Wegen umfangreicher Cd-Emissionen eines Betriebes in Bad Liebenstein kam es zur Cd-Anreicherung in diesem Lebensraum. Boden, Wasser und Flora spiegeln die Cd-Belastung wider.

A green, switchable water dispersive liquid–liquid microextraction (SWDLL-ME) method is introduced for the first time as a preconcentration/separation tool for measuring trace levels of cadmium (Cd) in real water and food samples. In the present study, a switchable aqueous solution of polar organic solvent (acetonitrile) was reversibly switched (on and off) from miscible monophasic to immiscible biphasic in aqueous medium by exposure to an anti-solvent trigger (CO₂). The developed SWDLL-ME was successfully applied as an extraction method for the extraction of a Cd–PAN complex (1-(2-pyridylazo)-2-naphthol) in polar organic solvent (PS). The solvent enriched phase containing Cd–PAN was separated from the switchable water (SW) and treated with 200 μL of 0.1 mol L⁻¹ HNO₃ with ethanol (1 : 1, v/v) in order to reduce its viscosity, and it was then easily injected into a GFAAS for analysis. The SW was reused for the next assay after the removal of CO₂. The switching phenomenon of the SW from low to high polarity was confirmed by FTIR spectroscopy and conductivity measurements. The enrichment factor and limit of detection of the proposed method were 22 and 0.38 ng L⁻¹, respectively. Validation of the developed method was carried out by analyzing certified reference materials (SLRS-4 Riverine water and NIST SRM 1515 Apple leaves).

A key aspect of modeling contaminant uptake by animals is knowledge of the route taken by the contaminant to enter the animal. To determine the relative importance of food and water as Cd sources for benthic insects, we measured Cd accumulation by the predatory alderfly Sialis velata (Megaloptera) from either water alone or from chironomid prey (Cryptochironomus sp.). We determined that Cd uptake from prey was far more important than that from water. Chironomid prey fed to S. velata also appeared to take up the bulk of their Cd from food (meiobenthic organisms). The efficiency with which Cd was assimilated by the predator from its prey is high (50%) and comparable with values reported for several other insects. In the predator, Cd taken up from food was largely stored in gut tissues (as is the case for insect larvae in nature), whereas a greater proportion of the metal taken up from water was stored in other animal parts.

The historical build up and future cadmium (Cd) concentrations in top soils and in crops of four Australian agricultural systems are predicted with a mass balance model, focusing on the period 1900-2100. The systems include a rotation of dryland cereals, a rotation of sugarcane and peanuts/soybean, intensive dairy production and intensive horticulture. The input of Cd to soil is calculated from fertilizer application and atmospheric deposition and also examines options including biosolid and animal manure application in the sugarcane rotation and dryland cereal production systems. Cadmium output from the soil is calculated from leaching to deeper horizons and removal with the harvested crop or with livestock products. Parameter values for all Cd fluxes were based on a number of measurements on Australian soil-plant systems. In the period 1900-2000, soil Cd concentrations were predicted to increase on average between 0.21 mg kg(-1) in dryland cereals, 0.42 mg kg(-1) in intensive agriculture and 0.68 mg kg(-1) in dairy production, which are within the range of measured increases in soils in these systems. Predicted soil concentrations exceed critical soil Cd concentrations, based on food quality criteria for Cd in crops during the simulation period in clay-rich soils under dairy production and intensive horticulture. Predicted dissolved Cd concentrations in soil pore water exceed a ground water quality criterion of 2 μg l(-1) in light textured soils, except for the sugarcane rotation due to large water leaching fluxes. Results suggest that the present fertilizer Cd inputs in Australia are in excess of the long-term critical loads in heavy-textured soils for dryland cereals and that all other systems are at low risk. Calculated critical Cd/P ratios in P fertilizers vary from <50 to >1000 mg Cd kg P(-1) for the different soil, crop and environmental conditions applied. | W. de Vries and M.J. McLaughlin

A new biosorbent material from eggshell membrane was synthesized through thiol functionalization, which is based on the reduction of disulfide bonds in eggshell membrane by ammonium thioglycolate. The thiol-functionalized eggshell membrane was characterized, and its application as an adsorbent for removal of Cr(VI), Hg(II), Cu(II), Pb(II), Cd(II), and Ag(I) from aqueous water has been investigated. The experimental results revealed that the adsorption abilities of the thiol-functionalized eggshell membrane toward Cr(VI), Hg(II), Cu(II), Pb(II), Cd(II), and Ag(I) improved 1.6-, 5.5-, 7.7-, 12.4-, 12.7-, and 21.1-fold, respectively, compared with that of the eggshell membrane control. The adsorption mechanism and adsorption performance, including the adsorption capacity and the kinetics of the thiol-functionalized eggshell membrane for the target heavy metals, were investigated. The effects of solution pH, coexisting substances, and natural water matrices were studied. The thiol-functionalized eggshell membrane can be used as column packing to fabricate a column for real wastewater purification.

The Three Gorges Reservoir (TGR) of China, the largest hydropower project over the world, has attracted much attention to the water impoundment and water-level manipulation. In this study, we evaluated potential effects of water impoundment and seasonal water-level manipulation on the bioaccumulation, trophic transfer and health risk of HMs (Cu, Fe, Zn, Hg, Cd and Pb) in food web components (seston, aquatic invertebrate and fish) in TGR. Our results show that, after the impoundment for eight years (2003–2010), all of the six metal concentrations in aquatic biota fell within the criteria of safety quality guidelines. The concentrations of Cu, Fe, Zn and Hg in fish and aquatic invertebrates were higher than those before impoundment, whereas Cd and Pb were lower than those before impoundment. Nonetheless, Hg, Cd and Pb in aquatic consumers underwent an increasing trend during the entire impoundment, implying potential reservoir effect in the future. Only the concentrations of Hg, Cd and Pb in aquatic consumers exhibited a declining trend towards the dam, showing consistent with the background level at the three reaches. Seasonal variations in HM concentrations of fish and aquatic invertebrates were ascribed to the water-level manipulation associated with reservoir management. Our findings show that Hg or Cd biomagnified through aquatic food web during different hydrological periods, whereas Pb, Cu, Fe and Zn exhibited weak biomagnification power. Overall, Hg, Cd and Pb showed a higher risk than that of Cu, Fe and Zn.

A simple and reliable method for rapid and selective extraction and determination of trace levels of Cd²⁺ was developed by dispersive liquid–liquid microextraction (DLLME) coupled to flame atomic absorption spectrometry (FAAS) detection. The main factors affecting the DLLME, such as concentration of DPTH, pH, extraction and disperser solvent type and their volume, were optimized for the best extract efficiency. Under the optimum conditions, i.e., pH 5.4, [DPTH] = 6 × 10⁻³%, a preconcentration factor of 55 was reached. The lower limit of detection (LOD) obtained under the optimal conditions was 0.4 μg L⁻¹. The precision for 14 replicate determinations at 30 and 100 μg L⁻¹ of Cd was 2.7% and 1.9% relative standard deviation (R.S.D.), respectively. The calibration graph using the preconcentration method was linear from 5 to 100 μg L⁻¹, with a correlation coefficient of 0.9898. The proposed method was successfully applied to the preconcentration and determination of cadmium in food, vegetation, and water samples and in a BCR-176 standard reference material.

The presence of cadmium (Cd) in food produced in Latin America has been highlighted in recent years. Cadmium can be toxic to humans at low levels, and therefore monitoring its presence in food is relevant for public health. Cadmium concentrations from different sources, such as water, soil, sediment, food, and beverages were examined and discussed to address the non-occupational exposure of the Latin American population to Cd. A literature review was conducted examining publications from 2015 to 2020 and data available in the ScienceDirect and PubMed databases. Twenty-eight papers reported on Cd in water, 49 reported Cd in soil and sediments, and 86 reported on Cd in food. We have identified and discussed the factors affecting the environmental behavior and bioaccumulation of Cd, the main species used in monitoring studies, and the necessity for future research. Brazil and Mexico are the countries that provided the most available information, whereas for some countries in Central America, no information was found. The Cd levels in food examined in these studies (mostly fish and cacao) were generally below the established maximum levels, indicating a low risk. When considering the presence of Cd in food, water, and soil, Cd fractionation and chemical speciation studies are fundamental to understanding which forms of Cd are the most toxic. In turn, studies on bioaccessibility and bioavailability of Cd in food are also needed for more adequate risk assessment, but they are currently scarce within Latin America.

A simple, rapid, sensitive and environmentally friendly separation and preconcentration procedure, based on the carrier element free coprecipitation (CEFC) of Cu(II) and Cd(II) ions by using an organic coprecipitant, 2-{[4-(4-fluorophenyl)-5-sulphanyl-4H-1,2,4-triazol-3-yl]methyl}-4-{[(4-fluorophenyl) methylene]amino}-5-(4-methylphenyl)-2,4-dihydro-3H-1,2,4-triazol-3-one (MEFMAT) was developed. The analyte ions were determined by flame atomic absorption spectrometric (FAAS) determinations. The optimum conditions for the coprecipitation process were investigated on several commonly tested experimental parameters such as pH of the solution, amount of MEFMAT, sample volume, standing time, centrifugation rate and time. The influences of some anions, cations and transition metals on the recoveries of analyte ions were also investigated, and no considerable interference was observed. The preconcentration factor was found to be 50. The detection limits for Cu(II) and Cd(II) ions based on the three times the standard deviation of the blanks (N:10) were found to be 1.49 and 0.45μgL⁻¹, respectively. The relative standard deviations were found to be lower than 3.5% for both analyte ions. The method was validated by analyzing two certified reference materials (CRM-TMDW-500 Drinking Water and CRM-SA-C Sandy Soil C) and spike tests. The procedure was successfully applied to sea water and stream water as liquid samples and tobacco, hazelnut and black tea as solid samples.

In this work, a new method based on dispersive liquid–liquid microextraction (DLLME) preconcentration using tetrachloromethane (CCl₄) as extraction solvent was proposed for the spectrophotometric determination of cadmium and copper in water and food samples. The influence factors relevant to DLLME, such as type and volume of extractant and disperser solvent, concentration of chelating reagents, pH, salt effect, were optimized. Under the optimal conditions, the limits of detection for cadmium and copper were 0.01ng/L and 0.5μg/L, with enhancement factors (EFs) of 3458 and 10, respectively. The tremendous contrast of EFs could come from the different maximum absorption wavelength caused by the different extraction acidity compared with some conventional works and the enhancement effect of acetone used as dilution solvent during the spectrophotometric determination. The proposed method was applied to the determination of water and food samples with satisfactory analytical results. The proposed method was simple, rapid, cost-efficient and sensitive, especially for the detection of cadmium.