The ability of fungi to act as bio-sorbent had been extensively evaluated and has shown excellent metal sequestering ability for heavy metals such as cadmium, copper, zinc, lead, iron, nickel, radium, thorium, and uranium from aqueous solution. In the present study, tolerance, removal efficiency and adsorption capacity of hexavalent chromium using isolated fungal strains were analysed. Total nine fungal isolates were obtained from organic pollutants and metals contaminated Gujarat Industrial Development Cooperation sites. Filamentous fungi isolated belonged to Aspergillus spp., Rhizopus spp., Trichoderma spp., and Penicillium spp. Chromium sorption experiments using isolated fungal strains were carried out to check adsorption capacity and adsorption intensity. At higher chromium concentration, removal efficiency and adsorption capacity were observed in the order of Aspergills candidus > Aspergillus ochraceus > Aspergillus flavus > Rhizopus spp. > Trichoderma spp. A. candidus showed higher adsorption capacity, 5.49mg/g with 98.75% chromium removal efficiency at 150ppm of hexavalent chromium. The observed RL value for Langmuir isotherm for all the three concentrations was less than 1, depicting favourable sorption and in Freundlich isotherm, the value of 1/n exceeds more than 1 showing co-operative or similar type of adsorption.

Trivalent chromium [Cr(III)] and tannins serve as necessary substances in leather processing and coexist in tannery site, which lead to the chromium contamination in site soil when disposed improperly. However, coexisting tannins are very likely to complex with Cr(III) and affect its properties, ultimately changing the mobility of chromium in soil. In this study, tannic acid (TA) was selected to investigate the complexation with Cr(III) and the influence on the solubility and sorption of Cr(III) in soils. Then, the transport behavior and mechanism of Cr(III)-TA complexes in soil was clarified. Dialysis results showed that the increase of TA concentration and solution pH promoted the formation of complexed Cr(III). The results of UV–Vis absorption spectroscopy, X-ray photoelectron spectroscopy, and density functional theory calculations indicated that the adjacent ionized phenolic hydroxyls in TA functioned as the binding sites with Cr(III) to form the Cr–O bonds and the degree of complexation increased with pH. The Cr(III)-TA complexes had higher solubility than free Cr(III) at pH ≥ 6.0. Batch sorption experiments demonstrated that the sorption capacity of Cr(III)-TA to soils with different pH was always lower than that of free Cr(III). These reasons led to the stronger mobility of Cr(III)-TA in soil columns than Cr(III). Our research reveals that the enhanced mobility of Cr(III) in soils coexisting with TA.

We aimed to explore the effects of mixtures of lead and various metals on blood pressure (BP) and the odds of pre-hypertension (systolic blood pressure (SBP) 120–139 mmHg, and/or diastolic blood pressure (DBP) 80–89 mmHg) and hypertension (SBP/DBP ≥140/90 mmHg) among Chinese adults in a cross-sectional study. This study included 11,037 adults aged 18 years or older from the 2017–2018 China National Human Biomonitoring. Average BP and 13 metals (lead, antimony, arsenic, cadmium, mercury, thallium, chromium, cobalt, molybdenum, manganese, nickel, selenium, and tin) in blood and urine were measured and lifestyle and demographic data were collected. Weighted multiple linear regressions were used to estimate associations of metals with BP in both single and multiple metal models. Weighted quantile sum (WQS) regression was performed to assess the relationship between metal mixture levels and BP. In the single metal model, after adjusting for potential confounding factors, the blood lead levels in the highest quartile were associated with the greater odds of both pre-hypertension (odds ratio (OR): 1.56, 95% CI: 1.22–1.99) and hypertension (OR:1.75, 95% CI: 1.28–2.40) when compared with the lowest quartile. We also found that blood arsenic levels were associated with increased odds of pre-hypertension (OR:1.31, 95% CI:1.00–1.74), while urinary molybdenum levels were associated with lower odds of hypertension (OR:0.68, 95% CI:0.50–0.93). No significant associations were found for the other 10 metals. WQS regression analysis showed that metal mixture levels in blood were significantly associated with higher SBP (β = 1.56, P < 0.05) and DBP (β = 1.56, P < 0.05), with the largest contributor being lead (49.9% and 66.8%, respectively). The finding suggests that exposure to mixtures of metals as measured in blood were positively associated with BP, and that lead exposure may play a critical role in hypertension development.

Most amyotrophic lateral sclerosis (ALS) cases are sporadic (∼90%) and environmental exposures are implicated in their etiology. Large industrial facilities are permitted the airborne release of certain chemicals with hazardous properties and report the amounts to the US Environmental Protection Agency (EPA) as part of its Toxics Release Inventory (TRI) monitoring program. The objective of this project was to identify industrial chemicals released into the air that may be associated with ALS etiology. We geospatially estimated residential exposure to contaminants using a de-identified medical claims database, the SYMPHONY Integrated Dataverse®, with ∼26,000 nationally distributed ALS patients, and non-ALS controls matched for age and gender. We mapped TRI data on industrial releases of 523 airborne contaminants to estimate local residential exposure and used a dynamic categorization algorithm to solve the problem of zero-inflation in the dataset. In an independent validation study, we used residential histories to estimate exposure in each year prior to diagnosis. Air releases with positive associations in both the SYMPHONY analysis and the spatio-temporal validation study included styrene (false discovery rate (FDR) 5.4e-5), chromium (FDR 2.4e-4), nickel (FDR 1.6e-3), and dichloromethane (FDR 4.8e-4). Using a large de-identified healthcare claims dataset, we identified geospatial environmental contaminants associated with ALS. The analytic pipeline used may be applied to other diseases and identify novel targets for exposure mitigation. Our results support the future evaluation of these environmental chemicals as potential etiologic contributors to sporadic ALS risk.

Soil contamination by potentially toxic elements (PTEs) is one of the greatest threats to environmental degradation. Knowing where PTEs accumulated in soil can mitigate their adverse effects on plants, animals, and human health. We evaluated the potential of using long-term remote sensing images that reveal the bare soils, to detect and map PTEs in agricultural fields. In this study, 360 soil samples were collected at the superficial layer (0–20 cm) in a 2574 km² agricultural area located in São Paulo State, Brazil. We tested the Soil Synthetic Image (SYSI) using Landsat TM/ETM/ETM+, Landsat OLI, and Sentinel 2 images. The three products have different spectral, temporal, and spatial resolutions. The time series multispectral images were used to reveal areas with bare soil and their spectra were used as predictors of soil chromium, iron, nickel, and zinc contents. We observed a strong linear relationship (−0.26 > r > −0.62) between the selected PTEs and the near infrared (NIR) and shortwave infrared (SWIR) bands of Sentinel (ensemble of 4 years of data), Landsat TM (35 years data), and Landsat OLI (4 years data). The clearest discrimination of soil PTEs was obtained from SYSI using a long term Landsat 5 collection over 35 years. Satellite data could efficiently detect the contents of PTEs in soils due to their relation with soil attributes and parent materials. Therefore, distinct satellite sensors could map the PTEs on tropics and assist in understanding their spatial dynamics and environmental effects.

Research over the last three decades showed that chromium, particularly the oxyanion chromate Cr(VI) behaves as a toxic environmental pollutant that strongly damages plants due to oxidative stress, disruption of nutrient uptake, photosynthesis and metabolism, and ultimately, represses growth and development. However, mild Cr(VI) concentrations promote growth, induce adventitious root formation, reinforce the root cap, and produce twin roots from single root meristems under conditions that compromise cell viability, indicating its important role as a driver for root organogenesis. In recent years, considerable advance has been made towards deciphering the molecular mechanisms for root sensing of chromate, including the identification of regulatory proteins such as SOLITARY ROOT and MEDIATOR 18 that orchestrate the multilevel dynamics of the oxyanion. Cr(VI) decreases the expression of several glutamate receptors, whereas amino acids such as glutamate, cysteine and proline confer protection to plants from hexavalent chromium stress. The crosstalk between plant hormones, including auxin, ethylene, and jasmonic acid enables tissues to balance growth and defense under Cr(VI)-induced oxidative damage, which may be useful to better adapt crops to biotic and abiotic challenges. The highly contrasting responses of plants manifested at the transcriptional and translational levels depend on the concentration of chromate in the media, and fit well with the concept of hormesis, an adaptive mechanism that primes plants for resistance to environmental challenges, toxins or pollutants. Here, we review the contrasting facets of Cr(VI) in plants including the cellular, hormonal and molecular aspects that mechanistically separate its toxic effects from biostimulant outputs.

The role of hydrogen sulfide (H₂S) is well known in the regulation of abiotic stress such as toxic heavy metal. However, mechanism(s) lying behind this amelioration are still poorly known. Consequently, the present study was focused on the regulation/mitigation of hexavalent chromium (Cr(VI) toxicity by the application of H₂S in wheat and rice seedlings. Cr(VI) induced accumulation of reactive oxygen species and caused protein oxidation which negatively affect the plant growth in both the cereal crops. We noticed that Cr(VI) toxicity reduced length of wheat and rice seedlings by 21% and 19%, respectively. These reductions in length of both the cereal crops were positively related with the down-regulation in the ascorbate-glutathione cycle, and were recovered by the application NaHS (a donor of H₂S). Though exposure of Cr(VI) slightly stimulated sulfur assimilation but addition of H₂S further caused enhancement in sulfur assimilation, suggesting its role in the H₂S-mediated Cr(VI) stress tolerance in studied cereal crops. Overall, the results revealed that H₂S renders Cr(VI) stress tolerance in wheat and rice seedlings by stimulating sulfur assimilation and ascorbate-glutathione which collectively reduce protein oxidation and thus, improved growth was observed.

The untreated effluents released from industrial operations have adverse impacts on human health, environment and socio-economic aspects. Environmental pollution due to chromium is adversely affecting our natural resources and ecosystem. Chromium is hazardous carcinogenic element released from spontaneous activities and industrial procedures. Chromium toxicity, mobility and bioavailability depend mainly on its speciation. Chromium mainly exists in two forms, first as an immobile, less soluble trivalent chromium [Cr(III)] species under reducing conditions whereas hexavalent chromium [Cr(VI)] as a mobile, toxic and bioavailable species under oxidizing conditions. Hexavalent chromium is more pernicious in comparison to trivalent form. Chromium negatively affects crop growth, total yield and grain quality. Exposure of chromium even at low concentration enhances its accretion in cells of human-beings and animals which may show detrimental health effects. Many techniques have been utilized for the elimination of chromium. The selection of the green and cost-efficient technology for treatment of industrial effluent is an arduous task. The present review highlights the problems associated with chromium pollution and need of its immediate elimination by suitable remediation strategies. Further, investigations are required to fill the gaps to overcome the problem of chromium contamination and implementation of sustainable remediation strategies with their real-time applicability on the contaminated sites.

The bioavailability of chromium (Cr) in soils is highly dependent on Cr fractions and soil physicochemical properties, but it is still unclear how the Cr fractions change in different soils. In this study, phytotoxicity to wheat root elongation was evaluated in different soils across China, and the kinetics of the biogeochemical processes of the added Cr(VI) were examined. After 105 days of soil Cr(VI) spiking, the added Cr(VI) causing 10% inhibition (EC₁₀) of wheat root elongation varied greatly in soils (0.92–151.12 mg kg⁻¹). The results of correlation analysis between EC₁₀ and soil properties showed that the toxicity of Cr was affected by pH, organic matter (OM), clay, cation exchange capacity (CEC), and amorphous Fe oxides. Moreover, the correlation analysis showed that wheat root elongation was more sensitive to extracted Cr(VI) than Cr(III) after 105 days of incubation. A kinetic model was established to evaluate the redox and aging-activating reactions of Cr(VI)/(III) over 105 days. The correlation analysis between the soil properties and rate constants of the model showed that the pH, clay, and amorphous Fe/Al oxides might be the key factors controlling the aging and reduction processes of Cr(VI), and the OM and CEC might greatly affect the aging process of Cr(III). This modeling study is helpful in understanding which soil properties control the transformation and toxicity of Cr in soils.

The promising response of chromium-stressed (Cr(VI)–S) plants to hydrogen sulphide (H₂S) has been observed, but the participation of nitric oxide (NO) synthesis in H₂S-induced Cr(VI)–S tolerance in plants remains to be elucidated. It was aimed to assess the participation of NO in H₂S-mediated Cr(VI)–S tolerance by modulating subcellular distribution of Cr and the ascorbate-glutathione (AsA-GSH) cycle in the pepper seedlings. Two weeks following germination, plants were exposed to control (no Cr) or Cr(VI)–S (50 μM K₂Cr₂O₇) for further two weeks. The Cr(VI)–S-plants grown in nutrient solution were supplied with 200 μM sodium hydrosulphide (NaHS, donor of H₂S), or NaHS plus 100 μM sodium nitroprusside (SNP, a donor of NO). Chromium stress suppressed plant growth and leaf water status, while elevated proline content, oxidative stress, and the activities of AsA-GSH related enzymes, as well as endogenous H₂S and NO contents. The supplementation of NaHS increased Cr accumulation at root cell walls and vacuoles of leaves as soluble fraction to reduce its toxicity. Furthermore it limited oxidative stress, improved plant growth, modulated leaf water status, and the AsA-GSH cycle-associated enzymes’ activities, as well as it further improved H₂S and NO contents. The positive effect of NaHS was found to be augmented on those parameters in the CrS-plants by the SNP supplementation. However, 0.1 mM cPTIO, the scavenger of NO, inverted the prominent effect of NaHS by decreasing NO content. The supplementation of SNP along with NaHS + cPTIO reinstalled the positive effect of NaHS by restoring NO content, which suggested that NO might have a potential role in H₂S-induced tolerance to Cr(VI)–S in pepper plants by stepping up the AsA-GSH cycle.