Pb Concentrations In Roots Research Articles

Immobilization of Pb, Cd, and Cr in contaminated soil around mining areas using Mg/Al LDH-zeolite and evaluation of maize growth

Abstract This study conducted simultaneous adsorption of Pb, Cd, and Cr ions using Mg/Al LDH-zeolite on contaminated soils from lead-zinc and tin mining areas. The optimal conditions were a 3% adsorbent-to-soil ratio, a 30-day incubation period, and 70% soil moisture. Characterization of the materials revealed that Mg/Al LDH-zeolite has superior physicochemical properties to natural zeolite, with a higher surface area and better adsorption capacity. Results indicated significant reductions in exchangeable heavy metal content: in lead-zinc mining area soil, exchangeable Pb decreased from 139.79 mg kg−1 to 10.95 mg kg−1, Cd−1 from 1.518 mg kg−1 to 0.533 mg kg−1, and Cr from 2.636 mg kg−1 to 0.461 mg/kg using Mg/Al LDH-zeolite. In tin mining area soil, exchangeable Pb decreased from 583.97 mg kg−1 to 48.22 mg kg−1, Cd−1 from 0.498 mg kg−1 to 0.122 mg kg−1, and Cr from 106.095 mg kg−1 to 38.038 mg/kg. Maize cultivation on post-adsorption soil showed improved growth performance, with plants exhibiting increased height and ear and reduced heavy metal accumulation in roots, shoots, and grains. Pb, Cd, and Cr concentrations in maize roots decreased significantly, with Pb reducing to 0.113 mg kg−1 in the lead-zinc area and 0.203 mg kg−1 in the tin area, Cd reducing to 0.061 mg kg−1 and 0.037 mg kg−1, respectively, and Cr reducing to 0.036 mg kg−1 and 0.243 mg kg−1 respectively. Mg/Al LDH-zeolite consistently demonstrated higher efficiency in reducing the bioavailability and translocation of heavy metals in maize tissues, confirming its potential as an effective adsorbent for soil remediation. Key mechanisms, including adsorption, surface complexation, ion exchange, precipitation, and structural incorporation, reduce metal mobility and bioavailability.

Efficacy of Fe-Mg-bimetallic biochar in stabilization of multiple heavy metals-contaminated soil and attenuation of toxicity in spinach (Spinacia oleracea L.)

Globally, soil contamination with heavy metals (HMs) pose serious threats to soil health, crop productivity, and human health. The present investigation involved synthesis and analysis of biochar with bimetallic combination of iron and magnesium (Fe-Mg-BC). Our study evaluated how Fe-Mg-BC affects the absorption of cadmium (Cd), lead (Pb), and copper (Cu) in spinach (Spinacia oleracea L.) and remediation of soil contaminated with multiple HMs. Results demonstrated the successful loading of iron (Fe) and magnesium (Mg) onto pristine biochar (BC) derived from peanut shells. The addition of Fe-Mg-BC (3%) notably increased spinach biomass, enhancing photosynthesis, transpiration, stomatal conductance, and intercellular CO2 levels by 22%, 21%, 103%, and 15.3%, respectively. Compared to control, Fe-Mg-BC (3%) suppressed metal-induced oxidative stress by boosting levels of superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT) in roots by 40.9%, 57%, 54.8 %, and in shoots by 55.5%, 65.5%, and 37.4% in shoots, respectively. The Fe-Mg-BC effectively reduced the uptake of Cd, Pb, and Cu in spinach tissues by transforming their bioavailable fractions to non-bioavailable forms. The Fe-Mg-BC (3%) significantly reduced the mobility of Cd, Pb and Cu in soil and limited the concentration of Cd, Pb, and Cu in plant roots by 34.1%, 79.2%, 47%, and shoots by 56.3%, 43.3%, and 54.1%, respectively, compared to control. These findings underscore the potential of Fe-Mg-BC as a promising amendment for reclaiming soils contaminated with variety of HMs, thereby making a significant contribution to the promotion of safer food production.

Nutrient strengthening and lead alleviation in Brassica Napus L. by foliar ZnO and TiO2-NPs modulating antioxidant system, improving photosynthetic efficiency and reducing lead uptake

With the anticipated foliar application of nanoparticles (NPs) as a potential strategy to improve crop production and ameliorate heavy metal toxicity, it is crucial to evaluate the role of NPs in improving the nutrient content of plants under Lead (Pb) stress for achieving higher agriculture productivity to ensure food security. Herein, Brassica napus L. grown under Pb contaminated soil (300 mg/kg) was sprayed with different rates (0, 25, 50, and 100 mg/L) of TiO2 and ZnO-NPs. The plants were evaluated for growth attributes, photosynthetic pigments, leaf exchange attributes, oxidant and antioxidant enzyme activities. The results revealed that 100 mg/L NPs foliar application significantly augmented plant growth, photosynthetic pigments, and leaf gas exchange attributes. Furthermore, 100 mg/L TiO2 and ZnO-NPs application showed a maximum increase in SPAD values (79.1%, 68.9%). NPs foliar application (100 mg/L TiO2 and ZnO-NPs) also substantially reduced malondialdehyde (44.3%, 38.3%), hydrogen peroxide (59.9%, 53.1%), electrolyte leakage (74.8%, 68.3%), and increased peroxidase (93.8%, 89.1%), catalase (91.3%, 84.1%), superoxide dismutase (81.8%, 73.5%) and ascorbate peroxidase (78.5%, 73.7%) thereby reducing Pb accumulation. NPs foliar application (100 mg/L) significantly reduced root Pb (45.7%, 42.3%) and shoot Pb (84.1%, 76.7%) concentration in TiO2 and ZnO-NPs respectively, as compared to control. Importantly, macro and micronutrient analysis showed that foliar application 100 mg/L TiO2 and ZnO-NPs increased shoot zinc (58.4%, 78.7%) iron (79.3%, 89.9%), manganese (62.8%, 68.6%), magnesium (72.1%, 93.7%), calcium (58.2%, 69.9%) and potassium (81.5%, 68.6%) when compared to control without NPs. The same trend was observed for root nutrient concentration. In conclusion, we found that the TiO2 and ZnO-NPs have the greatest efficiency at 100 mg/L concentration to alleviate Pb induced toxicity on growth, photosynthesis, and nutrient content of Brassica napus L. NPs foliar application is a promising strategy to ensure sustainable agriculture and food safety under metal contamination.

PIP family-based association studies uncover ZmPIP1;6 involved in Pb accumulation and water absorption in maize roots

Excessive lead (Pb) in the soil affects crop growth and development, thus threatening human beings via food chains. Plasma membrane intrinsic proteins (PIPs) facilitate the transport of substrates across cell membranes. Herein, we characterized maize PIPs and identified eight Pb accumulation-associated PIP genes using association studies. Among these, ZmPIP1;6 was simultaneously correlated with root Pb concentrations under various Pb treatment stages. Significant correlations were observed between the ZmPIP1;6 expression abundance and Pb accumulation in maize roots. Ectopic expression in yeast showed that ZmPIP1;6 conferred Pb accumulation in the cells and affected Pb tolerance in yeast. Overexpression in maize demonstrated that ZmPIP1;6 altered the Pb concentration performance and root moisture content under Pb stress. Meanwhile, protein interaction analyses suggested that ZmPIP1; 6 and three PIP2 members formed isoforms and facilitate water uptake in maize roots. However, ZmPIP1; 6 improved Pb absorption in maize roots probably by interacting with CASP-like protein 2C3 and/or another metal transporter. Moreover, the significant variants in the ZmPIP1;6 promoter caused the variations in ZmPIP1;6 expression level and Pb accumulation among various maize germplasms. Our study will contribute to understanding of PIP family-mediated Pb accumulation in crops and bioremediation of Pb-polluted soils.

Appropriate supply of sulfur alleviates lead toxicity and stimulates its accumulation in hyperaccumulator Arabis alpina

Widespread lead (Pb) contamination of agricultural soils is a global issue stemming from human activities. The remediation of Pb-contaminated soils used for agricultural purposes is critically important to safeguard food crop safety. Despite the modulating effects of sulfur (S) on plant responses to toxic heavy metals, the ecological, physiological, and molecular mechanisms driving such modulation in the Pb hyperaccumulator Arabis alpina L. remain unclear. Here, we investigated the effects of five S concentrations (0, 50, 100, 150, and 200 mg kg−1) on A. alpina grown in Pb-contaminated soil from a lead-zinc mining area. Under S50 (i.e., 50 mg kg−1) and S100 treatments, the Pb concentration in both shoots and roots of A. alpina significantly decreased compared to the control (S0). Specifically, the S50 treatment significantly enhanced Pb accumulation, plant biomass, and plant height, indicating that low S applications facilitate Pb accumulation from the soil and alleviate Pb toxicity. Additionally, S50, S100, and S150 treatments significantly improved photosynthetic rate, stomatal conductance, and intercellular CO2 concentration in A. alpina. Transcriptomic analysis showed that S50 and S100 treatments increased the expression of the LHCA, LHCB, psa, and psb genes, which had a significant impact on photosynthetic efficiency. S50 and S100 boosted glutathione (GSH) levels in A. alpina roots, and the increased expression of GST gene enhanced tolerance to environmental stress. In summary, these results suggest that an appropriate supply of S (S50 and S100) not only alleviates Pb toxicity by enhancing plant biomass, height, photosynthetic features, and sulfur metabolites but also stimulates Pb accumulation in the hyperaccumulator A. alpina. Our study elucidated the specific concentrations of sulfur that optimally enhance both Pb accumulation and stress tolerance in the hyperaccumulator A. alpina, providing novel insights into the practical application of sulfur in phytoremediation strategies and advancing our understanding of the underlying molecular mechanisms.

MTP family analysis and association study reveal the role of ZmMTP11 in lead (Pb) accumulation

The metal tolerance protein (MTP) gene family plays an essential role in the transport of heavy metals, however the function of the MTP family in transporting lead (Pb) was still unclear in plants. In this study, we identified and characterized 12 ZmMTPs in the whole genome of maize. These ZmMTP genes were divided into three subfamilies in evolution, namely Zn-CDF, Zn/Fe-CDF, Mn-CDF subfamilies, which showed diverse expression patterns in different tissues of maize. Using gene-based association analyses, we identified a Pb accumulation-related MTP member in maize, ZmMTP11, which was located in plasma membrane and had the potential of transporting Pb ion. Under the Pb treatment, ZmMTP11 showed a generally decreased expression relative to the normal conditions. Heterologous expressions of ZmMTP11 in yeast, Arabidopsis, and rice demonstrated that ZmMTP11 enhanced Pb accumulation in the cells without affecting yeast and plant growth under Pb stress. Remarkably, the increased Pb concentration in the plant roots did not cause changes in Pb content in the shoots. Our study provides new insights into the genetic improvement of heavy metal tolerance in plants and contributes to bioremediation of Pb-contaminant soils.

The influence of nZVI composites as immobilizing agents on the bioavailability of heavy metals and plant growth in mining metal-contaminated soil

<p>Under the greenhouse scale, nano zero valent iron (nZVI) have been evaluated evaluated by formulation with carboxymethyl cellulose (CMC-nZVI), chitosan (Ch-nZVI), biochar (BC-nZVI), and smectite (SC-nZVI) at rates of 0 and 0.5 and 1% (w/w). The properties of manufactured compounds and their impact on the soil ecosystem planted with safflower (Carthamus tinctorius L.) as a phytoremediation crop for inorganic contaminants in contaminated mining soils have been measured. After 33 days, growth parameters were recorded in harvested plants and the concentrations of some HMs in plant tissues. Furthermore, pH, EC, soluble Na and available Cd, Cu, Pb and Zn concentrations in the treated soil after harvest were analyzed. Results revealed that Ch-nZVI and SC-nZVI application at 0.5% led to a narrow non-significant increase in the dry biomass and the shoot length compared to the control. On the other hand, the application of CMC-nZVI and BC-nZVI resulted in reduced plant growth. All the applied amendments increased soil pH, EC, and soluble Na contents. The soils treated with synthesized nZVI composites showed a considerable increase (non-significant) in available heavy metals in treated soils compared to control. Application of CMC-nZVI1% resulted in increased shoot copper (Cu) and zinc (Zn) (182% and 114%, respectively, compared to control), while Ch-nZVI, SC-nZVI applied at 1%, and BC-nZVI0 applied at 5% resulted in reduce Cu, Zn, and Pb concentrations in roots by 65.2%, 31.4% and 85.5% in Cu, Zn and Pb respectively as compared to control). The phytoremediation indices showed that the uptake and extraction of HMs by safflower plants weren't significant in decreasing heavy metals in polluted soil and the applied materials disabled the actions of hyperaccumulated plant used. Results showed that these materials didn’t have a significant effect on immobilize of HMs in mining soil, while the application of Ch-nZVI, SC-nZVI, and BC-nZVI resulted in disabled hyperaccumulated plant to reducing the uptake of Pb, Cu, and Zn. It could be concluded that the application of synthesized nZVI composites to mining polluted soil might be restricted, mainly due to their negative impacts on soil ecosystem besides their side effects on HMs uptake by test hyperaccumulated crop.</p>

Impact of coconut-fiber biochar on lead translocation, accumulation, and detoxification mechanisms in a soil–rice system under elevated lead stress

Biochar, an environmentally friendly material, was found to passivate lead (Pb) in contaminated soil effectively. This study utilized spectroscopic investigations and partial least squares path modeling (PLS-PM) analysis to examine the impact of coconut-fiber biochar (CFB) on the translocation, accumulation, and detoxification mechanisms of Pb in soil-rice systems. The results demonstrated a significant decrease (p < 0.05) in bioavailable Pb concentration in paddy soils with CFB amendment, as well as reduced Pb concentrations in rice roots, shoots, and brown rice. Synchrotron-based micro X-ray fluorescence analyses revealed that CFB application inhibited the migration of Pb to the rhizospheric soil region, leading to reduced Pb uptake by rice roots. Additionally, the CFB treatment decreased Pb concentrations in the cellular protoplasm of both roots and shoots, and enhanced the activity of antioxidant enzymes in rice plants, improving their Pb stress tolerance. PLS-PM analyses quantified the effects of CFB on the accumulation and detoxification pathways of Pb in the soil–rice system. Understanding how biochar influences the immobilization and detoxification of Pb in soil–rice systems could provide valuable insights for strategically using biochar to address hazardous elements in complex agricultural settings.

Phytoremediation efficacy of Nerium oleander L. for removal of Cd, Ni, and Pb- contaminated soil

A pot experiment was conducted to assess the effectiveness of Nerium oleander L. in phytoremediation of cadmium (Cd), nickel (Ni), and lead (Pb)- contaminated soil. This evaluation included the application of ethylene diamine tetra-acetic acid (EDTA) and a nutrient solution containing NPK. The results revealed that the inclusion of EDTA and NPK, in combination with varying metal concentrations, significantly increased the dry weight of the plants. The results demonstrated that oleander, when aided by EDTA and NPK, exhibited a high capacity to efficiently absorb and accumulate Pb without any amendments. The addition of EDTA increased Pb concentrations in both aerial parts and roots (84.9 mg kg-1 and 80.2 mg kg-1, respectively). For Nickel, in the presence of NPK, the concentration in roots was 80,2 mg kg-1. Cd accumulation was highest in the treatment with 100 mg kg-1 EDTA, reaching 72.9 mg kg-1 in the aerial parts. Particularly, NPK reduced Ni levels in aerial parts, while EDTA enhanced root metal uptake. The Translocation Factor (TF) was greater than 1 for Cd and Ni treatments, indicating oleander's remarkable ability to absorb and accumulate these heavy elements. The treatment involving Pb50+EDTA displayed the highest Bioaccumulation Factor (BAF) value at 1.7. Furthermore, for Pb50, Ni50 and Cd50, the NPK treatment exhibited the highest Bioconcentration Factor (BCF) values, ranging from 0.3 to 1.69. Nerium oleander L. exhibits promise for both Ni phytoextraction and Cd and Pb phytostabilization, suggesting its potential as an effective phytoremediation agent. Future research should focus on optimizing metal uptake conditions and investigating long-term plant health and soil impacts to refine sustainable strategies for mitigating metal pollution in contaminated environments.

Iron-modified biochar improves plant physiology, soil nutritional status and mitigates Pb and Cd-hazard in wheat (Triticum aestivum L.).

Environmental quality and food safety is threatened by contamination of lead (Pb) and cadmium (Cd) heavy metals in agricultural soils. Therefore, it is necessary to develop effective techniques for remediation of such soils. In this study, we prepared iron-modified biochar (Fe-BC) which combines the unique characteristics of pristine biochar (BC) and iron. The current study investigated the effect of pristine and iron modified biochar (Fe-BC) on the nutritional values of soil and on the reduction of Pb and Cd toxicity in wheat plants (Triticum aestivum L.). The findings of present study exhibited that 2% Fe-BC treatments significantly increased the dry weights of roots, shoots, husk and grains by 148.2, 53.2, 64.2 and 148%, respectively compared to control plants. The 2% Fe-BC treatment also enhanced photosynthesis rate, transpiration rate, stomatal conductance, intercellular CO2, chlorophyll a and b contents, by 43.2, 88.4, 24.9, 32.5, 21.4, and 26.7%, respectively. Moreover, 2% Fe-BC treatment suppressed the oxidative stress in wheat plants by increasing superoxide dismutase (SOD) and catalase (CAT) by 62.4 and 69.2%, respectively. The results showed that 2% Fe-BC treatment significantly lowered Cd levels in wheat roots, shoots, husk, and grains by 23.7, 44.5, 33.2, and 76.3%. Whereas, Pb concentrations in wheat roots, shoots, husk, and grains decreased by 46.4, 49.4, 53.6, and 68.3%, respectively. Post-harvest soil analysis showed that soil treatment with 2% Fe-BC increased soil urease, CAT and acid phosphatase enzyme activities by 48.4, 74.4 and 117.3%, respectively. Similarly, 2% Fe-BC treatment significantly improved nutrients availability in the soil as the available N, P, K, and Fe contents increased by 22, 25, 7.3, and 13.3%, respectively. Fe-BC is a viable solution for the remediation of hazardous Cd and Pb contaminated soils, and improvement of soil fertility status.

Evaluation of calcium, phosphorus and soil organic matter effects on lead accumulation in Cenchrus ciliaris L. grown near a cement factory in Jazan region, Saudi Arabia

Heavy metals associated with cement production and their environmental impacts have received much attention recently. Lead (Pb) is the second most hazardous element after arsenic (As). However, information about its availability and uptake by plants in polluted soil as influenced by soil properties has shown some contradictions. We evaluated the influence of soil calcium (Ca), soil phosphorus (P), and soil organic matter (SOM) on Pb uptake by Cenchrus ciliaris L. based on distance from cement dust polluted soil near a cement factory in Jazan region, Saudi Arabia. We also evaluated the potential of Cenchrus ciliaris L. as a hyperaccumulator of Pb. Soil and plant samples were collected in triplicates from three zones based on distance from the fence of the factory: 10 – 100, 100 – 350, and 350 – 700 m. Concentrations of total Pb, total Ca, and total P in soil and plant tissues were detected using ICP-AES. SOM and other soil properties were also analyzed. Bioconcentration and translocation factors (BF&TF) of Pb were also calculated. Results showed that Pb concentration in Cenchrus ciliaris roots had a strong negative relationship with SOM (R2 = 0.93) and P concentration in soil (R2 = 0.97) but a moderate negative relationship with Ca concentration in soil (R2 = 0.69). The highest TF value was 1.87. It can be concluded that SOM, Ca, and P concentrations in soil negatively affected Pb availability and uptake by Cenchrus ciliaris. Also, based on the highest TF value, Cenchrus ciliaris could be used as a hyperaccumulator in Pb-contaminated soils.

Reducing lead uptake by plants as a way to lead-free food

In this research, an attempt was made to produce safe food from lead-contaminated soil. It was assumed that an increased amount of calcium (Ca) in plants would prevent them from lead (Pb) uptake. A new-generation agricultural product − an activator of Ca transport in plants “InCa” (from Plant Impact) − was used. The study was conducted on several crop species, Cucumis sativus L., Linum usitatissimum L., Medicago sativa L. and Solanum lycopersicum L., cultivated in mineral medium. The leaves were sprayed with InCa activator while the roots received Pb from the substrate in the form of Pb(NO3)2 dissolved in the medium. It was shown that spraying the leaves with InCa reduced Pb concentration in the roots of S. lycopersicum to 73%, in C. sativus to 60%, and in L. usitatissimum to 57%. Finally, it was found that foliar application of InCa reduced the concentration of Pb in plant roots by 53%, and in plant shoots by 57% (on average by about 55%). These observations were confirmed using histochemical and electron microscopy techniques. It was shown that one of the InCa activator components – Ca(NO₃)₂ – is responsible for such effects. This result was verified by using another experimental method – the Allium epidermis test. Visualization of Pb in epidermal cells of Allium cepa. L. using the Leadmium™Green fluorescent probe (confocal microscopy) showed a reduction in the amount of Pb that entered the epidermal cells after the application of the tested solutions. For the first time, it was shown that it is possible to reduce Pb uptake by plants by up to 55%. In the future, this offers the possibility of developing a foliar calcium preparation aimed at lowering the concentration of Pb in plants and thereby reducing the amount of Pb in the food chain.

Effect of biodegradable chelant nitrilotriacetic acid on lead (pb) phytoextraction efficiency of coronopus didymus grown in pb-contaminated soil

The current study investigated the use of nitrilotriacetic acid (NTA), a biodegradable chelating agent, on the phytoextraction of lead (Pb) from soil using Coronopus didymus. The plants were exposed to three different Pb concentrations: 3500, 4500, and 5500 mg kg-1 alone and in combination with 10 mM kg-1 of NTA. The morphological traits such as plant growth and biomass, the Bioconcentration Factor (BCF) values, and Pb accumulation in roots, stems, and leaves were measured. The plant growth and dry biomass were found to be maximum at 3500 mg kg-1 Pb and minimum at 5500 mg kg-1 Pb as compared to the control under Pb alone treatments and in combination with NTA. The supplementation of NTA significantly enhanced the Pb accumulation in different plant parts and was in the order: roots &gt; stems &gt; leaves. Compared to the BCF values of stems and leaves, the BCFroots values, which ranged from 89.3 to 257, were highest for all the treatments. NTA application resulted in the highest BCF value at 3500 mg kg−1 Pb concentration in roots. The present study suggests that the use of NTA as a chelating agent significantly increased the ability of C. didymus plants to remove Pb from the environment. This approach can be widely used for efficient remediation of contaminants from the metal-contaminated soils.

Lead accumulation and biochemical responses in Rhus chinensis Mill to the addition of organic acids in lead contaminated soils.

Adding organic acid is an effective approach to assist phytoremediation. The effects of organic acids on phytoremediation efficiency are unknown in Rhus chinensis. This study aimed to evaluate the effect of citric acid (CA) and oxalic acid (OA) on the lead phytoremediation potential of R. chinensis with significantly inhibited growth in Pb-contaminated soil. The experimental pot culture study evaluated the long-term physiological response and metal accumulation patterns of R. chinensis grown in varying Pb-treated soil, and examined the effects of 0.5 and 1.0 mmol L-1 CA and OA on the growth, oxidative stress, antioxidant system, and Pb subcellular distribution of R. chinensis grown in pots with 1000 mg kg-1 Pb. Compared with the control, the biomass, leaf area, root morphological parameters, and chlorophyll concentration of R. chinensis decreased, whereas the carotenoid, malondialdehyde, H2O2, and O2˙- concentrations, and superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity increased under Pb stress. A copious amount of Pb was taken up and mainly stored in the cell walls of the roots. The application of CA and OA increased plant growth. The highest shoots and roots biomass increase recorded was 44.4 and 61.2% in 1.0 mmol L-1 OA and 0.5 mmol L-1 CA treatment, respectively. The presence of CA and OA increased SOD, POD, and CAT activities and decreased the H2O2, O2˙- and malondialdehyde content. A concentration of 0.5 mmol L-1 CA significantly increased the Pb concentration in the organs. The other organic acid treatments changed root Pb concentrations slightly while increasing shoot Pb concentrations. The translocation factor values from organic acid treatments were increased by 38.8-134.1%. Our results confirmed that organic acid could alleviate the toxicity of stunted R. chinensis and improve phytoremediation efficiency.

Citric Acid and Poly-glutamic Acid Promote the Phytoextraction of Cadmium and Lead in Solanum nigrum L. Grown in Compound Cd-Pb Contaminated Soils.

Phytoextraction is an efficient strategy for remediating heavy metal-contaminated soil. Chelators can improve the bioavailability of heavy metals and increase phytoextraction efficiency. However, traditional chelators have gradually been replaced due to secondary pollution. In this study, a typical organic acid (citric acid, CA) and a novel biodegradable chelator (poly-glutamic acid, PGA), were investigated using pot experiments to compare the phytoextraction efficiency of Solanum nigrum L. (a Cd (hyper)accumulator) for cadmium (Cd) and lead (Pb) in contaminated soil. The results showed CA and PGA significantly improved plant growth, and total Cd and Pb amounts of S. nigrum, both CA and PGA significantly increased the shoot Cd and Pb concentrations. However, only PGA significantly increased the root Pb concentration. CA and PGA application promoted the bioavailability of Cd and Pb in rhizosphere soils and their translocations from roots to shoots in S. nigrum. Both CA and PGA increased the phytoextraction efficiency of Cd and Pb in S. nigrum plants, and the PGA for Cd and Pb phytoextraction was more effective than CA. Our findings demonstrate that the biodegradable chelator PGA has great potential for enhancing phytoextraction from compound Cd-Pb contaminated soils, suggesting that biodegradable chelator-assisted phytoextraction with (hyper)accumulator is strongly recommended in severely contaminated sites.

Effects of Soil Application of Chitosan and Foliar Melatonin on Growth, Photosynthesis, and Heavy Metals Accumulation in Wheat Growing on Wastewater Polluted Soil

Due to freshwater scarcity in developing countries, irrigating the arable land with wastewater poses potential ecological risks to the environment and food quality. Using cheap soil amendments and foliar application of a newly discovered molecule “melatonin” (ML) can alleviate these effects. The objectives of this pot study were to evaluate the effectiveness of the sole addition of chitosan (CH) and sugar beet factory lime (SBL) in wastewater impacted soil, foliar application of ML, and combining each soil amendment with ML on the heavy metals (HMs) accumulation, growth, nutritional quality and photosynthesis in wheat. Results showed that CH was more effective than SBL for reducing HMs bioavailability in soil, HMs distribution in plants, improving photosynthesis, nutritional quality, and growth. ML application also influenced plant parameters but less than CH and SBL. The CH+ML treatment was the most effective for influencing plant parameters and reducing HMs bioavailability in the soil. Compared to control, CH+ML significantly reduced the concentrations of Pb, Cd, Cr, Ni, Cu, and Co in roots, shoots, and grain up to 89%. We conclude that adding CH+ML in wastewater impacted soils can remediate the soil; reduce HMs concentrations in plants; and improve their photosynthesis, plant growth, grain yield, and nutrition.

Low-molecular-weight organic acid-mediated tolerance and Pb accumulation in centipedegrass under Pb stress

Lead (Pb) is one of the most harmful, toxic pollutants to the ecological environment and humans. Centipedegrass, a fast-growing warm-season turfgrass, is excellent for Pb pollution remediation. Exogenous low-molecular-weight organic acid (LMWOA) treatment is a promising approach for assisted phytoremediation. However, the effects of this treatment on the tolerance and Pb accumulation of centipedegrass are unclear. This study investigated these effects on the physiological growth response and Pb accumulation distribution characteristics of centipedegrass. Applications of 400 μM citric acid (CA), malic acid (MA) and tartaric acid (TA) significantly reduced membrane lipid peroxidation levels of leaves and improved biomass production of Pb-stressed plants. These treatments mainly increased peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) activities and enhanced free protein (Pro), ascorbic acid (AsA) and phytochelatins (PCs) contents, ultimately improving the Pb tolerance of centipedegrass. Their promoting effects decreased as follows: TA>CA>MA. All the treatments decreased root Pb concentrations and increased stem and leaf Pb concentrations, thus increasing total Pb accumulation and TF values. MA had the best and worst effects on Pb accumulation and Pb transportation, respectively. CA had the best and worst effects on Pb transportation and Pb accumulation, respectively. TA exhibited strong effects on both Pb accumulation and transport. Furthermore, all treatments changed the subcellular Pb distribution patterns and distribution models of the chemical forms of Pb in each tissue. The root Pb concentration was more highly correlated with the Pb subcellular fraction distribution pattern, while the stem and leaf Pb concentrations were more highly correlated with the distribution models of the chemical forms of Pb. Overall, TA improved plant Pb tolerance best and promoted both Pb absorption and transportation well and is considered the best candidate for Pb-contaminated soil remediation with centipedegrass. This study provides a new idea for Pb-contaminated soil remediation with centipedegrass combined with LMWOAs.

Influence of Silicon on Translocation, Compartmentation and Uptake of Lead in Leafy Vegetables

Lead (Pb) has phytotoxic and toxic effects on plants and animals. Leafy vegetables accumulate this element resulting in enrichment along the food chain. Silicon has beneficial effects in enhancing plants’ tolerance to biotic and abiotic stresses including heavy metals such as Pb. The study was carried out under greenhouse and field conditions aiming at determining the effects of silicon on transfer, mobility, and uptake of lead by leafy vegetables (spinach, kale, and amaranths). The greenhouse experiment was carried out as a split-plot arranged in Completely Randomized Design (CRD). The vegetable species were allocated to the main plots whereas the treatments (Pb, Pb+Si, Si, and Control) were assigned to the subplots. The field experiment was sited in polluted soils, and treatment included control and Si, applied to spinach, kale, and amaranths. Data was collected on Pb concentrations in roots, stems, and leaves, transfer factor, mobility index, and uptake of lead by leafy vegetables. Lead concentration was highest in roots, intermediate in stems, and least in leaves. Silicon application reduced concentration, transfer factor, mobility, and uptake of lead by 20, 40, 15, and 24%, respectively. The lead transfer factor and translocation index was less than one. Pearson correlation coefficient indicated a strong positive correlation between lead concentrations in soils and plant tissues of leafy vegetables. Application of silicon on polluted soils reduced transfer and mobility of lead in edible tissues of leafy vegetables. The study recommends silicon application to reduce the concentration of lead on vegetable tissues, however, it recommends against vegetable production for human consumption on polluted soils.

A new technique for reducing accumulation, transport, and toxicity of heavy metals in wheat (Triticum aestivum L.) by bio-filtration of river wastewater

The occurrence of contaminants such as heavy metals in an aqueous environment has become a global concern. In the present study, a bio-filter was designed to eliminate heavy metals from river wastewater contaminated with industrial effluents. Moreover, we analyzed simple tap water, bio-filtered water, and unfiltered river wastewater and measured the concentrations of different heavy metals in the samples, such as cadmium (Cd), nickel (Ni), lead (Pb), and copper (Cu). The current experiment explored irrigation effects of three water regimes (tap water, bio-filtered water, and wastewater) on two wheat (Triticum aestivum L.) varieties (NARC-2009 and NARC-2011). Results of the present study indicated that wastewater negatively influenced the growth parameters and photosynthetic contents along with a significant increase in oxidative damage in terms of electrolyte leakage (EL) (50 and 61%), hydrogen peroxide (H2O2) (52 and 61 μmol/g), and malondialdehyde (MDA) (16 and 17.7 μmol/g) contents in NARC-2009 and NARC-2011 respectively. However, bio-filtered water positively regulated the growth profile, activities of antioxidants such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), total soluble sugars, amino acids, total protein, and proline contents in wheat as compared with untreated wastewater. In addition, bio-filtered water had significant impacts on the reduction of Cd, Ni, Pb, and Cu concentrations in roots, shoots, and grains of both wheat varieties as compared to wastewater. The concentrations (mg/kg) of Cd (15 and 18), Ni (35 and 57), Pb (5 and 7), and Cu (69 and 72) in roots, Cd (5 and 6), Ni (24 and 43), Pb (3 and 4), and Cu (16 and 19) in shoots, and Cd (0.7 and 1.0), Ni (11 and 26), Pb (2 and 3), and Cu (1.6 and 1.5) in grains of NARC-2009 and NARC-2011 were found under river wastewater treatment. Overall, wastewater treatment through bio-filtration process is an effective strategy for the reduction of toxic elements in bio-filtered water and their accumulation by plants.

The assessment of cadmium and lead in organic and conventional root and tuber vegetables from the Serbian market

Global organic agriculture and consumption of organic food has continuously increased over the past decades. The aim of the research was to determine and compare cadmium (Cd) and lead (Pb) concentrations in organic and conventional root and tuber vegetables from the Serbian market. Samples of three root and tuber vegetables commonly consumed in Serbia, including potatoes, carrots and beetroots, were collected at two green markets and four supermarkets in the territory of the city of Belgrade, Serbia. Concentrations of Cd and Pb in fresh weight were determined by atomic absorption spectroscopy (AAS). Mean concentrations of Cd and Pb in two types of vegetables were compared by the t-test. Cd and Pb concentrations in both types of vegetables were below allowable limits. Potato mean Cd concentration was significantly lower in the organic than in the conventional type (0.021 mg kg-1 and 0.037 mg kg-1, respectively). In carrots, it was the opposite, Cd concentration was higher in the organic type, but the difference was not significant either between the two types or for beetroots. Results indicated lower Pb levels in organic potatoes and beetroots, and higher Pb levels in organic carrots, but differences between means were not significant in all tested vegetables. Obtained results are not conclusive, but they indicate lower or similar concentrations of both metals in organic vegetables in comparison to conventional types.