Mercury, cadmium, lead and arsenic levels in three pelagic fish species from the Atlantic Ocean: intra- and inter-specific variability and human health risks for consumption

Three commonly consumed and commercially valuable fish species (sardine, chub and horse mackerel) were collected from the Northeast and Eastern Central Atlantic Ocean in Portuguese waters during one year. Mercury, cadmium, lead and arsenic amounts were determined in muscles using graphite furnace and cold vapour atomic absorption spectrometry. Maximum mean levels of mercury (0.1715 ± 0.0857 mg/kg, ww) and arsenic (1.139 ± 0.350 mg/kg, ww) were detected in horse mackerel. The higher mean amounts of cadmium (0.0084 ± 0.0036 mg/kg, ww) and lead (0.0379 ± 0.0303 mg/kg, ww) were determined in chub mackerel and in sardine, respectively. Intra- and inter-specific variability of metals bioaccumulation was statistically assessed and species and length revealed to be the major influencing biometric factors, in particular for mercury and arsenic. Muscles present metal concentrations below the tolerable limits considered by European Commission Regulation and Food and Agriculture Organization of the United Nations/World Health Organization (FAO/WHO). However, estimation of non-carcinogenic and carcinogenic health risks by the target hazard quotient and target carcinogenic risk, established by the US Environmental Protection Agency, suggests that these species must be eaten in moderation due to possible hazard and carcinogenic risks derived from arsenic (in all analyzed species) and mercury ingestion (in horse and chub mackerel species).

N-acetyl-β -d-glucosaminidase activity in feral Carcinus maenasexposed to cadmium

Cadmium is a priority hazardous substance, persistent in the aquatic environment, with the capacity to interfere with crustacean moulting. Moulting is a vital process dictating crustacean growth, reproduction and metamorphosis. However, for many organisms, moult disruption is difficult to evaluate in the short term, what limits its inclusion in monitoring programmes. N-acetyl-β-d-glucosaminidase (NAGase) is an enzyme acting in the final steps of the endocrine-regulated moulting cascade, allowing for the cast off of the old exoskeleton, with potential interest as a biomarker of moult disruption. This study investigated responses to waterborne cadmium of NAGase activity of Carcinus maenas originating from estuaries with different histories of anthropogenic contamination: a low impacted and a moderately polluted one. Crabs from both sites were individually exposed for seven days to cadmium concentrations ranging from 1.3 to 2000 μg/L. At the end of the assays, NAGase activity was assessed in the epidermis and digestive gland. Detoxification, antioxidant, energy production, and oxidative stress biomarkers implicated in cadmium metabolism and tolerance were also assessed to better understand differential NAGase responses: activity of glutathione S-transferases (GST), glutathione peroxidase (GPx) glutathione reductase (GR), levels of total glutathiones (TG), lipid peroxidation (LPO), lactate dehydrogenase (LDH), and NADP+-dependent isocitrate dehydrogenase (IDH). Animals from the moderately polluted estuary had lower NAGase activity both in the epidermis and digestive gland than in the low impacted site. NAGase activity in the epidermis and digestive gland of C. maenas from both estuaries was sensitive to cadmium exposure suggesting its usefulness for inclusion in monitoring programmes. However, in the digestive gland NAGase inhibition was found in crabs from the less impacted site but not in those from the moderately contaminated one. Altered glutathione levels were observed in cadmium-treated crabs from the contaminated site possibly conferring enhanced tolerance to these animals through its chelator action. Investigation of enhanced tolerance should thus be accounted for in monitoring programmes employing NAGase as biomarker to avoid data misinterpretation.

Cadmium hyperaccumulation and genetic differentiation of Thlaspi caerulescens populations

Although the knowledge on heavy metal hyperaccumulation mechanisms is increasing, the genetic basis of cadmium (Cd) hyperaccurnulation remains to be elucidated. Thlaspi caerulescens is an attractive model since Cd accumulation polymorphism observed in this species suggests genetic differences between populations with low versus high Cd hyperaccumulation capacities. In our study, a methodology is proposed to analyse at a regional scale the genetic differentiation of T. caerulescens natural populations in relation to Cd hyperaccumulation capacity while controlling for different environmental, soil, plant parameters and geographic origins of populations. Twenty-two populations were characterised with AFLP markers and cpDNA polymorphism. Over all loci, a partial Mantel test showed no significant genetic structure with regard to the Cd hyperaccumulation capacity. Nevertheless, when comparing the marker variation to a neutral model, seven AFLP fragments (9% of markers) were identified as presenting particularly high genetic differentiation between populations with low and high Cd hyperaccurnulation capacity. Using simulations, the number of outlier loci was showed to be significantly higher than expected at random. These loci presented a genetic structure linked to Cd hyperaccumulation capacity independently of the geography, environment, soil parameters and Zn, Pb, Fe and Cu concentrations in plants. Using a canonical correspondence analysis, we identified three of them as particularly related to the Cd hyperaccumutation capacity. This study demonstrates that populations with low and high hyperaccurnulation capacities can be significantly distinguished based on molecular data. Further investigations with candidate genes and mapped markers may allow identification and characterization of genomic regions linked to factors involved in Cd hyperaccumulation.

Cadmium distribution in soils covering Jurassic oolitic limestone with high Cd contents in the Swiss Jura

Oolitic carbonates belonging to the Hauptrogenstein Formation of Bajocian (Middle Jurassic) age have been shown to be anomalously enriched in cadmium (Cd) throughout the Jura Mountains. Soils associated with this type of rock substratum may be naturally polluted with regards to Cd. At Schleifenberg (Canton Basel Land, Switzerland) the Hauptrogenstein Formation is almost entirely exposed along a trail on its SW flank. Cadmium concentrations were systematically measured throughout this formation and Cd enrichments in rocks are shown to occur to a maximum content of 4.9 mg kg(-1). We investigated associated soils, which cover the entire outcrop, and show that they have been formed through the weathering of the underlying bedrock and through the uptake of colluvial limestone fragments from the same and older formations. Cadmium contents in the soils reach a maximum value of 2.0 mg kg(-1), thereby exceeding the official Swiss indicative guideline value for soils fixed at 0.8 mg.kg(-1). Mineralogical analyses on the soils and associated bedrock suggest that no allochthonous component related to aeolian transport is present. Sequential extractions applied to selected soil samples show that about half of the Cd resides in the carbonate fraction coming from the fractured parent-rock, while the Cd released from the weathered carbonates is associated either with organic matter (over 10%) or with Fe and Mn-oxihydroxides (approximately 30%). No exchangeable Cd phase was found and this, together with the buffer capacity of this calcareous soil, suggests that the amount of mobile Cd is quite negligible in this soil, which also greatly reduces the amount of bioavailable

A search for the origin of cadmium in the soil of the Swiss Jura

The top soil of a 14.5 km(2) region at la Chaux-de-Fonds in the Swiss Jura is exceptionally rich in cadmium. It contains an average of 1.3 mg per kg of soil. The spatial distribution of the metal has no simple pattern that could be explained by atmospheric deposition or agricultural practices. Thin soil contained most of its Cd at the surface; in thicker soil Cd is mainly concentrated between 60 and 80 cm depth. No specific minerals or soil fractions could account for these accumulation, and the vertical distribution of Cd is best explained by leaching from the topsoil and further adsorption within layers of nearly neutral pH. The local Jurassic sedimentary rocks contained too little Cd to account for the Cd concentrations in the soil. Alpine gravels from glacial till were too sparse in soils to explain such a spreading of Cd. Moreover this origin is contradictory with the fact that Cd is concentrated in the sand fraction of soils. The respective distributions of Fe and Cd in soils, and soil fractions, suggested that the spreading of iron nodules accumulated during the siderolithic period (Eocene) was not the main source of Cd. Atmospheric deposition, and spreading of fertiliser or waste from septic tanks seem the only plausible explanation for the Cd concentrations, but at present few factors allow us to differentiate between them.

Genetics of cadmium hyperaccumulation variance in Thlaspi caerulescens natural populations from Switzerland

SUMMARY Heavy metal presence in the environment is a serious concern since some of them can be toxic to plants, animals and humans once accumulated along the food chain. Cadmium (Cd) is one of the most toxic heavy metal. It is naturally present in soils at various levels and its concentration can be increased by human activities. Several plants however have naturally developed strategies allowing them to grow on heavy metal enriched soils. One of them consists in the accumulation and sequestration of heavy metals in the above-ground biomass. Some plants present in addition an extreme strategy by which they accumulate a limited number of heavy metals in their shoots in amounts 100 times superior to those expected for a non-accumulating plant in the same conditions. Understanding the genetic basis of the hyperaccumulation trait - particularly for Cd - remains an important challenge which may lead to biotechnological applications in the soil phytoremediation. In this thesis, Thlaspi caerulescens J. & C. Presl (Brassicaceae) was used as a model plant to study the Cd hyperaccumulation trait, owing to its physiological and genetic characteristics. Twenty-four wild populations were sampled in different regions of Switzerland. They were characterized for environmental and soil parameters as well as intrinsic characteristics of plants (i.e. metal concentrations in shoots). They were as well genetically characterized by AFLPs, plastid DNA polymorphism and genes markers (CAPS and microsatellites) mainly developed in this thesis. Some of the investigated genes were putatively linked to the Cd hyperaccumulation trait. Since the study of the Cd hyperaccumulation in the field is important as it allows the identification of patterns of selection, the present work offered a methodology to define the Cd hyperaccumulation capacity of populations from different habitats permitting thus their comparison in the field. We showed that Cd, Zn, Fe and Cu accumulations were linked and that populations with higher Cd hyperaccumulation capacity had higher shoot and reproductive fitness. Using our genetic data, statistical methods (Beaumont & Nichols's procedure, partial Mantel tests) were applied to identify genomic signatures of natural selection related to the Cd hyperaccumulation capacity. A significant genetic difference between populations related to their Cd hyperaccumulation capacity was revealed based on somè specific markers (AFLP and candidate genes). Polymorphism at the gene encoding IRTl (Iron-transporter also participating to the transport of Zn) was suggested as explaining part of the variation in Cd hyperaccumulation capacity of populations supporting previous physiological investigations. RÉSUMÉ La présence de métaux lourds dans l'environnement est un phénomène préoccupant. En effet, certains métaux lourds - comme le cadmium (Cd) -sont toxiques pour les plantes, les animaux et enfin, accumulés le long de la chaîne alimentaire, pour les hommes. Le Cd est naturellement présent dans le sol et sa concentration peut être accrue par différentes activités humaines. Certaines plantes ont cependant développé des stratégies leur permettant de pousser sur des sols contaminés en métaux lourds. Parmi elles, certaines accumulent et séquestrent les métaux lourds dans leurs parties aériennes. D`autres présentent une stratégie encore plus extrême. Elles accumulent un nombre limité de métaux lourds en quantités 100 fois supérieures à celles attendues pour des espèces non-accumulatrices sous de mêmes conditions. La compréhension des bases génétiques de l'hyperaccumulation -particulièrement celle du Cd - représente un défi important avec des applications concrètes en biotechnologies, tout particulièrement dans le but appliqué de la phytoremediation des sols contaminés. Dans cette thèse, Thlaspi caerulescens J. & C. Presl (Brassicaceae) a été utilisé comme modèle pour l'étude de l'hyperaccumulation du Cd de par ses caractéristiques physiologiques et génétiques. Vingt-quatre populations naturelles ont été échantillonnées en Suisse et pour chacune d'elles les paramètres environnementaux, pédologique et les caractéristiques intrinsèques aux plantes (concentrations en métaux lourds) ont été déterminés. Les populations ont été caractérisées génétiquement par des AFLP, des marqueurs chloroplastiques et des marqueurs de gènes spécifiques, particulièrement ceux potentiellement liés à l'hyperaccumulation du Cd (CAPS et microsatellites). La plupart ont été développés au cours de cette thèse. L'étude de l'hyperaccumulation du Cd en conditions naturelles est importante car elle permet d'identifier la marque, éventuelle de sélection naturelle. Ce travail offre ainsi une méthodologie pour définir et comparer la capacité des populations à hyperaccumuler le Cd dans différents habitats. Nous avons montré que les accumulations du Cd, Zn, Fe et Cu sont liées et que les populations ayant une grande capacité d'hyperaccumuler le Cd ont également une meilleure fitness végétative et reproductive. Des méthodes statistiques (l'approche de Beaumont & Nichols, tests de Martel partiels) ont été utilisées sur les données génétiques pour identifier la signature génomique de la sélection naturelle liée à la capacité d'hyperaccumuler le Cd. Une différenciation génétique des populations liée à leur capacité d'hyperaccumuler le Cd a été mise en évidence sur certains marqueurs spécifiques. En accord avec les études physiologiques connues, le polymorphisme au gène codant IRT1 (un transporteur de Fe impliqué dans le transport du Zn) pourrait expliquer une partie de la variance de la capacité des populations à hyperaccumuler le Cd.

Cadmium availability and accumulation by lettuce and rice

Among the toxic elements, Cd has received considerable attention in view of its association with a number of human health problems. The objectives of this study were to evaluate the Cd availability and accumulation in soil, transfer rate and toxicity in lettuce and rice plants grown in a Cd-contaminated Typic Hapludox. Two simultaneous greenhouse experiments with lettuce and rice test plants were conducted in a randomized complete block design with four replications. The treatments consisted of four Cd rates (CdCl2), 0.0; 1.3; 3.0 and 6.0 mg kg-1, based on the guidelines recommended by the Environmental Agency of the State of São Paulo, Brazil (Cetesb). Higher Cd rates increased extractable Cd (using Mehlich-3, Mehlich-1 and DTPA chemical extractants) and decreased lettuce and rice dry matter yields. However, no visual toxicity symptoms were observed in plants. Mehlich-1, Mehlich-3 and DTPA extractants were effective in predicting soil Cd availability as well as the Cd concentration and accumulation in plant parts. Cadmium concentration in rice remained below the threshold for human consumption established by Brazilian legislation. On the other hand, lettuce Cd concentration in edible parts exceeded the acceptable limit.

Influence of digestion methods on the recovery of Iron, Zinc, Nickel, Chromium, Cadmium and Lead contents in 11 organic residues

There are currently many devices and techniques to quantify trace elements (TEs) in various matrices, but their efficacy is dependent on the digestion methods (DMs) employed in the opening of such matrices which, although "organic", present inorganic components which are difficult to solubilize. This study was carried out to evaluate the recovery of Fe, Zn, Cr, Ni, Cd and Pb contents in samples of composts and cattle, horse, chicken, quail, and swine manures, as well as in sewage sludges and peat. The DMs employed were acid digestion in microwaves with HNO3 (EPA 3051A); nitric-perchloric digestion with HNO3 + HClO4 in a digestion block (NP); dry ashing in a muffle furnace and solubilization of residual ash in nitric acid (MDA); digestion by using aqua regia solution (HCl:HNO3) in the digestion block (AR); and acid digestion with HCl and HNO3 + H2O2 (EPA 3050). The dry ashing method led to the greatest recovery of Cd in organic residues, but the EPA 3050 protocol can be an alternative method for the same purpose. The dry ashing should not be employed to determine the concentration of Cr, Fe, Ni, Pb and Zn in the residues. Higher Cr and Fe contents are recovered when NP and EPA 3050 are employed in the opening of organic matrices. For most of the residues analyzed, AR is the most effective method for recovering Ni. Microwave-assisted digestion methods (EPA3051 and 3050) led to the highest recovery of Pb. The choice of the DM that provides maximum recovery of Zn depends on the organic residue and trace element analyzed.

Transfer of cadmium and barium from soil to crops grown in tropical soils

Phytotoxicity and transfer of potentially toxic elements, such as cadmium (Cd) or barium (Ba), depend on the availability of these elements in soils and on the plant species exposed to them. With this study, we aimed to evaluate the effect of Cd and Ba application rates on yields of pea (Pisum sativum L.), sorghum (Sorghum bicolor L.), soybean (Glycine max L.), and maize (Zea mays L.) grown under greenhouse conditions in an Oxisol and an Entisol with contrasting physical and chemical properties, and to correlate the amount taken up by plants with extractants commonly used in routine soil analysis, along with transfer coefficients (Bioconcentration Factor and Transfer Factor) in different parts of the plants. Plants were harvested at flowering stage and measured for yield and Cd or Ba concentrations in leaves, stems, and roots. The amount of Cd accumulated in the plants was satisfactorily evaluated by both DTPA and Mehlich-3 (M-3). Mehlich-3 did not relate to Ba accumulated in plants, suggesting it should not be used to predict Ba availability. The transfer coefficients were specific to soils and plants and are therefore not recommended for direct use in risk assessment models without taking soil properties and group of plants into account.

Surface Complexation Modeling in Variable Charge Soils: Prediction of Cadmium Adsorption

ABSTRACT Intrinsic equilibrium constants for 22 representative Brazilian Oxisols were estimated from a cadmium adsorption experiment. Equilibrium constants were fitted to two surface complexation models: diffuse layer and constant capacitance. Intrinsic equilibrium constants were optimized by FITEQL and by hand calculation using Visual MINTEQ in sweep mode, and Excel spreadsheets. Data from both models were incorporated into Visual MINTEQ. Constants estimated by FITEQL and incorporated in Visual MINTEQ software failed to predict observed data accurately. However, FITEQL raw output data rendered good results when predicted values were directly compared with observed values, instead of incorporating the estimated constants into Visual MINTEQ. Intrinsic equilibrium constants optimized by hand calculation and incorporated in Visual MINTEQ reliably predicted Cd adsorption reactions on soil surfaces under changing environmental conditions.

Cadmium-free quantum dots in aqueous solution: potential for fingermark detection, synthesis and an application to the detection of fingermarks in blood on non-porous surfaces

The use of quantum dots (QDs) in the area of fingermark detection is currently receiving a lot of attention in the forensic literature. Most of the research efforts have been devoted to cadmium telluride (CdTe) quantum dots often applied as powders to the surfaces of interests. Both the use of cadmium and the nano size of these particles raise important issues in terms of health and safety. This paper proposes to replace CdTe QDs by zinc sulphide QDs doped with copper (ZnS:Cu) to address these issues. Zinc sulphide-copper doped QDs were successfully synthesized, characterized in terms of size and optical properties and optimized to be applied for the detection of impressions left in blood, where CdTe QDs proved to be efficient. Effectiveness of detection was assessed in comparison with CdTe QDs and Acid Yellow 7 (AY7, an effective blood reagent), using two series of depletive blood fingermarks from four donors prepared on four non-porous substrates, i.e. glass, transparent polypropylene, black polyethylene and aluminium foil. The marks were cut in half and processed separately with both reagents, leading to two comparison series (ZnS:Cu vs. CdTe, and ZnS:Cu vs. AY7). ZnS:Cu proved to be better than AY7 and at least as efficient as CdTe on most substrates. Consequently, copper-doped ZnS QDs constitute a valid substitute for cadmium-based QDs to detect blood marks on non-porous substrates and offer a safer alternative for routine use.

Origin of cadmium enrichments in carbonate rocks deposited in the Alpine Tethys area during the Middle-Late Jurassic

ABSTRACTThe pollution of air, soil and water by heavy metals through anthropogenic activities is an object of numerous environmental studies since long times. A number of natural processes, such as volcanic activity, hydrothermal fluid circulation and weathering of metal-rich deposits may lead to an additional and potentially important input and accumulation of heavy metals in the environment. In the Swiss and French Jura Mountains, anomalous high cadmium (Cd) concentrations (up to 16 ppm) in certain soils are related to the presence of underlying Cd-enriched (up to 21 ppm) carbonate rocks of Middle to Late Jurassic age. The aim of this study is to understand the processes controlling Cd incorporation into carbonate rocks of Middle and Late Jurassic age and to reconstruct the sedimentary and environmental conditions, which have led to Cd enrichments in these sedimentary rocks.Cd concentrations in studied hemipelagic sections in France vary between 0.1 and 0.5 ppm (mean 0.15 ppm). Trace-element behavior and high Mn concentrations suggest that sediment accumulation occurred in a well-oxygenated environment. Increases in Cd contents in the bulk-rock carbonate sediments may be related to increases in surface-water productivity under oxic conditions and important remineralization of organic matter within the water column. In platform settings preserved in the Swiss Jura Mountains, no correlation is observed between Cd contents and evolution of environmental conditions. Cd concentrations in these platform sections are often below the detection limit, with isolated peaks of up to 21 ppm. These important Cd enrichments are associated with peaks in Zn concentrations and are present in carbonate rocks independently of facies and age. The high Cd contents in these shallow-water carbonate rocks are partly related to the presence of disseminated, Cd-rich (up to 1.8%), sphalerite (ZnS) mineralization. The basement rocks are considered to be the source of metals for sulfide mineralization in the overlying Jurassic strata, as the sphalerite Pb isotope pattern is comparable to that of granite rocks from the nearby southern Black Forest crystalline massif. The Rb-Sr ages of sphalerite samples indicate that a main phase of sphalerite formation occurred near the boundary between the late Middle and early Late Jurassic, at around 162 Ma, as a result of enhanced tectonic and hydrothermal activity in Europe, related to the opening of the Central Atlantic and to the tectonic/thermal subsidence during spreading of the Alpine Tethys. I therefore propose to use unusually high Cd concentrations in carbonates as a tracer of tectonic activity in the Jura Mountains area, especially in the case when important enrichments in Zn co-occur. Paleoproductivity reconstructions based on records of authigenic Cd may be compromised not only by post-depositional redistribution, but also by incorporation of additional Cd from hydrothermal solutions circulating in the rock.The circulation of metal-rich hydrothermal fluids through the sediment sequence, in addition to specific environmental conditions during sedimentation, contributes to the incorporation of Cd into the carbonate rocks. However, only hydrothermal activity has led to the unusually high concentrations of Cd in carbonate rocks of Bajocian-Oxfordian age, through the formation of sphalerite mineralization.