Lead Uptake Research Articles

OsNRAMP5 Is a Major Transporter for Lead Uptake in Rice.

Lead (Pb) is one of the most toxic metals affecting human health globally. Food is an important source of chronic Pb exposure in humans. How Pb is taken up by rice, a staple food for over half of the global population, remains unknown. In the present study, we investigated the role of OsNRAMP5, a member of the NRAMP (Natural Resistance-Associated Macrophage Protein) transporter family, in Pb uptake by rice roots. Heterologous expression of OsNRAMP5 in yeast increased Pb uptake and sensitivity toward Pb. Knockout of OsNRAMP5 in rice by CRISPR/Cas9 gene editing resulted in significant decreases in root uptake of Pb and accumulation in rice shoots. The maximum influx velocity (Vmax) for Pb uptake of the knockout mutants was 70% lower than that of wild-type plants. When grown in Pb-contaminated paddy soil, OsNRAMP5 knockout mutants accumulated approximately 50 and 70% lower Pb concentrations in the grain and straw, respectively, than the wild type. OsNRAMP5 expression in rice roots was not affected by Pb exposure. These results indicate that OsNRAMP5 is a major transporter for Pb uptake in rice, in addition to its role in the uptake of manganese and cadmium. This study provides a mechanistic understanding of Pb uptake in rice plants and a potential strategy to limit Pb accumulation in rice grains.

Triacontanol priming as a smart strategy to attenuate lead toxicity in Brassica oleracea L.

The most prevalent heavy metal pollutant in the environment is lead (Pb). Lead potentially contribute 10% of overall heavy metal contamination. Lead uptake by plants has been found to have an impact on their metabolic functions, photosynthetic activity, growth, and productivity. The current experiment was conducted to investigate the impact of triacontanol (Tria) for attenuating Pb stress in Brassica oleracea var. italic (broccoli). Three different Tria concentrations (10, 20 and 30 µmol L−1) were used to prime broccoli seeds. Growth of broccoli was reduced when exposed to Pb-driven toxicity. Additionally, Pb had a deleterious impact on the protein quantity, stomatal conductance, transpiration and photosynthetic rate. Nevertheless, plants grown from seeds primed with Tria2 (20 µmol L−1 Tria) exhibited improved morphological characteristics, uptake of mineral content (Mn+2, Zn+2, K+1, Na+1) along with biomass production. There was 1.6-fold increase in photosynthetic rate, the phenol (1.3 folds), and DPPH activity (1.2 folds) in seed primed with Tria2. Additionally, plants treated with Tria2 demonstrated enhanced MTI and gas exchange characteristics that improves plant stress tolerance under Pb stress. Seed priming with Tria can be used to increase plant tolerance to Pb stress as evidenced by the improved growth and biochemical characteristics of broccoli seedlings.

Synergistic Enhancement of Lead and Selenate Uptake at the Barite (001)-Water Interface.

The interactions of heavy metals with minerals influence the mobility and bioavailability of toxic elements in natural aqueous environments. The sorption of heavy metals on covalently bonded minerals is generally well described by surface complexation models (SCMs). However, understanding sorption on sparingly soluble minerals is challenging because of the dynamically evolving chemistry of sorbent surfaces. The interpretation can be even more complicated when multiple metal ions compete for sorption. In the present study, we observed synergistically enhanced uptake of lead and selenate on the barite (001) surface through two sorption mechanisms: lattice incorporation that dominates at lower coverages and two-dimensional monolayer growth that dominates at higher coverages. We also observed a systematic increase in the sorption affinity with increasing co-sorbed ion coverages, different from the assumption of invariant binding constants for individual adsorption processes in classical SCMs. Computational simulations showed thermodynamically favorable co-incorporation of lead and selenate by simultaneously substituting for barium and sulfate in neighboring sites, resulting in the formation of molecular clusters that locally match the net dimension of the substrate lattice. These results emphasize the importance of ion-ion interactions at mineral-water interfaces that control the fate and transport of contaminants in the environment.

Alleviating cobalt and lead toxicity in rice using zero valent iron (Fe°) amendments

Simultaneous impact of zero valent iron (Fe°) and rice cultivar on uptake, translocation, and bioaccumulation of cobalt (Co) and lead (Pb) in rice (Oryza sativa L.) was investigated to alleviate Co and Pb toxicity in rice. Kilombero and Faya rice cultivars, amended with Fe° dosages of 0, 6.20, and 12.40 g Fe° kg−1 soil, were cultivated under continuous flooding in pots in a greenhouse. Shoot and grain-Co and Pb concentrations were determined using inductively coupled plasma mass spectrometry (ICP-MS). For Co, amending Faya rice with at least 6.20 g Fe° kg−1 reduced grain-Co accumulation by 33% or more compared to control plants (F = 17.5; p < 0.001) while inconsistent results were obtained for Kilombero. For Pb, Faya also accumulated more than 39% less grain-Pb than control plants (272 μg kg−1) while Kilombero accumulated more than 55% less grain-Pb than control plants under the same conditions. Despite reducing grain-Pb accumulation in both cultivar, Fe amendments of at least 6.20 g Fe° kg−1 reduced grain-Pb accumulation with greater magnitude in Kilombero (55%) than in Faya (39%). Nonetheless, Fe amendments inhibited greater shoots-Co and Pb translocation (≥32%) to grains in Faya compared to Kilombero (≤20%). The work provides a novel promising agronomical practice of reducing Co and Pb bioaccumulation in rice.

Accumulation of silicon in shoots is required for reducing lead uptake in rice

Silicon (Si) treatment has been shown to reduce the toxicity and accumulation of lead (Pb) in many plants, including rice. The mechanisms responsible for this effect are poorly understood. We investigated the effects of Si treatment on Pb toxicity and accumulation in two rice mutants (lsi1 and lsi2) defective in Si uptake and in their wild types. Si did not alleviate Pb-induced inhibition of root elongation in short-term experiments, but reduced Pb accumulation in wild types, but not in mutants, in long-term experiments. Pre-treatment with Si reduced Pb concentration in xylem sap and Pb accumulation in wild types but not in mutants. In split-root experiments, Si treatment reduced Pb accumulation but did not alter Pb localization in roots. Si treatment suppressed the expression of many genes encoding proteins that may participate in Pb uptake and transport in the wild type, but not in the lsi1 mutant. These results indicate that Si accumulation in shoots is required to reduce Pb uptake in rice and that the effect is achieved via Si-induced suppression of genes encoding proteins involved in Pb uptake and/or transport.

Uptake of lead and zinc from soil by blackberry plants (Rubus fruticosus L. agg.) and translocation from roots to leaves

• Pb and Zn in soil ofa the Innerste floodplain exceed precautionary limits. • Concentrations of Pb and Zn in soils and blackberries are positively correlated. • Uptake and translocation of Pb and Zn are reduced at higher soil levels. • R. fruticosus is a useful bioindicator but unsuited for phytoremediation. Heavy metals transported by rivers are deposited in sediments and floodplains, and floodplain soils act as both sinks and sources of these metals. The Innerste River is contaminated by historical metal ore mining, processing, and smelting in the Harz Mountains (Germany). Our study compared the uptake of lead (Pb) and zinc (Zn) in wild blackberries ( Rubus fruticosus L. agg.) growing within and outside the Innerste floodplain in a downstream area. The potential of blackberries as bioindicators and for phytoremediation of soils polluted by Pb and Zn was assessed based on bioconcentration factors (BCF) and the intra-plant mobility of the two metals based on translocation (TF) factors. Concentrations of Pb and Zn were significantly higher in soils and blackberry plants from the Innerste floodplain compared to adjacent non-flooded area, while soil pH and organic matter content did not differ significantly between the two zones. Mean concentrations (mg/kg d.w.) of Pb (1457.2) and Zn (1365.2) in the regularly flooded soils far exceeded the precautionary limits of the German Federal Soil Protection and Contaminated Sites Ordinance. Concentrations of both heavy metals in blackberry roots and leaves increased with their levels in soil. Except for BCF Root Pb, BCFs and TFs decreased exponentially with increasing heavy metal concentration in soil and roots, respectively. This indicates that the uptake of Pb and Zn by R. fruticosus and their translocation within the plant are reduced at higher soil levels of both heavy metals. BCF < 1 were determined for both heavy metals and a TF < 1 for Pb. Only blackberries growing outside the floodplain showed a TF > 1 for Zn. Our results indicate that blackberries can be used as bioindicators of soil contamination by Pb and Zn. Regarding their uptake characteristics, blackberries constitute excluders rather than accumulators, and are thus unsuited for phytoremediation.

Seed Priming with ZnO and Fe3O4 Nanoparticles Alleviate the Lead Toxicity in Basella alba L. through Reduced Lead Uptake and Regulation of ROS.

The increased lead (Pb) content in the environment has an impact on all living beings, including plant growth and quality. The present study aims to investigate the protective roles of zinc (Zn)- and iron (Fe)- nanoparticles (NPs) in alleviating stress symptoms caused by lead (Pb) exposure in Basella alba seedlings. For this purpose, 15 different treatment combinations of seed priming with two NPs at 0 and 200 mg L−1, and five Pb levels (0, 4, 8, 15, 20 mM) were chosen. Pb stress (20 mM) was found to reduce seed germination by 72.8% and seedling growth, particularly root length, by 92% when compared to the control. Under different Pb concentrations, seed priming with ZnNPs (200 mg L−1) and FeNPs (200 mg L−1) increased seed germination by 34.7% and 54.9%, respectively, and root length by 152.9% and 252.9%, respectively. In 20 mM Pb stress, NPs primed seedling showed decrease in Pb content by 33.7% with ZnNPs and 32.6% with FeNPs. Increased Pb stress resulted in increased reactive oxygen species (ROS) generation (H2O2) and lipid peroxidation (MDA) compared to non-Pb stressed seedlings. However, increased antioxidants in the NPs treatments such as SOD, CAT, POD and proline content, scavenged these ROS. Considering all the parameters under study, priming alleviated Pb stress in the following order: FeNPs > ZnNPs > hydropriming > control. To summarise, seed priming with Zn- and Fe-NPs has the potential to alleviate Pb toxicity via reduced Pb uptake, ROS generation and lipid peroxidation as well as increased proline content and activation of antioxidant enzymatic system.

Revalorizing a Pyrolytic Char Residue from Post-Consumer Plastics into Activated Carbon for the Adsorption of Lead in Water

This work focuses on the use of a char produced during the pyrolysis of a mixture of non-recyclable plastics as a precursor for the preparation of porous activated carbon with high developed adsorption uptake of lead in water. Physical and chemical activation was used to enhance the porosity, surface area, and surface chemistry of char. The final activated carbon materials were deeply characterized through N2 adsorption isotherms, scanning electron microscopy, Fourier transformed infrared spectroscopy, analysis of the metal content by inductively coupled plasma mass spectroscopy, and pH of point zero charge. The native char displayed a Pb adsorption uptake of 348 mg Pb·g−1 and considerably high leaching of carbon, mainly organic, ca. 12%. After stabilization with HCl washing and activation with basic character activators, i.e., CO2, NaOH, and KOH, more stable adsorbents were obtained, with no organic leaching and a porous developed structure, the order of activation effectiveness being KOH (487 m2·g−1) &gt; NaOH (247 m2·g−1) &gt; CO2 (68 m2·g−1). The activation with KOH resulted in the most effective removal of Pb in water with a saturation adsorption uptake of 747 mg Pb·g−1.

Аккумуляция тяжелых металлов представителями родового комплекса Iris L.

Abstract. Technogenic emission of heavy metals (HM) leads to their accumulation and migration in the “soil – plant” system. Herbaceous perennials occupy a significant place among the landscaping components exposed to toxicants. The purpose of the research is to study the accumulation and distribution of elements of hazard class I in plants of the genus Iris L. Methods. The research was carried out in 2020–2021 on the basis of the South-Ural Botanical Garden-Institute UFRC RAS. Objects of study: soil of the site and plant organs (Iris orientalis, I. pseudacorus, I. sibirica, I. spuria subsp. carthaliniae). The elemental composition was determined by the atomic absorption method with electrothermal atomization. Scientific novelty. For the first time, the distribution of pollutants was evaluated using the biological absorption coefficient (BAC) and total cumulation in organs. Results. It has been shown that the content of mobile forms of HM in the soil does not exceed the MPC and averages: Cd – 0.03, As – 0.59, Pb – 0.48 mg/kg. It was found that the distribution of cadmium in organs depends on the species: both basipetal (I. orientalis) and acropetal accumulation of the element (I. spuria subsp. carthaliniae) are possible. Accumulation in above-ground organs exceeds cumulation in roots from 1.4 to 7.5 times. It was shown that the roots of I. orientalis, I. pseudacorus, I. spuria subsp. carthaliniae perform a barrier function and accumulate arsenic in amounts exceeding the MPC. The root system of I. sibirica does not prevent the entry of the toxicant, which is concentrated in the generative organs at a concentration exceeding the MPC. It was determined that the BAC of arsenic in the leaves of all species is less than 1. Lead uptake is species-independent, as evidenced by close total elemental values, similar organ distribution, and consistently high MPC. A predominantly above-ground concentration of the pollutant was revealed. The result of the regression analysis showed that the content of the mobile form of lead in the soil does not affect its accumulation in the leaves.

Evaluation of Dittrichia viscosa Aquaporin Nip1.1 Gene as Marker for Arsenic-Tolerant Plant Selection.

Dittrichia viscosa (L.) Greuter is gaining attention for its high genetic plasticity and ability to adapt to adverse environmental conditions, including heavy metal and metalloid pollution. Uptake and translocation of cadmium, copper, iron, nickel, lead, and zinc to the shoots have been characterized, but its performance with arsenic is less known and sometimes contradictory. Tolerance to As is not related to a reduced uptake, but the null mutation of the aquaporin Nip1.1 gene in Arabidopsis makes the plant completely resistant to the metalloid. This aquaporin, localized in the endoplasmic reticulum, is responsible for arsenite and antimony (Sb) membrane permeation, but the uptake of arsenite occurs also in the null mutant, suggesting a more sophisticated action mechanism than direct uptake. In this study, the DvNip1 gene homologue is cloned and its expression profile in roots and shoots is characterized in different arsenic stress conditions. The use of clonal lines allowed to evidence that DvNip1.1 expression level is influenced by arsenic stress. The proportion of gene expression in roots and shoots can be used to generate an index that appears to be a promising putative selection marker to predict arsenic-resistant lines of Dittrichia viscosa plants.

Bioaccumulation of lead (Pb) and its effects in plants: A review

Heavy metals (HM) toxicity is becoming a major threat to living organisms in recent years due to the increase in population and anthropogenic activities. Lead (Pb) shares about 10% of total pollution produced by heavy metals. The uptake of lead by the primary producers (plants) is found to affect their metabolic functions, growth, and photosynthetic activity. The accumulation of lead in excess can cause up to a 42% reduction in the growth of the roots. The current review addresses the global status of lead contamination in soil, potential lead sources, and the mechanism of lead uptake by the plants. This article also provides information about the lead concentration in plants in polluted and non-polluted areas. Humans are directly or indirectly dependent on plants to meet their daily requirements. So, it becomes necessary to review the problems associated with lead pollution in plants and its mode of action affecting the plant system. Factors like bioaccumulation, bioavailability, bioconcentration, transfer factor, and the role of Casparian strips as a natural physical barrier are discussed. Further, the updated literature survey about the various bioremediation strategies utilized for its elimination is also presented. The current study suggests that more attention needs to be focused on evaluating the effectiveness of bioremediation methods.

Abstract 722: Metals in primary teeth and childhood acute lymphoblastic leukemia: A pilot study

Abstract Background: Acute lymphoblastic leukemia (ALL) is the most common childhood cancer, but few environmental risk factors have been confirmed, mostly due to imprecise self-reported questionnaire data. This highlights the need for epidemiological studies to employ novel exposure assessment methods to objectively measure early life exposures. Many metals are considered known or probable human carcinogens, primarily based on studies of adult cancers. We seek to determine the association between pre- and postnatal uptake of metals and ALL risk. Methods: Children with and without ALL were recruited from Texas Children’s Hospital. Each participant donated 2-5 primary teeth for analysis. Using laser ablation-inductively coupled plasma-mass spectrometry, we measured 8 metals (arsenic, cadmium, chromium, copper, lead, manganese, magnesium, zinc) and calcium in teeth from 61 children with ALL and 6 without. In teeth, dentin and enamel form at different times, creating visible growth rings, which allowed us to objectively measure metal uptake for every week from up to 20 weeks before birth to 55 weeks after birth. At each timepoint, the ratio of metal to calcium was calculated to normalize the data. For each metal, we calculated the average prenatal uptake (i.e., 20 weeks before birth to birth) and average postnatal uptake (i.e., first week after birth to last available measurement). The average metal uptake in cases were compared to controls. To identify more specific window(s) of susceptibility, we used distributed lag regression, allowing us to incorporate data measured at all timepoints. Results: Compared to children without ALL, children with ALL on average had higher prenatal uptake of chromium (0.50 vs 0.43; p=0.07), manganese (1,969 vs 1,888; p=0.20), and lead (0.04 vs 0.02; p=0.03) and lower prenatal uptake of cadmium (0.01 vs 0.02; p=0.0004), copper (0.07 vs 0.10; p=0.19), magnesium (0.24 vs 0.29; p=0.35), and zinc (22 vs 24; p=0.01). Average prenatal uptake of arsenic was similar between cases and controls (0.01 vs 0.01; p=0.13). A similar pattern was observed with postnatal uptake of metals. Using distributed lag regression, prenatal uptake of manganese 10 to 20 weeks before birth was significantly associated (p&amp;lt;0.05) with risk of ALL, but a significantly protective association was observed starting at ~5 weeks after birth. While no other metals had a significant association with ALL, there was suggestive evidence that pre- and postnatal uptake of lead and chromium were positively associated with ALL, while pre- and postnatal uptake of zinc and copper were inversely associated. Conclusion: Using a novel exposure method to measure metal uptakes at specific windows of susceptibility in primary teeth samples, our results suggest certain metals may contribute to the etiology of ALL. A larger study is needed to draw more definitive conclusions about early-life uptake of metals and risk of ALL. Citation Format: Thanh Hoang, Manish Arora, Christine Austin, Paul C. Curtin, Philip J. Lupo, Michael E. Scheurer. Metals in primary teeth and childhood acute lymphoblastic leukemia: A pilot study [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 722.

Fulvic Acid Alleviates Paper Sludge Toxicity in Canola (Brassica napus L.) by Reducing Cr, Cd, and Pb Uptake.

Heavy metal toxicity reduces the growth and development of crop plants growing in metal-contaminated regions. Disposal of industrial waste in agricultural areas has negative effects on the physiochemical activities of plants. This research aimed to examine the fulvic acid (FA)-mediated efficacy of Brassica napus L. regarding stress tolerance in soil amended with paper sludge (PS). For this purpose, plants were grown for 90 days under greenhouse conditions at various concentrations of PS-amended soils (0, 5, 10, and 15%) being irrigated with water containing FA (0, 10, and 20%). All the physicochemical parameters of PS were carried out before and after plant transplantation. Paper sludge toxicity reduced the growth (shoot/root length, fresh/dry weight of shoot/root, numbers of flowers and leaves) and physicochemical characteristics of exposed B. napus plants. In comparison, FA application improved growth by reducing the metal uptake in the shoot of plants grown at various concentrations of PS. An increasing trend in antioxidant enzyme activity was observed by increasing the FA concentration (0%-10% and 20%). Post-harvest analysis indicated that the amount of tested metals was significantly reduced at all PS concentrations. Minimum metal uptake was observed at 0% concentration and maximum at 15% concentration of paper sludge. Additionally, FA application at 20% concentration reduced Chromium (Cr), Cadmium (Cd), and Lead (Pb) uptake in the shoot from 6.08, 34.42, and 20.6 mgkg−1 to 3.62, 17.33, and 15.22 mgkg−1, respectively. At this concentration of paper sludge in the root, 20% FA reduced Cr, Cd, and Pb uptake from 11.19, 44.11, and 35.5 mgkg−1 to 7.88, 27.01, and 24.02 mgkg−1, respectively. Thus, FA at 20% concentration was found to be an effective stimulant to mitigate the metal stress in B. napus grown in paper sludge-polluted soil by reducing metal uptake and translocation to various plant parts.

Suppression of arbuscular mycorrhizal fungi increased lead uptake in maize leaves and loss via surface runoff and interflow from polluted farmland

Arbuscular mycorrhizal fungi (AMF) are ubiquitous in farmland. But the knowledge on AMF impact on lead (Pb) migration in farmland is limited. A field experiment was conducted in the rainy season (May–October) for two years in a Pb-polluted farmland. Benomyl was used to specifically suppress the native AMF growth in the farmland. The effect of benomyl-induced AMF suppression on the Pb uptake in maize, and Pb loss via surface runoff and interflows (20 cm and 40 cm depth) from the farmland was investigated. The benomyl significantly inhibited the AMF growth, resulting in decreases in the colonization rate, spore number, and contents of total and easily extractable glomalin-related soil protein (GRSP); and promoted the Pb migration into maize shoots and mainly enriched in leaves. The particulate Pb accounted for 83.2%–90.6% of Pb loss via surface runoff, while the proportion of particulate Pb loss via interflow was decreased and the proportion of dissolved Pb loss increased with the increase of soil depth. The AMF suppression led to a decrease in dissolved Pb concentration and loss, but an increase in particulate Pb concentration and loss, and enhanced the total Pb loss via surface runoff and interflows. Moreover, significant or very significant negative correlations were observed between the AMF colonization rate in roots with the Pb uptake in leaves, and the content of easily extractable GRSP with the particulate Pb loss. These results indicated the native AMF contributed to immobilizing Pb in soil and inhibited its migration to crops and the surrounding environment.

Toxic elements of hazard class I in ornamental herbal permanent plants

Technogenic emission of heavy metals (HM) leads to their accumulation and migration in the “soil-plant” system. Herbaceous perennials occupy a significant place among the landscaping components exposed to toxicants. The purpose of the research is to study the accumulation and distribution of elements of hazard class I in plants of the genus Iris L. The research was carried out in 2020-2021 on the basis of the South-Ural Botanical Garden-Institute. Objects of study: soil of the site and plant organs (Iris orientalis, I. pseudacorus, I. sibirica, I. spuria subsp. carthaliniae). The elemental composition was determined by the atomic absorption method with electrothermal atomization. The distribution of pollutants was evaluated using the biological absorption coefficient (BAC), total cumulation in vegetative and generative, as well as underground and aboveground organs. It is shown that the content of mobile forms of HM and metalloids in the soil does not exceed the maximum allowable concentrations (MAC) and averages: Cd – 0.03, As – 0.59, Pb – 0.48 mg/kg. It was found that the distribution of cadmium in organs depends on the species: both basipetal (I. orientalis – 0.05 mg/kg) and acropetal accumulation of the element (I. spuria subsp. carthaliniae – 0.05 mg/kg) are possible. Accumulation in above-ground organs exceeds cumulation in roots from 1.4 to 7.5 times. It was determined that the values of CBA for cadmium differ from 0.27 to 1.56. It was shown that the roots of I. orientalis, I. pseudacorus, I. spuria subsp. carthaliniae perform a barrier function and accumulate arsenic in amounts exceeding the MPC (0.67-0.85 mg/kg). The root system of I. sibirica does not prevent the entry of the toxicant concentrated in the generative organs at a concentration exceeding the MPC (0.61-0.78 mg/kg). It was determined that the CBA of arsenic in the leaves of all species is <1. Lead uptake is species-independent, as evidenced by close total elemental values, similar organ distribution, and consistently high MAC. A predominantly above-ground concentration of the pollutant was revealed (3.4-5.1). The result of the regression analysis showed that the content of the mobile form of lead in the soil does not affect its accumulation in the leaves.

Adsorption Capacity of Lead (II) (Pb2+) in Aqueous Solution by Brown Seaweed (Fucus spiralis)

The sorption uptake of lead by marine brown alga Fucus spiralis was investigated in bimetallic solutions. The experimental data fitted very well to Langmuir model. In bimetallic systems, the affinity of biomass for lead and cadmium increased and the sorption uptake of these metals was not affected by increasing concentrations. However, in solutions with both metals there was a significant mutual decrease of their sorption levels at high concentrations of the other metal. There is practical removal up to 100 ± 4% for biomass dosage 4.0 ±0.1 g which correspond to lowest adsorbed amount of 0.25 ± 0.1 mg/g. The highest adsorbed value was recorded with biomass dosage 0.25 ± 0.1 g but with the lowest percentage removal of 92.50 ± 6%. In this study at initial metal concentration of 10 mg/L the highest metal removal of 96% was achieved.

Plastic litter fate and contaminant transport within the urban environment, photodegradation, fragmentation, and heavy metal uptake from storm runoff

A significant portion of urban litter is plastic which contaminates the environment and threatens ecological safety. The conversion of plastic litter into small fragments called microplastics (MPs) intensifies their critical risks by facilitating their transport and altering their physicochemical features. This study focuses on low density polyethylene (LDPE) and polyethylene terephthalate (PET) as the main components of urban litter. The photodegradation of LDPE and PET MPs due to the accelerated weathering experiments is investigated through surface chemistry and morphology analysis. The influence of MPs’ photodegradation on their fragmentation behavior is evaluated through the innovative accelerated mechanical weathering experiments that simulated the abrasion of MPs with the road deposits. Furthermore, the role of MPs as the vehicles to transport the heavy metals from the urban environment to the water resources is evaluated by studying the kinetics of lead (Pb) uptake by new and weathered MPs in synthetic stormwater. The surface morphology investigation revealed the formation of crazes and the crack networks onto the MPs due to the weathering experiments. The surface chemistry analysis revealed the generation of several oxidized carbon surface functional groups onto the photodegraded MPs and their increased susceptibility to fragmentation due to the abrasion with the road deposits. The photodegradation increased the Pb accumulation onto the LDPE and PET MPs from 467 μg/m2 and 21 μg/m2 to 2290 μg/m2 and 725 μg/m2, after five days of metal exposure. The fundamental knowledge developed in this research provides a better conceptual understanding of the mechanisms controlling MPs persistence and contaminant transport within the urban environment, which is crucial to estimate their negative impacts on the ecosystem.

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.

Innovative Recovery of Winemaking Waste for Effective Lead Removal from Wastewater

Every year, important quantities of winemaking waste create problems for wine producers. These problems arise from the difficulty of disposing of grape marc, which can pollute the environment and affect nearby agricultural crops. The present research proposes a new direction for the valorization of this agri-food waste in residual water depollution. Four biomaterials obtained from winemaking waste were tested for Pb removal: raw Merlot grape marc (MR), raw Sauvignon Blanc grape marc (SbR), Merlot grape marc biorefined (ME) and Sauvignon Blanc grape marc biorefined (SbE). The effects of biosorbent mass and initial Pb concentration, adsorption kinetic, equilibrium isotherms and the matrix influence from a mine effluent were assessed. Very good perspectives for the practical application in lead uptake from wastewaters arise, with better results for biorefined grape marc compared to raw material. The lead removal percentage from an initial solution containing 20 mg Pb/L, at optimum pH (5.5 ± 0.5) was 71%—MR, 78%—SbR, 80%—ME, and 97%—SbE. A Langmuir model revealed a very good removal capacity for ME (40 mg/g) and SbE (64 mg/g). Thus, the grape marc, a polluting waste, can turn into a low-cost and easy-to-prepare sorbent for the bioremediation of contaminated water.

The protective role of selenium against uptake and accumulation of cadmium and lead in white oyster (Pleurotus ostreatus) and pink oyster (Pleurotus djamor) mushrooms

ABSTRACT Mushrooms are bioaccumulators and have been used to produce Se-enriched foods. However, these fungi can also bioaccumulate potentially toxic metals, producing food dangerous to human health. It is known that co-exposure to Se plays a protective role against metal accumulation and toxicity in some organisms due to its antioxidant properties. Thus, this study aimed to evaluate the protective effect of Se(IV) and Se(VI) on elemental uptake and accumulation as well as proteins and protein-bound Se, Cd, and Pb distribution in Pleurotus mushrooms. Pink oyster and white oyster mushrooms showed high ability to bioaccumulate Se (19–205 µg g−1), Cd (4.5 to 18.8 µg g−1), and Pb (1.6 to 7.0 µg g−1). Growth substrate supplementation with Se(IV) or Se(VI) decreased the Cd total concentration in mushrooms by 4 to 89%, while Se(VI) increased the Pb total concentration by 9% to 187%, compared to growth in absence of Se. It was found that despite molecular weights distributions of mushrooms grown on Se(IV) and Se(VI)-supplemented substrates being similar, Se(VI) supplementation favoured Se interaction with proteins of medium molecular weight (17–44 kDa), when compared to supplementation with Se(IV). Therefore, we propose the supplementation of growth substrates with Se(VI) to reduce eventual Cd accumulation and produce Se-enriched oyster mushrooms.