Μg Cd Research Articles

Xylem development, cadmium bioconcentration, and antioxidant defense in Populus × euramericana stems under combined conditions of nitrogen and cadmium

Populus species feature remarkable phytoremediation of cadmium (Cd) contamination. The influence of nitrogen (N) availability on Cd accumulation and tolerance in stems was investigated in a clone of Populus × euramericana. Secondary xylem development in stems was dramatically suppressed by the combined conditions of N deficiency and Cd exposure, but such suppression was partially alleviated by N application. Under adequate N condition, the Cd bioconcentration factor (BCF) in stems at moderate and high Cd exposures reached 3.07 and 0.91, respectively, whereas the Cd content in stems at high Cd exposure reached 164 μg Cd plant−1. However, Cd bioconcentration and accumulation in stems were sharply decreased due to N deficiency. The levels of phytohormones (abscisic acid, jasmonic acid, and salicylic acid) and antioxidants (free proline and peroxidase) in stems decreased in low N treatment because of poor tissue N concentration, thereby attenuating antioxidant defense and Cd tolerance. The decreased Cd tolerance and inhibited xylem development under low N condition led to the dramatic decrement of Cd accumulation in stems. Adequate N application increased the phytohormone and antioxidant levels in stems, thereby promoting antioxidant defense, as indicated by the low malondialdehyde (MDA) level. Moreover, both the improved antioxidant defense and appropriate N nutrient status contributed to xylem development. Consequently, the capacity for Cd bioconcentration and accumulation in Populus stems was promoted by N application, thereby facilitating the phytoextraction of Cd from Cd-contaminated soils.

Evaluation of Flax Plant as a Cadmium Phytoremediator for Polluted Soils under Different Chemical and Biological Treatments

A pot experiments was carried out in the greenhouse of Faculty of Agriculture Cairo University during the two successive winter seasons (2015-2016 and 2016-2017) to evaluate the potential of flax plants (Linum usitatissimum L.) as a Cd tolerant and accumulator for polluted soils. The experiment was laid out in a split-plot design with a randomized-complete design in three replicates. Surface sandy loam soil samples (0-20 cm) were collected from Abou-Rawash area, which received sewage sludge and sewage effluent for long time ( about 20 years).Three levels of soil Cd (initial 3.13), and two artificial ones 50 and 75mg kg-1 soil, were prepared using CdCl2 solution by wet and dry process for three months. The chemical (EDTA) and biological (AMF and Thiobacillus) treatments were allocated to sub plots. Each sub plot consisted of pots each containing 10kg soil and 100 flax plants. The results showed that by increasing soil cadmium levels, the flax plant dry weight (roots, stem and leaves) significantly decreased. Under different levels of soil Cd, the chemical and biological treatments recorded variable changes in flax plant dry weight. The highest increases in dry weight was recorded with AMF treatment (5.63 and 8.50% in 1st and 2nd seasons, respectively, with an average of 7.06%) compared with the control (initial).However, cadmium contents in the different parts of flax plant increased with increasing soil cadmium levels. The highest Cd concentration in flax roots, stem and leaves recorded in EDTA treatment which lead to increases of 1.73, 2.11 and 1.88 folds in roots, stem and leaves, respectively, compared with untreated soil at 75 µg Cd g-1 soil. The uptake of Cd by flax substantially affected by both levels of Cd in soil and different soil treatments. The highest Cd uptake was found in 75 µg g-1 soil level followed by 50µg g-1 and the lowest in 3.13 µg g-1 soil. Flax was uptake and accumulate cadmium from the soil with distributing evenly throughout plants (roots < stem < leaves). Both EDTA and AMF treatments recorded the highest phytoextraction of Cd from contaminated soil. Finally, the obtained results suggest that, flax plant can be considered as a Cd tolerant which can accumulate Cd, especially, with mycorrhiza fungi and EDTA treatments but could not be considered a hyperaccumulator of Cd from polluted soils.

Phytoremediation potential of Ulva ohnoi (Chlorophyta): Influence of temperature and salinity on the uptake efficiency and toxicity of cadmium

Ulva ohnoi is a green macroalga with fast growth and high rates of nitrogen and phosphorus absorption. Recently, this species has been recorded in several places with record green tide formation in some of them. Using molecular tools, we herein report the first occurrence of this species in Brazil and demonstrate its potential for phytoremediation in typical environmental concentrations of Cd (0.625–15 µg L-1). Similarly, the effects of physicochemical parameters (salinity and temperature) on the toxicity and uptake efficiency of this species were evaluated. Molecular analysis of two sequences (1141 bp) obtained corroborates another 34 sequences for U. ohnoi obtained from GenBank. The addition of Cd in the medium affected photosynthetic parameters and reduced growth rate. U. ohnoi showed resistance to Cd when cultivated at 18 °C, S15 and 18–25 °C, S35, at concentrations between 0.625 and 2.5 μg. L-1 of Cd; yet, positive growth rate was maintained. Dose-dependent accumulation was observed in all combinations of factors used with a maximum value of 4.20 μg Cd per gram of dry seaweed at 15 μg. L-1 of Cd at 18 °C and S35. Maximum value of the concentration factor was 81.3 ± 1.1% of Cd added at the concentration of 0.625 μg. L-1 to S15 and 18 °C. Our results demonstrate the potential of using U. ohnoi in the phytoremediation of Cd in saltwater or brackish water.

Effects of cadmium exposure on the composition and diversity of the intestinal microbial community of common carp (Cyprinus carpio L.)

Cadmium (Cd) is an environmental pollutant that poses serious health hazards. Due to the increasing contamination of aquatic systems with Cd, the increased accumulation of Cd in fish has become a food safety and public health concern. The present study was conducted to investigate the effects of waterborne Cd exposure on the microbial community composition and diversity in the gut of common carp. Common carp were exposed to three waterborne Cd concentrations (0, 50 and 500 μg Cd L−1) for 4 weeks. Our results indicated that Cd exposure profoundly affected the composition of the gut microbiota in the common carp. At the phylum level, Saccharibacteria were detected in only the 0 μg and 50 μg Cd L−1 exposure groups, and the abundance of Fusobacteria decreased with increasing Cd concentration, while the abundance of Firmicutes increased with increasing Cd concentration. At the genus level, Cetobacterium was the dominant group in the gut of the common carp, and the abundance of Cetobacterium decreased after Cd exposure. Notably, the abundance of Akkermansia muciniphila, a probiotic, was found to decrease after Cd exposure, and the proportions of some Cd-resistant bacteria were found to increase following Cd exposure. Our results also demonstrated that Cd exposure decreased the community diversity of the gut microbiota. These results suggest that Cd exposure may impact the gut homeostasis of common carp and further affect the health of the organism.

Arbuscular Mycorrhizal Fungi Favor the Initial Growth of Acacia mangium, Sorghum bicolor, and Urochloa brizantha in Soil Contaminated with Zn, Cu, Pb, and Cd.

This study evaluated the effect of inoculation with a mixture of spores of arbuscular mycorrhizal fungi (AMF) (Glomus macrocarpum, Paraglomus occultum, and Glomus sp.) on the initial establishment of Acacia mangium, Sorghum bicolor, and Urochloa brizantha in soil contaminated with heavy metals. The experiment was conducted in a greenhouse, in plastic pots containing 1.8kg of soil, which presented 7200, 1140, 480, and 72mg of Zn, Cu, Pb, and Cd, respectively. The chlorophyll content (SPAD index) of inoculated plants of A. mangium and U. brizantha was higher than those of non-inoculated plants (p < 0.05). No differences were detected for the concentration of heavy metals in plant shoots, whether the plant was inoculated or not. However, inoculated plants had greater root length (S. bicolor and U. brizantha) (p < 0.05) and greater plant height (A. mangium) (p < 0.05). The present results demonstrate that the beneficial effects of AMF on plant growth and the alleviation of contaminants are imperative factors for the rehabilitation of soils contaminated with heavy metals.

Estimation of weekly intake of cadmium and lead by consumption of commercial ready-to-feed infant foods

ABSTRACTThe purpose of this survey was to estimate the safety of ready-to-eat infant foods in terms of Pb and Cd content. The studied samples were ready-to-eat infant products: dinners (n = 74), soups (n = 27) and desserts (n = 82) containing components of animal origin: meat and/or milk. Cd and Pb content was determined using a GF-AAS method. The analysed products contained 1.82–3.54 µg Pb and 1.32–1.50 µg Cd per kg. The content of Pb per kg of the product can be represented as dinners > soups > desserts, whereas the content of Cd was dinners > desserts > soups. The analysed ready-to-eat products could be regarded as safe, because they supply 12-month-old infants with Pb in an amount accounting for nearly 22% BMDL01 and Cd accounting for ca. 8.6% of the total weekly intake.

Dietary cadmium intake from rice and vegetables and potential health risk: A case study in Xiangtan, southern China

Soil contamination in some areas of southern China has resulted in elevated dietary intake of cadmium (Cd), posing a potential risk to human health. A survey of paired soil-rice (n = 200) and soil-vegetable (n = 142) samples was conducted in Xiangtan county of Hunan province, southern China. The concentrations of Cd in all the samples were determined by inductively coupled plasma mass spectrometry. Dietary intakes of Cd from the consumption of locally produced rice and vegetables were estimated for different age groups. Among the 342 crop samples collected in the survey, 88% and 29% of rice grain and vegetable samples, respectively, exceeded the Chinese maximum permissible limit for Cd (0.2 mg dry weight kg−1, 0.2 mg fresh weight kg−1 and 0.1 mg fresh weight kg−1 for rice, leafy vegetables and for rootstalk and legume vegetables, respectively). The median dietary Cd intake varied from 66.5 to 116 μg Cd kg−1 body weight (BW) month−1, with children (4–11 years) exhibiting the highest intake. These values are 2.7–4.6 times the tolerable dietary intake of 25 μg kg−1 BW month−1 recommended by the Joint FAO/WHO Expert Committee on Food Additives. For the general population in Xiangtan county, rice contributed the majority (81%) of the Cd intake with vegetables contributing only 19%. The median hazard quotient calculated from dietary Cd intake was 2.4 times the permissible level, indicating a high risk to the local residents. This study highlights an urgent need to reduce the transfer of Cd from soil to the food chain in the investigated region.

Comparative Assessment of Trace Element Accumulation in Traditional and Improved Rice (Oryza sativa L.) Varieties Grown with Organic, Chemical and Non-Fertilizers

Oryza sativa L., is the most widely grown rice in Sri Lanka. At present, farmers are using both organic and chemical fertilisers for the paddy cultivation. There is growing concern about heavy metal (mainly As, Cd and Pb) build up in the soils because they enter the soil and the plants via application of fertilisers (anthropogenic). Heavy metals are also found in the soil (geogenic). Cd and As are both nephrotoxic and neurotoxic, and there is a concern that they may be involved in the chronic kidney disease of uncertain etiology (CKDu) prevalent in the North Central Province and neighboring areas. According to the Food and Agriculture Organization (FAO), the maximum allowable limit (MAL) of Cd and As is 0.2 μg g-1. This study was conducted to compare the heavy metal accumulation in traditional and improved rice varieties grown with organic fertilisers, chemical fertilisers and without fertilisers. Total of 126 paddy samples (including seven traditional and seven improved rice varieties) grown with organic, chemical and non-fertiliser, were collected directly from the paddy fields in Rice Research and Development Institute (RRDI) at Batalagoda. Soil samples from paddy plots with different fertiliser treatments were collected. Heavy metal analysis was done at the Geology Department of the University of Peradeniya by using ThermoICapQ Inductively Coupled Plasma Mass Spectrometry (ICP-MS). Rice cultivated with chemical fertilisers had the highest mean heavy metal concentrations. Cd concentration (0.32 μg Cd g-1) in traditional varieties grown with chemical fertilisers was significantly higher than in the other treatments. That value is 1.6 fold higher than the MAL. Organic fertiliser treated improved varieties had the lowest level of Cd and it was less than the MAL. All the other treatments had Cd levels more than the MAL. All treatments had lower content of As than the MAL. Taken as a whole, macro-nutrients (K, Ca, Mg) were higher in the chemical fertiliser treated rice than that of organic treated rice. Heavy metals and macro-nutrient concentrations varied from variety to variety. Keywords: Chemical fertiliser, Heavy metals, Improved rice, Organic fertilizer, Traditional rice

The effect of cadmium exposure on diversity of intestinal microbial community of Rana chensinensis tadpoles

Cadmium is a natural and widely distributed toxicant, and can be commonly found in environment. Intestinal microbiota plays a very important role in maintaining its host's health. The effects of cadmium on the intestinal microbiota composition and stability of amphibians are little known. We exposed Rana chensinensis (R. chensinensis) embryos to different concentrations of cadmium (0, 112 and 448 μg Cd L−1) until they reached Gosner stage 38, and analyzed their microbial communities using 16S rRNA amplicon sequencing. By measures of both alpha and beta diversity, intestinal microbial communities were significantly differentiated in 448 μg Cd L−1 exposure groups. Cadmium exposure significantly altered the intestinal microflora diversity and composition of R. chensinensis. At the phylum level, it is worth noting that Fusobacteria and Spirochaetae were not detected in 448 μg Cd L−1 exposure groups. Firmicutes rapidly decreased in 448 μg Cd L−1 exposure group. At the genus level, Succinispira (Firmicutes), Desulfovibrio (Proteobacteria) and Fusobacterium (Fusobacteria) vanished in 448 μg Cd L−1 exposure groups. Our results demonstrate that cadmium exposure changed the composition and decreased the community diversity of intestinal microbiota of R. chensinensis tadpoles. Our study may provide a new framework based on intestinal microbiota to evaluate the response of amphibians to environmental chemicals pollution.

Mobilization of cadmium from festuca ovina roots and its distribution between operational fractions in soil

Festuca ovina was grown hydroponically on the Hoagland medium supplemented with CdCl 2 (10 µg Cd ml -1 ). Next, the plants were transplanted into pots (100 plants in pots) with uncontaminated soil and incubated under controlled conditions for 12 months. Approximately 420 µg Cd were introduced into 200 g of soil via the plant roots, the released cadmium being distributed between fractions with varying stability and extractability. After 2 months, the pool of Cd exchangeable and bound to Fe and Mn oxides was 16% and 75%, respectively. After the end of the pot cultivation, the content of Cd in these fractions had decreased to 5% and 53%, respectively. In contrast, the percentage of Cd defined as organically bound increased from 6% (after 2 months) to 43% (after 12 months). The residual fraction was 2% of the metal present in the soil and was constant during plant cultivation. The results obtained indicate that the Cd stabilization by roots was dependent on time. Additionally, the distribution of Cd among the tested fractions was seen to have changed during the experiment. The amount of Cd bound to soil organic matter increased, lowering the amount of the bioavailable Cd form and Cd fraction bound to the oxide minerals .

Changes in metallothionein transcription levels in the mussel Mytilus galloprovincialis exposed to CdTe quantum dots.

Quantum dots (QDs) are a class of engineered nanoparticles (ENPs) with several biomedical, industrial and commercial applications. However, their metabolism and detoxification process in aquatic invertebrates and environmental health hazards remain unclear. This study investigate the transcriptional changes of metallothioneins (MTs) isoforms (mt10IIIa and mt20IV) induced by CdTe QDs, in comparison with its dissolved counterpart, in the marine mussel Mytilus galloprovincialis. Mussels were exposed to CdTe QDs and to the same Cd concentration (10 µg Cd L-1) of dissolved Cd for 14 days and mt transcription levels were measured by real time quantitative PCR (qPCR). Tissue specific mt transcription patterns were observed in mussels exposed to both Cd forms, wherein the gills were a more sensitive organ compared to the digestive gland. No significant changes were observed in mt10IIIa transcription levels in mussels exposed to both Cd forms. In contrast, transcription of mt20IV was tissue and exposure time dependent, with higher mt20IV mRNA levels in mussels exposed to QDs and dissolved Cd when compared to unexposed mussels. Multivariate analysis indicates particle-specific effects after 14 days of exposure and a dual role of MTs in the QD metabolism and in the protection against oxidative stress in mussels exposed to Cd-based ENPs.

Changes in enzyme activity and functional diversity in soil induced by Cd and glucose addition

Toxic heavy metal (HM) contamination is a major global issue as it may have an indirect effect on the health of soil, plants, animals and, consequently, on human health. Agricultural soils’ fertilization is one of the reported sources of HM pollution in the world. In this case simultaneous input of stimulating and inhibiting agents into soil takes place, and effects of the combined influence of these agents is hardly predictable. In this study, a simultaneous inhibiting and stimulating effect of Cd and glucose on soil microbes was studied in a model experiment. Enzyme activities (phosphatase, β-glucosidase and cellobiohydrolase) and functional diversity (BIOLOG®EcoPlates ™) were assessed as a test functions. Cd (300 μg Cd g−1 ) amendment had a negative effect only on phosphatase activity. Glucose (3 mg C g−1) addition inhibited β-glucosidase activity and stimulated functional diversity. In joint addition of Cd and Glucose the leading effect belonged to that agent which had the greatest effect in case when it was added separately.

Synthesis and Identification of novel azo-1,3,4-Thiadiazole Derivative and using to Spectrophotometric Determination for some of Transition metal Complexes

This search includes synthesis of ligand by a two-step, the first react between 4-hydroxy benzaoic acid and thiosemicarbazide to form compound (1) [4-(5-amino-1, 3, 4-thiadiazol-2-yl) phenol], the second step is coupling of diazonium salt [5-(4-hydroxyphenyl)-1, 3, 4-thiadiazole-2-diazonium] with 2-hydroxy-5-sulfobenzoic acid in basic ethanolic media to get compound (2) [(E)-2-hydroxy-3-((5-(4-hydroxyphenyl)-1, 3, 4-thiadiazol-2-yl) diazenyl)-5-sulfobenzoic acid] which characterized by FT-IR ,1H NMR and 13C-NMR , after that used for the spectrophotometric determination of cadmium Cd (II) and lead Pb (II). This method was simple, rapid, sensitive, and selective for reaction between cadmium and lead with the reagent. The maximum absorbance observed at 450 nm and 495 nm for Cd(II) and Pb(II) respectively. The molar absorptivity and sandell’s sensitivity for cadmium (II) and lead (II) complexes are 4.5077×10-4, 2.9709× 104 L.mol-1. cm-1 and 0.0212, 0.0353µg/cm2 respectively. The stability constant of 1:2 [M:L] complexes of Cd(II) and Pb(II) are 3.13 × 105 and 1.45 × 105 L.mol-1 respectively. The linear range of 0.1-9 µg mL-1, 0.2-12 µg mL-1 along with limit of detection 0.059 µg mL-1, 0.102 µg mL-1, relative standard deviation for seven replication measurements (5 µg Cd mL-1 and 5 µg Pb mL-1) of (0.059%) and (0.102%) ,and the recovery range of (98.6) and ( 99.2 ) were obtained for Cd(II) and Pb(II) ions respectively.

Dietary intake risks of trace metal(loid)s via maize–animal–human pathway and derivation of bioavailability-based soil criteria in Hezhang county, China

Historically metal-polluted agricultural soils are an important source of human exposure to toxic metals such as arsenic (As), cadmium (Cd), and lead (Pb) through food chains, especially in remote rural areas like Hezhang county, China. This paper aimed to investigate the processes by which a staple food crop, maize (Zea mays L.), became contaminated, identify the dominant exposure pathway and dietary intake risks, identify soils that were unsafe for growing maize, and share findings with farmers and decision-makers. A greenhouse experiment was performed using 20 historically metal-polluted soils with different soil types, properties, and contamination levels. Metal(loid) concentrations in maize grains, soil porewater (in situ), and DTPA (0.005 M) extracts of rooting-zone soils were measured to investigate the factors that influence the availability and the uptake of metal(loid)s. An investigation was performed to identify the main exposure pathway. Regression models describing metal(loid)s transfer from soils to maize grains were inversely used to derive bioavailability-based soil criteria. Soil results indicated that 28% of total Cd and 17% of total Pb in soils were potentially plant-available whereas the labile fractions in soil porewater were negligible due to high soil pH (> 7.5). For As in soils, approximately 2% was the non-specifically adsorbed fraction. Grain metal(loid)s (i.e., As, Cd, and Pb) levels were satisfactorily predicted using porewater concentrations and key properties such as pH and dissolved organic carbon contents (adj. R2 0.814 - 0.887). The bioaccumulation of As in maize was very limited. However, the level of Cd in 73% and Pb in 25% of grain samples exceeded Chinese food quality standard, thereby threatening food safety. Metal(loid)s transfer through maize → animal → human pathway would result in a substantial dietary intake of metals, e.g., 79.7 μg Pb day−1 and 217.9 μg Cd day−1. A more implementable soil criterion for DTPA-extractable Cd (0.6 mg kg−1) was derived allowing identification of soils that were unsafe for growing maize. Hezhang residents experience dietary intake risks of Pb and Cd. Excessive Cd and Pb in maize are the result of soil pollution. Soil with DTPA-extractable Cd concentration < 0.6 mg kg−1 can ensure a zero exceedance of Cd and other trace metals as well in maize. Findings are of importance to farmers and policy-makers to lower the risks of exceedance of Cd and Pb in food crops by soil management.

Magnetically responsive gels based on crosslinked gelatin: An overview on the synthesis, properties, and their potential in water remediation

ABSTRACTEfficient adsorbent ferrogels based on gelatin and dextrose were synthetized using freeze-thawing technique. Two different methodologies of magnetic particles incorporation were developed. An exhaustive morphologic and thermal characterization of hydro and ferrogels was achieved. The performance of ferrogel in water remediation was tested using Cd(II) as model contaminant. The adsorption ability was evaluated as a function of pH, initial heavy metal concentration, and contact time. The maximum adsorption capacity was 35 mg of Cd(II)/g of adsorbent. Ferrogel was regenerated by washing with distilled water, maintaining efficiency of almost 30% after the fourth cycle.

SYNTHESIZED CHITOSAN/ IRON OXIDE NANOCOMPOSITE AND SHRIMP SHELL IN REMOVAL OF NICKEL, CADMIUM AND LEAD FROM AQUEOUS SOLUTION

In this study, an easy synthesized method for preparation of chitosan/iron oxide nanocomposite as a bio-sorbent has been applied. Analytical techniques such as Fourier transform infrared spectroscopy, X-ray diffraction; Field emission scanning electron microscopy and transmission electron microscopy were utilized to survey of morphological structure and the functional groups characterization. The histogram of frequency of particle size confirmed that medium size of the synthesized nanoparticles was 50 nm. Beside the obtained nanocomposite, application of chitosan as the precursor and shrimp shell as natural chitin and a natural polymer were assessed as adsorbents for decontamination of Ni2+, Cd2+ and Pb2+ as examples of heavy metals from drinking water. Batch studies were performed for adsorption experiments by changing variables such as pH, contact time and adsorbent dose. Based on the experimental sorption capacities, 58, 202 and 12 mg of Ni, Cd and Pb per g of Chitosan-Fe2O3 nanocomposite as adsorbent respectively, confirm that combination of Fe2O3 nanoparticles with chitosan makes a more efficient adsorbent than chitosan and chitin. Adsorbents in uptake of the mentioned heavy metals are in the order of Chitosan-Fe2O3 nanocomposite > chitosan> chitin. In addition, the kinetics and isotherm investigations were surveyed. Moreover, it has been shown that the synthesized nanocomposite significantly reduces the amount of the mentioned ions from the real wastewater sample.

Unique Rhizosphere Micro-characteristics Facilitate Phytoextraction of Multiple Metals in Soil by the Hyperaccumulating Plant Sedum alfredii.

Understanding the strategies that the roots of hyperaccumulating plants use to extract heavy metals from soils is important for optimizing phytoremediation. The rhizosphere characteristics of Sedum alfredii, a hyperaccumulator, were investigated 6 months after it had been planted in weathered field soils contaminated with 5.8 μg of Cd g-1, 1985.1 μg of Zn g-1, 667.5 μg of Pb g-1, and 698.8 μg of Cu g-1. In contrast with the non-hyperaccumulating ecotype (NHE), the hyperaccumulating ecotype (HE) of S. alfredii was more tolerant to the metals, and higher levels of Cd and Zn accumulated. The HE was characterized by a unique rhizosphere, including extensive root systems, a reduced soil pH, a higher metal bioavailability, and increased rhizomicrobial activity. The bioavailability of metals was significantly correlated with the HE's unique bacterial communities (P < 0.005). The HE harbored abundant Streptomyces (9.43%, family Streptomycetaceae), Kribbella (1.08%, family Nocardioidaceae), and an unclassified genus (1.09%, family Nocardioidaceae) in its rhizosphere, a composition that differed from that of the NHE. PICRUSt analysis predicted high relative abundances of imputed functional profiles in the HE rhizosphere related to membrane transport and amino acid metabolism. This study reveals the rhizosphere characteristics, particularly the unique bacterial rhizobiome of a hyperaccumulator, that might provide a new approach to facilitating heavy metal phytoextraction.

The Health Risk of Cd Released from Low-Cost Jewelry.

The composition of the surface layer of 13 low-cost jewelry samples with a high Cd content was analyzed using an energy-dispersive X-ray fluorescence spectrometer (ED XRF). The analyzed jewels were obtained in cooperation with the Czech Environmental Inspectorate. The jewels were leached in two types of artificial sweat (acidic and alkaline) for 7 days. Twenty microliters of the resulting solution was subsequently placed on a paper carrier and analyzed by an LIBS (Laser-Induced Breakdown Spectrometry) spectrometer after drying. The Cd content in the jewelry surface layer detected by using ED XRF ranged from 13.4% to 44.6% (weight per weight—w/w). The samples were subsequently leached in artificial alkaline, and the acidic sweat and leachates were analyzed using laser-induced breakdown spectrometry (LIBS). The amount of released Cd into alkaline sweat ranged from 24.0 to 370 µg Cd per week, respectively 3.23–61.7 µg/cm2/week. The amount of released Cd into acidic sweat ranged from 16.4 to 1517 µg Cd per week, respectively 3.53–253 µg/cm2/week. The limit of Cd for dermal exposure is not unequivocally determined in the countries of the EU (European Union) or in the U.S. Based on the US EPA (United States Environmental Protection Agency) approach used to establish the reference dose (RfD) for Cd contained in food and information about the bioavailability of Cd after dermal exposure, we assessed our own value of dermal RfD. The value was compared with the theoretical amount of Cd, which can be absorbed into the organism from jewelry in contact with the skin. The calculation was based on the amount of Cd that was released into acidic and alkaline sweat. The highest amount of Cd was released into acidic sweat, which represents 0.1% of dermal RfD and into alkaline sweat, 0.5% of dermal RfD. These results indicate that the analyzed jewelry contains Cd over the limit for composition of jewelry available within the territory of the EU. The determined amount of Cd in analyzed jewelry does not, however, pose a threat in terms of non-carcinogenic toxic effects.

Osmoregulatory responses to cadmium in reference and historically metal contaminated Gammarus fossarum (Crustacea, Amphipoda) populations

In order to better understand the variable sensitivities of crustaceans to metals, we investigated the impact of cadmium exposure in 3 populations of Gammarus fossarum from different rivers of France. The first population lives in a Cd-contaminated river from a geochemical background, while the others inhabit Cd-free sites. Osmoregulation, a relevant biomarker to evaluate crustacean health following metal contamination, was used as a proxy to evaluate the intra- and inter-populationnal sensitivities to Cd. Specimens from each population were experimentally exposed to 9 μg Cd2+/L Cd for 7 days and hemolymph osmolality (HO) was then individually measured. In exposed populations, high inter-individual variations in HO values were noted, resulting in their separation into non-impacted and slightly or highly Cd-impacted (with lower HO) animals. In gills of impacted organisms, deep histopathological alterations and protein overexpression of Na+/K+-ATPase and V-H+-ATPase were observed through histology and immunolocalization, while non-impacted animals showed profiles comparable to controls. Moreover, the osmoregulatory processes in the population living in the Cd-contaminated site were impacted by acute Cd exposure in the laboratory as much as for one of the two populations originating from Cd-free sites. The observed changes did not reveal any obvious adaptive osmoregulatory phenomena at the population scale, but they may be due to differences in fitness between individuals and between populations in relation to the features of their respective environments, unrelated with the presence of the metal.

Cadmium Bioaccumulation in Aquatic Oligochaetes Using a Biodynamic Model: A Review of Values of Physiological Parameters and Model Validation Using Laboratory and Field Bioaccumulation Data.

This study reviews certain physiological digestive parameters in the literature that could be used to predict tissue residues in aquatic oligochaetes using the biodynamic model. Predictions were evaluated with independently measured Cd bioaccumulation data in sediment bioassays and field oligochaetes. The parameter review focused on three species commonly used in ecotoxicity testing and bioaccumulation studies: Tubifex tubifex (Tt), Limnodrilus hoffmeisteri (Lh) and Lumbriculus variegatus (Lv). Median Ingestion rates (g g-1 d-1, dw) at unpolluted conditions were 7.8 (Tt), 24.5 (Lh) and 11.5 (Lv), while results were lower (1.7-2.4) at polluted conditions. Assimilation efficiencies ranged from 3.4-19.6% (Tt), 2.7-16.1% (Lh), and 10.9-25.6% (Lv). The biodynamic model accurately predicted Cd tissue concentration in T. tubifex exposed to spiked sediments in laboratory bioassays. Comparisons of predicted vs. measured Cd tissue concentration in bioassays or field aquatic oligochaetes suggest that the biodynamic model can predict Cd tissue concentration within a factor of five in 81.3% of cases, across a range of measured tissue concentrations from 0.1 to 100 μg Cd g-1 dw. Predictions can be refined by using physiological parameter values that have been measured under varying environmental conditions (e.g. temperature, dissolved oxygen). The model can underestimate tissue concentration by up to one order of magnitude when worms are exposed to highly contaminated sediments. Contrarily, predictions overestimate tissue concentration by up to two orders of magnitude when the measured Cd < 0.1 μg g-1 dw, although in most cases these predictions do not fail bioaccumulation-based risk assessments, using a tissue threshold value of 1.5 μg Cd g-1 dw.