Bioavailability Of Cadmium In Soil Research Articles

Effect of Organic Amendments on Cadmium Bioavailability in Soil and its Accumulation in Rice Grain

A pot trial was conducted during the boro (dry) season to evaluate the impact of six traditional organic amendments(OAs) on the growth of SL-8 rice variety in both agricultural and cadmium (Cd) stressed soil at 2% and 4% application rates. Traditional OAs used in the study were cow dung, mustard oil cake (MOC), rice husk, saw dust, tea leaf and vermi compost (VC). Except for cow dung all other OAs were found to remove 99% of Cd from the aqueous solution, while cow dung removed 95%. Rice grain grown in OA-added soil in all application rates contained less Cd than the control. A 2% application rate was found to be more effective in reducing both Cd bioavailability and Cd in grain. OA application in soil significantly influenced soil pH in all cases. Though both bioavailable Cd in soil and grain Cd were reduced by the OA addition, the Cd uptake tendency of SL-8 rice variety markedly increased because of Cd spiking in soil.

Influences of biochar with selenite on bacterial community in soil and Cd in peanut

Cadmium (Cd) pollution in crops seriously affects the ecosystem and human health. Effective measures should be employed to reduce the absorption and accumulation of cadmium in crops. Currently, there are many pieces of research on the application of biochar (BC) and selenium (Se) alone to the remediation of soil Cd pollution; however, few investigations have been devoted to the application of BC and Se together to the remediation of soil Cd pollution. The peanut was taken as the target crop to explore the effects of exogenous selenium and biochar on the remediation of soil Cd pollution. The response of the soil bacterial community to two levels of Cd concentration and its relationship with soil properties and Cd availability are methodically investigated. This study sets two cadmium pollution concentrations of low Cd (5 mg/ kg) and high Cd (20 mg/kg), as well as six treatments: blank, BC, soil Se, soil Se-BC, leaf Se, and leaf Se-BC. The achieved results revealed that both Se and BC could noticeably enhance the yield of peanut seeds and reduce the Cd content in peanut seeds. Among them, Se-BC treatment on soil exhibits the most influence, which reduces the Cd content by 47.86%. Se and BC also affect the physical and chemical properties of soil and remarkably magnify the content of soil available phosphorus, organic matter, soil pH, and soil conductivity. For instance, then effect is detected in the case of applying selenium biochar to soil, leading to an increase of about 64.38%, 72.62%, 2.64%, and 61.15%, respectively, and reducing the content of soil available cadmium by 21.02%. Redundancy analysis confirms that these properties enhance the abundance of dominant bacteria Actinobacteria, Proteobacteria, and Chloroflexi. The correlation analysis also indicates that Saccharimonadales, Bacillus, Arthrobacter, and other bacteria with the function of reducing the bioavailability of cadmium in soil reveal a considerable positive correlation with the variations of physical and chemical properties. In general, exogenous Se and BC incorporate to drop the content of available Cd in the soil through direct passivation, passivation caused by soil environmental change, and passivation caused by altering the soil microbial community structure; as a result, the migration and enrichment of Cd in peanut seeds are blocked and reduced. Moreover, the mixed application of BC and soil Se exhibits the best effect.

Differences and mechanism of dynamic changes of Cd activity regulated by polymorphous sulfur in paddy soil

Sulfur (S) can decrease the bioavailability of Cd in paddy soil, and therefore reduce Cd uptake by rice. However, the dynamic influence mechanism of different forms of sulfur on the bioavailability of cadmium in soil has not been systematically studied. In this study, we used Diffusive gradients in thin films (DGT) technology and soil pore water sampling technology to investigate the effects of different types of S application on the bioavailability of Cd. The three forms of S are elemental sulfur (S0), sodium sulfate (SO42−), and mercapto-grafted palygorskite (MP), which have been treated in six ways according to CK, SL, SH, SO42L, SO42H, MP (L and H are the low and high levels of treatments). The results showed that soluble and labile Cd concentration was quickly fixed after flooding but activated after rice transplantation. Both MP and SL treatments increased the content of dissolved organic carbon (DOC) and significantly reduced the accumulation of Cd in roots and grains. The Cd content of roots treated with MP was only 0.50 mg kg−1, which was 77.6% lower than the Cd content in CK (2.22 mg kg−1). S promotes the reduction and dissolution of Fe, and the formation of FeS/FeS2 is also one of the reasons for the low bioavailability of Cd, while the SH treatment has a greater effect on lowering pH, so the effect of fixing Cd is not obvious. In addition, SO42− treatment delays the soil reduction process, so it cannot effectively fix Cd. At the stage of rice maturity, dissolved Cd increased in S treatment, but MP treatment did not have this phenomenon. The possible reason was the consumption of DOC or the oxidation of CdS which caused Cd to enter the soil solution. Taken together, Fe–S play a critical role in controlling the mobilization of Cd in paddy systems.

Effects of Mg-modified biochar on the bioavailability of cadmium in soil

The remediation effects of peanut shell biochar (HBC) and Mg-modified peanut shell biochar (MHBC) prepared under pyrolysis temperatures of 300 °C and 600 °C on Cd2+ polluted brown soil were investigated in a pot experiment. The results showed that the biochar treatment increased soil pH and decreased the bioavailable Cd2+ content in the soil. Compared with the control treatment (CK), the pH value increased by 0.32 to 2.5 upon treatment with 1% and 2% of HBC and MHBC. Bioavailable Cd2+ in the soil decreased by 5.64% to 21.33% with HBC. The MHBC presented better amendment effects than HBC; bioavailable Cd2+ in the soil decreased by 26.2% to 50.1% with the addition of MHBC. The addition of HBC and MHBC increased the shoot height and decreased the root length of the spinach. Moreover, they significantly decreased the accumulation of Cd2+ in the shoots and roots of the spinach. Compared to CK, the Cd2+ content in the shoots decreased by 7.0% to 46.8% upon treatment with 1% and 2% of HBC and MHBC, while the Cd2+ content in the roots decreased by 7.3% to 52.7%. The Cd2+ content in the shoots and roots was more greatly decreased with MHBC than with HBC.

Effect of rice straw biochar on the bioavailability of cadmium in soil to Indian Mustard (Brassica juncea L. czern.) in relation to cadmium spiking

A screenhouse experiment was conducted to study the effect of four rates of rice straw biochar (0, 1, 2 and 4%) on the bioavailability and accumulation of cadmium (Cd) by Indian mustard (Brassica juncea) in sewage water irrigated soil artificially spiked with Cd. Immobilization of Cd by rice straw biochar was assessed on the basis of DTPA-extractable Cd in soil and its content in shoots of Indian mustard. The results revealed a linear decrease in DTPA-Cd with the addition of rice straw biochar. Addition of biochar at the highest level (4%) decreased the mean Cd content in soil and in plant by 38.1 and 60.1%, respectively. Biochar addition increased dry matter yield (DMY) of Indian mustard and maximum yield increase of 19.3% was observed at 2% addition. The increase in DMY was decreased to 2.6% at 4% addition of biochar. The study indicated that rice straw biochar can be used as a remediation measure for contaminated sites and may prove to be a viable option for managing agricultural residues.

Distribution, Ecological Risk Assessment, and Bioavailability of Cadmium in Soil from Nansha, Pearl River Delta, China.

Background: Cadmium (Cd) pollution poses a threat to human health. Examination of the spatial distribution of Cd in soils can be used to assess the risks posed to humans and the environment. Objective: This study determined the enrichment rules and factors influencing Cd pollution in Nansha, and evaluated the pollution characteristics and bioavailability of Cd in quaternary sediments through 7 deep soil profiles (0–200 cm), 4 boreholes, and 348 topsoil (0–20 cm) samples. Methods: The geo-accumulation index (Igeo) and the potential ecological risk index (Er) were used to assess ecological risk, and bioavailability was determined using multivariate, spatial distribution, and correlation matrix analyses. Results: From the Er, 52% of Nansha was classed as being at very high risk of Cd pollution; a further 36% was classed as dangerous. Cadmium was more abundant in clay soils than in sandy soils. Bioavailable Cd in quaternary sediments was significantly affected by the total Cd, and labile Cd accounted for more than half of the total Cd. Changes in pH mainly affected bioavailable Cd rather than total Cd, affecting the overall bioavailability of Cd. Conclusions: Nansha soils are commonly and seriously contaminated with Cd. An appropriate remediation treatment approach should be used to reduce Cd bioavailability. Furthermore, planting structures in farmland should be adjusted to avoid the impact of heavy metals on human health.

Effect and Mechanism of Attapulgite and Its Modified Materials on Bioavailability of Cadmium in Soil

The effect of attapulgite (magnesium aluminium phyllosilicate) and its modified materials on the extractability of soil Cd and the accumulation of Cd in lettuce (Lactuca sativa) were investigated using a pot-culture experiment, and the immobilization mechanism of attapulgite and its modified materials was explored through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results showed that attapulgite and its modified materials could significantly reduce the Cd concentration in Lactuca sativa, with maximum reductions of 41.0% and 56.5%, respectively, and attapulgite modified materials treatments appeared more efficient than attapulgite treatments in reducing Cd uptake of Lactuca sativa. The saturated adsorption capacity for the adsorption of Cd2+ on attapulgite rose distinctly after being modified. Attapulgite and its modified materials could significantly reduce Cd content in soil CaCl2 extract at the dosage of 1%, with the maximum reduction rates of 34.2% and 34.3%, respectively. The attapulgite formed a complex to immobilize Cd mainly through the surface silanol and Cd2+ complexation reaction, while the modified attapulgite formed a complex mainly through the complexation of Cd2+ with carboxyl groups which existed in addition to the complexation with surface hydroxyl, thus reducing the mobility of Cd2+ and achieving remediation of Cd-contaminated soil. In summary, attapulgite and its modified materials can both be used for remediation of Cd-contaminated soil, and the mechanisms for this function were found to be different.

Improvement of cadmium phytoremediation by Centella asiatica L. after soil inoculation with cadmium-resistant Enterobacter sp. FM-1

This study examined the potential of a cadmium-resistant Enterobacter sp. FM-1 to promote plant growth and assist in cadmium accumulation in both mine-type C. asiatica L. and non-mine type C. asiatica L. tissues in highly cadmium-polluted soils. The results indicated that Enterobacter sp. FM-1 significantly promoted growth and alleviated metal toxicity in both types of C. asiatica L. Meanwhile, inoculation with Enterobacter sp. FM-1 in contaminated soil can increased cadmium bioavailability in soil. Furthermore, it will increase plant uptake and the accumulation of cadmium in C. asiatica L. leaves, stems and roots compared to that in an uninoculated plant. However, mine-type C. asiatica L. had better cadmium tolerance than the non mine-type C. asiatica L. Because of its native metal-tolerant ability, which could easily grow and proliferate, and had a better performance under cadmium-contamination conditions. Additionally, inoculation with Enterobacter sp. FM-1 significantly enhanced the bioaccumulation factor (BAF) and the translocation factor (TF) values in both types of C. asiatica L. even under high cadmium concentration soil condition. Hence, based on higher BAF and TF values and strong cadmium accumulation in the leaves and stems, we concluded that inoculation with Enterobacter sp. FM-1 is potentially useful for the phytoremediation of cadmium-contaminated sites by Centella asiatica L.

Impacts of Silicon Fertilizer as Base Manure on Cadmium Bioavailability in Soil and on Cadmium Accumulation in Rice Plants

The impacts of silicon (Si) on cadmium (Cd) bioavailability in soil and Cd accumulation in rice plants were investigated in pot experiments with rice (Oryza sativa L.) cultivation. Silicon fertilizer as the base manure (Si 0, 15, 30, and 60 mg·kg-1) was added in simulated slightly Cd-contaminated soil (total soil Cd of 0.72 mg·kg-1) and severe Cd-contaminated soil (total soil Cd of 5.08 mg·kg-1). It indicated that the application of 15-60 mg·kg-1 Si before the rice was transplanted improved soil pH values and reduced the contents of exchangeable-Cd and TCLP extractable-Cd in the soil by 24.2%-43.7% and 12.7%-46.8%, respectively, during the rice growing stages. The reduction in soil Cd bioavailability resulted from the complexing of Si and Cd, and the reduction followed the order:slightly Cd-contaminated soil > severely Cd-contaminated soil. It was obvious that silicon fertilizer improved rice biomass above ground, especially for rice grain yield. In the slightly Cd-contaminated soil, Si both promoted and restrained soil Cd transportation from the rice root to the shoot; the low application (Si 15 mg·kg-1) and high application (Si 60 mg·kg-1) of Si both promoted Cd transportation, but the medium application (Si 30 mg·kg-1) restrained Cd transportation. With increasing silicon fertilizer application, Cd contents in brown rice increased first and then decreased, ranging from 0.07-0.15 mg·kg-1, remaining lower than 0.2 mg·kg-1. In the severely Cd-contaminated soil, Si restrained the soil Cd transportation from the rice root to the shoot. The Cd contents in brown rice, husk, and straw were reduced by 38.7%-48.5%, 35.7%-70.7%, and 30.9%-40.7%, respectively, and Cd contents in brown rice were 0.23-0.28 mg·kg-1. Considering rice grain yields and Cd contents in brown rice, it was recommended that the Si application be 30 mg·kg-1 of Si in the slightly Cd-contaminated soil and Si 15-60 mg·kg-1 in the severely Cd-contaminated soil.

Comparison of in situ DGT measurement with ex situ methods for predicting cadmium bioavailability in soils with combined pollution to biotas.

To assess the capabilities of the different techniques in predicting Cadmium (Cd) bioavailability in Cd-contaminated soils with the addition of Zn, one in situ technique (diffusive gradients in thin films; DGT) was compared with soil solution concentration and four widely used single-step extraction methods (acetic acid, EDTA, sodium acetate and CaCl2). Wheat and maize were selected as tested species. The results demonstrated that single Cd-polluted soils inhibited the growth of wheat and maize significantly compared with control plants; the shoot and root biomasses of the plants both dropped significantly (P < 0.05). The addition of Zn exhibited a strong antagonism to the physiological toxicity induced by Cd. The Pearson correlation coefficient presented positive correlations (P < 0.01, R > 0.9) between Cd concentrations in two plants and Cd bioavailability indicated by each method in soils. Consequently, the results indicated that the DGT technique could be regarded as a good predictor of Cd bioavailability to plants, comparable to soil solution concentration and the four single-step extraction methods. Because the DGT technique can offer in situ data, it is expected to be widely used in more areas.

Multivariate test designs to assess the influence of zinc and cadmium bioavailability in soils on the toxicity toEnchytraeus albidus

AbstractMultivariate test designs were used to identify and quantify the soil parameters important for determining the ecotoxicological effects of zinc and cadmium to the potwormEnchytraeus albidus. The application of a fractional factorial design (FFD) revealed that the acute toxicity of zinc and cadmium toE. albiduscan vary over more than two orders of magnitude, depending on the composition of the (artificial) soils. The differences in metal ecotoxicity were determined mainly by pH and organic matter content or cation exchange capacity (CEC). Using a central composite design, models were developed describing the ecotoxicity of zinc and cadmium toE. albidusas a function of these parameters. To validate the developed surface response models, two field soils and the standard artificial soil prescribed by the Organization for Economic Cooperation and Development (OECD) were spiked with zinc and cadmium, and the acute toxicity toE. albiduswas assessed. These validation experiments confirmed that the toxicity of zinc and cadmium could be predicted by the pH and the CEC of a soil with toxicity decreasing with increasing pH and CEC.

Long-Term Changes in Cadmium Bioavailability in Soil

A study was conducted to examine changes in total and phytoavailable Cd in a soil that had received inputs of Cd due to fertilization with single superphosphate (SSP) at various rates since 1948. Accumulation of Cd in the soil was highly correlated to the application rate of SSP. No evidence was found to indicate offsite movement of Cd, either through horizontal transfer or via leaching through the profile. Increases in soil Cd led to an increase in the Cd content of wheat that was grown in the soil. However, using a radioisotope dilution technique, a significant proportion of the added Cd was found to exist in a non-bioavailable pool in the soil. A model was developed which estimated that Cd was being fixed in this soil at a rate of 1−1.5% of the total added Cd per year.

INFLUENCE OF CHLORIDE SALINITY ON CADMIUM UPTAKE BY SWISS CHARD

ABSTRACT The objective of the investigation was to determine the influence of chloride salinity on the bioavailability of cadmium in soil. The experiment consisted of treating a sandy loam soil with Cd(NO3)2 at two rates in combination with four rates of NaCl or CaCl2 and then assessing the availability of Cd in the soil with Swiss chard (Beta vulgaris ‘Cicla’). The procedure for assessing available Cd consisted of growing Swiss chard in pots containing the treated soils, harvesting, and then determining the Cd content of plant shoots. The Cd content of the shoot was taken as the measure of available Cd. Immediately after the plants were harvested, soil samples were collected for saturation extract analysis. The extracts were analyzed for all major cations, anions, and trace metals to have input data for chemically speciating Cd in the soil solution phase. The principal result showed the Cl treatment to cause a marked increase in soluble Cd, as well as an increase in leaf Cd levels; however, the distribution of estimated Cd species in the saturation extract changed with the Cl treatment. The treatment caused the percentage of estimated Cd2+ to decrease and that of estimated CdCl+ to increase. Leaf Cd was correlated better with the estimated activity of Cd2+ than with the concentration of total Cd.