Cd Concentration In Wheat Grain Research Articles

Effects of Applying Different N Sources on Cd Accumulation, Mineral Micronutrients, and Grain Yield of Durum Wheat

AbstractThis study aimed to investigate the effects of different nitrogen sources on Cd concentration in durum wheat grains in soils with low and high Cd contamination. Triticum turgidum L. durum, cv. Balcali-2000 was sown as test plant material in plastic pots containing 3.2 kg of soil. Low (0.5) and high Cd (5.0 mg Cd kg− 1 soil) were added to the culture media in the form of 3(CdSO4).8H2O. Nitrogen was also added in the form of Ca(NO3)2.4 H2O in low, sufficient, and high concentrations. In addition, a foliar application of 0.5% urea was used as a further nitrogen supply. The results showed that the total nitrogen content and the Cd concentration of the grains increased with increasing nitrogen application. This increase was more pronounced with a combination of soil nitrogen and foliar urea. While the Cd concentration in the grains was 354 µg kg− 1 at low soil Cd concentration and insufficient nitrogen supply, the Cd concentration in the grains increased by 40% to 498 µg kg− 1 at low Cd concentration and high nitrogen supply. This increase in Cd concentration in the grains was 32% higher under high nitrogen applications than at high Cd-insufficient conditions. In addition, foliar application of urea to durum wheat leaves at low soil Cd concentrations increased the Cd concentration in the grains from 354 µg kg− 1 to 484 µg kg− 1. This study showed that different treatments and amounts of nitrogen sources can affect the uptake and accumulation of Cd in wheat grains at different Cd levels.

Bayesian risk prediction model: An accessible strategy to predict cadmium contamination risk in wheat grain grown in alkaline soils

Excessive cadmium (Cd) concentration in wheat grain is becoming a widespread concern in China. Considering the complexity of Cd transfer in the soil-wheat system, how the Cd risk in wheat grain be accurately predicted from the limited details available is of great significance for the risk management of Cd. Bayes' theory could leverage existing data by combining prior information and observational data, providing a promising strategy with which to calculate a more robust posterior probability of a grain sample exceeding the food safety standard (FSS) for Cd (0.1 mg kg−1). In the current study, a risk prediction model, based on Bayes’ theory, was established to achieve a more accurate prediction of the wheat grain Cd risk from a limited number of soil parameters. The risk prediction model could predict the risk probability of wheat grain with a Cd concentration exceeding the FSS under a given soil concentration of either total Cd or diethylenetriaminepentaacetic acid (DTPA)-extractable Cd. Soil total Cd concentration proved to be a better variable for the model with greater predictive accuracy. The model predicted that fewer than 5% of the wheat grain would have a Cd concentration exceeding the FSS when grown in soil with a total Cd concentration of less than 0.299 mg kg−1. The risk probability rose significantly to 50% when the soil total Cd reached 0.778 mg kg−1. The accuracy of the model was greater than the widely applied multiple linear regression model, whereas previously published data from similar soil conditions also confirmed that the Bayesian model could predict wheat Cd risk with minimal error. The proposed model provides an accurate, accessible and cost-effective methodology for predicting Cd risk in wheat grown in alkaline soils before harvest. The wider application to other soil conditions, crops or contaminants using the Bayesian model is also promising for risk management authorities.

Foliar Application of Nanoparticles Reduced Cadmium Content in Wheat (Triticum aestivum L.) Grains via Long-Distance "Leaf-Root-Microorganism" Regulation.

Foliar application of beneficial nanoparticles (NPs) exhibits potential in reducing cadmium (Cd) uptake in crops, necessitating a systematic understanding of their leaf-root-microorganism process for sustainable development of efficient nano-enabled agrochemicals. Herein, wheat grown in Cd-contaminated soil (5.23 mg/kg) was sprayed with different rates of four commonly used NPs, including nano selenium (SeNPs)/silica (SiO2NPs)/zinc oxide/manganese dioxide. SeNPs and SiO2NPs most effectively reduced the Cd concentration in wheat grains. Compared to the control, Cd concentration in grains was significantly decreased by 35.0 and 33.3% by applying 0.96 mg/plant SeNPs and 2.4 mg/plant SiO2NPs, and the grain yield was significantly increased by 33.9% with SeNPs application. Down-regulated gene expression of Cd transport proteins (TaNramp5 and TaLCT1) and up-regulated gene expression of vacuolar Cd fixation proteins (TaHMA3 and TaTM20) were observed with foliar SeNPs and SiO2NPs use. SeNPs increased the levels of leaf antioxidant metabolites. Additionally, foliar spray of SeNPs resulted in lower abundances of rhizosphere organic acids and reduced Cd bioavailability in rhizosphere soil, and soil microorganisms related to carbon and nitrogen (Solirubrobacter and Pedomicrobium) were promoted. Our findings underscore the potential of the foliar application of SeNPs and SiO2NPs as a plant and rhizosphere soil metabolism-regulating approach to reduce Cd accumulation in wheat grains.

Control location could confuse the evaluation of passivation effect of iron-based biochar and selenium application on wheat grain cadmium accumulation

Inhibiting cadmium (Cd) accumulation in wheat grain could reduce the risk of Cd exposure to human. This study conducted a field experiment and evaluated the effect of iron-based biochar and selenium (Se) application individually or together on Cd accumulation in wheat grains in Cd contaminated soils. Considering the soil Cd heterogeneity in field, we set up 13 replicates of control (CK) and three replicates of each treatment. Results clearly showed that CK location could greatly affect the evaluation whether the difference in the wheat grain Cd concentration between treatments and CK was significant. When we assessed the difference between the treatments (foliar and soil application of Se, iron-based biochar application) and the adjacent CK, there was insignificant difference in the wheat grain Cd concentration between treatment and CK groups. Although soil application of 2 mg kg-1 Se or foliar application of 4 mg L-1 Se significantly increased the grain Se concentration as compared with the adjacent CK, but they still could not reduce the Cd concentrations in wheat grain. However, when we selected the CK that had the highest averaged grain Cd concentration, foliar and soil application of Se could significantly reduce the wheat grain Cd concentration by 47.7% and 41.3-46.1%, respectively. No matter which CK was selected, application of Fe-based biochar had no significant impact on Cd accumulation in wheat grain, and there was insignificant difference in DTPA-Cd concentrations between the iron-based biochar treatment and adjacent control. In conclusion, applying Fe-based biochar and Se in the field could not reduce the Cd accumulation in wheat grain in Cd contaminated weakly alkaline soils.

Genotypic variation in grain cadmium concentration in wheat: Insights into soil pollution, agronomic characteristics, and rhizosphere microbial communities

Soil cadmium (Cd) pollution poses a serious threat to both the productivity and quality of wheat. This study aimed to investigate the genotypic variation in grain Cd concentration in wheat through field and pot experiments. Among 273 wheat genotypes, a significant genotypic difference was found in grain Cd concentration, ranging from 0.01 to 0.14 mg kg−1. Two contrasting genotypes, X321 (a low grain Cd accumulator) and X128 (a high grain Cd accumulator), were selected for pot experiments. X321 exhibited a 17.9% greater reduction in yield and a 10.2% lower shoot-to-grain Cd translocation rate than X128 under Cd treatment. Grain Cd content showed a positive correlation with soil available Cd content and a negative correlation with Cu content. Soil catalase activity significantly decreased in X128 under Cd stress, whereas no difference was found in X321. The grains of X321 exhibited a more compact spatial distribution of starch grains and protein matrix than those of X128. Moreover, the size of A-type starch in X128 was larger than in X321. Meanwhile, X128 contained much B-type starch, with some surface pits observed on A-type granules under Cd stress. Cd treatment increased the abundance of rhizosphere microorganism communities, with Ellin6067 and Ramlibacter being enriched in X128 under Cd treatment, which might facilitate Cd uptake. The accumulation of Cd in grains demonstrated a strong positive correlation with the rhizosphere bacterial diversity (correlation coefficient = 0.78). These findings provide new insights into the basis of grain Cd accumulation in wheat and have potential implications for developing new verities with low Cd accumulation to ensure food safety and minimize human exposure.

Selenate reduced wheat grain cadmium accumulation by inhibiting cadmium absorption and increasing root cadmium retention

Selenium (Se) fertilizer has been recently used to reduce cadmium (Cd) accumulation in plant. A pot culture was performed to analyze Cd uptake, translocation, and distribution in wheat plants during the reproductive growth period in a Cd–contaminated soil after selenate was applied to the soil, and a hydroponic culture was carried out to investigate the effects of selenate application on Cd2+ influx, subcellular Cd distribution, and Cd accumulation in wheat seedlings. Results showed that selenate application had no significant effect on DTPA–Cd and Cd fraction in soil. The application of selenate greatly inhibited the whole–plant Cd absorption by 14%–23%. In addition, selenate prompted the retention of Cd in root by increasing the Cd distribution in the vacuole, which reduced the root–to–shoot Cd translocation by 18%–53%. The application of selenate increased the Cd concentration in nodes, inhibited Cd remobilization from nutritive organs to grain, and ultimately reduced Cd accumulation in wheat grain. Further, heading to grain filling was the key growth stage for exogenous selenate to regulate grain Cd accumulation. In summary, soil selenate application is an effective method to reduce grain Cd concentration in wheat, which provided scientific basis for remediation of Cd–contaminated soil.

Mercapto-palygorskite efficiently immobilizes cadmium in alkaline soil and reduces its accumulation in wheat plants: A field study

Cadmium (Cd) contamination in wheat fields has become a major environmental issue in many regions of the world. Mercapto-palygorskite (MPAL) is a high-performance amendment that can effectively immobilize Cd in alkaline wheat soil. However, MAPL as an in-situ Cd immobilization strategy for alkaline wheat soil remains to be evaluated on a field-scale and the underlying mechanisms requires further evaluation. Here, MPAL were used as soil amendment to evaluate their immobilization efficiency on Cd-contaminated alkaline soil in the field experiments. The field experiments showed that MPAL application significantly reduced wheat grain Cd concentration from 0.183 mg/kg to 0.056 mg/kg, with Cd concentration in wheat grain treated with MPAL all falling below the limit value of 0.1 mg/kg as defined in China's food safety standard (GB 2762–2022). The maximal immobilization efficiency of MPAL on soil Cd figured out by diethylenetriaminepentaacetic acid (DTPA) extraction was 61.5%. The mechanisms involved in Cd immobilization by MPAL were mainly related to the enhanced sorption of Cd onto Fe oxides, and the removal of amorphous or free Fe oxides from soil had a substantial impact on Cd immobilization efficiency by MPAL. Furthermore, the antagonistic effect between Mn and Cd uptake may also contribute to the reduction of wheat Cd accumulation after MPAL application. The current research can provide theoretical and technical support for the large-scale application of MPAL in Cd-contaminated wheat fields.

Remediation effects and mechanisms of typical minerals combined with inorganic amendment on cadmium-contaminated soil: a field study in wheat.

The remediation of cadmium (Cd)-contaminated soil has gained much attention recently because Cd in soil threatens human health through the food chain. Although tremendous progress has been made in the remediation of Cd-contaminated soil in rice acid soil system, the mechanism and effects of Cd-contaminated soil remediation under these amendments in wheat weak alkaline soil are still limited. In this study, the remediation effect and related mechanism of Cd in weakly alkaline soil were carried out using zeolite, diatomite, and sodium bentonite as the main remediation components, supplemented by calcium dihydrogen phosphate and fulvic acid. The results of field experiments showed that the concentration of Cd reduced by 27.3 ~ 31.2% in rhizosphere soil and 34.3 ~ 54.2% in non-rhizosphere soil, and the maximum reduction rate of Cd concentration in wheat grain was 25.5%. The main factors affecting the concentration of Cd in wheat grains include the change in exchangeable Cd, the absorption capacity of wheat root, and the inhibitory effect on Cd transport from stem to grain in this paper. In general, this work provides a new potential management feasible pathway to alleviate the Cd toxicity of weakly alkaline soil and wheat grain.

Foliar Spraying of Mannose Alleviates Cadmium Stress by Changing the Subcellular Distribution and Chemical Forms of Cadmium in Wheat Root

Cadmium (Cd)-contaminated soil has been receiving increasing attention worldwide due to the great harm it causes via food-chain enrichment through crops such as wheat. However, there is little research regarding the effects of mannose (MAN) on plants in response to Cd stress. Hence, hydroponic and potted soil experiments were conducted to investigate the mitigation effects of MAN on wheat under Cd stress and the possible mechanism. Compared with Cd treatment alone, foliar spraying of 160 μM MAN significantly reduced the Cd accumulation in shoots and increased the Cd retention in roots. The content of hemicellulose was increased by MAN treatment, and the proportion of Cd retained by hemicellulose in the cell wall of roots was increased. Furthermore, 160 μM MAN significantly reduced the water-extracted and ethanol-extracted Cd in roots, which are easily transported to shoots. In potted soil experiments using Cd-contaminated soil, MAN reduced the Cd content in wheat grain by 26.3%, compared with the control. These findings indicate that foliar spraying of 160 μM MAN resulted in less Cd being transported from roots to shoots by increasing the Cd retention in the cell wall and changing the Cd chemical forms in roots, which promoted wheat growth and reduced the Cd concentration in wheat grain.

Foliar spray of combined metal-oxide nanoparticles alters the accumulation, translocation and health risk of Cd in wheat (Triticum aestivum L.)

Nanotechnology is promising for improving sustainable crop production and ensuring food safety due to its unique properties and minimum environmental impacts. Here, we investigated the effectiveness of foliar combined metal-oxide nanoparticles (NPs, 100 mg/L) on cadmium (Cd) accumulation, translocation and exposure risk in wheat under field condition. Results showed that ZnO NPs combined with MgO or Fe3O4 NPs significantly increased the grain yield (13.8% and 14.8%) and straw biomass (16.9% and 18.4%) as compared to the control. Co-applied ZnO NPs with MgO, TiO2 or CeO2 NPs enhanced Cd uptake in aboveground wheat (12.4%−16.9%), while ZnO NPs combined with MnO2, CuO, Fe3O4 or Fe2O3 NPs remarkably reduced Cd concentration in wheat grains (23.8%−33.6%). According to the Cd bioaccessibility and daily intake, the health risk of Cd in wheat grains was significantly decreased by 36.1%−48.1% under ZnO NPs in combination with Fe3O4, Fe2O3, CuO or MnO2 NPs treatment. In addition, foliar spray of combined NPs also improved the nutritional quality of wheat grains by increasing micronutrients (Ca, S, Zn, Fe, B), protein content and reducing phytic acid content, especially in the combination of ZnO and MnO2 NPs. Taken together, this work demonstrates a feasible approach to achieve higher Cd removal efficiency and lower Cd levels and health risks in wheat grains with a tailored combination of metal-oxide NPs.

Foliar spray of silicon nanoparticles improved the growth and minimized cadmium (Cd) in wheat under combined Cd and water-limited stress.

The effects of foliar supply of silicon nanoparticles (Si-NPs) on growth, physiology, and cadmium (Cd) uptake by wheat (Triticum aestivum L.) were examined in different soil moisture levels. Seeds were sown in soil containing excess Cd (7.67mgkg-1) and Si-NPs were applied through foliar dressing with various levels (0, 25, 50, 100mg L-1) at different time intervals during growth period. Initially, all pots were irrigated with normal moisture level (70% water-holding capacity) and two moisture levels (35%, 70% WHC) were initiated after 6weeks of plant growth for remaining growth duration and harvesting was done after 124days of sowing. The results demonstrated the lowest plant growth, yield, and chlorophyll concentrations while the highest oxidative stress and Cd concentrations in plant tissues in water-stressed control (35% WHC) followed by normal control (75% WHC). Si-NPs enhanced the growth, photosynthesis, leaf defense system, and Si concentrations in tissues while minimized the Cd in wheat parts particularly in grains either soil normal or water-stressed conditions. Of the foliar spray, 100mg L-1 of Si-NPs showed the best results with respect to growth, Cd and Si uptake by plants, and soil post-harvest bioavailable Cd irrespective of soil water levels. In grain, Cd concentration was below threshold limit (0.2mgkg-1) for cereals in 100-mg kg-1 Si-NPs treatment irrespective of soil water levels. Si-NPs foliar dressing under Cd and water-limited stress might be an effective strategy in increasing growth, yield, and decreasing Cd concentration in wheat grains under experimental conditions. Thus, foliar dressing of Si-NPs minimized the Cd risk in food crops and NPs entry to surroundings, which might be possible after harvesting of crops in soil-applied NPs.

Cadmium concentrations in Idaho wheat grain and soil

AbstractCurrent efforts to reduce the maximum allowable cadmium (Cd) concentrations in wheat (Triticum aestivum L.) for at‐risk populations such as infants require sourcing wheat with low concentrations of Cd. Since Idaho (USA) is a major wheat supplier, there is a need to understand which varieties and locations in Idaho produce wheat containing low Cd. Therefore, the main objective of this paper is to report on a survey of total Cd concentrations in 469 wheat grain samples and 216 soil samples from several varieties and locations throughout Idaho. Total Cd concentrations in wheat grain ranged from <0.01 to 0.28 mg kg−1, varying by both wheat variety and location grown. Total soil Cd ranged from 0.450 to 1.85 mg kg−1. Bioaccumulation factor (BAF) was calculated by dividing the grain total Cd concentration by the soil total Cd concentration and ranged from 0.05 to 0.5. The variety ‘UI Sparrow’ had the lowest mean BAF (0.06), and several other varieties were also relatively low. Overall, almost all wheat varieties meet European Food Safety Authority (EFSA) requirements for Cd concentration for adult consumption. However, meeting the EFSA maximum allowable limit of Cd in infant food requires planting varieties noted for low Cd uptake, like UI Sparrow, and careful selection of growing regions with the lowest total soil Cd, such as northern, central, or western Idaho.

Foliar application of several reagents reduces Cd concentration in wheat grains.

Cadmium (Cd) in agricultural soils can be absorbed by wheat and transferred into the grains, risking human health. In order to find the optimal foliar treatment method to reduce Cd accumulation in wheat grain, nineteen single-factor foliar treatments and multi-factor combination treatments were used to study the effects of different foliar sprays on Cd accumulation of wheat grain. The results showed that the foliar application of ethylenediaminetetraacetate (EDTA), selenium (Se), and sodium nitroprusside (SNP) can significantly reduce Cd concentration in wheat grains by 49.2%, 29.6%, and 28.8%, respectively, in the field. Foliar application of EDTA, Se, zinc (Zn), ascorbic acid (ASC), silicon (Si), and molybdenum (Mo) can significantly reduce Cd concentration of wheat grains by 32.3%, 32.0%, 27.7%, 27.7%, 26.3%, and 25.9%, respectively, in pot experiment. Foliar application of 2 mM EDTA and 2 mM Se exerted excellent effects on controlling the Cd accumulation of wheat grains both in pot and field experiment. Foliar application with 0.1 mM Se or 2 mM EDTA significantly reduced Cd concentrations in grains both in grain filling stage and heading + grain filling stage. Spraying at the filling stage has a better effect on reducing Cd concentration in grains than spraying at the heading stage. In addition, the relationship between Cd concentration in grains and husks was significantly positive, while the Cd concentration in grains and flag leaves was significantly negative. Our research proves that foliar spraying of Se and EDTA is feasible to reduce the Cd concentration in wheat grains, which provides technical guidance for the safe production of wheat in low-Cd-contaminated soils.

Screening of Foliar Barrier Agents and Reduces the Absorption and Transport of Cd in Wheat.

Different foliar barrier agents (FBA) were used by foliar spraying in first season field and pot experiments to compare their effects on Cadmium (Cd) reduction in wheat grains. The best two FBA (50 µM SNP and 2 mM Na2EDTA) can significantly reduce Cd concentration in wheat grains, and the filling period was the most effective period for FBA application. Compared with the control (H2O), foliar spraying 50 µM SNP or 2 mM Na2EDTA inhibited the moving of Cd from the lower tissue to upper tissue in stem and also significantly reduced the Cd accumulation in grains. Furthermore, compared with normal wheat variety (AK58), foliar spraying 50 µmol SNP or 2 mM Na2EDTA as the best two FBA significantly reduced Cd concentration in shoots of Cd low accumulation varieties (HZB and HJBY), which can be used for the safe production of wheat in Cd-contaminated farmlands.

Ammonium-nitrogen addition at the seedling stage does not reduce grain cadmium concentration in two common wheat (Triticum aestivum L.) cultivars

High cadmium (Cd) concentration in common wheat (Triticum aestivum L.) grains poses potential health risks. Several management strategies have been used to reduce grain Cd concentration. However, limited information is available on the use of ammonium-nitrogen (NH4+-N) as a strategy to manage Cd concentration in wheat grains. In this study, NH4+-N addition at the seedling stage unchanged the grain Cd concentration in the high-Cd accumulator, Zhoumai 18 (ZM18), but dramatically increased that in the low-Cd accumulator, Yunmai 51 (YM51). Further analysis revealed that the effects of NH4+-N addition on whole-plant Cd absorption, root-to-shoot Cd translocation, and shoot-to-grain Cd remobilization were different between the two wheat cultivars. In ZM18, NH4+-N addition did not change whole-plant Cd absorption, but inhibited root-to-shoot Cd translocation and Cd remobilization from lower internodes, lower leaves, node 1, and internode 1 to grains via the down-regulation of yellow stripe-like transporters (YSL), zinc transporters (ZIP5, ZIP7, and ZIP10), and heavy-metal transporting ATPases (HMA2). This inhibition decreased the grain Cd content by 29.62%, which was consistent with the decrease of the grain dry weight by 23.26%, leading to unchanged grain Cd concentration in ZM18. However, in YM51, NH4+-N addition promoted continuous Cd absorption during grain filling, root-to-shoot Cd translocation and whole-plant Cd absorption. The absorbed Cd was directly transported to internode 1 via the xylem and then re-transported to grains via the phloem by up-regulated YSL, ZIP5, and copper transporters (COPT4). This promotion increased the grain Cd content by 245.35%, which was higher than the increased grain dry weight by 132.89%, leading to increased grain Cd concentration in YM51. Our findings concluded that the addition of NH4+-N fertilizer at the seedling stage is not suitable for reducing grain Cd concentration in common wheat cultivars.

Combined use of zinc nanoparticles and co-composted biochar enhanced wheat growth and decreased Cd concentration in grains under Cd and drought stress: A field study

Toxic metals present in soil and water severally affect the food crops and create serious health concerns. The current field study was focused on the impacts of foliar spray of zinc oxide nanoparticles (ZnO NPs) (100 mg/L) and soil applied co-composted biochar (0.5% w/w) on yield and cadmium (Cd) accumulation by grains of wheat ( Triticum aestivum L.) under simultaneous Cd and water limited stress. After 60 days of seeds sowing, drought stress was initiated in half plots by alternate irrigation compared to normal irrigation. Plants were harvested after 122 days and various physiological parameters were measured. Results showed that drought and Cd stress collectively decreased plant dry weight and chlorophyll contents and caused oxidative stress in leaves. While application of NPs and co-composted biochar improved the plants biomass and chlorophyll contents by overcoming the oxidative stress and alterating the antioxidants enzymatic activities in stressed plants. Combined application of NPs and co-composted biochar restricted the Cd uptake below its threshold level in grains (0.2 mg/kg). The current study concluded that the combination of ZnO NPs and co-composted BC was helpful to improve wheat growth and biomass, chlorophylls contents, antioxidant enzyme activities by scavenging ROS and reducing Cd uptake by plants under simultaneous Cd and drought stress. • Cadmium and drought stress inhibited wheat growth under field conditions. • NPs and co-composted biochar improved wheat growth and chlorophyll contents under stress. • The amendments enhanced activities of antioxidants enzymes in wheat plants. • The amendments reduced the Cd concentration in wheat grains.

Effects of foliar fungicide on yield, micronutrients, and cadmium in grains from historical and modern hard winter wheat genotypes.

Plant breeding and disease management practices have increased the grain yield of hard winter wheat (Triticum aestivum L.) adapted to the Great Plains of the United States during the last century. However, the effect of genetic gains for seed yield and the application of fungicide on the micronutrient and cadmium (Cd) concentration in wheat grains is still unclear. The objectives of this study were to evaluate the effects of fungicide application on the productivity and nutritional quality of wheat cultivars representing 80 years of plant breeding efforts. Field experiments were conducted over two crop years (2017 and 2018) with eighteen hard winter wheat genotypes released between 1933 and 2013 in the presence or absence of fungicide application. For each growing season, the treatments were arranged in a split-plot design with the fungicide levels (treated and untreated) as the whole plot treatments and the genotypes as split-plot treatments in triplicate. The effects on seed yield, grain protein concentration (GPC), micronutrients, phytic acid, and Cd in grains were measured. While the yield of wheat was found to increase at annualized rates of 26.5 and 13.0 kg ha-1 yr-1 in the presence and absence of fungicide (P < 0.001), respectively, GPC (-190 and -180 mg kg-1 yr-1, P < 0.001), Fe (-35.0 and -44.0 μg kg-1 yr-1, P < 0.05), and Zn (-68.0 and -57.0 μg kg-1 yr-1, P < 0.01) significantly decreased during the period studied. In contrast to the other mineral elements, grain Cd significantly increased over time (0.4 μg kg-1 yr-1, P < 0.01) in the absence of fungicide. The results from this study are of great concern, as many mineral elements essential for human nutrition have decreased over time while the toxic heavy metal, Cd, has increased, indicating modern wheats are becoming a better vector of dietary Cd.

Effects of mercapto-palygorskite on Cd distribution in soil aggregates and Cd accumulation by wheat in Cd contaminated alkaline soil

Cadmium (Cd) contamination in alkaline soils is a serious issue in China. As the basic structural units of soil, soil aggregates play an important role in the migration and transformation of heavy metal. However, there are few studies on the effects of adding amendments on Cd distribution in soil aggregates in alkaline soils. In this study, pot experiments were conducted to assess the effects of mercapto-palygorskite (MPAL) on soil aggregates and Cd accumulation in wheat. The results showed that MPAL application had no effect on wheat yield but significantly reduced the Cd uptake by the roots and the Cd transport to the adjacent internode. Application of 0.1% MPAL reduced the Cd concentration in two wheat grains (0.57 and 0.44 mg/kg, control) to 0.10 and 0.09 mg/kg in moderately Cd-contaminated soil, which are below the China national standard limit of 0.1 mg/kg (GB 2762-2017). MPAL application had no effect on soil pH, cation exchange capacity, mass proportion and mean weight diameter of soil aggregates, but increased soil organic matter content. Importantly, MPAL application promoted the migration of Cd from large particles (>0.25 mm) to small particles (<0.048 mm), reduced the unstable Cd fractions in >0.25 mm soil particles of clay soil and in >0.075 mm soil particles of sandy soil, and increased the stable Cd fractions in bulk soils and soil aggregates. The effects of MPAL addition on soil aggregates (grain size fraction metals loading and accumulation factor) of sandy soil were more prominent than on those of clay soil. Under MPAL treatments, wheat grains Cd concentration was significantly positively correlated with the available Cd in >0.075 mm soil particles and the total Cd in >0.25 mm soil particles. These results indicated that MPAL application in alkaline soils promoted the migration of Cd to micro-aggregates and inhibited the uptake and transport of Cd by wheat roots, thus reducing the Cd concentration in wheat grains.

Effects of node restriction on cadmium accumulation in eight Chinese wheat (Triticum turgidum) cultivars

Minimization of cadmium (Cd) accumulation in wheat is an effective method to prevent Cd-related health risks to humans. To understand the underlying mechanisms of restricting Cd transport, the role of nodes in Cd restriction was studied in eight Chinese wheat cultivars. The Cd accumulation differed significantly among the cultivars. The grain Cd concentrations were mainly dependent on the Cd concentrations in the roots and shoots. The Cd transport in the shoots controlled the wheat grain Cd accumulations. Nodes in the wheat stem have distinct functions in the transfer, distribution, and restriction of Cd. The node connected to the panicle showed the lowest translocation factors. The area of the vascular bundles, especially the diffuse vascular bundles, in the junctional node with the flag leaf was the key factor in restricting Cd transfer to the wheat grain. There was a significant relation between these areas and the grain Cd concentrations. The conclusion of this study is that screening or breeding cultivars with low Cd concentrations in the roots or with smaller areas of diffuse vascular bundles in the junctional nodes with the flag leaf is an effective strategy to decrease Cd concentration in wheat grains.

Health risk assessment of heavy metals in agricultural soils and identification of main influencing factors in a typical industrial park in northwest China

The accumulation of heavy metals (HMs) in the soil poses a threat to human health. In this study, 62 pairs of topsoil and wheat grain samples were collected from a typical industrial park in northwest China, and the human health risks associated with cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn) were assessed through multiple exposure pathways. Meanwhile, the contribution of different environmental factors and their interactions were explored by using geo-detector. Results showed that Cd concentration in the soil ranged from 0.307 to 2.491 mg kg−1, with a median value of 0.588 mg kg−1, and almost half of the samples exceeded the pollution threshold. In comparison, other elements in the soil were below their mandatory thresholds. However, it is noteworthy that in addition to the median Cd concentration in wheat grains of 0.062 mg kg−1 (0.018–0.246 mg kg−1), the Pb concentration also reached 0.2 mg kg−1 (0.1–0.7 mg kg−1), with a sample over-standard rate of 48.39%. In addition, the health risk assessment results showed that the average total hazard index (HIt) for adults and children was 1.22 and 1.53, and the total carcinogenic risk (TCRt) was 7.0 × 10−4 and 2.32 × 10−4, respectively, both above acceptable criteria. Dietary intake was the main route of exposure. Among various factors, distance from industrial enterprises, altitude, and soil pH, distance from major roads were the most influential contributors. Their interactions were more prominent than the effects of single factors and this synergy deserves attention.