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To test high cadmium (Cd) concentration may not be high in health risk when considering Cd bioavailability, we assessed variation of Cd relative bioavailability (RBA, relative to CdCl 2 ) using a mouse assay for 14 vegetables of water spinach, amaranth, and pakchoi. Cadmium concentration varied from 0.13 ± 0.01-0.37 ± 0.00 μg g -1 fw. Cadmium-RBA also varied significantly from 22.9 ± 2.12-77.2 ± 4.46%, however, the variation was overall opposite to that of Cd concentration, as indicated by a strong negative correlation between Cd-RBA and Cd concentration (R 2 = 0.43). Based on both Cd concentration and bioavailability, the identified high-Cd pakchoi variety resulted in significantly lower Cd intake than the high-Cd varieties of water spinach and amaranth (4.74 ± 0.05 vs. 10.1 ± 0.54 and 8.03 ± 0.04 μg kg -1 bw week -1 ) due to significantly lower Cd-RBA (22.9 ± 2.12 vs. 77.2 ± 4.46 and 51.3 ± 2.93%). The lower Cd-RBA in pakchoi was due to its significantly higher Ca and lower phytate concentrations, which facilitated the role of Ca in inhibiting intestinal Cd absorption. This was ascertained by observation of decreased Cd-RBA (90.5 ± 12.0% to 63.5 ± 5.53%) for a water spinach when elevating its Ca concentration by 30% with foliar Ca application. Our results suggest that to assess food Cd risk, both total Cd and Cd bioavailability should be considered., (Copyright © 2021 Elsevier B.V. All rights reserved.)

To determine the effectiveness of mineral dietary supplements to modulate cadmium (Cd) exposure, an in vivo mouse bioassay was conducted to determine Cd relative bioavailability (Cd-RBA) in Cd-contaminated rice (0.80 mg Cd kg -1 ) with and without Zn, Fe, or Ca supplements as nitrate or chloride salts. Without mineral supplements, Cd-RBA was 43 ± 5.3% based on average Cd accumulation in the liver plus kidneys as the end point. Among Ca(NO 3 ) 2 , Zn(NO 3 ) 2 , and Fe(NO 3 ) 2 supplements, 150-5000 mg kg -1 Ca was the most effective in reducing rice Cd-RBA by 31-80% to 8.5-29%, while 30-200 mg kg -1 Zn supplements was ineffective, with Cd-RBA being 33-57%. Low Fe at <40 mg kg -1 had little impact on rice Cd-RBA (39-47%), while high Fe at 80-200 mg kg -1 decreased Cd-RBA by 37% to 26-27%. The ineffectiveness of Zn supplements in reducing Cd-RBA was probably due to coinciding 8.3- and 3.1-fold increases in Zn accumulation in mouse kidneys and liver with Zn supplements, while Ca and Fe supplements led to much-smaller increases in Ca and Fe accumulation in mouse tissues (1.3-1.6 fold). In addition, compared to Ca(NO 3 ) 2 supplements, Cd-RBA values determined with CaCl 2 supplements were significantly higher (25-67% versus 8.5-29%), suggesting that chloride enhanced Cd-RBA. Results of this study have important implications for developing effective dietary strategies to reduce dietary Cd exposure and the associated health risks in humans.

A semi-static solution culture method was used to study the effects of Ca(2+) supply and interaction of Cd-Pb on the subcellular distribution of Cd and Pb in earthworm Eisenia fetida. The subcellular distribution of Cd and Pb was shown to be metal specific. About 80% of the Cd was distributed in the cytosol (fraction G), and only about 20% of total Cd was found in the tissue and cell membrane (fraction E) and the microsomes (fraction F). Nearly 50% of the Pb was rich in the tissue and cell membrane (fraction E). The supply of Ca(2+) ions significantly decreased Cd concentration in the cytosol (fraction G) and the whole tissue of the E. fetida. At the subcellular level, the addition of Pb(2+) ions significantly decreased the Cd percentage associated with fraction G from 83.7% to 58.4% and increased fraction E from 10.7% to 34.0%, respectively.

The purpose of this study was to characterize the individual effect of different cations (Ca(2+), Mg(2+), Na(+), K(+), and H(+)) on the acute toxicity of Cd to the earthworm Eisenia fetida. Higher activities of the considered cations increased the 48-h LC(50) (expressed as Cd(2+) activities) linearly to different extents in simulated soil solution. The conditional constants for the binding of H(+ )(log K = 5.41), Cd(2+ )(log K = 4.0), Ca(2+ )(log K = 3.35), Mg(2+ )(log K = 2.82), Na(+ )(log K = 1.57), and K(+ )(log K = 2.31) to the biotic ligand (BL) of E. fetida were derived from the toxicity data based on the biotic ligand model (BLM). Furthermore, it was calculated that on average 72% of the BL sites needed to be occupied by Cd(2+) to induce 50% lethal effect. Autovalidation of the model with the results of the test sets showed that 48-h LC(50 )could be predicted within a factor of two.

Glyphosate [N-(phosphonomethyl)glycine] (GPS; H3G) is a widely used pesticide throughout the world. It affects metal behaviors in soil-plant system due to its functional groups, which react with metal ions to form metal complexes. Adsorption and cosorption of cadmium and glyphosate on a Wushan soil (WS soil, Anthrosol) and a Zhuanhong soil (ZH soil, Udic Ferrisol) as affect by solution pH were studied by means of batch adsorption experiments. It indicated that the adsorption quantity of Cd or glyphosate was highly relevant to soil characteristics. The WS soil had higher adsorption capacity of Cd than the ZH soil, due to its high organic matter content and cation exchange capacity (CEC). In contrast, the adsorption quantity of glyphosate on the WS soil was less than that on the ZH soil, because the WS soil has lower iron and aluminum oxides content but higher pH than the ZH soil. The herbicide glyphosate affected Cd adsorption on the two soils when they coexisted in a same soil solution, which was attributed to a glyphosate-induced pH-decrease and the corresponding decline in negative surface charges of the soil. Beside that, glyphosate reacted with solution Cd to form the water-soluble complexes that had lower affinity to soil surface in comparison with Cd itself. On the other hand, the presence of Cd in the soil solution also affected the adsorption of glyphosate on the soils. The presence of Cd increased adsorption quantity of glyphosate on the WS and ZH soils, which was resulted from the decrease of equilibrium solution pH caused by Cd2+ exchange with H+ ions of soil surface. In addition to that, glyphosate adsorption possibly takes place on sites where Cd was previously adsorbed and acted as a bridge between the soil and glyphosate.

Abstract: A semi-static solution culture method was used to study the effects of Ca2+ supply and interaction of Cd–Pb on the subcellular distribution of Cd and Pb in earthworm Eisenia fetida. The subcellular distribution of Cd and Pb was shown to be metal specific. About 80% of the Cd was distributed in the cytosol (fraction G), and only about 20% of total Cd was found in the tissue and cell membrane (fraction E) and the microsomes (fraction F). Nearly 50% of the Pb was rich in the tissue and cell membrane (fraction E). The supply of Ca2+ ions significantly decreased Cd concentration in the cytosol (fraction G) and the whole tissue of the E. fetida. At the subcellular level, the addition of Pb2+ ions significantly decreased the Cd percentage associated with fraction G from 83.7% to 58.4% and increased fraction E from 10.7% to 34.0%, respectively. [Copyright &y& Elsevier]

Behaviors of soil heavy metals are often affected by coexisting herbicides due to their physical and chemical interaction. Effect of glyphosate, an herbicide containing -PO_3^{2-} and -COOH groups, on cadmium adsorption in montmorillonite was studied in detail. The results showed that cadmium adsorption quantity in montmorillonite increased with increasing soil solution pH and cadmium concentration as usual, but decreased with glyphosate, which is due to the formation of a low affinity complex of Cd and glyphosate and decreasing solution pH induced by glyphosate addition. When the equilibrium solution pH was below 6.7, glyphosate has little effect on cadmium adsorption, but when the equilibrium solution pH was above 6.7, glyphosate significantly decreased cadmium adsorption quantity in montmorillonite. In addition, the adding order of Cd and glyphosate also influenced Cd adsorption quantity in montmorillonite. [ABSTRACT FROM AUTHOR]