Lead (Pb) contamination of agricultural soils, and subsequently of crops, has been widely reported. Soybean (Glycine max (L.) Merr.) has been indicated as a plant that accumulates Pb, even in soils that do not exceed the maximum permissible levels. Considering the toxicity of this heavy metal, the aim of the present study was to assess different concentrations of Pb, from low to extremely high (0.25 mM, 1 mM, and 2.5 mM), in soybean seedlings and their tolerance by analyzing morpho-physiological parameters in hydroponic experiments. Soybean seedlings were exposed to control and Pb treatments during 8 days, coinciding with the early growth stages, and the following variables were analyzed: biomass, Pb content in roots, stems and leaves, photosynthetic efficiency, leaf area, biochemical response (antioxidant power, chlorophylls, malondialdehyde), and relative water content of leaves. Results showed that roots accumulated much more Pb than the other organs, with Pb accumulation in roots being saturated even at the lowest Pb concentration, which was reflected in root biomass. Moreover, absorption of culture solutions was lower in Pb treatments, which was also reflected in the lower leaf relative water content. Lead toxicity symptoms in leaves (chlorosis and dark spots, and a decrease of biomass and leaf area, chlorophyll content, and photosynthetic efficiency), and an increase of the oxidative defense system were associated only with the highest Pb concentration (2.5 mM). Our findings support the evidence of soybean as a species tolerant to Pb, showing the effects of toxicity at very high concentrations. | Instituto de Fisiología y Recursos Genéticos Vegetales | Fil: Blanco, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Instituto Multidisciplinario de Biología Vegetal (IMBIV). Área Contaminación y Bioindicadores; Argentina | Fil: Blanco, Andrés. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina | Fil: Pignata, María L. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Instituto Multidisciplinario de Biología Vegetal (IMBIV). Área Contaminación y Bioindicadores; Argentina | Fil: Pignata, María L. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina | Fil: Lascano, Hernán Ramiro. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Fisiología Vegetal; Argentina | Fil: Lascano, Hernán Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Unidad de Estudios Agropecuarios (UDEA); Argentina | Fil: Lascano, Hernán Ramiro. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales. Argentina | Fil: Rodriguez, Judith H. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Instituto Multidisciplinario de Biología Vegetal (IMBIV). Área Contaminación y Bioindicadores. Argentina | Fil: Rodriguez, Judith H. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina

Glycine max (L.) Merr. (soybean) crop plants have been found to have high lead (Pb) levels in aerial organs; however, knowledge about the processes involved in the incorporation, and subsequent translocation and accumulation of the metal in the plants is scarce. Considering the toxicity of this heavy metal, the aim of the present study was to evaluate Pb uptake and translocation, and their toxic effects on soybean seedlings via experiments of ionic competition with Ca2+ (2.5 mM, Ca:Pb 1:1) and alteration of the transpiration flow [0.25 mM Pb(NO3)2]. The following variables were analyzed: biomass, leaf area (morphological parameters), photosynthetic efficiency, biochemical response (considered physiological stress markers: antioxidant power, chlorophylls, carotenoids, starch, proteins, sugars, and malondialdehyde), and Pb content. Results showed that soybean seedlings can accumulate high Pb concentration in its organs; however, in general, no morpho-physiological Pb stress symptoms were observed, except for lipid peroxidation and antioxidant power. The treatment with Ca ions was not effective in reducing Pb entry into root over time when both Ca and Pb where present in the grow solution. Alteration of the transpiration rate in soybean showed that the air flow increased the consumption of solutions, regardless of the treatments. | Instituto de Fisiología y Recursos Genéticos Vegetales | Fil: Blanco, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal (IMBIV). Área Contaminación y Bioindicadores; Argentina | Fil: Blanco, Andrés. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina | Fil: Pignata, María L. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal (IMBIV). Área Contaminación y Bioindicadores; Argentina | Fil: Pignata, María L. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina | Fil: Lascano, Hernán Ramiro. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Cátedra de Fisiología Vegetal; Argentina | Fil: Lascano, Hernán Ramiro. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Estudios Agropecuarios (UDEA); Argentina | Fil: Lascano, Hernán Ramiro. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Fisiología y Recursos Genéticos Vegetales; Argentina | Fil: Salazar, María J. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal (IMBIV). Área Contaminación y Bioindicadores; Argentina | Fil: Salazar, María J. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina | Fil: Rodriguez, Judith H. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Multidisciplinario de Biología Vegetal (IMBIV). Área Contaminación y Bioindicadores; Argentina | Fil: Rodriguez, Judith H. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina

International audience | The aim of this study is to assess the annual balance of the fluxes of Cd, Cu, Ni, Pb and Zn within different cropping systems, in an experimental site located near Versailles, France. Four fluxes through the cultivated horizon were considered to assess the annual heavy metal balance in these systems: 1) atmospheric depositions, 2) fertilisers as inputs, 3) crops and 4) leaching water as outputs. The water mass flow was estimated with a model (CERES) while the other parameters were actually measured through field sampling. Some large uncertainties are related to analytical detection limits, specially for Pb which presents very low concentrations in nitrogen fertilisers, in crops and in soil solution. Cd was also close to the detection limits in atmospheric deposition and in soil water, and Zn could not be analysed in soil solution. Nevertheless, the following trends clearly appeared: firstly, atmospheric deposition is the major input way of Cu, Ni, Pb and Zn in the soil, whatever the cropping system, whereas Cd is introduced mainly by fertilisers. Secondly, the uptake of heavy metal by wheat is generally larger than by a pea culture, except for Ni. Finally, the global pattern shows an accumulation of Cd, Ni and Pb in the cultivated horizon while Cu decreased. The annual balances, during the cropping year 2001–2002, represented about 0.33, −0.024, 0.014 and 0.014% of the actual stocks in the cultivated horizon, of Cd, Cu, Ni, and Pb, respectively.

International audience | The aim of this study is to assess the annual balance of the fluxes of Cd, Cu, Ni, Pb and Zn within different cropping systems, in an experimental site located near Versailles, France. Four fluxes through the cultivated horizon were considered to assess the annual heavy metal balance in these systems: 1) atmospheric depositions, 2) fertilisers as inputs, 3) crops and 4) leaching water as outputs. The water mass flow was estimated with a model (CERES) while the other parameters were actually measured through field sampling. Some large uncertainties are related to analytical detection limits, specially for Pb which presents very low concentrations in nitrogen fertilisers, in crops and in soil solution. Cd was also close to the detection limits in atmospheric deposition and in soil water, and Zn could not be analysed in soil solution. Nevertheless, the following trends clearly appeared: firstly, atmospheric deposition is the major input way of Cu, Ni, Pb and Zn in the soil, whatever the cropping system, whereas Cd is introduced mainly by fertilisers. Secondly, the uptake of heavy metal by wheat is generally larger than by a pea culture, except for Ni. Finally, the global pattern shows an accumulation of Cd, Ni and Pb in the cultivated horizon while Cu decreased. The annual balances, during the cropping year 2001–2002, represented about 0.33, −0.024, 0.014 and 0.014% of the actual stocks in the cultivated horizon, of Cd, Cu, Ni, and Pb, respectively.

Inhalation represents the most prevalent route of exposure with Thorium-232 compounds (Th-nitrate/Th-dioxide)/Th-containing dust in real occupational scenario. The present study investigated the mechanism of Th response in normal human alveolar epithelial cells (WI26), exposed to Th-nitrate or colloidal Th-dioxide (1–100 μg/ml, 24–72 h). Assessment in terms of changes in cell morphology, cell proliferation (cell count), plasma membrane integrity (lactate dehydrogenase leakage) and mitochondrial metabolic activity (MTT reduction) showed that Th-dioxide was quantitatively more deleterious than Th-nitrate to WI26 cells. TEM and immunofluorescence analysis suggested that Th-dioxide followed a clathrin/caveolin-mediated endocytosis, however, membrane perforation/non-endocytosis seemed to be the mode of Th internalization in cells exposed to Th-nitrate. Th-estimation by ICP-MS showed significantly higher uptake of Th in cells treated with Th-dioxide than with Th-nitrate at a given concentration. Both Th-dioxide and nitrate were found to increase the level of reactive oxygen species, which seemed to be responsible for lipid peroxidation, alteration in mitochondrial membrane potential and DNA-damage. Amongst HSPs, the protein levels of HSP70 and HSP90 were affected differentially by Th-nitrate/dioxide. Specific inhibitors of ATM (KU55933) or HSP90 (17AAG) were found to increase the Th- cytotoxicity suggesting prosurvival role of these signaling molecules in rescuing the cells from Th-toxicity.

Biochar has been widely used in the mitigation of soil potentially toxic metals due to its high efficiency and low cost. Crayfish shell biochar (CSBC) was prepared at 300, 500, and 700 °C (referred to as CS300, CS500, and CS700, respectively) and the performance and mechanism of CSBC for mitigating Pb polluted water and soil was investigated. The results indicated that CSBC prepared at higher temperatures possessed higher pH value and ash content, more abundant pore structure, and higher stability. Pb²⁺ adsorption onto CSBC fitted well with the pseudo second order and intraparticle diffusion models. The maximum adsorption capacity of Pb²⁺ increased with the pyrolysis temperature, being 599.70, 1114.53, and 1166.44 mg·g⁻¹ for CS300, CS500 and CS700, respectively. Compared with the control soil samples, the content of available Pb after applying 0.05%–5% CSBC was reduced by 1.87%–16.48% in acidic soils and 1.00%–11.09% in alkaline soils. Moreover, the fractionation of exchangeable Pb was converted to stable organic matter bound, Fe-Mn oxide bound, and residue fractions. XRD, SEM-EDS, and FTIR analysis showed that ion exchange, complexation, precipitation, and C−π interaction are the dominant interaction mechanisms. Therefore, CSBC can employ as an effective immobilizing agent for the mitigation of Pb contaminated water and soil.

Microbial biofilms can rapidly colonize plastic debris in aquatic environments and subsequently, accumulate chemical pollutants from the surrounding water. Here, we studied the microbial colonization of different plastics, including polyethylene terephthalate (PET), polypropylene (PP), polyvinyl chloride (PVC), and polyethylene (PE) exposed in three freshwater systems (the Qinhuai River, the Niushoushan River, and Donghu Lake) for 44 days. We also assessed the biofilm mass and associated metals attached to plastics. The plastics debris characteristics, such as contact angle and surface roughness, greatly affected the increased biofilm biomass. All types of metal accumulation onto the plastic substrate abundances significantly higher than the concentrations of heavy metal in the water column, such as Ba (267.75 μg/g vs. 42.12 μg/L, Donhu Lake), Zn (254 μg/g vs. 0.023 μg/L the Qinhuai River), and Cr (93.75 μg/g vs. 0.039 μg/L, the Niushoushan River). Compared with other metals, the heavy metal Ba, Cr and Zn accumulated easily on the plastic debris (PET, PP, PVC, and PE) at all incubation sites. Aquatic environmental factors (total nitrogen, total phosphorus, and suspended solids concentrations) largely shaped metal accumulation onto plastic debris compared with plastic debris properties.

Neuroinflammation induced by lead exposure (Pb) is a major cause of neurotoxicity of Pb in the central nervous system (CNS). The NLR family, domain of pyrin containing 3 (NLRP3) involves in various neurological diseases, while the question of whether NLRP3 plays a role in lead-induced neuroinflammation has not yet been reported.Developmental and knockout (KO) NLRP3 mice were used to establish two in vivo models, and BV2 cells were used to establish an in vitro model. Behavioral and electrophysiologic tests were used to assess the neurotoxicity of Pb, and immunofluorescence staining was used to assess neuroinflammation. Real-time PCR and western blot were performed to examine the mRNA and protein levels of inflammatory cytokines and NLRP3 inflammasomes. siRNA technology was used to block NLRP3 expression.Pb exposure led to neural injure and microglial activation in the hippocampus region, while minocycline intervention attenuated Pb-induced neurotoxicity by inhibiting neuroinflammation. Pb increased the expression of NLRP3 and promoted cleavage of caspase-1 in mRNA and protein levels, and minocycline partially reversed the effects of Pb on NLRP3 inflammasomes. Blocking of NLRP3 by KO mice or siRNA attenuated neural alterations induced by Pb, weakened microglial activation in vivo and in vitro as well, without affecting the accumulation of Pb. Pb increased autophagic protein levels and phosphorylation of NF-κB, while suppressing autophagy or NF-κB inhibited Pb's effects on NLRP3.NLRP3 is involved in the regulation of Pb-induced neurotoxicity. These findings expand mechanism research of Pb neurotoxicity and may help establish new prevention strategies for Pb neurotoxicity.

Lead (Pb) is one of the predominant heavy metals in e-waste recycling arears and recognized as a notorious environmental neurotoxic substance. However, whether Pb at environmentally relevant concentrations could cause neurobehavioral alteration and even what kind of signaling pathway Pb exposure would disrupt in zebrafish were not fully uncovered. In the present study, 6 h postfertilization (hpf) zebrafish embryos were exposed to Pb at the concentrations of 0, 5, 10, and 20 μg/L until 144 hpf. Then the neurobehavioral indicators including locomotor, turnings and social behaviors, and the expressions of selected genes concerning brain-derived neurotrophic factor (BDNF) signaling were investigated. The results showed that significant changes were obtained under 20 μg/L Pb exposure. The hypoactivity of zebrafish larvae in locomotor and turning behaviors was induced during the dark period, while hyperactivity was observed in a two-fish social assay during the light period. The significantly downregulation of genes encoding BDNF, its receptor TrkB, and N-methyl-D-aspartate glutamate receptor (NMDAR) suggested the involvement of NMDAR-dependent BDNF signaling pathway. Overall, our study demonstrated that developmental exposure to Pb at environmentally relevant concentrations caused obvious neurobehavioral impairment of zebrafish larvae by disrupting the NMDAR-dependent BDNF signaling, which could exert profound ecological consequences in the real environment.

Plastic polymers such as polyvinyl chloride (PVC) may contain chemical additives, such as lead (Pb), that are leachable in aqueous solution. The fragmentation into microplastics (MPs) of plastics such as PVC may facilitate desorption of chemical additives and increase exposure of aquatic animals. In this study, the role of chemical additives in the aqueous toxicity of PVC, high-density polyethylene (HDPE) and polyethylene terephthalate (PET) MPs were investigated in early-life stage zebrafish (Danio rerio) by assessment of changes in expression of biomarkers. Exposure of zebrafish larvae to PVC for 24 h increased expression of metallothionein 2 (mt2), a metal-binding protein, but no changes in expression of biomarkers of estrogenic (vtg1) or organic (cyp1a) contaminants were observed. HDPE and PET caused no changes in expression of any biomarkers. A filtered leachate of the PVC also caused a significant increase in expression of mt2 and indicated that a desorbed metal additive likely elicited the response in zebrafish. Metal release was confirmed by acid-washing the MPs which mitigated the response in mt2. Metal analysis showed Pb leached from PVC into water during exposures; at 500 mg PVC L⁻¹ in water, 84.3 ± 8.7 μg Pb L⁻¹ was measured after 24 h. Exposure to a Pb-salt at this concentration caused a comparable mt2 increase in zebrafish as observed in exposures to PVC. These data indicated that PVC MPs elicited a response in zebrafish but the effect was indirect and mediated through desorption of Pb from PVC into the exposure water. Data also indicated that PVC MPs may act as longer-term environmental reservoirs of Pb for exposure of aquatic animals; the Pb leached from PVC in 24 h in freshwater equated to 2.52% of total Pb in MPs leachable by the acid-wash. Studies of MPs should consider the potential role of chemical additives in toxicity observed.