Magnetic biochar (MBC) has been used to remove hexavalent chromium (Cr(VI)) from water, but the roles of Fe₃O₄ and persistent free radicals (PFRs) in MBC in Cr(VI) removal are still less investigated. In this work, the MBC synthesized by microwave co-pyrolysis of solid-state FeSO₄ and rice husk was employed to remove Cr(VI) from water. In comparison to the rice husk biochar (BC), the MBC exhibits the 3.2- and 11.7-fold higher adsorption and reduction efficiency of Cr(VI), resulting in the higher Cr(VI) removal efficiency (84.3%) and equilibrium adsorption capacity of MBC (8.35 mg g⁻¹) than that (26.5% and 2.63 mg g⁻¹) of BC. Multiple characterization results revealed that the high Cr(VI) removal performance of MBC was mainly attributed to the presence of active Fe₃O₄ and carbon-centered PFRs in the porous and graphitic MBC. The Fe₃O₄ not only provided active chemisorption/reduction sites for Cr(VI) via its Fe(II)ₒcₜ and Fe(III)ₒcₜ coordination, but also facilitated the generation of more active electron donating carbon-centered PFRs than carbon-centered PFRs with an oxygen atom in the graphitic structure to reduce Cr(VI). The presence of Fe₃O₄ also elevated 36.7 m² g⁻¹ of BET-surface area and 0.043 cm² g⁻¹ of pore volume of MBC, promoting the Cr(VI) removal. The Fe₃O₄ and carbon-centered PFRs contributed to ∼81.8% and ∼18.2% of total Cr(III) generation, respectively. In addition, the initial solution pH was responsible for determining the relative significance of Cr(VI) adsorption and reduction. This study provides new insights into the mechanisms of Cr(VI) removal from water by the MBC.

In order to clarify whether the mitochondrial dysfunction is closely related to the cell homeostasis maintenance after particulate matter (PM₂.₅) exposure, oxidative, inflammatory, apoptotic and mitochondrial endpoints were carefully studied in human bronchial epithelial BEAS-2B, normal human bronchial epithelial (NHBE) and chronic obstructive pulmonary disease (COPD)-diseased human bronchial epithelial (DHBE) cells acutely or repeatedly exposed to air pollution-derived PM₂.₅. Some modifications of the mitochondrial morphology were observed within all these cell models repeatedly exposed to the highest dose of PM₂.₅. Dose- and exposure-dependent oxidative damages were reported in BEAS-2B, NHBE and particularly COPD-DHBE cells acutely or repeatedly exposed to PM₂.₅. Nuclear factor erythroid 2-p45 related factor 2 (NRF2) gene expression and binding activity, together with the mRNA levels of some NRF2 target genes, were directly related to the number of exposures for the lowest PM₂.₅ dose (i.e., 2 μg/cm²), but, surprisingly, inversely related to the number of exposures for the highest dose (i.e., 10 μg/cm²). There were dose- and exposure-dependent increases of both nuclear factor kappa-B (NF-κB) binding activity and NF-κB target cytokine secretion in BEAS-2B, NHBE and particularly COPD-DHBE cells exposed to PM₂.₅. Mitochondrial ROS production, membrane potential depolarization, oxidative phosphorylation, and ATP production were significantly altered in all the cell models repeatedly exposed to the highest dose of PM₂.₅. Collectively, our results indicate a cytosolic ROS overproduction, inducing oxidative damage and activating oxygen sensitive NRF2 and NF-ₖB signaling pathways for all the cell models acutely or repeatedly exposed to PM₂.₅. However, one of the important highlight of our findings is that the prolonged and repeated exposure in BEAS-2B, NHBE and in particular sensible COPD-DHBE cells further caused an oxidative boost able to partially inactivate the NRF2 signaling pathway and to critically impair mitochondrial redox homeostasis, thereby producing a persistent mitochondrial dysfunction and a lowering cell energy supply.

In this paper, results from receptor modelling performed on a well-characterised PM₁ dataset were combined to chemical light extinction data (bₑₓₜ) with the aim of assessing the impact of different PM₁ components and sources on light extinction and visibility at a European polluted urban area. It is noteworthy that, at the state of the art, there are still very few papers estimating the impact of different emission sources on light extinction as we present here, although being among the major environmental challenges at many polluted areas. Following the concept of the well-known IMPROVE algorithm, here a tailored site-specific approach (recently developed by our group) was applied to assess chemical light extinction due to PM₁ components and major sources.PM₁ samples collected separately during daytime and nighttime at the urban area of Milan (Italy) were chemically characterised for elements, major ions, elemental and organic carbon, and levoglucosan. Chemical light extinction was estimated and results showed that at the investigated urban site it is heavily impacted by ammonium nitrate and organic matter. Receptor modelling (i.e. Positive Matrix Factorization, EPA-PMF 5.0) was effective to obtain source apportionment; the most reliable solution was found with 7 factors which were tentatively assigned to nitrates, sulphates, wood burning, traffic, industry, fine dust, and a Pb-rich source. The apportionment of aerosol light extinction (bₑₓₜ,ₐₑᵣ) according to resolved sources showed that considering all samples together nitrate contributed at most (on average 41.6%), followed by sulphate, traffic, and wood burning accounting for 18.3%, 17.8% and 12.4%, respectively.

Pesticides move to surface water via various pathways including surface runoff, spray drift and subsurface flow. Little is known about the relative contributions of surface runoff and spray drift in agricultural watersheds. This study develops a modeling framework to address the contribution of spray drift to the total loadings of pesticides in receiving water bodies. The modeling framework consists of a GIS module for identifying drift potential, the AgDRIFT model for simulating spray drift, and the Soil and Water Assessment Tool (SWAT) for simulating various hydrological and landscape processes including surface runoff and transport of pesticides. The modeling framework was applied on the Orestimba Creek Watershed, California. Monitoring data collected from daily samples were used for model evaluation. Pesticide mass deposition on the Orestimba Creek ranged from 0.08 to 6.09% of applied mass. Monitoring data suggests that surface runoff was the major pathway for pesticide entering water bodies, accounting for 76% of the annual loading; the rest 24% from spray drift. The results from the modeling framework showed 81 and 19%, respectively, for runoff and spray drift. Spray drift contributed over half of the mass loading during summer months. The slightly lower spray drift contribution as predicted by the modeling framework was mainly due to SWAT's under-prediction of pesticide mass loading during summer and over-prediction of the loading during winter. Although model simulations were associated with various sources of uncertainties, the overall performance of the modeling framework was satisfactory as evaluated by multiple statistics: for simulation of daily flow, the Nash-Sutcliffe Efficiency Coefficient (NSE) ranged from 0.61 to 0.74 and the percent bias (PBIAS) < 28%; for daily pesticide loading, NSE = 0.18 and PBIAS = −1.6%. This modeling framework will be useful for assessing the relative exposure from pesticides related to spray drift and runoff in receiving waters and the design of management practices for mitigating pesticide exposure within a watershed.

To evaluate the seasonal distribution of antibiotic resistance genes (ARGs) and explore the reason for their patterns in different seasons and different systems, two wastewater treatment systems were selected and analyzed using high-throughput qPCR. Linear discriminant analysis (LDA) effect size (LEfSe) was used to discover the differential ARGs (biomarkers) and estimate the biomarkers’ effect size. We found that the total absolute abundances of ARGs in inflows and excess sludge samples had no obvious seasonal fluctuations, while those in winter outflow samples decreased in comparison with the inflow samples. Eleven differentially abundant ARGs (biomarker genes, BmGs) (aadA5-02, aac-6-II, cmlA1-01, cmlA1-02, blaOXA10-02, aadA-02, tetX, aadA1, ereA, qacEΔ1-01, and blaTEM) in summer samples and 10 BmGs (tet-32, tetA-02, aacC2, vanC-03, aac-6-I1, tetE, ermB, mefA, tnpA - 07, and sul2) in winter samples were validated. According to 16S rRNA gene sequencing, the relative abundance of bacteria at the phylum level exhibited significant seasonal changes in outflow water (OW), and biomarker bacteria (BmB) were discovered at the family (or genus) level. Synechococcus and vadinCA02 are BmB in summer, and Trichococcus, Lactococcus, Pelosinus, Janthinobacterium, Nitrosomonadaceae and Sterolibacterium are BmB in winter. In addition, BmB have good correlations with BmGs in the same season, which indicates that bacterial community changes drive different distributions of ARGs during seasonal changes and that LEfSe is an acute and effective method for finding significantly different ARGs and bacteria between two or more classes.In conclusion, this study demonstrated the seasonal changes of BmGs and BmB at two wastewater treatment systems.

The increasing application of iron-based nanoparticles (NPs), especially high concentrations of zero-valent iron nanoparticles (nZVI), has raised concerns regarding their environmental behavior and potential ecological effects. In the environment, iron-based NPs undergo physical, chemical, and/or biological transformations as influenced by environmental factors such as pH, ions, dissolved oxygen, natural organic matter (NOM), and biotas. This review presents recent research advances on environmental transformations of iron-based NPs, and articulates their relationships with the observed toxicities. The type and extent of physical, chemical, and biological transformations, including aggregation, oxidation, and bio-reduction, depend on the properties of NPs and the receiving environment. Toxicities of iron-based NPs to bacteria, algae, fish, and plants are increasingly observed, which are evaluated with a particular focus on the underlying mechanisms. The toxicity of iron-based NPs is a function of their properties, tolerance of test organisms, and environmental conditions. Oxidative stress induced by reactive oxygen species is considered as the primary toxic mechanism of iron-based NPs. Factors influencing the toxicity of iron-based NPs are addressed and environmental transformations play a significant role, for example, surface oxidation or coating by NOM generally lowers the toxicity of nZVI. Research gaps and future directions are suggested with an aim to boost concerted research efforts on environmental transformations and toxicity of iron-based NPs, e.g., toxicity studies of transformed NPs in field, expansion of toxicity endpoints, and roles of laden contaminants and surface coating. This review will enhance our understanding of potential risks of iron-based NPs and proper uses of environmentally benign NPs.

Daily mean concentrations of air pollutants have been widely used as exposure indicators to estimate the short-term mortality effects of outdoor air pollution. However, daily mean concentrations might insufficiently represent the true exposure level because of the diurnal variations of air pollutants and various human activity patterns. Daytime or rush-hour concentrations may lead to better estimations.Our study aimed to imitate the true exposure level under assumptions about human activity patterns and to examine the short-term mortality effects of the exposure to air pollution during a) the morning-evening rush hours (ME), b) the morning-lunch-evening rush hours (MLE), and c) the whole daytime (WDT) in Chengdu, Sichuan Basin, China.We investigated the diurnal variations of PM₂.₅, SO₂, and O₃ and examined the associations between the three pollutants and nonaccidental mortality, cardiovascular mortality, respiratory mortality using generalized additive model. Three novel exposure indicators (ME, MLE, and WDT) were employed to imitate the most probable exposure levels. Relative change of excess risk (ER) was used to compare effects estimated from models with different exposure indicators.In the relationship of PM₂.₅ and mortality, ERs estimated from the novel-indicator models decreased by 4.88%–11.89% in comparison with ERs from the daily-indicator models. All the three novel indicators of SO₂ offered lower ERs of respiratory mortality than the daily indicator did. Significant associations were observed in O₃-nonaccidental mortality at lag0 in both winter and spring, and O₃-cardiovascular mortality at lag0 in winter. Overall, majority of effect estimates based on rush-hour or daytime indicators were lower than the estimates based on daily mean concentrations.The use of daily mean concentrations may bias exposure assessment and thus inflating effect estimates. This study highlights the importance of rush-hour and daytime exposure and provides alternative indicators for estimating acute effects of air pollution.

Sediments nearby harbors are dredged regularly, and the sediments require the stringent treatment to meet the regulations on reuse and mitigate the environmental burdens from toxic pollutants. In this study, FeCl₃ was chosen as an extraction agent to treat marine sediment co-contaminated with Cu, Zn, and total petroleum hydrocarbons (TPH). In chemical extraction process, the extraction efficiency of Cu and Zn by FeCl₃ was compared with the conventional one using inorganic acids (H₂SO₄ and HCl). Despite the satisfactory level for extraction of Cu (78.8%) and Zn (73.3%) by HCl (0.5 M) through proton-enhanced dissolution, one critical demerit, particularly acidified sediment, led to the unwanted loss of Al, Fe, and Mg by dissolution. Moreover, the vast amount of HCl required the huge amounts of neutralizing agents for the post-treatment of the sediment sample via the washing process. Despite a low concentration, extraction of Cu (70.1%) and Zn (69.4%) was done by using FeCl₃ (0.05 M) through proton-enhanced dissolution, ferric-organic matter complexation, and oxidative dissolution of sulfide minerals. Ferric iron (Fe³⁺) was reduced to ferrous iron (Fe²⁺) with sulfide (S²⁻) oxidation during FeCl₃ extraction. In consecutive chemical oxidations using hydrogen peroxide (H₂O₂) and persulfate (S₂O₈²⁻), the resultant ferrous iron was used to activate the oxidants to effectively degrade TPH. S₂O₈²⁻ using FeCl₃ solution (molar ratio of ferrous to S₂O₈²⁻ is 19.8–198.3) removed 42.6% of TPH, which was higher than that by H₂O₂ (molar ratio of ferrous to H₂O₂ is 1.2–6.1). All experimental findings suggest that ferric is effectively accommodated to an acid washing step for co-contaminated marine sediments, which leads to enhanced extraction, cost-effectiveness, and less environmental burden.

Sea turtles are globally endangered and face daily anthropogenic threats, including pollution. However, there is a lack of ecotoxicological information on sea turtles, especially in the Asia-Pacific region. This study aims to determine pollutant levels of foraging green turtles (Chelonia mydas) in South China, including Hong Kong, Guangdong and Taiwan, as a basis for their conservation. Scute, liver and muscle tissues of stranded green turtles were analysed for levels of 17 trace elements and methylmercury (MeHg) (n = 86 for scute and n = 14 for liver) and polybrominated diphenyl ethers (PBDEs) (n = 11 for muscle and n = 13 for liver). Ten-fold higher levels of Pb, Ba, V and Tl and 40-fold greater Cd levels were measured in green turtle livers in South China relative to other studies conducted over 10 years ago. Measured PBDE levels were also 27-fold and 50-fold greater than those reported in Australia and Japan. These results warrant further investigation of potential toxicological risks to green turtles in South China and their source rookeries in Malaysia, Micronesia, Indonesia, Marshall Islands, Japan and Taiwan. Research should target monitoring pollutant levels in sea turtles within the West Pacific/Southeast Asia regional management unit spanning East Asia to Southeast Asia to fill in knowledge gaps, in particular in areas such as Thailand, Vietnam, Indonesia, Malaysia and the Philippines where less or no data is available and where foraging grounds of sea turtles have been identified.

Airborne systems such as lightweight and highly portable unmanned aerial vehicles (UAVs) are becoming increasingly widespread in both academia and industry - with an ever-increasing range of applications, including (but not limited to), air quality sampling, wildlife monitoring and land-use mapping.In this work, high-resolution airborne photogrammetry obtained using a multi-rotor system operating at low survey altitudes, is combined with ground-based radiation mapping data acquired at an interim storage facility for wastes removed as part of the large-scale Fukushima clean-up program. The investigation aimed to assess the extent to which the remediation program at a specific site has contained the stored contaminants, as well as present a new methodology for rapidly surveying radiological sites globally. From the three-dimensional rendering of the site of interest, it was possible to not only generate a powerful graphic confirming the elevated radiological intensity existing at the location of the waste bags, but also to also illustrate the downslope movement of contamination due to species leakage from the large 1m³ storage bags. The entire survey took less than 1 h to perform, and was subsequently post-processed using graphical information software to obtain the renderings. The conclusions within this study not only highlight the usefulness of incorporating three-dimensional renderings within radiation mapping protocols, but also conclude that current methods of monitoring these storage facilities in the long term could be improved through the integration of UAVs within the standard protocol.