Efficient remediation of different concentrations of Cr-contaminated soils by nano zero-valent iron modified with carboxymethyl cellulose and biochar.

Nano zero-valent iron (nZVI) is widely used in soil remediation due to its high reactivity. However, the easy agglomeration, poor antioxidant ability and passivation layer of Fe-Cr coprecipitates of nZVI have limited its application scale in Cr-contaminated soil remediation, especially in high concentration of Cr-contaminated soil. Herein, we found that the carboxymethyl cellulose on nZVI particles could increase the zeta potential value of soil and change the phase of nZVI. Along with the presence of biochar, 97.0% and 96.6% Cr immobilization efficiency through CMC-nZVI/BC were respectively achieved in high and low concentrations of Cr-contaminated soils after 90-days remediation. In addition, the immobilization efficiency of Cr(VI) only decreased by 5.1% through CMC-nZVI/BC treatment after 10 weeks aging in air, attributing to the strong antioxidation ability. As for the surrounding Cr-contaminated groundwater, the Cr(VI) removal capacity of CMC-nZVI/BC was evaluated under different reaction conditions through column experiments and COMSOL Multiphysics. CMC-nZVI/BC could efficiently remove 85% of Cr(VI) in about 400 hr when the initial Cr(VI) concentration was 40 mg/L and the flow rate was 0.5 mL/min. This study demonstrates that uniformly dispersed CMC-nZVI/BC has an excellent remediation effect on different concentrations of Cr-contaminated soils.

Toward a more realistic estimate of exposure to chromium and nickel in soils of geogenic and/or anthropogenic origin: importance of oral bioaccessibility.

To enhance risk assessment for contaminated sites, incorporating bioavailability through bioaccessibility as a corrective factor to total concentration is essential to provide a more realistic estimate of exposure. While the main in vitro tests have been validated for As, Cd, and/or Pb, their potential for assessing the bioaccessibility of additional elements remains underexplored. In this study, the physicochemical parameters, pseudototal Cr and Ni concentrations, soil phase distribution, and oral bioaccessibility of twenty-seven soil samples were analysed using both the ISO 17924 standard and a simplified test based on hydrochloric acid. The results showed wide variability in terms of the concentrations (from 31 to 21,079 mg kg-1 for Cr, and from 26 to 11,663 mg kg-1 for Ni) and generally low bioaccessibility for Cr and Ni, with levels below 20% and 30%, respectively. Bioaccessibility variability was greater for anthropogenic soils, while geogenic enriched soils exhibited low bioaccessibility. The soil parameters had an influence on bioaccessibility, but the effects depended on the soils of interest. Sequential extractions provided the most comprehensive explanation for bioaccessibility. Cr and Ni were mostly associated with the residual fraction, indicating limited bioaccessibility. Ni was distributed in all phases, whereas Cr was absent from the most mobile phase, which may explain the lower bioaccessibility of Cr compared to that of Ni. The study showed promising results for the use of the simplified test to predict Cr and Ni bioaccessibility, and its importance for more accurate human exposure evaluation and effective soil management practices.

Chromium removal by microbial mats: understanding the effect of salinity and pH.

Environmental contamination by chromium represents a serious public health problem. Therefore, it is crucial to develop and optimize remediation technologies to reduce its concentration in the environment. The aims of this study were to evaluate the uptake of chromium by live and complete microbial mats in experimental mesocosms under different pH and salinity conditions to understand how these factors affect the microphytobenthic community and, consequently, how chromium removal process is influenced. Microbial mats from the estuarine environment were exposed to 15 mg Cr/L under different pH (2, 4, and 8) and salinity (2, 15, and 33) conditions. Salinity, redox potential, and pH were measured throughout the trial in solutions and in microbial mats, while total Cr determinations were performed at the end of the assay. The results demonstrated that the removal efficiency of Cr by microbial mats was significantly improved in solutions at pH 2, remaining unaffected by variations in salinity. Notably, both cyanobacteria and diatoms showed remarkable resistance to Cr exposure under all conditions tested, highlighting their exceptional adaptability. Microbial mats have proved to be effective filters for reducing the concentration of chromium in aqueous solutions with varying pH and salinity levels.

Resistance mechanisms of cereal plants and rhizosphere soil microbial communities to chromium stress.

Agricultural soils contaminated with heavy metals poison crops and disturb the normal functioning of rhizosphere microbial communities. Different crops and rhizosphere microbial communities exhibit different heavy metal resistance mechanisms. Here, indoor pot studies were used to assess the mechanisms of grain and soil rhizosphere microbial communities on chromium (Cr) stress. Millet grain variety 'Jingu 21' (Setaria italica) and soil samples were collected prior to control (CK), 6 hours after (Cr_6h), and 6 days following (Cr_6d) Cr stress. Transcriptomic analysis, high-throughput sequencing and quantitative polymerase chain reaction (qPCR) were used for sample determination and data analysis. Cr stress inhibited the expression of genes related to cell division, and photosynthesis in grain plants while stimulating the expression of genes related to DNA replication and repair, in addition to plant defense systems resist Cr stress. In response to chromium stress, rhizosphere soil bacterial and fungal community compositions and diversity changed significantly (p < 0.05). Both bacterial and fungal co-occurrence networks primarily comprised positively correlated edges that would serve to increase community stability. However, bacterial community networks were larger than fungal community networks and were more tightly connected and less modular than fungal networks. The abundances of C/N functional genes exhibited increasing trends with increased Cr exposure. Overall, these results suggest that Cr stress primarily prevented cereal seedlings from completing photosynthesis, cell division, and proliferation while simultaneously triggering plant defense mechanisms to resist the toxic effects of Cr. Soil bacterial and fungal populations exhibited diverse response traits, community-assembly mechanisms, and increased expression of functional genes related to carbon and nitrogen cycling, all of which are likely related to microbial survival during Cr stress. This study provides new insights into resistance mechanisms, microbial community structures, and mechanisms of C/N functional genes responses in cereal plants to heavy metal contaminated agricultural soils. Portions of this text were previously published as part of a preprint (https://www.researchsquare.com/article/rs-2891904/v1).

In silico analysis of the impact of toxic metals on COVID-19 complications: molecular insights.

COVID-19 can cause a range of complications, including cardiovascular, renal, and/or respiratory insufficiencies, yet little is known of its potential effects in persons exposed to toxic metals. The aim of this study was to answer this question with in silico toxicogenomic methods that can provide molecular insights into COVID-19 complications owed to exposure to arsenic, cadmium, lead, mercury, nickel, and chromium. For this purpose we relied on the Comparative Toxicogenomic Database (CTD), GeneMANIA, and ToppGene Suite portal and identified a set of five common genes (IL1B, CXCL8, IL6, IL10, TNF) for the six metals and COVID-19, all of which code for pro-inflammatory and anti-inflammatory cytokines. The list was expanded with additional 20 related genes. Physical interactions are the most common between the genes affected by the six metals (77.64 %), while the dominant interaction between the genes affected by each metal separately is co-expression (As 56.35 %, Cd 64.07 %, Pb 71.5 %, Hg 81.91 %, Ni 64.28 %, Cr 88.51 %). Biological processes, molecular functions, and pathways in which these 25 genes participate are closely related to cytokines and cytokine storm implicated in the development of COVID-19 complications. In other words, our findings confirm that exposure to toxic metals, alone or in combinations, might escalate COVID-19 severity.

Rapidly and simply detecting Cr (VI) in aqueous media via a diketopyrrolopyrrole-based chemosensor with both high selectivity and low LOD.

BACKGROUND: The high toxicity of hexavalent chromium [Cr (VI)] could not only cause harmful effects on humans, including carcinogenicity, respiratory issues, genetic damage, and skin irritation, but also contaminate drinking water sources, aquatic ecosystems, and soil, impairing the reproductive capacity, growth, and survival of organisms. Due to these harmful effects, detecting toxic Cr (VI) is of great significance. However, the rapid, simple, and efficient detection at a low Cr (VI) concentration is extremely challenging, especially in an acidic condition (existing as HCrO4-) due to its low adsorption free energy. RESULTS: A diketopyrrolopyrrole-based small molecule (DPPT-PhSMe) is designed and characterized to act as a chemosensor, which allows a high selectivity to Cr (VI) at an acidic condition with a low limit of detection to 10-8 M that is two orders of magnitude lower than the cut of limit (1 µM) recommended by World Health Organization (WHO). Mechanism study indicates that the rich sulfur atoms enhance the affinity to HCrO4-. Combining with favorable features of diketopyrrolopyrrole, DPPT-PhSMe not only allows dual-mode detection (colorimetric and spectroscopic) to Cr (VI), but also enables disposable paper-based sensor for naked-eye detection to Cr (VI) from fully aqueous media. The investigation of DPPT-PhSMe chemosensor for the quantification of Cr (VI) in real life samples demonstrates a high reliability and accuracy with an average percentage recovery of 102.1 % ± 4 (n = 3). SIGNIFICANCE: DPPT-PhSMe represents the first diketopyrrolopyrrole-derived chemosensor for efficient detection to toxic Cr (VI), not only providing a targeted solution to the bottleneck of Cr (VI) detection in acidic conditions (existing as HCrO4-) caused by its low adsorption free energy, but also opening a new scenario for simple, selective, and efficient Cr (VI) detection with conjugated dye molecules.

NaHS immersion alleviates the stress effect of chromium(III) on alfalfa seeds by affecting active oxygen metabolism.

OBJECTIVE: This study aimed to investigate the regulatory effects of exogenous hydrogen sulfide (H2S) on seed germination, seedling growth, and reactive oxygen species (ROS) homeostasis in alfalfa under chromium (Cr) ion (III) stress. METHODS: The effects of 0-4 mM Cr(III) on the germination and seedling growth of alfalfa were first assessed. Subsequently, following seed NaHS immersion, the influence of H2S on alfalfa seed germination and seedling growth under 2 mM Cr(III) stress was investigated, and the substance contents and enzyme activities associated with ROS metabolism were quantified. RESULTS: Compared to the control group, alfalfa plant germination was delayed under 2 mM Cr(III) stress for up to 48 h (p < 0.05). At 120 h, the total seedling length was approximately halved, and the root length was roughly one-third of the control. Treatment with 0.02-0.1 mM NaHS alleviated the delay in germination and root growth inhibition caused by 2 mM Cr(III) stress, resulting in an increased ratio of root length to hypocotyl length from 0.57 to 1 above. Additionally, immersion in 0.05 mM NaHS reduced hydrogen peroxide (H2O2) and oxygen-free radicals (O2· -) levels (p < 0.05), boosted glutathione (GSH) levels (p < 0.05), and notably enhanced catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities (p < 0.05) compared to the 2 mM Cr(III) stress treatment group. CONCLUSION: Seed immersion in NaHS mitigated the delay in germination and inhibition of root elongation under 2 mM Cr(III) stress. This effect is likely attributed to the regulation of intracellular ROS homeostasis and redox balance through enzymatic and non-enzymatic systems; thus, providing a potential mechanism for combating oxidative stress.

Effective removal of chromium by adsorption using Delonix regia bark derived activated carbon from aqueous solution: a sustainable approach.

This study introduces a new biosorbent derived from Delonix regia bark-activated carbon to efficiently remove Chromium Cr(VI) metal ions from aqueous systems. The biosorbent was synthesized from the bark powder of the plant species and chemically activated with phosphoric acid. The biosorbent was characterized using FTIR, SEM, and BET to determine its functional properties and structural morphology. The batch adsorption experiments examined the optimal conditions for Cr(VI) metal ion adsorption, identifying that the highest removal efficiency occurred at pH levels of 2. The ideal adsorbent dosage was determined to be 2.5 g/L, with equilibrium achieved at a contact time of 60 min at the optimal temperature of about 303 K for a Cr(VI) metal ion concentration of 20 mg/L. Various isotherm models were applied to the adsorption equilibrium values, revealing that the adsorbent had a maximum removal capacity of approximately 224.8 mg/g for Cr(VI) metal ions. The adsorption process of Cr(VI) on the DAC biosorbent was best described by the Freundlich isotherm, indicating multilayer adsorption. The kinetic data fit well with the pseudo-second-order model. Thermodynamic parameters suggested that the adsorption process was spontaneous, exothermic, and feasible across different temperatures. Furthermore, the desorption studies showed that the DAC biosorbent can easily be rejuvenated and utilized several cycles with high adsorption capacity. These findings indicate that the developed adsorbent is environmentally friendly and effective for removing Cr(VI) from water systems.

Control of paleoclimate and paleoweathering on chromium contents in a non-ultramafic aquifer hosting high chromium groundwater.

Cr(VI) is a carcinogen with proven mutagenic and genotoxic effects. The effects of the depositional environment (e.g., paleoweathering, paleoclimate, and paleoredox condition) on Cr enrichment in non-ultramafic aquifer solids are unclear. In this study, we presented the sedimentary characteristics of a borehole from a typical non-ultramafic aquifer with high Cr groundwater in Jingbian, central Ordos Basin, China. Chromium was enriched in the K1h sandstone aquifer, especially at depths of 400-500 m, with the highest value of mass transport coefficient (τAl,Cr) up to 92.13% and τAl,Fe up to 33.5%. The provenance of aquifer Cr was predominantly intermediate and felsic igneous rocks with a mafic rock mixture. This mafic source was inferred from Cr-rich granodiorite and mafic/ultramafic rocks in the Yinshan (Daqingshan-Wulashan) Block, northern Ordos Basin. The Cr-rich aquifer in K1h was developed due to a moderate chemical index of alteration (CIA) (mean, 56.7) under relatively warm and humid paleoclimate, as evidenced by high CIA-temperature (CIA-Temp) (mean, 6.79 °C) and paleoclimatic index values (mean, 0.40). Fe-Mn redox cycling in the oxic to suboxic environments contributed to aquifer Cr accumulation. Using path analysis, we identified that paleoclimate created favorable weathering conditions and enrichment of Fe contributed to the formation of high-Cr aquifers. The study reveals the formation of positive Cr anomalies in non-ultramafic aquifers, which is the potential source of groundwater Cr, and highlights the effects of depositional factors on Cr accumulation during aquifer deposition or early diagenesis. It can provide new insights into the natural processes of high-Cr sediments occurring in non-ultramafic aquifers.

Synergistic impacts of antibiotics and heavy metals on Hermetia illucens: Unveiling dynamics in larval gut bacterial communities and microbial metabolites.

Hermetia illucens larvae showcases remarkable bioremediation capabilities for both antibiotics and heavy metal contaminants. However, the distinctions in larval intestinal microbiota arising from the single and combined effects of antibiotics and heavy metals remain poorly elucidated. In this study, we delved into the details of larval intestinal bacterial communities and microbial metabolites when exposed to single and combined contaminants of oxytetracycline (OTC) and hexavalent chromium (Cr(VI)). After conversion, single contaminant-spiked substrate showed 75.5% of OTC degradation and 95.2% of Cr(VI) reductiuon, while combined contaminant-spiked substrate exhibited 71.3% of OTC degradation and 93.4% of Cr(VI) reductiuon. Single and combined effects led to differences in intestinal bacterial communities, mainly reflected in the genera of Enterococcus, Pseudogracilibacillus, Gracilibacillus, Wohlfahrtiimonas, Sporosarcina, Lysinibacillus, and Myroide. Moreover, these effects also induced differences across various categories of microbial metabolites, which categorized into amino acid and its metabolites, benzene and substituted derivatives, carbohydrates and its metabolites, heterocyclic compounds, hormones and hormone-related compounds, nucleotide and its metabolites, and organic acid and its derivatives. In particular, the differences induced OTC was greater than that of Cr(VI), and combined effects increased the complexity of microbial metabolism compared to that of single contaminant. Correlation analysis indicated that the bacterial genera, Preudogracilibacillus, Enterococcus, Sporosarcina, Lysinibacillus, Wohlfahrtiimonas, Ignatzschineria, and Fusobacterium exhibited significant correlation with significant differential metabolites, these might be used as indicators for the resistance and bioremediation of OTC and Cr(VI) contaminants. These findings are conducive to further understanding that the metabolism of intestinal microbiota determines the resistance of Hermetia illucens to antibiotics and heavy metals.

Microbially induced carbonate precipitation with Arthrobacter creatinolyticus: An eco-friendly strategy for mitigation of chromium contamination.

Chromium contamination from abandoned industrial sites and inadequately managed waste disposal areas poses substantial environmental threat. Microbially induced carbonate precipitation (MICP) has shown promising, eco-friendly solution to remediate Cr(VI) and divalent heavy metals. In this study, MICP was carried out for chromium immobilization by an ureolytic bacterium Arthrobacter creatinolyticus which is capable of reducing Cr(VI) to less toxic Cr(III) via extracellular polymeric substances (EPS) production. The efficacy of EPS driven reduction was confirmed by cellular fraction analysis. MICP carried out in aqueous solution with 100 ppm of Cr(VI) co-precipitated 82.21% of chromium with CaCO3 and the co-precipitation is positively correlated with reduction of Cr(VI). The organism was utilized to remediate chromium spiked sand and found that MICP treatment decreased the exchangeable fraction of chromium to 0.54 ±â€¯0.11% and increased the carbonate bound fraction to 26.1 ±â€¯1.15% compared to control. XRD and SEM analysis revealed that Cr(III) produced during reduction, influenced the polymorph selection of vaterite during precipitation. Evaluation of MICP to remediate Cr polluted soil sample collected from Ranipet, Tamil Nadu also showed effective immobilization of chromium. Thus, A. creatinolyticus proves to be viable option for encapsulating chromium contaminated soil via MICP process, and effectively mitigating the infiltration of Cr(VI) into groundwater and adjacent water bodies.

Heavy metals and elderly kidney health: A multidimensional study through Enviro-target Mendelian Randomization.

Chronic Kidney Disease (CKD), closely linked to environmental factors, poses a significant public health challenge. This study, based on 529 triple-repeated measures from key national environmental pollution area and multiple gene-related public databases, employs various epidemiological and bioinformatics models to assess the impact of combined heavy metal exposure (Chromium [Cr], Cadmium [Cd], and Lead [Pb]) on early renal injury and CKD in the elderly. Introducing the novel Enviro-Target Mendelian Randomization method, our research explores the causal relationship between metals and CKD. The findings indicate a positive correlation between increased levels of metal and renal injury, with combined exposure caused renal damage more significantly than individual exposure. The study reveals that metals primarily influence CKD development through oxidative stress and metal ion resistance pathways, focusing on three related genes (SOD2, MPO, NQO1) and a transcription factor (NFE2L2). Metals were found to regulate oxidative stress levels in the body by increasing the expression of SOD2, MPO, NQO1, and decreasing NFE2L2, leading to CKD onset. Our research establishes a new causal inference framework linking environmental pollutants-pathways-genes-CKD, assessing the impact and mechanisms of metal exposure on CKD. Future studies with more extensive in vitro evidence and larger population are needed to validate.

ATF4-mediated different mode of interaction between autophagy and mTOR determines cell fate dependent on the level of ER stress induced by Cr(VI).

Hexavalent chromium [Cr(VI)] exists widely in occupational environments. The mechanistic target of rapamycin (mTOR) has been well-documented to regulate autophagy negatively. However, we found that low concentration of Cr(VI) (0.2 µM) elevated both mTOR and autophagy and promote cell survival. Conversely, high concentration of Cr(VI) (6 µM) caused cell death by inhibiting mTOR and subsequently inducing autophagy. Tunicamycin (Tm), as an Endoplasmic reticulum (ER) stress activator was used to induce mild ER stress at 0.1 µg/ml and it activated both autophagy and mTOR, which also caused cell migration in a similar manner to that observed with low concentration of Cr(VI). Severe ER stress caused by Tm (2 µg/ml) decreased mTOR, increased autophagy and then inhibited cell migration, which was the same as 6 µM Cr(VI) treatment, although Cr(VI) in high concentration inhibited ER stress. Activating transcription factor 4 (ATF4), a downstream target of ER stress, only increased under mild ER stress but decreased under severe ER stress and 6 µM Cr(VI) treatment. Chromatin immunoprecipitation (ChIP) experiment indicated that ATF4 could bind to the promoter of ATG4B and AKT1. To sum up, our data revealed that mild ER stress induced by low concentration of Cr(VI) could enhance transcriptional regulation of ATG4B and AKT1 by ATF4, which induced both autophagy and mTOR to promote cell viability.

Removal of hypertoxic Cr(VI) from water by polyaniline-coated ZIF-67-derived nitrogen-doped magnetic carbon.

Heavy metals are highly toxic and nonbiodegradable, posing a serious threat to the water environment and human beings. Therefore, it is crucial to develop a highly efficient adsorbent that is easy to recover and separate for the removal of heavy metals. In this paper, nitrogen-doped magnetic carbon (NC-67) was prepared by carbonization and hydrochloric acid treatment using cobalt-containing MOF (ZIF-67) as precursor. Then, polyaniline (PANI) was grown directly on NC-67 with high specific surface area by in situ polymerization to prepare polyaniline-coated nitrogen-doped magnetic carbon (NC-67@PANI), which was characterized by XRD, SEM, TEM and VSM, etc. and used for the removal of Cr(VI)from wastewater. The experimental results showed that the adsorption process of Cr(VI) by NC-67@PANI was spontaneous and endothermic, which conformed to the pseudo-second-order model and Freundlich adsorption isotherm model. Due to the synergistic effect of adsorption and reduction, the experimental adsorption capacity of NC-67@PANI for Cr(VI) was 410.2 mg/g. NC-67@PANI maintained a removal efficiency of 65.8% for Cr(VI) after five cycles. In addition, NC-67@PANI had good magnetism and was easy to separate under external magnetic field. The excellent adsorption capacity and easy separation characteristics of NC-67@PANI indicate that it is a promising adsorbent for Cr(VI) removal from wastewater.

Effects of ionic strength and bentonite ratio on the migration of Cr(VI) in clayey soil-bentonite engineered barrier.

Soil-bentonite (S-B) barriers have been widely used for heavy metal pollution containment. This study conducted batch adsorption tests and diffusion-through tests to evaluate how ionic strength and bentonite ratio influence the migration of Cr(VI) in natural clay-bentonite mixtures. The test results indicated that the adsorption of Cr(VI) exhibited an obvious anion adsorption effect, the pH of the soil mixture increased with the addition of bentonite, resulting in a decrease in the positive surface charge. This change led to a decrease in Cr(VI) adsorption capacity, from 775.19 mg/kg for pure clay to 378 mg/kg for mixture samples with excessive bentonite. Furthermore, as the ionic strength increases from 0 to 0.1 M, the Cr(VI) adsorption capacity increases slightly due to the weakening of electrostatic repulsion on the clay particle surface, but the effective diffusion coefficient (De) increases by 21.97%. The compression of the diffusion double layer (DDL) under high ionic strength conditions enlarges the diffusion path and enhances the migration of Cr(VI) through the pore flow paths. Moreover, hydrated bentonite effectively fills the interaggregate pores of natural clay, thus creating narrower and more tortuous flow paths. However, excessive bentonite increases the pH value and pore volume, resulting in changes to the soil microstructure and disrupting the continuous skeleton of natural clay, which is unfavorable for Cr(VI) containment. Based on the study of the Cr(VI) contaminated site, a bentonite ratio of 2:10 is recommended for optimal natural performance of the natural clay-bentonite barrier.

Intrauterine chromium exposure and cognitive developmental delay: The modifying effect of genetic predisposition.

There is limited evidence on the effects of intrauterine chromium (Cr) exposure on children's cognitive developmental delay (CDD). Further, little is known about the genetic factors in modifying the association between intrauterine Cr exposure and CDD. The present study involved 2361 mother-child pairs, in which maternal plasma Cr concentrations were assessed, a polygenic risk score for the child was constructed, and the child's cognitive development was evaluated using the Bayley Scales of Infant Development. The risks of CDD conferred by intrauterine Cr exposure in children with different genetic backgrounds were evaluated by logistic regression. The additive interaction between intrauterine Cr exposure and genetic factors was evaluated by calculating the relative excess risk due to interaction (RERI), attributable proportion due to interaction (AP), and synergy index (SI). According to present study, higher intrauterine Cr exposure was significantly associated with increased CDD risk [each unit increase in ln-transformed maternal plasma Cr concentration (ln-Cr): adjusted OR (95 % CI), 1.18 (1.04-1.35); highest vs lowest quartile: adjusted OR (95 % CI), 1.57 (1.10-2.23)]. The dose-response relationship of intrauterine Cr exposure and CDD for children with high genetic risk was more prominent [each unit increased ln-Cr: adjusted OR (95 % CI), 1.36 (1.09-1.70)]. Joint effects between intrauterine Cr exposure and genetic factors were found. Specifically, for high genetic risk carriers, the association between intrauterine Cr exposure and CDD was more evident [highest vs lowest quartile: adjusted OR (95 % CI), 2.33 (1.43-3.80)]. For those children with high intrauterine Cr exposure and high genetic risk, the adjusted AP was 0.39 (95 % CI, 0.07-0.72). Conclusively, intrauterine Cr exposure was a high-risk factor for CDD in children, particularly for those with high genetic risk. Intrauterine Cr exposure and one's adverse genetic background jointly contribute to an increased risk of CDD in children.

Speciation-specific chromium bioaccumulation and detoxification in fish using hydrogel microencapsulated biogenic nanosilver and zeolite synergizing with biomarkers.

Grass carp intestinal waste-mediated biosynthesized nanosilver (AgNPs) was valorized using guaran and zeolite matrices, resulting in AgNPs-guaran, AgNPs-zeolite, and AgNPs-guaran -zeolite composites. The valorized products were examined using Environmental Scanning Electron Microscopy, Energy Dispersive X-ray analysis and X-ray Diffraction analysis to confirm uniform dispersion and entrapment of AgNPs within the matrixes. These valorized products were evaluated for their efficacy in detoxifying the ubiquitous and toxic hexavalent chromium (Cr6+) in aquatic environments, with Anabas testudineus exposed to 2 mg l-1 of Cr6+ for 60 days. Remarkable reduction of Cr6+ concentration to 0.86 ± 0.007 mg l-1 was achieved with AgNPs-guaran-zeolite composite, indicating successful reclamation of contaminated water and food safety assurance. Consistency in results was further corroborated by minimal stress-related alterations in fish physiological parameters and integrated biomarker response within the experimental group treated with the AgNPs-guaran-zeolite composite. Despite observed chromium accumulation in fish tissues, evidence of physiological stability was apparent, potentially attributable to trivalent chromium accumulation, serving as an essential nutrient for the fish. Additionally, the challenge study involving Anabas testudineus exposed to Aeromonas hydrophila exhibited the lowest cumulative mortality (11.11%) and highest survival rate (87.5%) within the same experimental group. The current study presents a novel approach encompassing the valorization of AgNPs for Cr6+ detoxification under neutral to alkaline pH conditions, offering a comprehensive framework for environmental remediation.

Quantification of sources and potential risks of cadmium, chromium, lead, mercury and arsenic in agricultural soils in a rapidly urbanizing region of southwest China: the case of Chengdu.

Rapid urbanization a major factor affecting heavy metal contamination on suburban agricultural soils. In order to assess the dynamic contamination of heavy metals in soil from agricultural land bordering a rapidly urbanizing area and the transfer of human health risks from contaminants in this process, 186 and 293 soil samples from agricultural land in suburban Chengdu were collected in September 2008 and September 2017, respectively. Several indicators, such as the integrated pollution index (PI) and the potential ecological risk index (RI), were employed for analyzing the heavy metal contamination levels, and the APCS-MLR receptor model were applied for analyzing the heavy metal sources. As a result, mean concentrations for five elements did not exceed the national soil pollution risk screening values in the two periods mentioned above. Nemerow's composite contamination index revealed an increase in soil contamination of arable land after 10 years of urbanization, with 3.75 and 1.02% of light and moderate sample plots, respectively, by 2017. The assessment for potential ecological risk indicated an increased level of eco-risk to high for most of the sample plots. Based on the APCS-MLR model, the origin and contribution to the five elements varied considerably between the two periods mentioned above. Among them, soil Pb changed from "industrial source" to "transportation source," soil Cr changed from "natural source" to "transportation source," and As and Hg changed from "industrial source" to "transportation source." As and Hg were associated with agricultural activities in both periods, and Cd was derived from industrial activities in both periods. The study suggests that inhalation has become a major contributor to non-cancer health risks in urbanization, unlike intake routes in previous periods, and that the increase in cancer risk is mainly due to children's consumption of agricultural products with As residues. The change in the main source of As to "transportation" also indicates a decrease in air quality during urbanization and the development of the transportation industry. This study provides a reference for the governments of rapidly urbanizing cities to formulate relevant highway and agricultural policies to safeguard the health of the people based on the current situation.

Preparation of composites with MgAl-LDH-modified commercial activated carbon for the quick removal of Cr(VI) from aqueous solutions.

The problem of soil and water contamination caused by Cr(VI) discharged from the dyeing, electroplating, and metallurgical industries is becoming increasingly serious, posing a potentially great threat to the environment and public health. Therefore, it is crucial to develop a fast, efficient, and cost-effective adsorbent for remediating Cr-contaminated wastewater. In this work, MgAl-LDH/commercial-activated carbon nanocomposites (LDH-CACs) are prepared with hydrothermal. The effects of preparation and reaction conditions on the composite properties are first investigated, and then its adsorption behavior is thoroughly explored. Finally, a potential adsorption mechanism is proposed by several characterizations like SEM-EDS, XRD, FTIR, and XPS. The removal of Cr(VI) reaches 72.47% at optimal conditions, and the adsorption study demonstrates that LDH-CAC@1 has an extremely rapid adsorption rate and a maximum adsorption capacity of 116.7 mg/g. The primary removal mechanisms include adsorption-coupled reduction, ion exchange, surface precipitation, and electrostatic attraction. The reusability experiment illustrates that LDH-CAC@1 exhibits promising reusability. This study provides an effective adsorbent with a remarkably fast reaction, which has positive environmental significance for the treatment of Cr(VI) wastewater.

A unified framework of response surface methodology and coalescing of Firefly with random forest algorithm for enhancing nano-phytoremediation efficiency of chromium via in vitro regenerated aquatic macrophyte coontail (Ceratophyllum demersum L.).

Nano-phytoremediation is a novel green technique to remove toxic pollutants from the environment. In vitro regenerated Ceratophyllum demersum (L.) plants were exposed to different concentrations of chromium (Cr) and exposure times in the presence of titania nanoparticles (TiO2NPs). Response surface methodology was used for multiple statistical analyses like regression analysis and optimizing plots. The supplementation of NPs significantly impacted Cr in water and Cr removal (%), whereas NP × exposure time (T) statistically regulated all output parameters. The Firefly metaheuristic algorithm and the random forest (Firefly-RF) machine learning algorithms were coalesced to optimize hyperparameters, aiming to achieve the highest level of accuracy in predicted models. The R2 scores were recorded as 0.956 for Cr in water, 0.987 for Cr in the plant, 0.992 for bioconcentration factor (BCF), and 0.957 for Cr removal through the Firefly-RF model. The findings illustrated superior prediction performance from the random forest models when compared to the response surface methodology. The conclusion is drawn that metal-based nanoparticles (NPs) can effectively be utilized for nano-phytoremediation of heavy metals. This study has uncovered a promising outlook for the utilization of nanoparticles in nano-phytoremediation. This study is expected to pave the way for future research on the topic, facilitating further exploration of various nanoparticles and a thorough evaluation of their potential in aquatic ecosystems.