 12 U/g, and a soil pH maintained within the range of 7.8–8.2. Corn stover biochar significantly enhanced urease activity—being 49.4% higher than that in the coconut shell biochar group and 25% higher than that in the bamboo biochar group—and increased the microbial survival rate by 25.4%. Group D1, which adopted the sequence of “EK treatment first, followed by biochar-synergized MICP treatment,” exhibited the best performance. It achieved stabilization efficiency of 51.90%, 73.40%, and 36.26% for bioavailable Cu, Cd, and Pb, respectively—all higher than those of individual EK and MICP treatments. Additionally, the residual fractions of heavy metals increased significantly, the leaching concentration of Cd in the anode region was below 1 mg/L, and energy consumption was 12.16% lower than that of the EK group. Microstructural analysis confirmed that the combined method promoted the formation of stable calcite, thereby improving soil aggregation and alleviating soil compaction. These findings collectively validate the proposed technology as a highly effective and sustainable strategy for stabilizing heavy metal-contaminated soil.

In the current study, we synthesized nano zinc sulfide (nZnS) and studied the effects of root zone (RZ) and foliar application (FS) of nZnS (0 and 50 mg/L) on cadmium (Cd) stressed maize (0 and 1 mM CdCl2) using completely randomized design (CRD). After 20 d of nZnS supplementation, growth and biochemical responses were recorded. The study highlights the critical issue of Cd stress in maize and investigates how nZnS influences plant tolerance mechanisms. We explored the novelty of application of RZ and FS of nZnS, focusing on its role in Cd/Zn homeostasis, growth and stress resilience. The RZ supplementation with nZnS recovered growth and enhanced maize protein and phenolic content under Cd stress. Exogenous application of nZnS improved chlorophyll under Cd stress. Whereas, exposure to Cd stress markedly reduced Zn in shoots (0.0015 mg/g DW; −99.1%) compared to the control (0.186 mg/g DW). The nZnS application enhanced Zn fraction in shoots (2.03 mg/g DW by RZ; and 1.46 mg/g DW by FS), especially in Cd-stressed plants (2.68 mg/g DW by RZ; and 2.36 mg/g DW) by FS. Exposure to Cd stress resulted in an increased shoot Cd fraction (0.376 mg/g DW), which was further increased by root zone nZnS supply (0.673 mg/g DW; +44.0% compared to Cd-stressed plants. Foliar application of nZnS also enhanced the Cd concentration in the shoots (0.579 mg/g DW; +35.0% compared to the Cd-stressed plants). Although the Cd fraction was synergistically increased due to nZnS supply which can be explained based on Cd/Zn homeostasis reinforced by sulfur (S) supply. In conclusion, the use of nZnS alleviated Cd stress in maize, suggesting that it is an effective strategy for improving Cd tolerance in crops like maize.

Soil cadmium (Cd) contamination poses significant risks to human health and environmental sustainability. Despite advances in bioremediation, effective bioagents with clear mechanistic insights for Cd detoxification are lacking. We first deciphered the whole-genome sequence of a novel Cd-tolerant Trichoderma nigricans T32781 and its in vivo heavy metal tolerance. In five independent pot and field trials, we revealed the T32781-induced alleviation mechanisms of plant-microbe-soil interactions in wheat and barley in response to Cd toxicity using a combination of agronomic, physiological, microbiome and metabolome approaches. We discovered that T32781 inoculation in soil significantly increased grain yield and decreased grain Cd concentration in barley and wheat exposed to different soil Cd levels. T32781 predominantly colonized soils, mitigating Cd toxicity by reducing soil Cd availability and promoting beneficial soil microbial communities and metabolites. These beneficial effects were further validated in the field, where the exogenous application of key metabolites induced by T32781 inoculation in soils and plants significantly increased grain yield and reduced grain Cd concentration in barley. This work highlights the potential of T32781 to enhance plant‒microbe-soil interactions and support sustainable and safe crop production in Cd-contaminated soils, addressing the increasing global demand for cereal production for food and feed.

Plant health and agricultural productivity are seriously threatened by heavy metal contamination. Due to the expansion of cereal agricultural lands into marginal areas close to urban areas and unpaved roads that are polluted by many pollutants, especially that of cadmium (Cd), this study examined the effects of Cd and salicylic acid (SA) separately and in combination on the growth, physiological, biochemical, and reproductive responses of barley (Hordeum vulgare L.). Three SA treatments (0, 86, and 172 mg/kg soil) and four Cd concentrations (0, 10, 20, and 30 mg/kg soil) were used in a factorial pot experiment. The findings showed that high Cd (Cd30) reduced vegetative growth but increased spike number and harvest index, indicating reproductive compensation, moderate Cd levels (Cd20) improved some growth traits, including plant height by 4.00% and flag leaf area by 13.11% compared to the control treatment, suggesting a possible hormetic effect. Particularly under moderate Cd stress, SA at 86 mg/kg markedly enhanced plant height, yield components, and antioxidant balance. On the other hand, SA at 172 mg/kg increased grain number and spike length but decreased overall yield, as a result of metabolic effects and hormonal interferences. Under extreme stress, endogenous defense mechanisms might be sufficient, and external SA could upset homeostasis, according to the interaction effects, which showed that Cd20 × SA86 maximized growth and productivity while Cd30 × SA0 produced an increase in grain and biological yields by an amount of 10.95 and 9.73%, respectively, compared to the control treatment. These results show that the performance of growth and yield components of H. vulgare L. was significantly and variably affected by both Cd and SA, both separately and in combination, depending on the concentration and the interaction. Data suggest that SA is most effective at moderate Cd stress levels.

This study investigates the accumulation, influencing factors, sources, and health risks of eight potential toxic elements (PTEs) in soils from the central–southern Shandong Peninsula, a region characterized by a high geological background and intensive human activities. Concentrations of Cr, Cd, Cu, Ni, Pb, Zn, As, and Hg were analyzed in 19,484 topsoil samples. The results showed that Cr, Cu, and Ni levels exceeded national background values, primarily linked to basalt distribution. Utilizing positive matrix factorization (PMF), spatial analysis, and comparative assessment, four primary sources were identified: natural sources (36.79%), combined traffic and agricultural activities (34.20%), coal combustion (17.32%), and industrial emissions (11.69%). A health risk assessment indicated that while non-carcinogenic risk was within the acceptable limits for the general population, it exceeded the threshold for children in 2.53% of cases, with As from coal combustion being the predominant contributor. These findings provide a critical theoretical basis for implementing targeted, source-oriented control strategies to mitigate PTE pollution in areas where high geological background and anthropogenic activities intersect.

Sodium alginate-synthesizing regulatory gene algB in Pseudomonas putida XMS-1 decreases Cd uptake in Allium tuberosum in the Cd-polluted soil.

Kinetics and potential risk of heavy metal release from commercial organic fertilizers in northern China.

Consumption of fermented Cd and Pb contaminated wheat flour increases potential health risk.

Metallomics of dill: Influence of environmental stress and contamination of commercial samples.

Enhanced effects of species richness on cadmium phytoextraction across eastern China: A meta-analysis.

Species and element-specific associations of trace elements with body size in mesopelagic fish and crustaceans from the North-East Atlantic.

Spatial heterogeneity of soil Cd and Pb driven by combined effects of pedogenesis and anthropogenic activities: A case study in the mountainous and hilly region of Fujian Province, China.

Karst regions are characterized by naturally high levels of heavy metals such as cadmium (Cd), lead (Pb), and zinc (Zn). In these areas, traditional methods of non-ferrous metal smelting, which often lack treatment for wastewater, gases, and slag, frequently result in significant exogenous heavy metal contamination. This study investigates the effect of two contaminated soils; i) geological high background soil without external pollution (G) and ii) zinc smelting contaminated soil (Z) with external pollution from zinc powder factory and two Chinese cabbage (Brassica rapa L. var. pekinensis) varieties: i) Jincai No. 3 (J), and ii) Beijing Xin No. 3 (B) having high and low Cd accumulation capability on plant heavy metal accumulation, soil enzyme activities, microbial communities, and soil fauna diversity to elucidate how different plant varieties interact with distinct soil conditions. The results revealed significant variations in heavy metal uptake between cabbage varieties, influenced by soil properties. Cd concentrations in J and B varieties were 0.93 and 0.97mg/kg in Z soil, respectively, compared to 0.19 and 0.15mg/kg in G soil. Similarly, Zn concentrations were almost four times higher in Z soil. Soil enzyme activities varied between treatments, with higher catalase (CAT) and urease (URE) activities observed in Z soil, while G soil exhibited greater acid phosphatase (ACP) and sucrase (SUC) activities. High-throughput sequencing and soil fauna studies revealed substantial differences in microbial and faunal community composition and diversity associated with two soils and two cabbage varieties. Redundancy analysis (RDA) showed that As, URE, and Ni significantly influenced the bacterial community structure, whereas CEC, ACP, and pH were critical for the fungal communities. The study offers insights into phytoremediation strategies and soil health management by highlighting the complex interactions between soil contamination, heavy metal uptake by plants, and microbial community dynamics, with the goal of reducing pollution and enhancing ecosystem health in contaminated karst areas.

Pb, Cd, and Cu concentrations in Scyliorhinus canicula (Linnaeus, 1758) and M. merluccius (Linnaeus, 1758): Accumulation trends and interspecific biomonitor potential.

Impact mechanisms of polyethylene microplastic on Cd adsorption and passivation by KMnO4-modified biochar in different soils.