Health risk assessment of bread wheat grown under cadmium and nickel stress and impact of silicic acid application on its growth, physiology, and metal uptake.

Heavy metal stress poses a significant threat to the productivity of agricultural systems and human health. Silicon (Si) is widely reported to be very effective against the different heavy metal stresses in crops. According to reports, it can help plants that are under cadmium (Cd) and nickel (Ni) stress. The presented work investigated how silicon interacted in Cd- and Ni-stressed wheat and mitigated metal toxicity. A pot experiment was carried out in which wheat crop was irrigated with Cd- and Ni-contaminated water. Application of Cd and Ni-contaminated water to wheat significantly reduced the root and shoot growth parameters and physiological and biochemical factors while increasing the antioxidant enzymatic activity and bioaccumulation of Cd and Ni metal in shoot and root as compared to the control. Application of Si led to an improvement in physiological parameters, i.e., greenness of leaves, i.e., SPAD values (17% and 26%), membrane stability (26% and 25%), and growth parameters i.e., root surface area (42% and 23%), root length (81% and 79%), root dry weight (456% and 190%), root volume (64% and 32%), shoot length (41% and 35%), shoot dry weight of shoot (111% and 117%), and overall grain weight (62% and 72%) under Cd and Ni stress, respectively. It increased the activity of antioxidant activity (max. up to 20%) whereas decreased the metal bioaccumulation of Cd and Ni in the roots and shoot (max. up to 62%) of wheat. It was concluded that the application of Si potentially increases antioxidant activity and metal chelation resulting in decreased oxidative damage and reducing the effect of Cd and Ni stress on wheat which improves growth and physiological parameters as well as inhibits Cd and Ni inclusion in food chain under Cd and Ni toxicity reducing health risks associated with these metals.

Cadmium and lead accumulation in important food crops due to wastewater irrigation: Pollution index and health risks assessment.

The contamination of farm soils with heavy metals (HMs) has raised significant concerns due to the increased bioavailability and accumulation of HMs in agricultural food crops. To address this issue, a survey experiment was conducted in the suburbs of Multan and Faisalabad to investigate the spatial distribution, bioaccumulation, translocation, and health risks of cadmium (Cd) and lead (Pb) in agricultural crops. The results show a considerable concentration of Cd and Pb in soils irrigated with wastewater, even though these levels were below the permissible limits in water and soil matrices. The pollution index for Cd was mostly greater than 1 at the selected sites, indicating its accumulation in soil over time due to wastewater irrigation. Conversely, the pollution index for Pb was below 1 at all sites. Among the plants, Zea mays accumulated the highest concentration of Cd and Pb. The translocation factor from soil to root was highest for Brassica olearecea (7.037 for Cd) and Zea mays (6.383 for Pb). The target hazard quotient (THQ) value of Cd exceeded the non-carcinogenic limit for most vegetables. The highest value was found in Allium cepa (5.256) and the lowest in Allium sativum (0.040). In contrast, the THQ level of Pb was below the non-carcinogenic limit for most vegetables, except for Allium cepa (1.479), Solanum lycopersicum (1.367), and Solanum tuberosum (1.326). The study highlights that Allium cepa poses the highest health risk for humans, while Medicago sativa poses the highest risk for animals due to Cd and Pb contamination. These results underscore the urgent need for effective measures to mitigate the health risks associated with HM contamination in crops and soils.

Divergent effects of cerium oxide nanoparticles alone and in combination with cadmium on nutrient acquisition and the growth of maize (Zea mays).

Introduction: The increasing use of cerium nanoparticles (CeO2-NPs) has made their influx in agroecosystems imminent through air and soil deposition or untreated wastewater irrigation. Another major pollutant associated with anthropogenic activities is Cd, which has adverse effects on plants, animals, and humans. The major source of the influx of Cd and Ce metals in the human food chain is contaminated food, making it an alarming issue; thus, there is a need to understand the factors that can reduce the potential damage of these heavy metals. Methods: The present investigation was conducted to evaluate the effect of CeO2-10-nm-NPs and Cd (alone and in combination) on Zea mays growth. A pot experiment (in sand) was conducted to check the effect of 0, 200, 400, 600, 1,000, and 2,000 mg of CeO2-10 nm-NPs/kg-1 dry sand alone and in combination with 0 and 0.5 mg Cd/kg-1 dry sand on maize seedlings grown in a partially controlled greenhouse environment, making a total of 12 treatments applied in four replicates under a factorial design. Maize seedling biomass, shoot and root growth, nutrient content, and root anatomy were measured. Results and discussion: The NPs were toxic to plant biomass (shoot and root dry weight), and growth at 2,000 ppm was the most toxic in Cd-0 sets. For Cd-0.5 sets, NPs applied at 1,000 ppm somewhat reverted Cd toxicity compared with the contaminated control (CC). Additionally, CeO2-NPs affected Cd translocation, and variable Ce uptake was observed in the presence of Cd compared with non-Cd applied sets. Furthermore, CeO2-NPs partially controlled the elemental content of roots and shoots (micronutrients such as B, Mn, Ni, Cu, Zn, Mo, and Fe and the elements Co and Si) and affected root anatomy.

Influence of ionic cerium and cerium oxide nanoparticles on Zea mays seedlings grown with and without cadmium.

Cerium (Ce4+) and cerium oxide nanoparticles (CeO2-NPs) have diversified reported effects on plants. Once dispersed in the environment their fate is not well understood, especially in co-existence with other pollutants like cadmium (Cd). The effect of co-application of Ce and Cd are reported in various studies, but the role of Ce source (ionic or bulk) and nanoparticle size is still unknown in cereal plants like maize (Zea mays). To better understand the synergistic effects of Ce and Cd, 500 mg kg-1 Ce coming from ionic (Ce4+ as CeSO4) and CeO2 nano sources (10 nm, 50 nm, and 100 nm) alone and in combination with 0.5 mg Cd kg-1 sand were applied to maize seedlings. Growth, physiology, root structure, anatomy, and ionic homeostasis in maize were measured. The results revealed that Ce4+ resulted in overall decrease in seedling growth, biomass and resulted in higher heavy metal (in control sets) and Cd (in Cd spiked sets) uptake in maize seedlings' root and shoot. The effects of CeO2-NPs were found to be dependent on particle size; in fact, under Cd-0 (non-Cd spiked sets) CeO2-100 nm showed beneficial effects compared to the control. While under co-application with Cd, CeO2-50 nm showed net beneficial effects on maize seedling growth parameters. The Ce alone, and in combination with Cd, altered the root suberin barrier formation. Both ionic and nano Ce sources alone and in co-existence with Cd behaved differently for tissue elemental concentrations (Ce, Cd, micronutrients like B, Mn, Ni, Cu, Zn, Mo, Fe and elements Co, Si) suggesting a strong influence of Cd-Ce coexistence on the element's uptake and translocation in maize.

Effect of soil texture and zinc oxide nanoparticles on growth and accumulation of cadmium by wheat: a life cycle study.

Cadmium (Cd) is getting worldwide attention due to its continuous accumulation in agricultural soils which is due to anthropogenic activities and finally Cd enters in food chain mainly through edible plants. Cadmium free food production on contaminated soils is great challenge which requires some innovative measures for crop production on such soils. The current study evaluated the efficiency of zinc oxide nanoparticles (ZnONPs) (0, 150 and 300 mg/kg) on the growth of wheat in texturally different soils including clay loam (CL), sandy clay loam (SCL), and sandy loam (SL) which were contaminated with were contaminated with 25 mg/kg of Cd before crop growth. Results depicted that doses of ZnONPs and soil textures significantly affected the biological yields, Zn and Cd uptake in wheat plants. The application of 300 mg/kg ZnONPs caused maximum increase in dry weights of shoot (66.6%), roots (58.5%), husk (137.8%) and grains (137.8%) in CL soil. The AB-DTPA extractable Zn was increased while Cd was decreased with doses of NPs depending upon soil textures. The maximum decrease in AB-DTPA extractable Cd was recorded in 300 mg/kg of ZnONPs treatment which was 58.7% in CL, 33.2% in SCL and 12.1% in SL soil as compared to respective controls. Minimum Cd concentrations in roots, shoots, husk and grain were found in 300 mg/kg ZnONPs amended CL soil which was 58%, 76.7%, 58%, and 82.6%, respectively. The minimum bioaccumulation factor (0.14), translocation index (2.46) and health risk index (0.05) was found in CL soil with the highest dose of NPs. The results concluded that use of ZnONPs significantly decreased Cd concentration while increased Zn concentrations in plants depending upon doses of NPs and soil textures.

Residual effects of frequently available organic amendments on cadmium bioavailability and accumulation in wheat.

Wheat (Triticum aestivum L.) cultivation in cadmium (Cd) polluted soil is a core concern to food quality and food security all over the world. Cadmium toxicity is mainly associated with a Cd influx from contaminated soils to human via grain consumption. Organic amendments are widely used for Cd immobilization and enhancement in plant growth, but the residual effects of these amendments are mostly unknown. The present study addressed the long-term effects of organic amendments in contaminated soils by evaluating their residual effects on 3rd crop (wheat) in the sequence. Initially six organic amendments viz. rice husk biochar (RHB), wheat-straw biochar (WSB), cotton-stick biochar (CSB), poultry manure (PM), press mud (PrMd) and farm manure (FM) were applied once at a rate of 2% in Cd (50 mg kg-1) contaminated soil with wheat-rice rotation. After the harvest of wheat and rice crops, wheat (Var. Galaxy) was again grown in the same pots. Results revealed that plants grown under Cd stress (without any amendment) contain more tissue (root, shoot and grain) and soil AB-DTPA extractable Cd. The soil amended with RHB has shown lowest AB-DTPA extractable Cd (69% lower than control). Similarly, RHB application has significantly reduced wheat root, shoot and grain Cd concentrations compared to control and other amendments. Results have confirmed the effectiveness of RHB residual contents as an active amendment for restriction of Cd in non-bioavailable pool of soil and better growth and yield of wheat.

Comparative effectiveness of different biochars and conventional organic materials on growth, photosynthesis and cadmium accumulation in cereals.

Although biochar and conventional organic materials have been widely studied for lowering cadmium (Cd) uptake by plants but information regarding their comparative effectiveness is lacking. In this study, biochars from different feedstocks viz. rice husk biochar (RHB), cotton sticks biochar (CSB) and wheat straw biochar (WSB) were compared with conventional organic materials viz. farm manure (FM), poultry manure (PM) and press mud (PrMd) for their effectiveness to promote plant growth and to reduce Cd uptake by wheat and rice plants grown rotationally in a Cd-spiked (50 mg kg-1) soil. Each amendment was applied at the rate of 2% (w/w) in three replicates. Results showed that the application of amendments improved the soil properties and plant growth, by retaining Cd in the soil and restricting its uptake by plants. The amendments decreased the ammonium bicarbonate diethylene penta acetic acid extractable soil Cd, and improved soil organic carbon (SOC) and cation exchange capacity (CEC) as compared to only Cd-contaminated soil. The highest SOC content of 2.68 and 1.68% and CEC of 8.77 and 9.39 cmolc kg-1 were found in RHB treated post-wheat and post-rice soil, respectively. Amendments treated soil showed lower concentrations of bioavailable Cd and the maximum reduction was recorded in RHB and PrMd amended soil. Similarly, bioaccumulation of Cd was decreased with the application of all amendments; the maximum decrease was recorded in RHB and PrMd treated soil. Our results suggested that RHB and PrMd could be used for reducing the bioaccumulation of Cd in cereal grains in alkaline soils.

Split application of silicon in cadmium (Cd) spiked alkaline soil plays a vital role in decreasing Cd accumulation in rice (Oryza sativa L.) grains.

Food contamination with cadmium (Cd) is a serious health threat to humans worldwide and Cd accumulation by rice is a major source of Cd entrance to the food chain. Silicon (Si) application decreases the Cd content in rice but the timing of Si application may need further investigation. The present study investigated the effect of split application of Si in the soil (600 kg/ha of Si) at different growth stages of rice on the growth and Cd accumulation by rice under Cd stress. Rice plants were grown in the presence and absence of Cd and Si was applied in the soil at different growth stages of rice under Cd stress. The results indicated that Cd stress alone reduced the growth and photosynthesis and increased the Cd content in different tissues and grains of rice. Silicon application improved the plant growth and reduced the Cd accumulation, translocation factor, and bioaccumulation factor in rice especially in grains, whereas the response of Si varied with the application of Si at different growth stages. The application of Si in three splits (transplanting (S1), tillering (S2), panicle initiation (S3)) was the best in improving growth and reducing Cd concentrations in plants compared to other combinations of Si application. Silicon application in three splits (S1+S2+S3) reduced the grain Cd concentrations below the threshold level (0.2 mg/kg) and reduced the Cd health risk index under the experimental conditions. Overall, split application of Si at three growth stages may function as remediator and diminishes Cd uptake into rice grains.