Search Results (665)

The karst region of Southwest China represents a typical high geological background area characterized by extensive carbonate bedrock and secondary enrichment of heavy metals, particularly cadmium (Cd), in residual soils. Under natural carbonate-buffered conditions, Cd is largely immobilized through mineral associations and surface complexation, resulting in elevated total concentrations but low bioavailability. However, intensified anthropogenic pressures–including acid deposition, mining, excessive fertilization, and improper irrigation—have accelerated soil acidification in paddy fields. Acidification disrupts carbonate geochemical equilibria, weakens buffering capacity, and drives Cd speciation shifts toward more labile forms, thereby enhancing plant uptake and accumulation. These effects are especially pronounced in paddy fields and other systems subject to hydrological and redox fluctuations that further increase Cd mobility. To evaluate these coupled geogenic and anthropogenic controls, we conducted a structured literature synthesis (2016–2026) focusing on peer-reviewed studies of Cd dynamics in Southwestern China’s karst agroecosystems. We critically examine (i) the formation mechanisms and spatial heterogeneity of high-background Cd, (ii) acidification-driven speciation transformation and soil–crop transfer pathways, and (iii) in situ remediation and precision risk assessment strategies. By integrating geological inheritance, geochemical activation, and ecological risk perspectives, this review proposes a conceptual framework to support soil quality standard refinement and adaptive risk management in high-background karst regions. Full article

The switch in land use of abandoned tailings can precondition their reuse as newly built parks. This study investigated the feasibility of reusing a remediated mercury (Hg) retorting site in Wanshan, Guizhou Province, China, as a functional urban park by assessing residual heavy metal risks and associated vegetation responses. Field investigations were conducted across 31 park sites distributed along an east–west geographical gradient from the former mining area to urban parks, using replicated plots to sample the surface soils and dominant plant species. The concentrations of arsenic (As), cadmium (Cd), mercury (Hg), manganese (Mn), and lead (Pb) in soil and plant tissues were quantified using inductively coupled plasma–mass spectrometry, and vegetation structure and diversity were evaluated using standard community indices. The results showed significant spatial variability in soil and plant metal concentrations, with higher levels generally observed near historically impacted areas of the mine. However, all soil metal concentrations were below the national safety thresholds. Plant tissues exhibit controlled metal accumulation within normal or regulated ranges, reflecting the effective screening of tolerant and hyperaccumulating species. Increasing heavy metal concentrations were associated with reduced vegetation coverage, height, and diversity along the gradient. Overall, the findings indicate that the reclaimed Hg retorting site almost met ecological safety requirements, but more data on deep soils, groundwater, and long-term observations are needed to draw more conclusive conclusions. Full article

Non-food cropping provides a practical strategy for the safe utilization of severely cadmium (Cd)-contaminated farmland. In this study, a field experiment was conducted to evaluate the effectiveness of layered double hydroxides (LDHs) in reducing Cd transfer from soil to Artemisia argyi, a plant used for non-food applications, and to estimate Cd release potential during moxa burning. Our results demonstrated that the application of LDHs increased soil pH and decreased the extractable Cd concentration based on CaCl₂ extraction, suggesting a reduction in Cd bioavailability. Furthermore, BCR fractionation analysis indicated a shift of Cd from more active to more stable forms, further supporting the reduction in Cd bioavailability in the soil. SEM–EDS and FTIR confirmed the lamellar morphology, CaAl composition, and hydroxyl-rich functional groups of the LDH conditioner. Plant growth was not negatively affected by LDH treatment, and Cd concentrations in roots, stems, and leaves were significantly reduced. LDHs also reduced Cd levels in processed moxa and the mass-balance-based estimate of Cd release during combustion. These findings suggest that LDHs application may help reduce Cd transfer in non-food cropping systems on severely contaminated farmland. Full article

Communities in Mississippi located near petrochemical refining facilities face ongoing risks from heavy metal contamination in soils, threatening environmental quality, food safety, and public health. This pilot study evaluated the phytoremediation potential of Nerium oleander and cabbage (Brassica oleracea) in a residential fence-line community within the Cherokee Forest subdivision of East Pascagoula, Mississippi, impacted by long-term petrochemical and shipyard activities. Plants were grown directly in contaminated garden soils under natural field conditions. Soil and plant tissue concentrations of lead (Pb), cadmium (Cd), zinc (Zn), and nickel (Ni) were measured using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) (PerkinElmer, Waltham, MA, USA). Phytoremediation effectiveness was assessed through removal efficiency, translocation factor, and bioaccumulation factor. Results showed significant reductions (p < 0.01) in all soil metals, with cadmium removal exceeding 97%. Nerium oleander exhibited substantially higher metal uptake and translocation capacity than cabbage, achieving a maximum cadmium translocation factor of 9.99 and bioaccumulation factors up to 5.67. In contrast, cabbage showed lower translocation efficiency, suggesting that limited remediation potential but suitability as a food crop after soil treatment. These findings highlight Nerium oleander as an effective, sustainable, and community-acceptable phytoremediation solution. Full article

This study assessed, in two coastal locations of Ecuador (Cerecita, Guayas; Bajada de Chanduy, Santa Elena), cadmium (Cd) occurrence in cacao cultivated soils, its transfer to plant tissues (leaves and cotyledon/beans), and its implications for producers’ economic sustainability. Twelve cacao-producing sites in Cerecita and eleven in Bajada de Chanduy were georeferenced, and thematic GIS maps were generated to identify potential Cd hotspots. Sampling comprised topsoil (0–10 cm), leaves (fourth fully expanded leaf), and dried/fermented beans, followed by laboratory Cd quantification. In addition, producer surveys were conducted to characterize productive and economic structure, the economic sustainability index (IK) was calculated using Sarandón’s methodology, and interviews with collectors and agri-export companies were performed. Soil Cd levels were comparable between locations (0.24–1.55 mg kg⁻¹), whereas higher concentrations were detected in cotyledons/beans (0.53–5.01 mg kg⁻¹) and leaves (1.13–11.07 mg kg⁻¹), following the pattern leaves > cotyledon > soil. From an economic perspective, all farms exhibited IK < 2, with a marked territorial gap (≈1.6 in Cerecita vs. ≈0.5 in Chanduy). Cadmium in cocoa beans poses a long-term risk to marketing; in addition, total cadmium in the soil did not consistently predict cadmium in the cotyledons, and adverse impacts are amplified in territories with limited economic capacity to respond. Full article

Crops can accumulate heavy metals (HMs) from soil, leading to human exposure through dietary intake. However, the influence of interregional food trade on dietary HMs exposure remains underexplored. In this study, using data derived from existing literature, the occurrence and distribution patterns of six HMs, namely arsenic (As), cadmium (Cd), chromium (Cr), nickel (Ni), lead (Pb), and zinc (Zn), in soil and crops across China were investigated. Furthermore, the influence of food trade on human exposure to soil-derived HMs was assessed. The average total concentration of the six HMs in soil was 234.01 ± 29.54 mg/kg, while concentrations in rice and wheat were 16.06 ± 2.91 mg/kg and 22.48 ± 4.22 mg/kg, respectively. The hazard quotients (HQs) for As in rice exceeded 1 in the Central, Central Coast, South Coast, Southwest, and Northeast regions, indicating potential health risks. Interregional food trade significantly redistributed these risks. Through rice consumption, the Central and Northeast regions accounted for up to 36.78% and 45.08% of the daily intakes of As and Cd in other regions, respectively. Similarly, through wheat consumption, the Central and Southwest regions accounted for up to 51.33% and 25.97% of the daily intakes of As and Cd, respectively. This redistribution is largely attributed to the concentration of major crop production in the Central, Northeast, and Southwest regions. Overall, this study highlights the critical role of interregional food trade in modulating population health risks associated with contaminants, providing a more accurate and comprehensive assessment of dietary HMs exposure. Full article

Three biodegradable organic acids, citric acid (CA), malic acid (MA), and oxalic acid (OA), were evaluated for their ability to remove cadmium (Cd), lead (Pb), and copper (Cu) from contaminated soils. The effects of organic acid concentration, solution pH, and treatment time on metal removal were systematically investigated. Response surface methodology (RSM) was used to optimize these parameters. Sequential extraction was performed to track changes in heavy metal speciation. Under single-factor conditions (75 mmol/L CA, pH 5.0, 60 min), the removal efficiencies were 12.81% for Cd, 10.36% for Pb, and 14.94% for Cu, respectively. Under the optimized conditions (70 mmol/L, pH 5.0, 100 min), the removal efficiencies were further enhanced. The organic acids preferentially targeted bioavailable fractions (water-soluble, exchangeable, and carbonate-bound), which lowered ecological risk. Although CA was less efficient than chemical chelators such as EDTA, it caused much less nutrient loss. Organic acids, especially CA, provide an environmentally friendly alternative for heavy metal extraction with minimal side effects on soil fertility. They represent a promising low-impact option under the tested laboratory conditions. Nevertheless, the absolute removal values in a single washing step remained below 20% for all three metals, indicating that while the method is sustainable and eco-friendly, it is not suited for heavily contaminated soils as a standalone treatment. Full article

This study investigated the macro- and microelement profiles and bioactive substances (BAS) in the herbaceous species of the genus Rheum collected from two villages near Almaty, Kazakhstan, and the accumulation of heavy metals (HMs) in wild plants of Eastern Kazakhstan. Representative zonal species from the steppes and desert–steppes (Eastern Kazakhstan) were analyzed—totaling one hundred samples across 18 species from six families. According to the research, different plant species have a selective ability to accumulate heavy metals, even when growing in the same type of soil. Long-term observations reveal dominant patterns of HM (Cu, Zn, Mn, Co, Pb, Cd) occurrence in dry-steppe vegetation. It was found that Cu and Co demonstrate moderate bioadsorption with minimal accumulation, while Zn, Mn, and Pb show strong biological enrichment. Cadmium falls under elements with pronounced biological retention. Copper and cobalt are classified as moderately absorbed with limited buildup. Native plants in this region contain substantially greater amounts of lead relative to cobalt, and reflect cadmium–zinc geochemical specificity: Cd 3.85, Zn 0.15, Mn 0.10, Pb 0.09, Co 0.07, Cu 0.04, per Clark’s concentration index. Samples of collected Rheum tataricum L. in the village of Miyaly were found to have higher levels of flavonoids, phenolic compounds, and organic acids, while raw materials from the village of Bakbakty showed increased accumulation of anthracene derivatives and tannins. Flavonoids constituted the largest proportion of the studied groups of biologically active substances in both samples, confirming the high biological and pharmacological value of the plant material studied. The results obtained during the research can be successfully applied to the development of a strategy for the conservation of plant biodiversity in the studied areas and the sustainable management of plant resources. Full article

Anthropogenic pollution may impose additional pressure on European populations of large protected carnivores due to the systemic toxicity of contaminants such as cadmium, lead, and radiocaesium (¹³⁷Cs). Our aim was to carry out ¹³⁷Cs, radiopotassium (⁴⁰K), and stable element distribution analysis through seven tissues of grey wolves (Canis lupus) from temperate forests of Croatia using ultra-low background gamma-ray spectrometry and ICPMS, respectively. In addition, radiolead (²¹⁰Pb) massic activity was quantified in femoral bone. The massic activity of ¹³⁷Cs in the heart, kidney, liver, spleen, lungs, and femoral bone (in decreasing order) ranged from 9–61% relative to muscle and showed strong inter-tissue correlations. However, correlations between radionuclides and their stable analogues in wolf tissues indicated considerable uncertainty in the use of stable element data for radiological risk assessment. In addition, concentration ratios (CR_{whole organism-soil}) derived from stable element data should be applied with caution when radionuclide data are lacking. Overall, radionuclide activities and element levels not subject to homeostatic regulation in grey wolves were comparable to or lower than those reported for other populations, particularly those from sub-Arctic regions. Despite being apex terrestrial predators, wolves inhabiting temperate ecosystems do not currently appear to be at risk of adverse health effects from exposure to the most relevant inorganic anthropogenic pollutants. Full article

Soil contamination by heavy metals is a significant sustainability and ecological issue, impacting on the health of ecosystems and groundwater. This study assessed the efficacy of malic acid as a biodegradable and environmentally benign agent for the remediation of soils contaminated with cadmium, chromium, copper, and zinc. Two soils with contrasting textures were treated with a 10% malic acid solution at solid/liquid ratios of 1:5 and 1:10 for contact times of 2, 4, 6, and 8 h. The extraction efficiency varied depending on metal type, soil texture, and washing conditions. Cadmium removal ranged from 26% to 55%, zinc removal ranged from 10% to 25%, while copper showed variable extraction (5–45%) depending on initial soil concentration. Chromium exhibited the highest removal efficiency (30–90%), quantified as total chromium; however, the absence of speciation analysis (Cr(III)/Cr(VI)) represents a key limitation and may affect the interpretation of the removal performance. FTIR and UV–Vis analyses confirmed the formation of metal–carboxylate complexes and changes in soil functional groups during the washing process. In addition, significant mobilization of nitrogen and potassium was observed, whereas phosphorus remained relatively stable. The results highlight the influence of soil texture and multi-metal interactions on malic acid washing efficiency and provide a laboratory-scale environmental assessment of malic acid as a sustainable remediation alternative for soil remediation, while emphasizing the need for further evaluation regarding chromium speciation and post-treatment soil quality and sustainability impacts. Full article

Soils contaminated with heavy metals including cadmium, lead, zinc, copper, and chromium continue to represent a significant environmental issue, particularly in areas affected by industrial activities. In this context, the present study aimed to assess the feasibility and efficiency of an integrated bioremediation technique that combines, in a synergistic approach, phytoremediation with the use of natural amendments in order to reduce soil pollution with heavy metals. In addition, the potential for heavy metal recovery was investigated. The experiments were conducted under field conditions in the vicinity of the CET II Holboca power plant, using two plant species, Trifolium repens and Brassica napus, as bioaccumulators, while biochar was applied as a natural amendment. The analyses focused on metal concentrations, translocation factors, the degree of heavy metal recovery, and morpho-structural characteristics. The results indicated a high accumulation of metals in plant roots, particularly in soils treated with higher doses of biochar (4905.93 mg/kg iron for B. napus), and a significant growth stimulation (root elongation increases of up to 78% in T. repens and up to 29% in B. napus). B. napus exhibited greater translocation of metals to the aerial parts (with values up to 0.83 for zinc), whereas T. repens predominantly retained metals within the root system. The highest recovery efficiency values were observed in the case of lead, reaching 224.7% in T. repens and 86.7% in B. napus in soil amended with increased amounts of biochar. Overall, biochar application stimulated plant growth and enhanced metal uptake efficiency, suggesting a viable and practically applicable method for the ecological reconversion of contaminated land. Full article

Thallium (Tl) and cadmium (Cd) are highly toxic heavy metals that frequently co-occur in sulfide ores, posing a serious food safety risk through accumulation in rice. Although calcium-based (Ca-based) amendments have been widely applied to remediate heavy metal-contaminated soils, their effectiveness in Tl–Cd co-contaminated paddy soils remains unclear. A pot experiment was conducted to evaluate four Ca-based amendments—limestone powder, dolomite powder, hydrated lime, and oyster shell powder—on Tl and Cd bioavailability and uptake in paddy soil near a mining area. Ca-based amendments effectively reduced Tl and Cd bioavailability, with DTPA-Tl reducing by 11.2–17.2% and DTPA-Cd by 8.9–21.3%. These reductions were attributed to increased soil pH and decreased DOC, Fe, and Mn in the pore water. Additionally, Ca-based amendments shifted Tl and Cd from acid-extractable to residual fractions, reducing mobility. Additionally, Ca-based amendments promoted Fe/Mn plaque formation on rice roots, reducing Tl and Cd uptake. Consequently, Tl and Cd concentrations in brown rice decreased by over 14%, with the lowest levels observed under oyster shell powder. However, Cd concentrations still exceeded the maximum permissible limit, indicating that, although Ca-based amendments show considerable potential for in situ remediation of Tl–Cd co-contaminated paddy soils, further optimization and additional measures are required to achieve safe production. Full article

With the rapid progression of global industrialization and urbanization, heavy metal contamination has emerged as a major global threat, especially cadmium pollution. Consequently, optimizing remediation measures has become a pivotal means to solve cadmium contamination. Compared to traditional physical and chemical remediation methods, microbial remediation has great potential in addressing cadmium pollution. In this study, a novel bacterial strain, Chryseobacterium sp. HGX-24, exhibiting high cadmium resistance was successfully isolated and screened from cadmium-contaminated environments. A preliminary discussion of the response mechanisms of this strain under cadmium stress is provided. Additionally, preliminarily explored the synergistic remediation of microbial-plant in cadmium-contaminated soil. Under conditions of high cadmium concentration, cadmium ions were effectively adsorbed by strain HGX-24 through extracellular polymers and functional groups on the cell wall surface, including −COOH, −CONH−, −NH, −OH, and >C=O. Extracellular proteins and polysaccharides were secreted by strain HGX-24 to regulate the adverse effects of heavy-metal cadmium ions on bacterial growth. Furthermore, the expression of genes such as antioxidant defense and ROS scavenging (katG, fabG, ybjT), Fe-S cluster assembly (sufB, sufD), sulfur metabolism (cysAU), amino acid metabolism (hisA, cysD, aspC), phenylacetic acid catabolism (paaC), and ribosomal proteins (rplC, rpsC, rpsL, rplA, rplY, rpmC) was regulated, affecting the synthesis and metabolism of membrane transporters (ABC transporters and efflux RND transporters), antioxidant enzymes (SOD, COT, POD), Fe-S clusters, thioredoxin family proteins, and ribosomal proteins, thereby enhancing resistance to cadmium toxicity. Moreover, strain HGX-24 was found to regulate the activities of redox enzymes in Zea mays L., thereby alleviating oxidative stress and reducing the negative feedback effects of reactive oxygen species in Z. mays. Full article

The occurrence and concentration of potentially toxic elements (PTE) in fertilizers are a concern in tropical regions, and soil properties affect their bioavailability for crops. Cadmium is the most easily bioavailable for plants and so the food chain, and it represents a stepping-stone toward safe food production. So, this study aimed to evaluate the ionomics, metabolism, and growth of potato, tobacco, and rice in response to liming and to monoammonium phosphates (MAP) from different geographic origins and PTE contents (MAP 1, MAP 2, MAP 3). For this, independent experiments were conducted with each crop using MAP fertilizers as a phosphorus source applied to a Red-Yellow Latosol, with and without liming. Our findings indicated that physiological changes were primarily influenced by liming rather than PTE. Most acidic soils negatively impacted plant growth and sugar content and induced metabolic adjustments related to proline. The higher level of Cd in MAP 3 reduced manganese and zinc and increased sugar in plant shoots. Rice also had a lower Cd bioaccumulation than potato and tobacco, followed by a higher tolerance to acidic soil. The concentrations of As, Cd, and Cr present in fertilizers did not impair the growth and life cycle of the evaluated plants; however, metabolic adjustments were observed. Full article

Pb–Zn slag and smelting activities represent a persistent global source of soil contamination, releasing toxic heavy metals—lead (Pb), zinc (Zn), cadmium (Cd), and arsenic (As)—with documented risks to ecosystems and human health. Although previous reviews have addressed heavy metal contamination near smelters and pollution indices as assessment tools, no review has specifically mapped environmental assessment methods for Pb–Zn slag-contaminated soils, and evidence from Central Asia remains absent. This scoping review, following PRISMA-ScR 2018 guidelines, maps the global evidence base on soil contamination from Pb–Zn slag and associated assessment methods. Searches across Dimensions, PubMed, and OpenAlex identified 410 records; 56 studies (2010–2025) met the inclusion criteria. Studies were concentrated in China (35.7%), Poland (8.9%), and Brazil (7.1%); no studies from Kazakhstan were identified despite major Pb–Zn smelting operations in the Shymkent region. All studies reported heavy metal concentrations exceeding regulatory thresholds, with cadmium as the primary ecological risk driver and lead posing the greatest health risk to children. Assessment methods included pollution indices (73.2%), ecological risk assessment (67.9%), GIS-based spatial analysis (57.1%), human health risk frameworks (51.8%), and source apportionment models (50.0%). Post-2018 studies increasingly applied integrated multi-method frameworks. Critical gaps include the absence of Central Asian research, limited predictive modeling, and a lack of standardized protocols. Findings provide a structured evidence map to guide environmental monitoring and remediation at slag-contaminated sites globally. Full article