Extractable Cd Research Articles

Machine learning-based identification of critical factors for cadmium accumulation in rice grains.

The aggregation of Cadmium (Cd) in rice grains is a significant threat to human healthy. The complexity of the soil-rice system, with its numerous influencing parameters, highlights the need to identify the crucial factors responsible for Cd aggregation. This study uses machine learning (ML) modeling to predict Cd aggregation in rice grains and identify the influencing factors. Data from 474 data points from 77 published works were analyzed, and eight ML models were established using different algorithms. The input variables were total soil Cd concentration (TS Cd) and extractable Cd concentration (Ex-Cd), while rice Cd concentration (Cdrice) was the output variable. Among the models, the Extremely Randomized Trees (ERT) model performed the best (TS Cd: R2 = 0.825; Ex-Cd: R2 = 0.792), followed by Random Forest (TS Cd: R2 = 0.721; Ex-Cd: R2 = 0.719). The ERT feature importance ranking analysis revealed that the essential factors responsible for Cd aggregation are cation exchange capacity (CEC), TS Cd, Water Management Model (WMM), and pH for total soil Cd as input variables. For extractable Cd as an input variable, the vital factors are CEC, Ex-Cd, pH, and WMM. The study highlights the importance of the Water Management Model and its impact on Cd concentration in rice grains, which has been overlooked in previous research.Please check and confirm that the authors and their respective affiliations have been correctly identified and amend if necessary.The authors and their respective affiliations are correct.Author details: Kindly check and confirm whether the corresponding author is correctly identified.It is correct.

Tomato sprayed monocalcium phosphate had production-phytoremediation dual function with high soil Cd extraction and safer fruit production

In order to make use of the large biomass of tomato plant to fulfill the purpose of remediating-while-producing, two commercial tomato varieties, ‘Baiguoqiangfeng’ (BG) and ‘Ouguan’ (OG) were grown in Cd contaminated acidic soil to compare their performance on Cd phytoextraction, and monocalcium phosphate (Ca) was foliar applied to reduce their fruit Cd concentration. The results showed that the BG was a more Cd tolerant variety, comparing with OG, it suffered lighter tissue peroxidation and photosynthesis obstacle, owning weaker amino acid metabolism, secondary metabolism and stress signal transduction under Cd stress. The Ca application reduced its ABA level but increased the GSH, IAA, ZR and GA3 level, and enhanced its lysine degradation, tyrosine metabolism, alanine, asparagine and glutamate metabolism, plant hormone signal transduction and phenylpropanoid biosynthesis under Cd stress. With these metabolic regulations, the Ca application promoted its leaf biomass accumulation, guaranteeing the total Cd extraction amount (0.88 mg pot−1 as 0.20 mg kg −1), and reduced the fruit Cd partition, decreasing the fruit Cd concentration by 71.4% with higher yield. Meanwhile, the OG had lower Cd phytoextraction capacity than the BG, and Ca spray enhanced its cell energy generation, flavonoids biosynthesis and photosynthetic carbon fixation, but had no effect on fruit Cd concentration. The two tomato varieties had different responses to Ca application under Cd stress in their hormone signaling, energy metabolism, secondary metabolism and amino acids metabolism, which furtherly differed their Cd phytoextraction capacity and production safety. Therefore, the monocalcium phosphate spray combined ‘Baiguoqiangfeng’ tomato realized the dual function of production-phytoremediation, and the mechanism of plant Cd sensitivity adjustment through phenylpropanoid biosynthesis and amino acids metabolism deserved further study.

Optimizing multi-surface modelling of available cadmium as measured in soil pore water and salt extracts of soils amended with compost and lime: The role of organic matter and reactive metal

The effectiveness of strategies to reduce cadmium (Cd) availability for crop uptake can be assessed using various measures of Cd availability, such as Cd concentration in pore water and Cd extracted with salt solutions. This study evaluated the performance of multi-surface modelling (MSM) to predict dissolved Cd in two Irish tillage soils treated with lime, zinc (Zn) and spent mushroom compost (SMC). Predictions were assessed against Cd measured in three solution media, i.e., 1 mM Ca(NO3)2 and 0.1 M CaCl2 extractions, as well as in soil pore water. Results indicate that reactive soil organic matter (SOM) may be underestimated using a single 0.1 M NaOH extraction in the investigated soils, leading to substantial overestimation of dissolved Cd by MSM, particularly at higher pH. Repeating the 0.1 M NaOH extraction three times substantially improved model predictions. Additionally, using reactive Cd determined by isotopic dilution instead of 0.43 M HNO3 improved model predictions for one of the soils that was rich in manganese (Mn) oxides, revealing a possible role of Mn oxides in determining the reactive Cd fraction. After optimizing reactive SOM and reactive Cd, residuals between predicted and measured Cd showed an increasing trend along with increasing solution pH and decreasing dissolved Cd. This is likely related to Cd binding to high affinity sites due to uncertainties in the binding parameters for these sites and/or to slow desorption kinetics for Cd bound to these sites. Despite significant variations in solution properties, including higher dissolved Ca and reactive dissolved organic matter (DOM), 1 mM Ca(NO3)2 extracts exhibited similar extractable Cd levels, model performance, and Cd speciation compared to soil pore water especially at higher pH. Thus, 1 mM Ca(NO3)2 can be a reliable proxy for soil pore water in assessing Cd availability for crop uptake in soils with circumneutral to alkaline pH.

Enhanced phytoremediation of Cd-contaminated soil by Solanum nigrum L. through the addition of earthworm and organic wastes

BackgroundPhytoremediation is considered to have great development potential to deal with soil Cd contamination, and assisted measures are necessary to improve the efficiency of Cd extraction from soil by hyperaccumulator plants. Based on this, a pot experiment was conducted to determine the growth indices, physiological indices, Cd content of Solanum nigrum L. and soil bacterial community under single and combined application of earthworm and organic wastes [chili straw and spent mushroom substrate (SMS)].ResultsPot experiments revealed that adding earthworms, chili straw, or SMS alone did not affect the growth of S. nigrum. However, the combination of earthworms + chili straw and earthworms + SMS, significantly increased the total dry weight of S. nigrum by 20.94% and 74.69% compared to the control. The chlorophyll content of S. nigrum in the treatment groups with earthworms, SMS, and earthworms + SMS was also significantly higher than that in the control. Meanwhile, adding earthworms and organic wastes also reduced the malondialdehyde content in the leaves of S. nigrum and increased the activity of superoxide dismutase and peroxidase. In addition, applying earthworm + chili straw and earthworm + SMS also increased the availability of Cd in the soil, promoted the absorption of Cd by S. nigrum, and significantly increased its total extraction amount of Cd by 41.55% and 92.83%, respectively. The diversity of soil bacterial communities increased when earthworms and organic wastes coexisted. Adding earthworms and organic wastes also increased the relative abundance of Verrucomicrobia at the phylum level and of Sphingomonas, Ohtaekwangia, Saccharibacteria_genera_incertae_sedis, and Aridibacter at the genus level in the soil. At the same time, this process reduces the relative abundance of Proteobacteria and Firmicutes at the phylum level and Devosia and Bacillus at the genus level.ConclusionsThe combined application of earthworms and SMS enhanced phytoextraction of Cd-contaminated soil by S. nigrum. It also improved soil nutrient conditions and reduced external environmental stress on bacteria, increasing their diversity and restructuring the community structure, which was conducive to forming a good soil microecological environment. The results of this study can provide a scientific basis for the treatment of Cd contaminated soil, but field experiments need to be conducted for verification and optimization before practical application in the future.Graphical

Removal, mechanistic and kinetic studies of Cr(VI), Cd(II), and Pb(II) cations using Fe3O4 functionalized Schiff base chelating ligands.

The Schiff base chelating ligands; (E)-2-(3,3-dimethoxy-2-oxa-7,10-diaza-3-silaundec-10-en-11-yl)phenol (L1), (E)-N-(2-((pyridine-2ylmethylene)amino)ethyl)-3-(trimethoxysilyl)propan-1-amine (L2) and (E)-N-(2-((thiophen-2-ylmethylene)amino)ethyl)-3-(trimethoxysilyl)propan-1-amine (L3) were immobilized on Fe3O4 magnetic nanoparticles (MNPs) and utilized in the extraction of Cr(VI), Cd(II) and Pb(II) metal cations from aqueous solutions. The compounds synthesized, denoted as L1@ Fe3O4, L2@Fe3O4, and L3@Fe3O4, were characterized using FT-IR spectroscopy, TEM-SEM, VSM, and BET/BHJ techniques for analysis of functional groups, surface morphology, magnetic properties, and degree of porosity of the adsorbents, respectively. BET/BHJ technique confirmed the mesoporous nature of the compounds as their pore diameters ranged between 15 and 17nm. The initial optimization conditions of pH, adsorbent dosage, initial metal concentration, and contact time on adsorption were studied using L1@ Fe3O4. The optimum efficiencies recorded were 68% and 46% for Cr(VI) and Cd(II), respectively, obtained at pH 3, and a metal concentration of 20ppm while an efficiency of 99% was recorded for Pb(II) cations at pH 7 and a metal concentration of 100ppm. Compounds L2@Fe3O4 and L3@ Fe3O4 were also used in the extraction of metal cations from aqueous solution and gave efficiencies of 22%, 56%, and 78% for L2@ Fe3O4 and 19%, 90%, and 59% using L3@ Fe3O4 for Cr(VI), Cd(II), and Pb(II), respectively. The maximum adsorption capacities of L1@ Fe3O4 for Cr(VI), Cd(II), and Pb(II) cations were obtained from the Langmuir isotherm as 32.84, 41.77, and 450.45mg/g, respectively. The experimental data was analyzed using pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich kinetic models. Both linear and non-linear forms of kinetic isotherms; Langmuir, Freundlich, Redlich-Peterson, and Temkin were utilized to investigate the nature of adsorption on L1@Fe3O4. The mechanistic studies deduced that the Langmuir isotherm and pseudo-second-order kinetic model better described the adsorption process both yielding high correlation coefficient values (R2 > 0.98).

Differential effects of pH on cadmium accumulation in Artemisia argyi growing in low and moderately cadmium-contaminated paddy soils

BackgroundPhytoremediation is affected by physical and chemical properties of the soil such as soil pH, moisture, and nutrient content. Soil pH is a key element influencing Cd bioavailability and can be easily adjusted in agricultural practices. The soil pH level may relate to the effectiveness of phytoremediation; however, this has not been extensively investigated. In the current study, we evaluated the effect of Cd contamination level (0.56 and 0.92 mg/kg) and soil pH (5, 6, and 7) on Cd accumulation and allocation in Artemisia argyi, a fast-growing perennial crop.ResultsOur results indicated that higher soil Cd concentrations reduce A. argyi biomass, and the loss of the root mass was particularly significant. Higher soil pH decreased Cd content in stems and roots of A. argyi cultivated in moderately Cd-polluted soil, and increased Cd content in stems and roots of the plant grown in low Cd-polluted soil. Higher soil pH decreased the percentage of Cd distributed in the soluble fraction and cell walls and increased the percentage of Cd in the organelles of leaf cells for moderate soil Cd levels. The bioconcentration and translocation factor exceeded 4.0 and 1.0, respectively, across all tested treatments, indicating that A. argyi is a promising candidate for phytoremediation. Notably, the effects of soil pH on Cd accumulation and subcellular distribution in A. argyi differed between low and moderately Cd-contaminated soils.ConclusionAdjustments to soil pH based on the degree of Cd contamination can enhance Cd extraction by A. argyi, thereby reducing the overall remediation cycle of cadmium-polluted paddy fields of South China.Graphical

A New Approach to Differentiate the Causes of Excessive Cadmium in Rice: Soil Cadmium Extractability or Rice Variety

In order to effectively decrease cadmium (Cd) in rice grains in contaminated paddy soil and maintain the safe production of rice, identifying excessive Cd in rice caused by rice varieties or soil Cd is critical, but it is currently lacking. In the present study, the soil ethylenediaminetetraacetic acid (EDTA)-extractable Cd (EDTA-Cd) and the bioaccumulation factors of rice based on EDTA-Cd (BCFEDTA-Cd) were used to develop an approach to identify excessive Cd in rice caused by rice varieties or soil Cd. Based on an empirical soil–plant transfer model and species sensitivity distribution (SSD), BCFEDTA-Cd and EDTA-Cd were divided into five grades. The results showed that the five grades of the EDTA-Cd (minimum value less than 0.11 mg/kg and maximum value greater than 2.93 mg/kg) and BCFEDTA-Cd (minimum value less than 0.09 and maximum value greater than 1.40) were classified in the normal soil pH range. Further, the conversion equation between EDTA-Cd and diethylene triamine pentaacetic acid (DTPA)-Cd was obtained through linear regression analysis using 67 sets of soil data from the literature. In addition, the four selected rounding thresholds for the percentage of EDTA-Cd to total soil Cd (EDTA-Cd) (%) were 52.5, 67.5, 82.5, and 97.5%. A selected soil EDTA-Cd (%) (about 75%) can be used to identify the status of soil bioavailability, especially in soil with high background Cd. Finally, a set of 1084 pairs of rice and soil data for Cd-contaminated soils was used to investigate the respective contributions of rice varieties and soil Cd when Cd in rice exceeds the limit (0.2 mg/kg). Based on field experiment data, a systematic identification approach for the causes of rice Cd exceeding the limit, soil Cd or rice variety, was established and applied. In conclusion, under Cd exposure conditions, the importance of the causes of Cd in soil and rice varieties can be identified, and their contributions can be distinguished, thus helping to identify the causes of Cd contamination in rice.

Phytoremediation of contaminated urban soils spiked with heavy metals

Urban environments worldwide face toxic heavy metal pollution originating from industrial discharge, municipal waste disposal, vehicular emissions, and atmospheric deposition. Kazakhstan, experiencing accelerated economic growth and extensive mining activities, contends with widespread heavy metal contamination in its soil-plant-air-water ecosystems. This study explores the potential of hyperaccumulating plants for phytoremediation in urban soils of Kazakhstan contaminated with Pb, Cd, and Co. Twelve plant species, including Korean Mint (Lamiaceae), Ornamental Cabbage (Brassica oleracea), Ageratum (Ageratum houstonianum), Coneflower (Echinacea purpurea), Amaranth (Amaranthus Perfect and Amaranthus Emerald), Fescue (Festuca glauca), Burning Bush (Kochia scoparia), Marigold (Tagetes patula nana), White Cabbage (Brassica-Cavolo cappuccino BIANKO), Tepary Bean (Phaseolus acutifolius), and Rapeseed (Brassica napus), were evaluated for growth and biomass production in urban soils spiked with two maximum permissible addition (MPA) treatments of Pb, Co, and Cd. The selected plants demonstrated varied responses to heavy metal stress, with Marigold (8.4 g shoot biomass/plant), Korean mint (10.5 g shoot biomass/plant), Rapeseed (19.9 g/shoot biomass), and Tepary bean (25.9 g shoot biomass/plant) exhibiting resilience or tolerance to Pb, Co, and Cd stresses. The results highlight the significant potential of these plants for efficient phytoremediation, showcasing their unique abilities to absorb and accumulate specific metals. Marigold, particularly, displayed noteworthy Pb accumulation (40.3 mg/kg biomass), resulting in reduced residual Pb concentrations in the soil (74.7 mg/kg). Conversely, White cabbage and Amaranth showed limited efficiency in Cd extraction, while Rapeseed and Tepary bean emerged as promising candidates for Cd phytoremediation. This study emphasizes the critical role of tailored plant species selection in designing effective phytoremediation strategies for specific metal-contaminated urban sites. A comprehensive understanding of the dynamics of metal accumulation and residual concentrations is crucial for the development of sustainable and efficient environmental remediation approaches. Further research is warranted to explore the long-term effects of different plant species on soil metal concentrations, refining and optimizing phytoremediation methods for urban soils grappling with toxic heavy metal contamination.

Coupling of biochar and silicon for Phyto-management of Cd contaminated soil using Brachiariamutica

Contamination of soil with heavy metals is a threatening global environmental problem. With increasing urbanization, it is very important to design economical and environment-friendly mitigation measures to have pollutant free soil. Phytoremediation is an advancing technique to extract pollutants from soil to achieve eco-sustainability. This study aimed to investigate the combined impact of biochar and silicon on growth attributes of Brachiaria mutica grown in cadmium (Cd) contaminated soil. The biochar was prepared by co-pyrolysis of agricultural left-over biomass (rice husk, bamboo leaves and corn cob in a 1:1:1 ratio) and physio-chemical characters were studied by FTIR, SEM-EDX and proximate analysis. A pot study was conducted to evaluate the potency of biochar and silicon in lowering the Cd uptake by para grass grown under Cd spiked soil. Total 8 treatments were planned by taking 1 % and 2 % biochar with 0.01 % and 0.02 % silicon. The results have shown that treatment 8 (2 % biochar and 0.02 % silicon) exhibited maximum improvement in growth parameters such as shoot length by 2.64-fold and root length by 44.9 %, along with improving the antioxidant defense system of Para grass (CAT by 2-fold and POD by 56.4 %). Application of treatment 8 also decreased Cd concentration in the shoot and root by 48.8 % and 47.4 %, respectively. Treatment 8 was most effective in reducing CaCl2 extractable Cd in soil up to 56.1 %. Based on this data, treatment 8 was most effectual in suppressing Cd stress. Biochar produced from other agricultural waste material along with Si as inorganic amendment can be used to immobilize other toxic heavy metals at field level. Heavy metals immobilization potential of Si and biochar can be tested by harvesting other grasses and oil seed crop species.

Long-Term Amendment with Sewage Sludge: Effects on Nutrient Value and Trace-Metal Content in Different Parts of Maize Plants

Agricultural soils play a key role in the achievement of a circular nutrient economy. The use of sewage sludges as fertilizers is important for such an achievement, assisting in the maintenance of soil health and nutritional crop value. This study was established, after 23 years of a fertilization experiment, in calcareous soil under a maize monoculture. The treatments included mineral fertilization as a control (MIN, 225 kg N ha−1) and two sludge treatments, where doses followed a threshold sludge nitrogen criterion (SNC, 170 kg org-N ha−1) or a threshold soil phosphorus criterion (SPC; when the soil Olsen-P value exceeded 40–60 kg P ha−1, the sludge application was stopped). A detailed study was performed on Cd, Cu, F, Mn, Pb, and Zn soil extractable with diethylenetriaminepentaacetic acid (DTPA), as well as the nutrient and heavy metal concentration of different fractions of the maize plant (grain, cob, and the rest of the plant). Extractions were also quantified. No biomass-yield differences were observed in the different parts of the maize plant in the year of sampling. Sludges increased the soil DTPA extraction of Cd, Cu, Fe, and Zn and diminished Mn extraction, without differences in extractable Pb. The SNC, when compared with MIN, showed increased P cob concentrations, and in grain, it showed increased Fe, Cr, and Co concentrations. The SPC figures of the studied parameters were, in general, between both treatments (MIN and SNC), although Cr extractions in grain diminished vs. SNC. Based on the results, the SPC can be recommended as it also avoids excessive available-P build up.

Enhanced phytoremediation of cadmium-contaminated soil using chelating agents and plant growth regulators: effect and mechanism.

The heavy metal cadmium (Cd) is a major threat to food safety and human health. Phytoremediation is the most widely used remediation technology, and how to improve the remediation efficiency of phytoremediation has become a key issue. In this study, we constructed an intensive phytoremediation technology for remediation of Cd-contaminated soil with biodegradable chelating agent and plant growth regulator combined with maize and investigated the mechanism of this technology. The results showed that the best remediation effect was achieved in the treatment with 10-6 mol l-1 gibberellic acid (GA3) and 6 mmol kg-1 aspartate diethoxysuccinic acid (AES) combined with maize. In this treatment, the total biomass and extraction efficiency of maize were 3.6 and 8.67 times higher than those of the control, respectively, and the antioxidant enzyme activities of maize were also increased. The soil was enriched with dominant bacterial genera that promote plant growth and metabolism and tolerance to heavy metal stress, which in turn promoted maize growth and Cd accumulation. Structural equation modelling results indicated a large effect of plant Cd concentration and plant antioxidant enzyme activity on plant Cd extraction. The enhanced phytoremediation technology showed good potential for safe use of Cd-contaminated soil.

Plant growth promoting endophyte modulates soil ecological characteristics during the enhancement process of cadmium phytoremediation

Endophyte assisted phytoremediation of cadmium (Cd) contaminated soil represents a promising strategy. However, the precise soil ecological regulatory mechanisms by which endophyte enhance the Cd phytoextraction remain unclear. Here, we employed the plant growth promoting endophyte (PGPE) Pseudomonas sp. E3, which has been validated to effectively enhance Cd extraction in Solanum nigrum L., to investigate its regulatory mechanism on soil ecology. The results demonstrated that while PGPE inoculation resulted in minimal alterations to the physicochemical properties of the bulk soil, it led to a notable increase in acid phosphatase activity by 17.86% and urease activity by 24.85% in the rhizosphere soil. This, in turn, significantly raised the available nitrogen and phosphorus contents by 16.93% and 21.27%, respectively, in the rhizosphere soil. Additionally, PGPE inoculation effectively replenished the bioavailable fractions of Fe and Cd, which had been depleted due to root uptake. Importantly, the inoculation specifically augmented the abundance of biomarkers p_Patescibacteria, f_Saccharimonadales, and g_Saccharimonadales in the rhizosphere soil. These biomarkers exhibited a significant positive correlation with the available nutrient and metal element contents. Moreover, the co-occurrence network analysis demonstrated that the inoculation resulted in a simplified bacterial community network, which may have facilitated community synergism by displacing bacteria with a negative association. This regulation appears to occur independently of PGPE colonization. Overall, our findings suggested that PGPE also exerts a regulatory influence on soil ecological features, significantly aiding hyperaccumulators in nutrient acquisition and heavy metal accumulation.

Application of a novel deep eutectic solvent as an eco-friendly medium for green extraction of cadmium from herbal medicines

In this research, hydrophobic DESs were successfully prepared using components with hydrophobic and sulfydryl group, which were applied to develop a green and eco-friendly method to extract and detect the cadmium (Cd) in herbal medicine (HM). The basic properties of the DESs were studied, which showed good hydrophobicity, low density and sufficient absorption capacity. In extraction process, the extraction efficiency (EE) of Cd employing proposed process ranged from 89.12 %∼94.59 % and the maximal enrichment factor (EF) was 46.85. The DES based method demonstrated a good linear response in the range of 1 ∼ 50 µg·L-1 with a detection limit (LOD) of 0.29 μg L-1, which was detected by Inductively coupled plasma mass spectrometry (ICP-MS). Additionally, the accuracy of method (as recoveries %) was obtained with the recoveries ranging from 98.38 %∼105.48 %. The extraction process was also compared with microwave digestion (MD) method and showed basically equivalent effect with good propensity to enrichment. The mechanism was explored by DFT calculation to reveal the interaction of extraction process. The greenness of the proposed method was also evaluated using the Green Analytical Procedure Index (GAPI) and Analytical Eco-Scale (AES), which indicated excellent environmental protection. This study successfully prepared novel DESs and established an eco-friendly and effective analytical process integrating adsorption, collection, separation and detection for the detection of heavy metals in HM, and the DESs were contributed to the first three parts as a multifunctional role. The absorption mechanism related to the formation of molecular complexes in quantum chemistry perspective, which were attribute to the electrostatic attraction and H+ exchange between Cd and adsorbent. This method showed vast potential in heavy metal research involving complex matrices such as HM and its processed products, and the proposed process provides the way for a greener alternative for Cd extraction rather than conventional polluting processes.

GLDA exhibits advantages in the phytoextraction of Cd and Ni in land-applied municipal sludge.

Landscape utilization is a green and environment-friendly way of disposing of compost sludge. Garden plants can extract heavy metals from the sludge of land use, but the effect is not enough to be widely used. Chelating agents have been found to facilitate the extraction of heavy metals from plants and are expected to be popularized if they are also environmentally friendly. In this study, the effects of methylglycinediacetic acid trisodium salt (MGDA), tetrasodium glutamate diacetate (GLDA), and ethylene diamine tetraacetate (EDTA) on the extraction of Ni and Cd from compost sludge by SymphytumofficinaleL. were studied through the pot experiment. Compared with the control group, the application of 5-10 mmol kg-1 MGDA and 1-9 mmol kg-1 GLDA promoted plant growth, while the application of 3-4 mmol kg-1 EDTA inhibited plant growth. The highest Ni content in shoots appeared in 4 mmol kg-1 GLDA treatment, which was 4.2 times that of the CK group. The highest shoot Cd concentration appeared in 4 mmol kg-1 EDTA treatment, 6.5 times that of CK. The promotion effects of the three reagents on the acid-extractable state of Cd were similar, while that of GLDA on the acid-extractable state of Ni was outstanding. The results of this study suggested that S. officinale could be a potential phytoextraction plant for Cd and Ni, and GLDA could friendly promote the Ni phytoextraction ability of the plant. The study provides a new and efficient method for phytoremediation of heavy metals in soil.

Harmonizing soil restoration and microbial diversity: Insights from a Two-Year field experiment with Sedum-Rice rotation systems

Phytoremediation coupled with agroproduction (PCA) model contributes to sustainable agriculture and environmental management. This study investigated the impact of continuous cropping early/late season rice (RR) and Sedum alfredii-rice rotation (SR) on soil physical and chemical properties, as well as their relationships with soil microbial community. In 2022, SR treatment significantly increased pH value and organic matter content by 7 % and 17 %, respectively, compared to the levels in 2020, while RR treatment showed no change. RR treatment resulted in a significant decrease in soil concentrations of Ca, Mg, and K by 18.42 %, 29.01 %, and 7.77 %, respectively. Furthermore, SR treatment saw reductions of 29.62 % in total Cd and 38.30 % in DTPA extractable Cd in the soil. Over the two years, both treatments notably influenced the diversity, structure, and network of the rhizosphere bacterial and fungal communities, which are crucial for nutrient cycling and plant health. Notably, SR treatment exhibited a more complex network compared to RR, suggesting a greater impact on the interconnected systems. Therefore, these findings highlight the potential of Sedum rotation system to rehabilitate contaminated soils while supporting agricultural practices, which is essential for food security and environmental sustainability. This research direction holds promise for future exploration and application in the fields of phytoremediation and agroecology.

Biochar is an organomineral tool for mitigation of Cd toxicity in rice embedded soil and plant

Cadmium (Cd) contamination poses a significant threat to plants and human, as it can easily accumulate in plant tissues, leading to biochemical and physiological disorders. There is a growing interest in using biochar to mitigate the absorption of heavy metals by rice plants. This study tested peach biochar (PB) and its various levels of applications to evaluate the promising level for Cd remediation in contaminated soil. The application of PB3 had a significant impact on Cd mitigation, with extractable Cd (AB-DTPA) in soil decreasing from 66 mg kg−1 to 18 mg kg−1. Cd content in shoots decreased from 2.5 mg kg−1 to 0.9 mg kg−1, and in grains decreased from 1.1 mg kg−1 to 0.5 mg kg−1. Moreover, the PB treatment led to increased rice yield, from 4.9 to 10 g pot−1, and biological yield, from 4 to 20 g pot−1. The soil also showed improved organic matter content, increasing from 0.4% to 0.7%, and enhanced levels of nitrogen (N), phosphorus (P), and potassium (K), by increases from 2.1 g pot−1 to 5 g pot−1, 58 mg kg−1 to 83 mg kg−1, and 40 mg kg−1 to 63 mg kg−1, respectively. These findings demonstrate the potential of PB in mitigating Cd contamination in soil and reducing its uptake by rice plants.

High cadmium-accumulating Salix ecotype shapes rhizosphere microbiome to facilitate cadmium extraction

Cadmium (Cd) contamination poses a significant threat to agricultural soils and food safety, necessitating effective remediation strategies. Salix species, with their high coverage and Cd accumulating capacity, hold promise for remediation efforts. The rhizosphere microbiome is crucial for enhancing Cd accumulating capacity for Salix. However, the mechanisms by how Salix interacts with its rhizosphere microbiome to enhance Cd extraction remains poorly understood. In this study, we compared the remediation performance of two Salix ecotypes: 51–3 (High Cd-accumulating Ecotype, HAE) and P646 (Low Cd-accumulating Ecotype, LAE). HAE exhibited notable advantages over LAE, with 10.80 % higher plant height, 43.80 % higher biomass, 20.26 % higher Cd accumulation in aboveground tissues (93.09 μg on average), and a superior Cd translocation factor (1.97 on average). Analysis of the rhizosphere bacterial community via 16S rRNA amplicon sequencing revealed that HAE harbored a more diverse bacterial community with a distinct composition compared to LAE. Indicator analysis identified 84 genera specifically enriched in HAE, predominantly belonging to Proteobacteria, Actinobacteria, and Firmicutes, including beneficial microbes such as Streptomyces, Bacillus, and Pseudomonas. Network analysis further elucidated three taxa groups specifically recruited by HAE, which were highly correlated with functional genes that associated with biosynthesis of secondary metabolites, glycan biosynthesis and metabolism, and metabolism of cofactors and vitamins. These functions contribute to enhancing plant growth, Cd uptake, and resistance to Cd in Salix. Overall, our findings highlight the importance of the rhizosphere microbiome in facilitating Cd extraction and provide insights into microbiome-based strategies for sustainable agricultural practices.

Role of Silicon in Counteracting Cadmium Stress in Pea Plants (Pisum sativum L.): Insights Into Cadmium Binding Mechanisms and Pectin Methylesterase Activity

Purpose: The aim of this study was to investigate the role of silicon (Si) in counteracting a cadmium (Cd) stress to pea plants (Pisum sativum L.) and to identify the mechanism by which Cd is bound within pea roots. Methods: These goals were achieved through (i) a histochemical study of Cd localization in pea roots, (ii) spectrophotometric determination of pectin content and the activity of pectin methylesterase (PME), (iii) speciation of Cd extracted from pea roots conducted through size exclusion chromatography (SEC) and inductively coupled plasma mass spectrometry (ICP/MS). Results: Cd was found mainly in the root stele of the Cd-stressed plants. The pectin content and PME activity were lower in the Cd-stressed plants, but Si supplementation reversed these effects. Selectivity was noticed in Cd extraction efficiency with water being the least effective and enzymatic-assisted extraction proving to be the most effective. Speciation analysis revealed significant heterogeneity in molar mass, ranging from approximately 295 to 95 kDa. Galacturonic acid was identified the dominant species responsible for Cd binding. The choice of solvent for extraction markedly influenced the Cd binding profile, indicating shifts in the distribution of species’ molar mass and their relative concentrations in extracts. Conclusions: Si alleviates Cd toxicity in pea plants, and one of the mechanisms through which it operates involves increasing pectin levels and PME activity. Pectin plays an active role in Cd detoxification in the root cell walls, forming electrostatic bonds with Cd cations through its carboxyl groups.

Enhancement of cadmium uptake in Sedum alfredii through interactions between salicylic acid/jasmonic acid and rhizosphere microbial communities

The focus on phytoremediation in soil cadmium (Cd) remediation is driven by its cost-effectiveness and eco-friendliness. Selecting suitable hyperaccumulators and optimizing their growth conditions are key to enhance the efficiency of heavy metal absorption and accumulation. Our research has concentrated on the role of salicylic acid (SA) and jasmonic acid (JA) in facilitating Cd phytoextraction by “Sedum alfredii (S. alfredii)” through improved soil-microbe interactions. Results showed that SA or JA significantly boosted the growth, stress resistance, and Cd extraction efficiency in S. alfredii. Moreover, these phytohormones enhanced the chemical and biochemical attributes of the rhizosphere soil, such as pH and enzyme activity, affecting soil-root interactions. High-throughput sequencing analysis has shown that Patescibacteria and Umbelopsis enhanced S. alfredii's growth and Cd extraction by modifying the bioavailability and the chemical conditions of Cd in soil. Structural Equation Model analysis further verified that phytohormones significantly enhanced the interaction between S. alfredii, soil, and microbes, leading to a marked increase in Cd accumulation in the plant. These discoveries emphasized the pivotal role of phytohormones in modulating the hyperaccumulators' response to environmental stress and offered significant scientific support for further enhancing the potential of hyperaccumulators in ecological restoration technologies using phytohormones.

Development of a Dispersive Liquid-Liquid Aerosol Phase Extraction Method for the Quantification of Ag, Cd, Cu, Ni, and Pb in Seawater by Inductively Coupled Plasma Optical Emission Spectroscopy.

The dispersive liquid-liquid aerosol phase extraction (DLLAPE) method was applied for the determination of Ag, Cd, Cu, Ni, and Pb in seawater samples by inductively coupled plasma optical emission spectroscopy (ICP-OES). Key parameters such as sample pH and extractant concentration were systematically evaluated, with ammonium O,O'-diethyldithiophosphate (DDTP) identified as the optimal chelating agent. Optimal extraction conditions were achieved at pH 2.5 for Ag, Cu, Ni, and Pb, while Cd extraction efficiency was found to be pH independent. The extractant concentration did not greatly improve the extraction efficiency. Furthermore, the influence of nebulizer gas flow rate and extraction time was evaluated, achieving the maximum extraction yield at 0.6 L min-1 and 120 s, respectively. The method was evaluated for accuracy and bias through recovery studies, and the results showed that most elements had recovery rates close to 100% with relative standard deviation values in between 3 and 9%. However, in the case of Ag and Ni, 1.184 and 1.089 correction factors were, respectively, applied to compensate for the bias. Moreover, the procedural limits of quantification (pLOQs) found for Ag, Cd, Cu, Ni, and Pb were 0.4, 0.14, 0.2, 0.2, and 0.2 μg L-1, respectively. The in-house validation of the method provided expanded uncertainty values lower than 6% for all elements except for Ag (16.6%). Finally, the application of the method to real seawater samples from coastal areas in Alicante and San Juan (Spain) confirmed its suitability for trace metal analysis in complex marine matrices, underscoring its potential for environmental monitoring and research.