Cd Concentration In Grain Research Articles

Safe Utilization Effect of Passivator, Foliar Inhibitor, and Their Combined Application on Cadmium-contaminated Farmland

This study sought to explore the effects of passivator, leaf inhibitor, and their combination on cadmium （Cd）-contaminated farmland and to realize the safe utilization of cultivated land. Coconut shell biochar and calcium magnesium phosphate fertilizer were selected as soil passivators and foliar selenium fertilizer was used as a foliar inhibitor. The best combination was selected through a wheat-maize rotation experiment. The results showed that： ① The soil pH, organic matter content, and CEC could be improved to varying degrees by the application of passivators. ② The grain yield of wheat and maize increased to different degrees after the application of the passivator and foliar inhibitor. ③ The BFL treatment （biochar 1 800 kg·hm-2 +calcium magnesium phosphate 600 kg hm-2 + foliar inhibitor 3 L·hm-2） during the maize season had the best effect, which was significantly lower than that in CK by 13.85%. The effect of the BF treatment （biochar 1 800 kg·hm-2 + calcium magnesium phosphate 600 kg·hm-2） in wheat season was the best, which was significantly reduced by 11.21% compared with that in CK. ④ The BF treatment （biochar 1 800 kg·hm-2 + calcium magnesium phosphate 600 kg·hm-2） had the best effect on reducing Cd content in roots, straws, and grains of maize and wheat, reducing Cd content in roots of wheat and maize by 20.55% and 27.81%, Cd content in straws by 11.39% and 13.70%, and Cd content in grains by 48.97% and 50.44%, respectively. Therefore, considering all the indexes, the combination of passivators and foliar inhibitor, especially biochar combined with calcium magnesium phosphate fertilizer and biochar and calcium magnesium phosphate fertilizer combined with foliar inhibitor, could more effectively reduce the absorption, transport, and enrichment of Cd in maize and wheat and could be popularized and applied in safe use cultivated land.

Quantitative assessment of Cd sources in rice grains through Cd isotopes and MixSIAR model in a typical e-waste dismantling area of Southeast China

Identification of Cd sources and quantification of their contribution to rice grain Cd is crucial for controlling accumulation of this toxic metal in rice grains. However, accurate assessment of the contribution of different Cd sources to grain Cd concentration in rice under actual field conditions is a challenge. In this study, we determined Cd concentration and their isotopic compositions in rice grains with respect to three potential Cd sources around an e-waste dismantling area in Taizhou City, Zhejiang Province, China. Results demonstrated that average Cd concentrations in grains, surface soils, atmospheric deposition and surface water were 0.32, 0.91, 1.99 mg kg−1 and 2.02 μg L−1, respectively. The δ114/110Cd values of grains, surface soils, surface water and atmospheric deposition ranged from 0.00 ‰ to 0.31 ‰, −0.21 ‰ to 0.14 ‰, −0.04 ‰ to 0.47 ‰, and − 0.25 ‰ to −0.18 ‰, respectively. The MixSIAR model indicated that contribution of soils, irrigation water and atmospheric deposition to grain Cd was 56.8 %, 24.8 % and 18.4 %, respectively, demonstrating soils as the major source of grain Cd in the study area. This study also highlighted significant contribution of irrigation water and atmospheric deposition to Cd concentration in rice grains. The Cd isotopic analysis provides a practical approach for source apportionment of grain Cd and data support for controlling Cd accumulation in rice around the e-waste dismantling area.

Predicting Cd accumulation in crops and identifying nonlinear effects of multiple environmental factors based on machine learning models

The traditional prediction of the Cd content in grains (Cdg) of crops primarily relies on the multiple linear regression models based on soil Cd content (Cds) and pH, neglecting inter-factorial interactions and nonlinear causal links between external environmental factors and Cdg. In this study, a comprehensive index system of multi-type environmental factors including soil properties, geology, climate, and anthropogenic activity was constructed. The machine learning models of the tree-based ensemble, support vector regression, artificial neural network for predicting Cdg of rice and wheat based on the environmental factor indexes significantly improved the accuracy than the traditional models of linear regression based on soil properties. Among them, the tree-based ensemble models of XGboost and random forest exhibited highest accuracies for predicting Cdg of rice and wheat, with R2 in the test dataset of 0.349 and 0.546, respectively. This study found that soil properties, including Cds, pH, and clay, have greater impacts on Cdg of rice and wheat, with combined contribution rates accounting for 65.2 % and 29.7 % respectively. Since wheat sampling areas are located in central and northern China, they are more constrained by precipitation and temperature than rice sampling areas in the south. Geologic and climate factors have a greater impact on Cdg of wheat, with a combined contribution rate of 49.9 %, which is higher than the corresponding rate of 20.9 % in rice. Furthermore, the Cdg of rice and wheat did not exhibit an absolute linear relationship with Cds, and excessively high Cds can reduce the bioconcentration factor of Cd accumulation in crops. Meanwhile, other environmental factors such as temperature, precipitation, elevation have marginal effects on the increase of Cdg of crops. This study provides a novel framework to optimize traditional soil plant transfer models, as well as offer a step towards realizing high precision prediction of Cd content in crops.

Citric Acid Inhibits Cd Absorption and Transportation by Improving the Antagonism of Essential Elements in Rice Organs.

Excessive cadmium (Cd) in rice is a global environmental problem. Therefore, reducing Cd content in rice is of great significance for ensuring food security and human health. A field experiment was conducted to study the effects of foliar application of citric acid (CA) on Cd absorption and transportation in rice under high Cd-contaminated soils (2.04 mg·kg-1). This study revealed that there was a negative correlation between Cd content in vegetative organs and CA content, and that foliar spraying of CA (1 mM and 5 mM) significantly increased CA content and reduced Cd content in vegetative organs. The Cd reduction effect of 5 mM CA was better than that of 1 mM, and 5 mM CA reduced Cd content in grains and spikes by 52% and 37%, respectively. CA significantly increased Mn content in vegetative organs and increased Ca/Mn ratios in spikes, flag leaves, and roots. CA significantly reduced soluble Cd content in vegetative organs and promoted the transformation of Cd into insoluble Cd, thus inhibiting the transport of Cd from vegetative organs to grains. The foliar field application of 1 mM and 5 mM CA could inhibit Cd absorption and transportation by reducing Cd bioactivity and increasing the antagonistic of essential elements in rice vegetative organs. These results provide technical support and a theoretical basis for solving the problem of excessive Cd in rice.

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

This 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.

Determination of arsenic and cadmium uptake by rice from topsoil

AbstractTopsoil is the main sink of various pollutants and the direct source of heavy metal uptake by crops. In a 2‐year field experiment conducted in central China from 2016 to 2017, the significant role of topsoil in pollutant absorption, in particular the arsenic (As) and cadmium (Cd) uptake in rice was examined quantitatively. Two soil treatments, removing half of the topsoil (TR) and a control (CK), were applied alongside two rice varieties ‐ Huanghuazhan (HHZ, indica inbred) and Yangliangyou6 (YLY6, indica hybrid). On average, TR reduced the As and Cd concentrations in grain by 10.0% and 56.2%, respectively. The reduction was linked to lower pollutant concentrations in soil above the hardpan and rice straw. TR also decreased shoot As and Cd accumulation by 30.7% and 67.8% at maturity, with topsoil at 12–15 cm depth contributing an average of 2372 μg As m−2 (30.1%) and 138 μg Cd m−2 (66.1%) to total uptake of As and Cd, respectively. Contribution of topsoil to total As uptake remained consistent across growing stages, while for Cd, topsoil contributed 24.8% before heading and 81.2% after. Moreover, varietal differences were observed, with TR significantly reducing grain As and Cd concentrations of YLY6 but no difference in HHZ. This study quantifies topsoil's impact on As and Cd uptake in rice, and underscores genotypic variations in their response to topsoil removal.

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.

Effects of foliar application of Zn combined with organic matters on Cd accumulation and its chemical forms in rice.

Rice consumption is a key Cd exposure pathway, which poses a health risk to humans. Reducing cadmium (Cd) concentrations in rice remains challenging. In this study, a pot experiment was conducted to examine the effects of foliar spray of Zn combined with organic matters (including Zn-lysine (Zn-Lys), Zn-fulvic acid (Zn-FA), Zn-amino acid (Zn-AA), and Zn combined with glutathione (Zn + GSH)) on Cd accumulation in rice grains. Compared with the control group, all treatment groups exhibited reduced Cd concentration in rice grains, while improving plant growth, and reducing Cd transport from other tissues to the grains. Zn-FA was found to be the most effective fertilizer, which considerably reduced Cd concentrations in grains from 0.77 ± 0.068 to 0.14 ± 0.021mg/kg and yielded reductions of up to 81%, which is within the Chinese food maximum tolerable limit of 0.2mg/kg. Furthermore, the analysis of the chemical forms of Cd of rice tissues indicated that the treatment groups had increased proportions of integrated with pectates and protein in the stems. Except for the group treated with Zn-Lys spray, the percentages of undissolved Cd phosphate in the leaves were increased in all treatment groups, which reduced Cd toxicity to rice plants. The foliar application of Zn combined with organic matters may be a promising strategy to decrease Cd concentration in rice grains cultivated in severely Cd-contaminated agricultural soil, particularly in the karst area in southwest China with limited available cultivable agricultural land.

Overexpression of vacuolar transporters OsVIT1 and OsVIT2 reduces cadmium accumulation in rice.

Excessive cadmium in rice grain in agricultural production is an important issue to be addressed in some southern regions of China. In this study, we constructed transgenic rice overexpressing OsVIT1 and OsVIT2 driven by 35S promoter in the cultivar ZH11. Compared with ZH11, OsVIT1 expression in leaves was significantly increased by 3-6.6 times and OsVIT2 expression in leaves was significantly increased by 2-2.5 times. Hydroponic experiments showed that overexpression of OsVIT1 and OsVIT2 increased the tolerance to Fe deficiency, significantly reduced Cd content in shoot and xylem sap, and had no effect on Cd tolerance in rice. Two years of field trials showed that the Fe content in the grain of OsVIT1 and OsVIT2 overexpressed materials was significantly reduced by 20-40% and the straw Fe content was significantly increased by 10-45%, and the grain Fe content distribution ratio was significantly decreased and the straw Fe distribution ratio was significantly increased compared with the wild type. The OsVIT1 and OsVIT2 overexpressed materials significantly reduced the Cd content of grain by 40-80% and the Cd content of straws by 37-77%, and the bioconcentration factor of Cd was significantly reduced in both grains and straw of OsVIT1 and OsVIT2 overexpressed materials. Overexpression of OsVIT1 and OsVIT2 did not affect the concentration of other metal ions in rice straw and grain. qRT-PCR analysis showed that the expression of the low affinity cation transporter OsLCT1 was significantly downregulated in the OsVIT1 and OsVIT2 overexpressed materials. In conclusion, overexpression of OsVIT1 and OsVIT2 reduced Cd accumulation in straw and grains, providing a strategy for Cd reduction in rice.

Genetic engineering low-arsenic and low-cadmium rice grain.

Rice is prone to take up the toxic elements arsenic (As) and cadmium (Cd) from paddy soil through the transporters for other essential elements. Disruption of these essential transporters usually adversely affects the normal growth of rice and the homeostasis of essential elements. Here we report on developing low-As and low-Cd rice grain through the co-overexpression of OsPCS1, OsABCC1, and OsHMA3 genes under the control of the rice OsActin1 promoter. Co-overexpression of OsPCS1 and OsABCC1 synergistically decreased As concentration in the grain. Overexpression of OsPCS1 also decreased Cd concentration in the grain by restricting the xylem-to-phloem Cd transport in node I, but paradoxically caused Cd hypersensitivity as the overproduced phytochelatins in OsPCS1-overexpressing plants suppressed OsHMA3-dependent Cd sequestration in vacuoles and promoted Cd transport from root to shoot. Co-overexpression of OsHAM3 and OsPCS1 overcame this suppression and complemented the Cd hypersensitivity. Compared with non-transgenic rice control, co-overexpression of OsABCC1, OsPCS1, and OsHMA3 in rice decreased As and Cd concentrations in grain by 92.1% and 98%, respectively, without causing any defect in plant growth and reproduction or of mineral nutrients in grain. Our research provides an effective approach and useful genetic materials for developing low-As and low-Cd rice grain.

Effect of green-synthesized copper oxide nanoparticles on growth, physiology, nutrient uptake, and cadmium accumulation in Triticum aestivum (L.)

Cadmium (Cd) stress in crops has been serious concern while little is known about the copper oxide nanoparticles (CuO NPs) effects on Cd accumulation by crops. This study investigated the effectiveness of CuO NPs in mitigating Cd contamination in wheat (Triticum aestivum L.) cultivation through a pot experiment, presenting an eco-friendly solution to a critical agricultural concern. The CuO NPs, synthesized using green methods, exhibited a circular shape with a crystalline structure and a particle size ranging from 8 to 12 nm. The foliar spray of CuO NPs was applied in four different concentrations i.e. control, 25, 50, 75, 100 mg/L. The obtained data demonstrated that, in comparison to the control group, CuO NPs had a beneficial influence on various growth metrics and straw and grain yields of T. aestivum. The green CuO NPs improved T. aestivum growth and physiology under Cd stress, enhanced selected enzyme activities, reduced oxidative stress, and decreased malondialdehyde levels in the T. aestivum plants. CuO NPs lowered Cd contents in T. aestivum tissues and boosted the uptake of essential nutrients from the soil. Overall, foliar applied CuO NPs were effective in minimizing Cd contents in grains thereby reducing the health risks associated with Cd excess in humans. However, more in depth studies with several plant species and application methods of CuO NPs are required for better utilization of NPs in agricultural purposes.

Maize straw application reduced cadmium and increased arsenic uptake in wheat and enhanced the rhizospheric bacterial communities in alkaline-contaminated soil

Many fields where wheat is grown in northern China are co-polluted by arsenic (As) and cadmium (Cd). Thus, remediation of As and Cd-contaminated alkaline soils is crucial for safe wheat production. In this study, a pot experiment was carried out to investigate the impact of 1% and 2% maize straw (MS) incorporation on As and Cd bioavailability, binding forms, uptake by winter wheat (Triticum aestivum L.), and bacterial communities in smelter (SS) and irrigation (IS) alkaline contaminated soils. The results indicated that 2% MS incorporation significantly (p < 0.05) increased bioavailable-As by 37% (SS) and 39% (IS) with no significant change in the bioavailable-Cd in SS2% (31.95%) from 31.95% (SSCK) and IS2% (33.33%) from 32.82% (ISCK). Incorporation of 2% MS increased the grain As concentration from 0.22 mg kg−1 (SSCK) to 0.51 mg kg−1 (SS2%) and from 0.59 mg kg−1 (ISCK) to 0.84 mg kg−1 (IS2%) which is above the acceptable standard of 0.5 mg kg−1 (GB2726-2017). In contrast, the Cd content in grains was maintained at 0.09 (SS1%), 0.04 (SS2%) and 0.03 (IS1%), 0.02 (IS2%) below the acceptable standard of 0.10 mg kg−1 (GB2762–2017). The amendment through dissolved organic carbon mediated As desorption enhanced As transfer to wheat grain, decreasing DTPA-Cd in the soils and its consequent translocation to wheat leaves and grain. The 2% MS incorporation increased the active As fractions, reduced mobile Cd into immobile fractions, and promoted the abundance of Actinobacteria, Bacteroidetes, and Firmicutes in the two soils. These attributes of MS in decreasing the accumulation of Cd in wheat leaves and grains signified its potential as a suitable ingredient for Cd sequestration and food safety in Cd-contaminated soils.

Phytoavailability of cadmium in rice amended with organic materials and lime: Effects of rhizosphere chemical changes and cadmium sequestration in iron plaque

Excessive Cd in rice grains produced with acidic paddy soil is receiving increasingly widespread attention because it endangers human health. Applying organic materials (OM) and lime (L) is a common technique used to reduce Cd concentration in grains (CdG). Nevertheless, the mechanism by which their simultaneous application affects the Cd phytoavailability in soilrice systems remains ambiguous. In the current study, we adopted a rhizobag pot culture test to explore the influences of single application of OM [rice straw (RS), milk vetch (MV)], L, and their co-utilization on Cd phytoavailability and the associated mechanisms. The results showed that the application of RS, MV, L, L + RS (LRS), and L + MV (LMV) significantly decreased CdG by 26.9%, 38.2%, 48.6%, 50.0%, and 53.0%, respectively. Fe plaque (IP) formation was not affected by these treatments; however, Cd sequestration in IP (CdIP) was significantly reduced. CdIP was significantly reduced by 18.3%, 23.6%, 43.8%, 33.1%, and 41.4%, after RS, MV, L, LRS, and LMV treatments, respectively. Additionally, available Cd concentrations in rhizospheric soil (RHS) were significantly reduced by 11.5%, 14.8%, 15.1%, and 18.4%, after MV, L, LRS, and LMV treatments, respectively. Cd availability in RHS was significantly influenced by pH, dissolved organic carbon concentration, and Zn, Fe, and Mn availability. The results of the structure equation mode showed that CdG was mainly affected by CdIP, followed by Cd availability and the pH of RHS. In conclusion, the reduction of CdG by OM, L, and their co-utilization was the results of their combined effects of reducing Cd availability in RHS, CdIP, and Cd uptake by the roots. This study emphasizes that the reduction of CdG is a result of the dual effects of reducing Cd availability in RHS and CdIP after amendments application. L application alone or in conjunction with OM is an efficient practice to reduce CdG in acidic Cd-contaminated paddy fields.

Low Accumulation Characteristics of Sweet-waxy Maize in Pb and Cd Complex Contaminated Soils Based on Field Trials

To screen out sweet-waxy maize varieties with low accumulation characteristics suitable for planting in lead (Pb) and cadmium (Cd) complex contaminated soils, 39 maize varieties were selected, and the enrichment characteristics and differences of grains and straws on Pb and Cd were studied through field trials. Maize yield, bioaccumulation factors, and soil Pb and Cd risk thresholds were used as evaluation indicators for screening low accumulation maize varieties. The results showed that there were significant differences between the yield and Pb and Cd contents in grains and straws of different varieties of maize (P<0.05). Bioaccumulation factors of grains for Pb and Cd were in the range of 0.00003-0.00230 and 0.01-0.15, respectively, and those of straws for Pb and Cd were in the range of 0.003-0.065 and 0.64-4.28, respectively. Through the cluster analysis of bioaccumulation factors, the soil Pb and Cd risk thresholds of different varieties of maize were comprehensively obtained:Huitian 5, Xinmeitian 818, and Yunuo 9 could be safely produced in the farmland with Pb and Cd content exceeding the risk control value, and Tianguinuo 937 and Jinwannuo 2000 could be safely produced in the farmland with Cd content exceeding the risk screening value. Huitian 5, Xinmeitian 818, and Yunuo 9, as low Pb and Cd accumulation varieties, were suitable to be popularized on Pb and Cd polluted soil in Guangxi, China. Tianguinuo 937 and Jinwannuo 2000, as low grain and high Cd accumulation varieties, are suggested to be used as phytoremediation resources.

Effects of soil amendments and foliar selenium applications on soil cadmium immobilization and wheat accumulation

Wheat cadmium (Cd) contaminationis one of the environmental and agricultural concerns worldwide. Here, the effects of foliar selenium (Se) and soil amendments (lime, biofuel ash and sodium sulfide (DSO), iron mine tailing and alkali lignin (MX)) applications on the soil Cd fractions and wheat Cd accumulations were studied by incubation, greenhouse pot, and field plot experiments. The results showed that in soil incubation experiment, lime and MX applications significantly increased soil pH and DSO applications significantly decreased soil pH, while all the three amendments can significantly reduce the available Cd fractions by 16-21%. Foliar spraying can significantly increase the growth and yield of the high-Cd-accumulating-cultivar (Puxing5). In the greenhouse experiment, lime and MX applications considerably decreased grain Cd concentrations by 53-56% and 41-52% for Puxing5 and by 9-38% and 23-28% for Zhoumai30, respectively. In the field experiment, the Cd concentrations were significantly reduced by 67-69% and 69-74% in Puxing5 grain by lime and MX applications, respectively. DSO applications also significantly reduced Cd concentrations in grains by 56-59% for Puxing5 and by 22-27% for Zhoumai30 in the greenhouse experiment, but in contrast, increased Cd concentrations in field experiment by 20-23%. Our results implicate that the incubation and greenhouse experiments are necessary to be verified in the field and the foliar Se application is recommended when considered both the financial costs and production safety.

Silicon inhibits the upward transport of Cd in the first internode of different rice varieties in a Cd stressed farm land

Silicon spraying on leaves can reduce the accumulation of cadmium (Cd) in rice grain. However, it has been found that not all rice varieties decrease in Cd content after silicon (Si) application. A field study was conducted to check the performance of Si on the accumulation and transport of Cd in four rice varieties. TY390 and YXY2, having 51.5%− 60.6% Cd content of grain was inhibited by foliar Si, were classified as CRS varieties; BXY9978 and YXYLS, having Cd content of grain is nonresponsive with Si, were classified as CNS varieties. The Cd contents were mainly accumulated in stem, especially in the first stem node. While foliar Si reported no changes in the Cd content of first node in four different rice varieties. Comparing the correlation between Si and Cd contents in the above part of the first internode of CRS and CNS, as well as the relative expression of Cd transport genes in the first internode suggested that first internode was the key site to effect Cd transport through Si application, and OsZIP7 is a key Cd transporter protein responsive to Si, leading to different response of Cd transport and accmulation between the CRS and the CNS varieties of rice.

Mitigation of heavy metal stress in maize (Zea mays L.) through application of silicon nanoparticles

The ability of silicon to increase plant resistance to abiotic stress is well recognised, but less well known is the ability of silicon nanoparticles (SiNPs) to diminish abiotic stress. In this study, therefore, we compared the effect of sodium silicate and SiNPs on plant growth, biomass, pigments, soluble protein, proline, oxidative stress, antioxidant enzymes, and Cd accumulation in maize grown in cadmium (Cd) contaminated soil in a pot experiment arranged in randomized complete block design. Soils were contaminated with varying concentrations of Cd (0, 25, and 50 mg/kg). SiNPs showed specific agglomerated structure having remarkable surface area for nutrients adsorption. Cd stress caused a significant reduction in agronomic attributes by enhancing oxidative stress. Conversely, foliar spraying of Si and SiNPs significantly overcomes the Cd-induced decline in maize plants. Si and SiNPs significantly enhanced the agronomic and physiological attributes of maize by upregulating the activities of SOD, POD, CAT, and APX and reducing the MDA and H2O2 contents under Cd stress. Si significantly reduced the Cd contents in grains by 60.6% (TE) and 43.2% (TF) under Cd 25 and 50 mg/kg stress, respectively, whereas SiNPs decreased the Cd contents in grains by 62.2% (TH) and 48.7% (TI) under Cd 25 and 50 mg/kg stress, respectively. It was noted that the individual delivery of Si and SiNPs had no statistically significant influence on the protective nature. Thus, foliar application of both forms of silicon might be helpful in enhancing plant resilience under Cd stress conditions.

Multi-Target Element-Based Screening of Maize Varieties with Low Accumulation of Heavy Metals (HMs) and Metalloids: Uptake, Transport, and Health Risks

Mitigating heavy metals (HMs) contamination and ensuring the safe production of crops is of paramount importance for sustainable agriculture development. The purpose of the current field plot study was to select maize varieties with low HMs and metalloids in their edible parts but high accumulation in other parts. The cadmium (Cd), arsenic (As), lead (Pb), and chromium (Cr) contents of 11 maize varieties were measured by atomic absorption spectrometry, and the plant growth and bioconcentration factors (BFs) were examined. Furthermore, the average daily intake (ADDi) of HMs in maize grains was calculated to assess the associated health risks. The results revealed that the growth of variety TZ23 was minimally impacted HMs and metalloids. The grains of all of the tested maize varieties contained Cr, As, and Pb contents in accordance with National Food Safety Standards (NFSSs, GB2762-2017, ≤0.1 mg·kg−1), while the Cd concentration in grains of varieties QJN1, LSCR, and JN20 were 0.084 mg·kg−1, 0.094 mg·kg−1, and 0.077 mg·kg−1, respectively, in accordance with NFSSs. The translocation factor (TF) of As, Pb and Cr in the grains of 11 maize varieties were found to be less than 1. However, the TF of grain Cd in varieties LYN9, JYN9, and QJN3 exceeded 1. For varieties HNY21, TZ23, and LYN9, the TF of Cd, As, Pb, and Cr in the stems/leaves was less than 1. Cluster analysis revealed that the grains of variety HNY21 had the lowest accumulation capacity of all four HMs. Importantly, the variety JN20 exhibited a high accumulation capacity for Pb and a low capacity for As, while both varieties SKN11 and QJN3 had high accumulation capacities for Cd and low capacities for As. Health risk (HR) indices of the different age groups displayed an overall trend of children &gt; elderly &gt; young adult. Among the HMs and metalloids, Cd and Cr pose the greatest health risks of maize intake. Variety QJN3 posed a significant HR due to chronic toxicity. This study provides a scientific basis for multi-element pollution control and screening of maize varieties suitable for cultivation in mining areas and the remediation of HMs-contaminated soils.

Effect of Ca–modified biochar coupling with low–Cd accumulation maize cultivars on remediation of Cd contaminated soils and microbial community composition

To investigate the remediation efficiency of Ca–modified biochar (CBC) coupling with low cadmium (Cd)–accumulation cultivars on weakly alkaline Cd–contaminated farmland, a field experiment was conducted to explore the distribution of Cd in soil aggregates, Cd uptake in maize (Zea mays L.) grain, and soil microbial communities. Our results showed that treatments of CBC were observed to reduce available Cd in the bulk soil and soil aggregates by 12.09–16.20 % and 3.67–24.72 %. The grain size fraction metals loading (GSFloading) and distribution factors (DFx) analysis showed that Cd was preferentially enriched on fine particle fractions in soil, and CBC promoted the redistribution of Cd from micro–aggregates to macro–aggregates. Compared with the control group, Cd content in grains of low–Cd varieties of Liyu16 and Sanbei218 after the addition of CBC was significantly reduced by 37.55–50.80 % and 23.60–51.20 %, respectively. High–throughput sequencing results indicated that the microbial community structure and composition changed significantly after the addition of CBC, which were characterized by a significant increase in the number of operational taxonomic units (OTUs), the alpha diversity indices (including Shannon, Chao1 and ACE indies) and the abundance of the dominant phylum. The above results showed that the management of combining CBC and low Cd accumulation maize should be an efficient way to remediate weakly alkaline Cd contaminated soils, associated with ensuring of grain production safety and improvement of soil eco–environment function.

Effect of titanium dioxide nanoparticles and co-composted biochar on growth and Cd uptake by wheat plants: A field study

Cadmium (Cd) is a common toxic trace element found in agricultural soils which is mainly due to anthropogenic activities. Cadmium posed a significant risk to humans all around the world due to its cancer-causing ability. The current study demonstrated the effects of soil-applied biochar (BC) and foliar-applied titanium dioxide nanoparticles (TiO2 NPs) (at a rate of 0.5% and 75 mg/L respectively) alone or in combination on growth and Cd accumulation in wheat plants under field experiment. Soil applied BC and foliar TiO2 NPs, as well as BC coupled with TiO2 NPs, reduced Cd contents in grains by 32%, 47%, and 79%, than control respectively. The usage of NPs and BC boosted the plant height as well as chlorophyll contents by lowering oxidative injury and changing selected antioxidant enzyme activities in leaves than control plants. The combined use of NPs and BC prevented excess Cd accumulation in grains over the critical level (0.2 mg/kg) for cereals. The health risk index (HRI) due to Cd was reduced by 79% by co-composted BC + TiO2 NPs treatment than control. Although, HRI was lower than one for all treatments but this may exceed the limit if grains obtained from such field consumed over long periods. In conclusion, TiO2 NPs and BC amendments can be implemented in fields across the globe where excess Cd is present in soils. Additional studies on the use of such approaches in more precise experimental settings are needed in order to address this environmental problem at larger scale.