Microplastics (MPs) have caused increasing global concerns due to their detrimental effects on marine ecosystems. However, the role of photodegradation in altering toxicity of MPs to marine organisms ...is poorly understood. We therefore investigated the photolytic transformation of pristine polystyrene fragments (P-PS) by 60-day ultraviolet (UV) irradiation, and compared the toxicity of P-PS, photodegraded PS (PD-PS), and commercially available polystyrene microbeads (C-PS) to juvenile grouper (Epinephelus moara). Photodegradation reduced the size from ∼55.9 μm of P-PS to ∼38.6 μm of PD-PS, even produced nanoparticles (∼75 nm) with a yield of 7.03 ± 0.37% (w/w), and induced surface oxidation and formation of persistent free radicals (e.g., CO•, COO•). Also, endogenous pollutants (chemical additives and polymer fragments) were leached out. Thus, PD-PS had the highest growth inhibition and lipidosis-driven hepatic lesions of grouper, followed by P-PS and C-PS, which was mainly explained by increased hepatic bioaccumulation of MPs/NPs and released endogenous toxicants. Furthermore, oxidative stress-triggered mitochondrial depolarization, suppression of fatty acid oxidation and transport, and promotion of inflammation were identified as the key mechanisms for the enhanced hepatotoxicity after photodegradation. This work provides new insight into the potential hazard and harm of MPs in marine environments after photodegradation.
Interest in the use of biochar to improve soil productivity has rapidly increased. Nitrogen (N) loss, retention and bioavailability in biochar-amended soils fertilized with NH4+–N and NO3−–N were ...studied using leaching and pot experiments. NO3−–N leaching from the soils fertilized with NH4+–N and NO3−–N was significantly reduced by biochar addition. NH4+–N leaching from the NO3−–N fertilized soil was also significantly reduced by biochar, while no significant effect was observed for the NH4+–N fertilized soil. Also lower NH4+–N and NO3−–N were leached from NO3−–N fertilized soil with maize (Zea mays L.) grown. Mitigation of N leaching loss following biochar addition is mainly attributed to the increase in soil water holding capacity (WHC), NH4+ adsorption and enhanced N immobilization. Biochar addition stimulated maize growth, both above and below ground. Biochar also increased N utilization efficiency (NUE) of maize but decreased N accumulation efficiency (NAE), indicating that biochar addition may improve N bioavailability in agricultural soils. Therefore, reduction of N leaching, and increase of N retention and bioavailability in agricultural soils can potentially decrease the N fertilizer demand for crop growth.
•Biochar reduced NO3−–N and/or NH4+–N leaching from soils.•Biochar addition improved maize growth including biomass and root morphology.•Biochar increased N utilization efficiency, but reduced N accumulation efficiency.•Biochar could increase N retention and bioavailability in agricultural soils.
Graphene-like porous carbon nitride nanosheets with enhanced charge carrier separation and efficient photocatalytic activity were synthesized by a novel thermal exfoliation approach.
•The ...graphene-like g-C3N4 nanosheets were prepared by thermal exfoliation.•The band structure of the g-C3N4 nanosheets was modified due to quantum effect.•The lifetime of charge carriers of g-C3N4 nanosheets were significantly prolonged.•The visible photocatalytic DeNOx activity of g-C3N4 nanosheets was enhanced.•The improved photo-oxidation ability of charge carriers can be achieved.
Graphene-like porous g-C3N4 nanosheets were synthesized via direct pyrolysis of thiourea followed by a thermal exfoliation. With increased exfoliation temperature, the color of the resulting samples gradually became shallow, and the thickness and size of the layers were decreased. A formation mechanism involving layer-by-layer exfoliation coupled with layer splitting was proposed. The band structure of the g-C3N4 nanosheets was continuously tuned because of quantum size effect. Time-resolved decay spectra indicated that the radiative lifetime of charge carriers (τ1 and τ2) increased from 4.13 and 26.23ns for bulk g-C3N4 to 5.36 and 36.57ns for graphene-like g-C3N4 nanosheets. The g-C3N4 nanosheet samples were applied for visible light photocatalytic removal of NOx in air. The performance of porous g-C3N4 nanosheets was significantly enhanced with increased exfoliation temperature from 450 to 550°C. Moreover, photochemical and structural stability was well maintained after multiple reaction cycles. By monitoring the reaction intermediate NO2, it was found that the generation of NO2 was inhibited. The activity enhancement of graphene-like g-C3N4 nanosheets can be predominantly ascribed to the prolonged lifetime and improved photo-oxidation ability of charge carriers arising from the unique electronic structure. As the synthesis method for graphene-like g-C3N4 nanosheets with high a performance is simple, the g-C3N4 nanosheets can be envisioned to be applicable in environmental remediation and solar energy conversion.
Sustainable agriculture is a key component of the effort to meet the increased food demand of a rapidly increasing global population. Nano-biotechnology is a promising tool for sustainable ...agriculture. However, rather than acting as nanocarriers, some nanoparticles (NPs) with unique physiochemical properties inherently enhance plant growth and stress tolerance. This biological role of nanoparticles depends on their physiochemical properties, application method (foliar delivery, hydroponics, soil), and the applied concentration. Here we review the effects of the different types, properties, and concentrations of nanoparticles on plant growth and on various abiotic (salinity, drought, heat, high light, and heavy metals) and biotic (pathogens and herbivores) stresses. The ability of nanoparticles to stimulate plant growth by positive effects on seed germination, root or shoot growth, and biomass or grain yield is also considered. The information presented herein will allow researchers within and outside the nano-biotechnology field to better select the appropriate nanoparticles as starting materials in agricultural applications. Ultimately, a shift from testing/utilizing existing nanoparticles to designing specific nanoparticles based on agriculture needs will facilitate the use of nanotechnology in sustainable agriculture.
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•Evaluation of dust retention effect of green space at street scale.•PM2.5 dry deposition rate parameters of native vegetation.•Simulation of the greening vegetation types by ...microclimate model ENVI-met.•Comprehensive consideration of the effects of plants on the diffusion and settlement of pollutants.
The establishment of the road green belt (RGB) is an effective means to reduce particle matter (PM2.5) emissions from road traffic. This study tested the ability of 23 common tree species in Shenzhen to reduce PM2.5 concentrations using field investigations and wind tunnel tests. The association between leaf microstructure and individual reduction ability was also analyzed. Finally, the impact of three RGB configurations (i.e., arbor, shrub, arbor + shrub) on road PM2.5 dispersion and deposition was simulated using the ENVI-met three-dimensional aerodynamic model, based on which an optimal RGB configuration was proposed. There were three key findings of the tests. First, the wind speed was the main factor affecting the PM2.5 concentration (54.2%), followed by vehicle flow (27.7%), temperature (14.2%), and time factor (7.6%). Second, the range of dry deposition velocity (Vd) was 0.04–6.4 m/s, and the dominant dust-retaining plant species were the evergreen trees, Ficus microcarpa and Ficus altissima, and the evergreen shrubs, Codiaeum variegatum and Fagraea ceilanica. A higher proportion of grooves or larger stomata would increase the probability that the blade would capture PM2.5. Third, the shrub RGB demonstrated the best performance in terms of pollutant dispersion; its PM2.5 concentration at the respiratory height (RH, 1.5 m) on the pedestrian crossing was 15–20% lower than the other RGB configurations. In terms of pollutant deposition, the arbor + shrub composite RGB was two-fold better than the other RGB configurations. Moreover, it was more advantageous to plant shrub RGBs in street canyons to achieve a balance between the lowest concentration and the largest deposition of PM2.5 pollutants. The findings of this study will facilitate the RGB configurations with good dust retention ability.
The dominant aroma compounds in the breast skin and breast muscle of Beijing roasted duck were investigated by gas chromatography–olfactometry–mass spectrometry (GC-O-MS), odor-activity values, and ...aroma recombination. The results demonstrated that a total of 42 aroma compounds were identified in Beijing roasted duck, including aldehydes, ketones, alcohols, acids, phenols, sulfur-containing compounds, and nitrogen-containing compounds. Among the 42 aroma compounds, 18 were identified as important odorants with odor-activity values (OAVs) greater than 1. Aroma-recombination–omission experiments and sensory evaluation demonstrated that nine aroma compounds significantly contributed to the characteristic aroma of Beijing roasted duck. These nine key aroma compounds were 2-furfurylthiol, dimethyl trisulfide, hexanal, heptanal, octanal, nonanal, methional, 1-octen-3-ol, and (E,E)-2,4-decadienal. Among these, 2-furfurylthiol (3620 ≤ OAV ≤ 31 606) and dimethyl trisulfide (2515 ≤ OAV ≤ 23 470) significantly contributed to the aroma of roasted duck (p < 0.01). Sensory evaluation of the recombination model with the nine aroma compounds scored 4.5 out of 5 points. The major aroma profile of Beijing roasted duck included strong fatty, roasty, and meaty aromas. The key aroma compounds of Beijing roasted duck were concluded to be 2-furfurylthiol, dimethyl trisulfide, hexanal, heptanal, octanal, nonanal, methional, 1-octen-3-ol, and (E,E)-2,4-decadienal.
As a fast emerging topic, van der Waals (vdW) heterostructures have been proposed to modify two-dimensional layered materials with desired properties, thus greatly extending the applications of these ...materials. In this work, the stacking characteristics, electronic structures, band edge alignments, charge density distributions and optical properties of blue phosphorene/transition metal dichalcogenides (BlueP/TMDs) vdW heterostructures were systematically studied based on vdW corrected density functional theory. Interestingly, the valence band maximum and conduction band minimum are located in different parts of BlueP/MoSe2, BlueP/WS2 and BlueP/WSe2 heterostructures. The MoSe2, WS2 or WSe2 layer can be used as the electron donor and the BlueP layer can be used as the electron acceptor. We further found that the optical properties under visible-light irradiation of BlueP/TMDs vdW heterostructures are significantly improved. In particular, the predicted upper limit energy conversion efficiencies of BlueP/MoS2 and BlueP/MoSe2 heterostructures reach as large as 1.16% and 0.98%, respectively, suggesting their potential applications in efficient thin-film solar cells and optoelectronic devices.
Sorption of sulfonamides on biochars is poorly understood, thus sulfamethoxazole (SMX) sorption on biochars produced at 300–600 °C was determined as a function of pH and SMX concentration, as well as ...the inorganic fractions in the biochars. Neutral SMX molecules (SMX0) were dominant for sorption at pH 1.0–6.0. Above pH 7.0, although biochars surfaces were negatively-charged, anionic SMX species sorption increased with pH and is regulated via charge-assisted H-bonds. SMX0 sorption at pH 5.0 was nonlinear and adsorption-dominant for all the biochars via hydrophobic interaction, π–π electron donor–acceptor interaction and pore-filling. The removal of inorganic fraction reduced SMX sorption by low-temperature biochars (e.g., 300 °C), but enhanced the sorption by high-temperature biochars (e.g., 600 °C) due to the temperature-dependent inorganic fractions in the biochars. These observations are useful for producing designer biochars as engineered sorbents to reduce the bioavailability of antibiotics and/or predict the fate of sulfonamides in biochar-amended soils.
•Sulfamethoxazole (SMX) sorption on biochars at pH 5.0 was adsorption-dominant.•Removal of inorganic fractions in low-temperature biochars reduced SMX sorption.•Removal of inorganic fractions in high-temperature biochars enhanced SMX sorption.•Anionic SMX was adsorbed on negatively charged biochar via charge-assisted H-bond.
Solution pH and biochar property control the sorption amount and mechanisms of antibiotic sulfamethoxazole.
Graphene-family nanomaterials (GFNs) including pristine graphene, reduced graphene oxide (rGO) and graphene oxide (GO) offer great application potential, leading to the possibility of their release ...into aquatic environments. Upon exposure, graphene/rGO and GO exhibit different adsorption properties toward environmental adsorbates, thus the molecular interactions at the GFN–water interface are discussed. After solute adsorption, the dispersion/aggregation behaviors of GFNs can be altered by solution chemistry, as well as by the presence of colloidal particles and biocolloids. GO has different dispersion performance from pristine graphene and rGO, which is further demonstrated from surface properties. Upon exposure in aquatic environments, GFNs have adverse impacts on aquatic organisms (e.g., bacteria, algae, plants, invertebrates, and fish). The mechanisms of GFNs toxicity at the cellular level are reviewed and the remaining unclear points on toxic mechanisms such as membrane damage are presented. Moreover, we highlight the transformation routes of GO to rGO. The degradation of GFNs upon exposure to UV irradiation and/or biota is also reviewed. In view of the unanswered questions, future research should include comprehensive characterization of GFNs, new approaches for explaining GFNs aggregation, environmental behaviors of metastable GO, and the relationship between dispersion of GFNs and the related adsorption properties.
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