High Concentrations Of Cd Research Articles

Associations of Stool Metal Exposures with Childhood Gut Microbiome Multiomics Profiles in a Prospective Birth Cohort Study.

Metal exposures are closely related to childhood developmental health. However, their effects on the childhood gut microbiome, which also impacts health, are largely unexplored using microbiome multiomics including the metagenome and metatranscriptome. This study examined the associations of fecal profiles of metal/element exposures with gut microbiome species and active functional pathways in 8- to 12-year-old children (N = 116) participating in the GESTation and Environment (GESTE) cohort study. We analyzed 19 stool metal and element concentrations (B, Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Mo, Cd, Ba, and Pb). Covariate-adjusted linear regression models identified several significant microbiome associations with continuous stool metal/element concentrations. For instance, Zn was positively associated with Turicibacter sanguinis (coef = 1.354, q-value = 0.039) and negatively associated with Eubacterium eligens (coef = -0.794, q-value = 0.044). Higher concentrations of Cd were associated with lower Eubacterium eligens (coef = -0.774, q-value = 0.045). Additionally, a total of 490 significant functional pathways such as biosynthesis and degradation/utilization/assimilation were identified, corresponding to different functions, including amino acid synthesis and carbohydrate degradation. Our results suggest links among metal exposures, pediatric gut microbiome multiomics, and potential health implications. Future work will further explore their relation to childhood health.

Poa pratensis Mitigates Benzo(a)Pyrene (B[a]P) and Cadmium (Cd) Co-Contamination Toxicity by Regulating Antioxidant Activity and Water-Use Efficiency.

The effects of B[a]P and Cd on the growth, free-radical metabolism, antioxidants, and photosynthetic fluorescence parameters of Poa pratensis were studied by pot experiments. Results showed that low-concentration Cd (≤ 10mg·kg- 1) increased fresh weight, dry weight, malondialdehyde, superoxide anion radical, glutathione, and ascorbic acid. Conversely, high-concentration Cd (≥ 50mg·kg- 1) significantly decreased the fresh weight and dry weight, photosynthetic gas exchange, and fluorescence parameters. Water-use efficiency increased by 1.55 times compared with the control at high concentrations of B[a]P (≥ 25mg·kg- 1) and Cd (≥ 50mg·kg- 1). Principal component analysis showed that Cd played an important role in co-pollution. P. pratensis mitigated B[a]P and Cd co-contamination toxicity by regulating antioxidant activity and water-use efficiency. P. pratensis can tolerate 1, 5, and 25mg·kg- 1 B[a]P, as well as 1 and 10mg·kg- 1 Cd. P. pratensis was also highly capable of degrading B[a]P and extracting Cd in soils co-contaminated with B[a]P and Cd.

Histochemical and gene expression changes in Cannabis sativa hypocotyls exposed to increasing concentrations of cadmium and zinc

Hemp (Cannabis sativa L.) is a versatile crop that produces cellulosic bast fibres used in textiles and biocomposites. Is also finds use in phytoremediation, being a good candidate for the cultivation on marginal lands, such as those contaminated by heavy metals (HMs). HMs like cadmium (Cd) and zinc (Zn) are known to affect plant growth and impair the biosynthesis of cellulose and lignin at the cell wall level. Since cellulose is the major component in the gelatinous layer of bast fibres, HMs can impact the structure of hemp fibres and, consequently, their mechanical properties. This study investigates how varying concentrations of Cd and Zn in the soil affect the bast fibres of hemp plantlets. The chosen model is the hypocotyl, as it is ideal for studying bast fibre development: it exhibits a temporal separation between the elongation and thickening phases within a short period of approximately three weeks. C. sativa plantlets were grown for 20 days, and the hypocotyls sampled to perform histochemical observations, gene expression analysis, as well as to quantify biomass yield and Cd/Zn accumulation. Hemp plantlets grown in soils with the three highest Zn concentrations were smaller than the control group, whereas no decrease in size was observed under elevated Cd concentrations. However, at the highest Cd concentration, the root system exhibited enhanced development, accompanied by a significant increase in dry weight across all the concentrations tested. The quantification of Cd and Zn showed that the roots were the main organs accumulating HMs. Cd at the two highest concentrations decreased significantly the lumen area of bast fibres and increased their cell wall thickness. Zn decreased significantly the lumen area, but it did not impact the thickness of the cell wall at the highest concentration. Cd also increased the number of secondary fibres. Immunohistochemistry highlighted a different pattern of crystalline cellulose distribution with a signal that was less homogeneous in the presence of Cd and Zn. Gene expression analysis revealed changes in transcripts encoding cellulose synthases, fasciclin-like arabinogalactan proteins, class III peroxidases. The results obtained shed light on the molecular response and bast fibre histological changes occurring in young hemp plants exposed to Cd and Zn.

Melatonin improves cadmium tolerance in Salix viminalis by enhancing amino acid and saccharide metabolism, and increasing polyphenols

As a short-rotation woody plant, Salix viminalis has the potential for phytoremediation of cadmium (Cd), but it has poor tolerance to high Cd concentrations. Melatonin (MEL), a candidate bio-promoter, was considered to play an active role in plant responses to Cd. However, the molecular mechanism by which MEL regulates metabolic processes in plants to defend against Cd stress remain unclear. Transcriptomics and global untargeted metabolomic sequencing were used to investigate the rapid response of S. viminalis to high Cd concentrations during initial growth stage after foliar application of MEL. Four treatments were set up in a pot experiment involving foliar application of MEL on the first day, followed by irrigation with a Cd solution the next day. Significant variations in the relevant defence genes and metabolites in leaves exposed to Cd were observed between willows treated with and without MEL. Foliar application of MEL upregulated sulphur metabolism-related genes such as methionine and S-adenosylmethionine synthases in leaves exposed to Cd; glutamine content, which is the key point of nitrogen assimilation, also increased. Additionally, glycolysis and sucrose metabolic genes, including hexokinase, sucrose synthase, invertase, and the inositol phosphate metabolic gene myo-inositol-1-phosphate synthase were also upregulated in leaves. Moreover, MEL also upregulated genes related to the synthesis of flavonoids, anthocyanins, and proanthocyanins in the leaves. These results demonstrated that MEL improved amino acid and saccharide metabolism in the leaves of S. viminalis in response to Cd. It also improved the antioxidant capacity and Cd tolerance in S. viminalis leaves by enhancing synthetic capacity of polyphenol compounds. MEL may be involved in processes of photorespiration, ethylene metabolism, GABA shunt, nitric oxide metabolism, osmotic adjustment, and the synthesis of glutathione and ascorbate in S. viminalis under Cd stress. This series of metabolic changes in S. viminalis occurred within 24 h of the foliar application of MEL, which provided a sufficient substrate for subsequent defence reactions to cope with Cd stress. Our findings will help elucidate the molecular mechanism by which MEL regulates metabolic processes in plants in response to Cd challenges and guide the application of MEL to improve Cd phytoremediation efficiency.

Potentiality of Amaranthus viridis (L.) to accumulation of heavy metals and its relation to protein profile

The present study was undertaken to assess the levels of heavy metals (Cd, Fe, Ni and Zn) in soil and plant parts. The phytoremediation potential of Amaranthus viridis (amaranth) was determined by calculating the bioconcentration factor (BCF) and translocation factor (TF). Soil and plant samples were collected from eight different sites in their native habitats, distributed along Ismailia irrigation canal located in the east of the Nile Delta region, Egypt. Roots of amaranth had the higher concentrations of Cd, Fe and Ni means which were 2.75, 547.3 and 7.25 mg g-1 DW at sites SH8, SH6 and SH4 respectively, as compared to the other sampling sites. Whereas, shoots had the higher concentrations of Zn (283.6 mg g-1 DW) at site SH5. All sites were found with BCF more than 1 for all heavy metals. Except for Zn, TF values of Cd, Fe and Ni at all sites were lower than one. Depending on BCF and TF results, amaranth showed significant potential for phytostabilization of Cd, Fe and Ni and phytoextraction of Zn as well. Moreover, the protein profile showed different bands with varied molecular weights. Both relationships between studied accessions and similarity were elucidated, with high similarity (96% between SH2 and SH3 accessions), lowest similarity (72% between SH4 and SH8) and degree of polymorphism calculated as 62.5%. The variation in the similarity index may be due to the induction of a variety of proteins under heavy metal stress and also ecological features in various sites that cause protein polymorphism.

Controllability of optical, electrical, and magnetic properties of synthesized Cd-doped MgFe2O4 nanostructure

This study explores the synthesis of cadmium-magnesium co-doped magnesium ferrite (Mg1+xCdxFe2–2xO4, 0.00 ≤ x ≤ 0.30, Δx = 0.05) via a citric acid-assisted sol-gel auto-combustion method. X-ray diffraction (XRD) analysis revealed crystal structure changes due to Cd and Mg co-doping, with the 0.25 Cd sample showing the smallest crystallite size and highest lattice strain. High-resolution transmission electron microscopy (HRTEM) confirmed the nanostructure and largest surface area for this sample. Diffuse reflectance spectra, analyzed using the Kubelka-Munk relation, indicated that the 0.25 Cd sample had the lowest energy gap (2.08 eV), supported by band position calculations. Electrical conductivity and charge transport mechanisms were examined at various temperatures. Magnetization studies showed reduced saturation magnetization at x = 0.25, ascribed to cation distribution changes and spin canting, with coercivity and anisotropy decreasing with higher Cd content. Overall, the 0.25 Cd sample exhibited optimized optical, electrical, and magnetic properties due to its distinct microstructure.

Enhanced cadmium immobilization in soil using Fe- and Zn-doped biochar: Mechanisms and safety implications for Cicer arietinum L

Cd toxicity emerges as a major environmental concern with detrimental impacts on global agricultural systems and food safety. Therefore, there is an urgent need to cope with the high concentration of Cd in the soil and crops. This study elucidates the potential of iron (FeBC) and zinc doped biochar (ZnBC) on the growth and yield of chickpea (Cicer arietinum L.) in Cd-contaminated soil. The parallels of biochemical attributes and Cd absorption of Cicer arietinum L. were investigated after a 120-day pot trial under 1% (w/w) biochar doses and two Cd concentrations (25 and 50 mg kg−1). The results demonstrated that FeBC was more effective in promoting plant growth by reducing Cd mobility in soil than ZnBC and normal biochar (NBC). Additionally, the application of FeBC resulted in significant improvement in photosynthesis rate (53.98%), transpiration rate (91.53%), stomatal conductance (197%), and sub-stomatal conductance (213.33%) compared to other applied treatments. Cd uptake in roots, shoots, and grains was reduced by 44.19%, 56.89%, and 88.25% respectively with the application of FeBC. Notably, the highest decrease in Cd bioaccumulation factor (99.72% and 99.65%) and Cd translocation factor (99.89% and 99.85%) were recorded under FeBC application in 25 and 50 mg kg−1 Cd-contaminated soils, respectively. The improved plant growth and reduced Cd buildup with FeBC under Cd stress suggest that FeBC is a promising strategy to remediate Cd-contaminated soil and simultaneously promote sustainable production of legume crops in Cd-contaminated soils.

Assessing metals and metalloids impact of roadside dust on human health in Osogbo, Osun state, Nigeria

BackgroundMetals and metalloids in roadside dust pose considerable threats to both human health and the environment. ObjectivesThis study assesses human health risks of metal exposure to roadside dust by conducting a health risk assessment (HRA) for metals and metalloids uptake rates for children and adults via exposure pathways. MethodsSettled dust samples were collected from the major roads in Osogbo, Osun state. These samples were subjected to standard laboratory procedures for metals and metalloids analysis using Atomic Absorption Spectroscopy (AAS). ResultsAll the metals and metalloids except Cd had their concentration below the WHO limit. The average concentration of Cd was 1.54 mg kg-1, significantly above the WHO guideline of 0.80 mg kg-1, indicating a possible health concern. A strong positive correlation exits between Ni and Cd (0.774⁎⁎) (p < 0.01), Pb (0.662⁎⁎) (p < 0.01), Zn (0.606⁎⁎) (p < 0.01), and as (0.549*) (p < 0.05), showing that greater Ni concentrations are associated with higher concentrations of Cd, Pb, Zn, and As. Two principal components were identified, accounting for 80 % of the overall variation. PC1 has an eigenvalue of 60.834; however, PC2 has a higher eigenvalue of 74.952, implying that PC2 explains more of the variation in the data than PC1. Non-carcinogenic risk evaluations identify possible health risks linked with Cu, Cd, Cr, and As exposure, primarily through inhalation routes. Carcinogenic risk showed that Cd demonstrated high CR values ranging from 3740 to 1.30×1012 for adults and children throughout the study's various exposure paths. ConclusionThis study offered significant insight into the metals and metalloids pollution status in Osogbo, Nigeria, employing data and statistics, highlighting the need for evidence-based actions for environmental preservation to safeguarding people's health.

Adsorption Characteristics of Cadmium onto Calcite and Its Agricultural Environmental Relevance

Calcite (CaCO3), a common component of calcium-based fertilizers, has been recognized for its effectiveness as a cadmium (Cd) immobilization agent in the solidification/stabilization (S/S) method. This strategy is a widely used chemical remediation technique aimed at reducing the bioavailability and toxicity of Cd in contaminated soils. This study comprehensively evaluated the potential of calcite for Cd remediation through geochemical analyses, including adsorption isotherms, saturation index, ion concentration changes, and X-ray diffraction (XRD) analysis. Adsorption isotherm experiments indicated that Cd adsorption onto calcite aligns more closely with the Freundlich isotherm model, suggesting a heterogeneous surface with a maximum adsorption capacity of 1.56 mg g−1. Based on chemical states result, optimal conditions for CdCO3 precipitation with low Cd concentrations were identified at pH above 7.9. XRD analysis confirmed the formation of Ca0.67Cd0.33CO3 at higher Cd concentrations, indicating that chemisorption is the dominant immobilization mechanism. Additionally, variations in Ca2+ and CO32− concentrations supported the substitution of Cd for Ca on the calcite surface. These findings highlight calcite’s potential as an effective material for Cd immobilization, providing valuable insights for the developing more sustainable soil remediation strategies.

Cadmium (Cd) detoxification and activation of plant defense enzymes in wheat (Triticum aestivum) through the use of endophytic Bacillus thuringiensis and Salix alba root powder

Cadmium (Cd) is a toxic heavy metal and a threat to the ecosystem therefore the current investigation was designed to use endophytic bacteria from the Salix alba roots and to investigate its plant growth promoting and Cd detoxification ability with and without Salix alba root powder. In a complete randomized design (CRD), the cadmium sulfate was applied at the rate of 20 mg/kg and 40 mg/kg soil. The Bacillus thuringiensis (Accession # MW979616) was identified from Salix alba roots. The combination of Bacillus thuringiensis inoculated seeds +0.5gm root powder showed significant increase in wheat shoot dry weight, root fresh weight, catalase, and ascorbate peroxidases by 457%, 223%, 105% and 74%, respectively. The application of Bacillus thuringiensis with Salix alba root powder boosted the plant growth and defense at higher concentrations of Cd. In another treatment with Bacillus thuringiensis inoculated seeds + CdSO4 40 mg/kg + 0.5gm root powder significantly increased the shoot fresh weight, root fresh weight, root dry weight, proline, sugar, superoxide dismutase, and peroxidase by 456%, 650%, 115%, 91%, 80%, 350%, and 250%, respectively with 80% reduction in plant Cd accumulation and increased bacterial population. Bacillus thuringiensis and Salix alba root powder can be useful for plant growth, Cd toxicity mitigation, accelerating bacterial activity in Cd-contaminated soil and uplifting the plant defense under heavy metal stress.

Transfer and biological effects of cadmium along a tomato – thrip – predatory bug food chain

The heavy metal, cadmium (Cd) is an increasingly serious issue in agricultural ecosystems, mediating bottom-up effects on plants, herbivores and natural enemies. We measured how Cd modifies interactions between tomato Solanum lycopersicum, western flower thrips Frankliniella occidentalis, and the predatory bug Orius sauteri by examining Cd effects on the growth of tomato, the fitness of western flower thrips, and the survival and behavior of predators. The photosynthetic parameters of Pn (net photosynthetic rate), Gs (stomatal conductance), Ci (intercellular CO2 concentration), and Tr (transpiration rate) of tomato plants significantly decreased with the increase of Cd concentration. The total survival number of western flower thrips fed on tomato plants treated with different concentrations of Cd was significantly lower than that of the control, and sex ratios (female/male) gradually increased with the increase of Cd concentration. The numbers of thrips predated by O. sauteri on tomato plants treated with high concentrations of Cd (2.0 or 4.0 mg/L) were significantly reduced by the second day. Cadmium was accumulated and bioconcentrated in the roots, stems, leaves of tomato plants, and transferred to F. occidentalis, and O. sauteri. Cadmium translocated in significant quantities from roots to the stems and leaves of tomato plants, and from the tomato leaf to F. occidentalis. However, there was minimal (non-significant) transfer of Cd from F. occidentalis to O. sauteri. The presence of Cd significantly reduced the growth of tomato plants, the fitness of F. occidentalis, and the predation efficiency of O. sauteri. Collectively, Cd can mediate bottom-up effects on tomato, thrip, and predatory bug along food chain, potentially interrupting pest biological control in tomato in heavy metal-contaminated ecosystems.

Interactive effects of microplastics and cadmium on soil properties, microbial communities and bok choy growth

The simultaneous presence of microplastics (MPs) and cadmium (Cd) in soil environments has raised concerns regarding their potential interactive effects on soil-plant ecosystems. This study explores how polyethylene (PE) at concentrations of 0.5 % (w/w), 1 % (w/w), and 2 % (w/w), and Cd at concentrations of 3 mg kg−1 and 12 mg kg−1, either alone or combined, impact soil physicochemical properties, microbial community structures, and bok choy growth through a 40-day pot experiment. Our findings reveal that the addition of 2 % (w/w) PE significantly increased soil organic carbon (SOC). However, when 2 % PE coexisted with Cd, SOC levels decreased, potentially due to a reduction in enzyme activity (β-1,4-glucosidase). PE increased the proportion of 1–2 mm soil aggregates, while the coexistence of 2 % PE and Cd significantly increased the content of soil aggregates larger than 2 mm. The coexistence of PE and Cd increased available potassium (AK) in the soil by approximately 13 % to 41 %. Regarding bok choy growth, the aboveground biomass under 2 % PE was approximately 210 % of that under 0.5 % PE, possibly because of the enhancement in soil nutrients. The presence of Cd, however, reduced the chlorophyll content of bok choy by approximately 18 % to 34 %. Notably, the coexistence of high PE concentration (2 % w/w) and low Cd concentration (3 mg kg−1) resulted in the highest aboveground biomass among all coexistence treatments. Furthermore, the addition of PE and Cd significantly altered the structure of soil bacterial and fungal communities, with fungi showing a greater response. Bacteria were significantly associated with soil inorganic N content and plant growth. This study provides new insights into the interactions of microplastics and Cd within microbial-soil-plant systems.

Effects of cadmium doping on the physical and sensing properties of nanostructured CuO thin films

This investigation used sol-gel deposition to create undoped CuO and CuO: Cd thin films. All films of undoped CuO and CuO: Cd phase exhibit four dominating peaks at 35.52°, 38.84°, 53.37°, and 68.23°, which are correspondingly assigned to the (022), (200), (020), and (220) planes, according to X-ray diffraction analysis. The dislocation density reduced from 60.55 to 49.94, the strain decreased from 26.98 to 24.60, and the grain size of the produced films measured by XRD was 12.85–14.15 nm. Atomic force microscopy (AFM) was used to study the morphology. SEM analysis showed increased aggregation with higher Cd content, resulting in a more uniform porous structure. The optical band gap decreases for all samples as the cadmium content increases, ranging from 2.28 to 2.14 eV. Similarly, the refractive index and extinction coefficient values decrease as the cadmium content increases for all samples. The gas sensor detects H2 (375 ppm) using CuO film cadmium doping, which enhances sensitivity, CuO: 4% exhibits highest resistance. Sensitivity decreases with higher doping, indicating reduced sensor responsiveness.

Effects of cadmium on the intestinal health of the snail Bradybaena ravida Benson.

The heavy metal cadmium (Cd) is a toxic and bioaccumulative metal that can be enriched in the tissues and organs of living organisms through the digestive tract. However, more research is needed to determine whether food-sourced Cd affects the homeostasis of host gut microflora. In this study, the snail Bradybaena ravida (Benson) was used as a model organism fed with mulberry leaves spiked with different concentrations of Cd (0, 0.052, 0.71, and 1.94 mg kg-1). By combining 16S rRNA high-throughput sequencing with biochemical characterization, it was found that there were increases in the overall microbial diversity and abundances of pathogenic bacteria such as Corynebacterium, Enterococcus, Aeromonas, and Rickettsia in the gut of B. ravida after exposure to Cd. However, the abundances of potential Cd-resistant microbes in the host's gut, including Sphingobacterium, Lactococcus, and Chryseobacterium, decreased with increasing Cd concentrations in the mulberry leaves. In addition, there was a significant reduction in activities of energy, nutrient metabolism, and antioxidant enzymes for gut microbiota of snails treated with high concentrations of Cd compared to those with low ones. These findings highlight the interaction of snail gut microbiota with Cd exposure, indicating the potential role of terrestrial animal gut microbiota in environmental monitoring through rapid recognition and response to environmental pollution.

Fluorescent sphalerite rich in tungsten, copper, gallium, silver, and other elements from the Cordilleran-style, polymetallic veins of Philipsburg, Montana

Sphalerite from the central, high-sulfidation zone (enargite-stable) of the Philipsburg polymetallic mining district, southwest Montana, displays unusually bright fluorescence (red, orange, yellow, blue, purple, green) under longwave UV light (365 nm). LA-ICP-MS analysis reveals the fluorescent sphalerite has very low Fe (average < 100 ppm) and variable content of other trace elements that correlate to luminescence color banding. Mean/maximum content (in ppm) in fluorescent sphalerite for selected elements are 5.7/7900 Ag, 107/11800 As, 1400/4730 Cd, 917/30400 Cu, 381/5000 Ga, 32/696 Ge, 119/2130 In, 230/8190 Mn, 43/3000 Pb, 16/1700 Sb, and 89/1980 W. This study is the first to document elevated tungsten content (>10 ppm) in sphalerite. Copper is closely correlated with Ga, consistent with the coupled substitution: Cu+ + Ga3+ = 2Zn2+. Similar coupled substitution reactions can be written for Ag+, In3+, As3+, Sb3+, Bi3+, and Ge4+. However, the brightest red fluorescent bands are most closely related to the unexpected presence of W. Sphalerite with high Cu and Ga but lacking W fluoresces yellow and shows a single Raman peak at 349 cm−1 corresponding to pure sphalerite. In contrast, red-fluorescent sphalerite shows the presence of a second peak at 427 cm−1 that increases in intensity with increased W content. We propose that tungsten enters the sphalerite lattice as W6+ via a substitution such as W6+ + 4Cu+ = 5Zn2+ and that this substitution creates lattice strain that results in the anomalous fluorescence and Raman signals. Sphalerite bands with low concentrations of Cu and Ga fluoresce blue or green. Vivid blue fluorescence is displayed by sphalerite with high Cd (>1000 ppm) but low concentrations of all other trace elements. Sphalerite from the low-sulfidation peripheral mines of the Philipsburg district contains high Fe (>10,000 ppm) and does not fluoresce. Nonetheless, this sphalerite is also highly enriched in trace metals, including Ag (mean 2480/max 8660 ppm), Cu (1610/3440), Mn (7020/8100), and Sb (1960/6390). The results of this study underscore the importance of including tungsten in the list of analytes in future studies of trace elements in sphalerite. In addition, a hand-held UV lamp may be a rapid and cost-effective method to screen sphalerite of variable composition in outcrop or drill core. It may be a useful exploration tool to vector towards a high-sulfidation zone of a zoned porphyry or epithermal deposit, when it is present.

Accumulation of Cd and Pb in soils irrigated with sewage and non-sewage water in Prayagraj, India

Unmanaged agricultural fields and the extended usage of sewage irrigation water can raise the concentration of heavy metals (Cd and Pb) in the soil, turning it into barren soil. The study was conducted during 2022-23 at four sewage and non-sewage irrigated sites in Prayagraj namely Naini, Baxibandh, Rasulabad and Draupadi Ghat. The representative soil samples were taken at depths of 0-15, 15-30, 30-45 and 45-60 cm. Di-acid mixture method was used for the estimation of heavy metals (Cd and Pb) in the soil sample by AAS (Atomic Absorption Spectrophotometer) (AAnalyst600, Perkin Elmer Inc., MA, USA). Contamination factor (CF) and enrichment factor % (EF) of different sites showed various results which fulfill the basic criteria of present and future prospective of research. The highest concentration of Cd and Pb was found in the surface layer (0-15 cm) of sewage and non-sewage irrigated sites at Naini i.e., Cd (4.46±0.42 and 1.05±0.08 mg/kg) and Pb (6.53±0.62 and 1.18±0.12 mg/kg) respectively. The lowest concentration of Cd and Pb was found in the sub-surface layer (45-60 cm) of sewage and non-sewage irrigated sites at Draupadi Ghat i.e., Cd (1.02±0.09 and 0.16±0.01 mg/kg) and Pb (1.68±0.12 and 0.18±0.01 mg/kg) respectively. The concentration of heavy metals cadmium (Cd) and lead (Pb) declined with soil profile depth in both sewage and non-sewage irrigated soils. The long-term persistence of heavy metal contamination in soil can lead to severe issues; therefore, regular monitoring of sewage-irrigated soils is necessary to minimize heavy metal pollution.

Heavy metals in the surface sediments of Farwa Lagoon, NW Libya: Assessment and correlation with other Mediterranean lagoons

The present study aims to evaluate the heavy metal pollution in the Farwa Lagoon, which is one of the most important coastal lagoons in NW Libya. The concentrations of six heavy metals (Fe, Zn, Pb, Ni, Cu, Cd) are measured in the surface sediment of the lagoon. Moreover, the contamination indices, including contamination factor, degree of contamination, pollution load index, geo-accumulation index, enrichment factor, risk factor, and potential ecological risk index, are applied. The results indicate that, Fe has the highest concentration, followed by Zn, Pb, Ni, Cu and Cd. The distribution patterns of metals reflect that the levels of Fe, Cu and Zn increase in the central part of the lagoon, whereas Cd and Pb increase in the central and western parts. In addition, the values of contamination factor reflect that the examined sites are moderately contaminated with Pb and Zn, whereas they are very highly contaminated with Cd. These findings lead to very high degree of contamination. Moreover, pollution load index reflects that the Farwa Lagoon is polluted. Finally, the study area is very highly ecological risk with Cd. The concentration of metals in the Farwa Lagoon is correlated with those from other regions in the Mediterranean region, such as Egypt, Algeria, Tunisia, Italy, France, and Turkey. The comparison reflects that the Farwa Lagoon has the highest concentrations of Cd and Zn.

High geological background concentrations of As and Cd in karstic soils may not contribute to greater risks to human health via rice consumption

High geological background concentrations of toxic metal(loid)s arsenic (As) and cadmium (Cd) from natural enrichment in soils of karst regions have attracted much attention. In this study, paired soil-rice samples were collected from karst and non-karst regions in Guangxi, China to assess the potential risks of metal(loid) transfer from soil to rice grains, and rice grains to humans. Our results indicate that the karstic soils had greater As (25.7 vs. 12.4 mg·kg-1) and Cd (2.12 vs. 1.04 mg·kg-1) contents than those in non-karstic soils. However, metal(loid) transfer from soil to rice grains (ratio of rice grains to soil content) of As and Cd was 40 % and 49 % lower in karst regions, which may relate to their 42 % and 61 % lower HNO3-extractable As and CaCl2-extractable Cd, resulting in similar As/Cd contents in karstic and non-karstic rice grains. In vitro assay using a modified physiologically-based extraction test shows that karstic rice grains had a lower As/Cd bioaccessibility than non-karstic grains, which can be attributed to their ∼50 % greater P content, which negatively correlated with As/Cd bioaccessibility. Additionally, karstic rice grains had 39 % greater phytate and exhibited 45 % and 9.4 % lower As and Cd bioaccessibility in the gastric phase with phytate supplement at 0.6 %. Our work indicates that despite the greater As/Cd contents in karstic soils, the risks of As/Cd transfer from soil to rice grains as well as their exposure risks to humans via rice consumption may not be greater than non-karst regions.

The Potential of Helichsryum splendidum (Thunb.) Less. for the Restoration of Sites Polluted with Coal Fly Ash.

The disposal of coal fly ash (CFA) generated from coal-fired power stations has serious impact on the ecosystem, by converting large pieces of land to barren ash dams with the potential to contaminate groundwater, surface water, air and soil. The aim of this study was to clarify the potential of phytoremediation using Helichrysum splendidum (Thunb.) Less. in areas polluted by CFA through conduction of pot trial experiments for 14 weeks. Plants of the same age were cultivated in CFA to assess their growth, photosynthetic rate and tolerance towards metal toxicity. This study revealed that the CFA was moderately polluted with heavy metals, and a lower photosynthetic rate was recorded for the CFA plants in comparison to the controls (plants grown in soil). Although the CO2 assimilation rate was lower for the CFA plants, increased growth was recorded for all the plants tested. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify the amount of trace elements in samples and parameters including translocation factor (TF) and bioconcentration factor (BCF) were used to evaluate the phytoremediation potential of H. splendidum (Thunb.) Less. The results revealed that higher concentrations of Cd, Co, Cr, Cu, Mn and Pb were accumulated in the roots, while As, Ni and Zn were found in the shoots. Elements including As, Cr and Zn reported TF values above 1, indicating the plants' phytoextraction potential. The BCF values for As, Cu and Zn were 1.22, 1.19 and 1.03, indicating effectiveness in the phytostabilization processes. A removal rate efficiency ranging from 18.0 to 56.7% was recorded confirming that, H. splendidum (Thunb.) Less. can be employed for restoration of CFA dams.

Cd mobilization in mining-impacted soils with different bedrock lithology: Insights from stable Cd isotopes

The environmental risk of Cd in soils strongly depends on the mobilization of Cd in soils. However, limited knowledge exists on the redistribution of exogenic Cd inputs in soils, especially across diverse lithological regions. Herein, we aimed to investigate the fate of Cd in soils from two mining areas with contrasting lithologies (siliceous and calcareous) using stable Cd isotopes. The isotope tracing results confirm that mining activities are the main Cd source in both areas. The positive correlation between δ114/110Cd values and goethite/dolomite content indicates the release of heavy Cd isotopes during the dissolution of exogenetic minerals. Additionally, high contents of exchangeable Cd (11 % to 36 %) and Fe oxide-bound Cd (29 % to 42 %) drive plant pumps to transport heavy Cd isotopes from the deeper to upper horizons of the soils from the siliceous area. In the calcareous area, the total organic carbon content is positively correlated with the Cd concentration and δ114/110Cd value, suggesting potential complexation of Cd with organic matter due to the stabilizing effect of carbonate minerals on soil organic matter. This study highlights the different redistributions of exogenous Cd in soils from diverse lithological regions, emphasizing the need to consider regional lithology when developing soil quality standards for Cd.