Carbon nano-onions (CNOs) are fascinating zero-dimensional carbon materials owning distinct multi-shell architecture. Their physicochemical properties are highly related to the parent material selected and the synthesis protocol involved. In the present work, we report for the first time novel CNO structures encompassing discrete carbon allotropes, namely, H₁₈ carbon, Rh6 carbon, and n-diamond. These structures were cost-effectively synthesized in gram scale by facile flame pyrolysis of paraffinum liquidum, a highly refined mineral oil. The as-synthesized and chemically refashioned CNOs are quasi-spherical self-assembled mesopores, manifesting remarkable stability and hydrophilicity. The CNO structures exhibit excellent dye adsorption characteristics with high removal capacity of 1397.35 mg/g and rapid adsorption kinetics with a minimal adsorbent dosage of 10 mg/L, for a low concentration of 20 mg/L methylene blue dye. The novel CNOs assure potential implementation in the remediation of low concentration and high volume of dye-contaminated wastewater.Graphical abstract

The evaluation of the concentration of pesticides in drinking water presents a real concern. In this study, a simple and rapid method based on solid-phase microextraction (SPME) followed by gas chromatography–mass spectrometry and electron capture detectors was developed aiming at multiclass determination of 23 pesticides regulated by the Brazilian legislation. The extraction was carried out by direct immersion mode (DI-SPME) using DVB/Car/PDMS fiber coating. In order to improve the extraction efficiency, parameters such as temperature, salting-out effect, and extraction time were optimized. The method was evaluated using drinking water samples spiked with the analytes at different concentrations, and it showed good linearity in the range studied. The values obtained for limits of quantification (LOQ) were below the limits established by Brazilian regulations. Accuracy and precision of the method exhibited satisfactory results, providing relative recoveries from 70 to 123.34% at three spiked levels, and the relative standard deviations ranged from 0.53 to 24.8%. The method was applied in 20 drinking water samples from 13 cities in the State of Santa Catarina, Brazil.

In this study, graphene oxide (GO) was prepared using modified Hummer’s method and doped with Fe-Ni nanoparticles. Morphological characterization of the Fe-Ni nanoparticles showed flake-like structure correlating to taenite phase, while Raman spectroscopy suggested that graphene oxide was multi-layered. Batch adsorption experiments were performed to determine the effect of solution pH, initial uranium (VI) concentration, adsorbent dosage, contact time, and specific anions (SO₄²⁻ and NO₃²⁻) on the adsorption of U (VI). Solution pH had significant effect on U (VI) sorption on Fe-Ni/GO, with maximum removal of 98.4% at pH 4, while it was 98% at pH 8 for GO. Sorption kinetics revealed fast adsorption within 15 min. The kinetic and equilibrium data was evaluated using pseudo-first-order, pseudo-second-order, Elovich, Langmuir, Freundlich, and Temkin models. The mechanism of U (VI) sorption appeared to be a combination of chemisorption and possible pore diffusion of the U (VI) moieties to the porous structure of GO and Fe-Ni/GO. Overall, Fe-Ni/GO was a better adsorbent than GO with higher sorption capacities. U (VI) sorption on GO and Fe-Ni/GO followed pseudo-second-order reaction kinetics (R² > 0.99). Good fit to Langmuir isotherm model (R² > 0.98) suggested favorable monolayer adsorption, with a maximum U (VI) adsorption capacity on Fe-Ni/GO to be 25.64 mg/g. Moderate to insignificant effect of specific anions even at high concentrations on U (VI) removal capacities makes Fe-Ni/GO an excellent candidate.

This study calculates the green investment level of each province in China and objectively estimates the provincial environmental regulation level from the perspective of the government to examine the effectiveness and impact of the government’s environmental protection policy on the environmental regulation level. The carbon emission trading pilot policy is determined through a quasi-natural experiment difference in difference model to examine the impact and assess the effectiveness of green environmental protection policies on the environmental regulation level empirically. Results show that (i) the green investment level of the carbon emission trading pilot provinces is significantly lower than that of other nonpilot provinces after 2013, and (ii) the introduction of environmental protection policies has reduced the government’s green investment level by approximately 8%. These findings confirm that environmental regulation policies play a significant role in promoting the environmental regulation level. Further mechanism analysis shows that environmental regulation policies influence this level through carbon dioxide emissions. This study provides a reference for environmental regulation policy making.

Ecosystems play critically important roles in supporting human society, while human activities seriously disturb their initial balance. Lots of researches on ecosystem services are conducted due to the increasing concern on ecological security worldwide. In order to provide valuable insights for understanding the primary performance of ecosystem services–related studies, a qualitative and quantitative analysis by using a bibliometric tool is performed in this study. Journal impact factor, CiteScore, and h-index are used for identifying influential journals, while h-index is used for recognizing productive countries/territories and institutions. Social network analysis of countries/territories and institutions is visualized, respectively, so that relationships among them can be uncovered. Citation analysis of publications and co-occurrence analysis of high-frequency keywords are also performed to explore hotspots and popular methods in this field. This study uncovers a holistic picture on the primary performance of ecosystem services–related literatures published from 1997 to 2016, including journals, countries/territories, and institutions. Results find that forest, agriculture, and wetland ecosystems attract lots of attention. Finally, major methods used for ecosystem services evaluation are identified and discussed. Research outcomes will provide valuable insights to stakeholders interested in ecosystem services.

Microplastics have become a major environmental concern globally due to their potential impact on ecosystem function. They are known to be ubiquitously present, persistent and bio-accumulative, yet there is a lack of abundance quantifications in freshwater shorelines. Furthermore, there is little understanding of combined effects of seasonality and human population density on the extent of microplastic pollution. In this study, we assessed microplastics in sediment along a subtropical reservoir shoreline across three seasons and seven sites to understand microplastic pollution dynamics along a human population gradient. Multivariable analysis was used to assess relationships among substrate embeddedness, sediment organic matter, human population density and microplastic particle densities and characteristics. Microplastic densities were relatively high during the hot–dry season (mean range 120–6417 particles kg⁻¹ dwt) whilst the hot–wet season had the lowest densities (mean range 5–94 particles kg⁻¹ dwt). Microplastic abundances were positively correlated with population density, demonstrating the direct effects of human activity on microplastic contamination. These results highlight the need to further explore microplastic distribution patterns in freshwater ecosystems in the Southern Hemisphere. Furthermore, our findings suggest particular risk for fauna during low rainfall periods through microplastic concentration effects.

In recent years, the problem of rising salinity levels in the Shatt al-Arab river in southern Iraq has been repeated, which has directly affected the living and health situation and the agricultural activity of these areas. Six sampling stations were selected along Shatt al-Arab to estimate the concentration of total dissolved solids (TDS) in the river; these stations included the following: Qurna, Labani, City Centre, Kateban, Corniche, and Sihan. In addition, three Landsat-8 satellite images which were taken at the same time as collected samples also used for detecting the salinity in the river. After processing of atmospheric correction and inserted remote sensing indices, the reflectance of water extracted from satellite images was used to express the spectral characteristics of different TDS concentrations. Correlation and regression were used to obtain accurate models for detecting the salinity depending on the spectral reflectance of Landsat 8 operational land image OLI. The results presented Pearson correlation (r) value of 0.70, 0.97, and 0.71, and correlation coefficient (R²) of 0.56, 0.94, and 0.85 between field data with spectral data of salinity index 2 (SI-2) derived from the green and blue bands of Landsat obtained in 2015, 2017, and 2018 respectively. In conclusion, remote sensing and GIS technologies coupled with spectral modeling are useful tools for providing a solution of future water resources planning and management, and also offer great undertaking as a means to improve knowledge of water quality and support water decision making.

Sulfadiazine (SDZ) was effectively removed by the heterogeneous catalytic sulfate radical (SO₄•⁻) oxidation using a novel composite material of mesoporous carbon (MC) loaded nano zero-valent iron (nZVI). Possessing larger specific area (433.3 m² g⁻¹) and high mesopores volume (2.537 cm³ g⁻¹), the composite material (nZVI/MC) was used as the activator to activate persulfate for the degradation of SDZ. The results of degradation experiments indicated that the removal efficiency of SDZ in nZVI/MC+ persulfate (PS) process reached the highest, due to good dispersing property of MC for nZVI. The removal of SDZ was further enhanced by the increase of nZVI loading as well as the nZVI/MC composite content. Quenching experiments showed that SO₄•⁻ acted a crucial role in the degradation process of SDZ. Both the FT-IR and XPS analyses showed that the FeO contents decreased after degradation reaction, which indicated the occurrence of active oxidation reaction between SO₄•⁻ and Fe²⁺ from the breakage of the Fe–O bond. The LC-MS analysis indicated that the cleavages of C–N bond in the heterocyclic ring and N–S bond were the major degradation pathway of SDZ, attributing to the attack of SO₄•⁻ and •OH. These results demonstrated that the novel nZVI/MC composite with excellent stability could be used for the effective degradation of SDZ through activating PS to produce SO₄•⁻. Graphical Abstract

Cross-linking of polymer hydrogels can be achieved by exposing the polymer to gamma radiation that induces production of polymer chain radicals resulting in cross-linking of chains. The present study was focused on fabrication of hydrogel by gamma irradiation for immobilization of bacterial cells. Hydrogels were prepared using 30 and 40% acrylamide at gamma irradiation dose of 5 kGy. Five bacterial strains BR-6, BR-14, BR-18, BR-21, and BR-26 screened for resistance to strontium were immobilized in hydrogels and evaluated for the bioremoval of strontium. Strontium content for different strains was 4.21–4.68 μg/ml after 3 days in the presence of free cells grown in 5 μg/ml strontium, while for immobilized cells, the strontium content was 3.35–3.81 μg/ml (30% acrylamide gel) and 3.46–3.99 μg/ml (40% acrylamide gel). After 10 days of incubation, the strontium content was reduced to 0.94–1.26 μg/ml (30% acrylamide gel) and 0.82–1.07 μg/ml (40% acrylamide gel), and for free cells, strontium content was 1.34–1.41 μg/ml. 72–75% bioremoval of strontium by free cells of different strains BR-6, BR-14, BR-18, BR-21, and BR-26 was observed after 10 days of incubation. 77–83% reduction in strontium content was observed in the presence of cells immobilized in 30% acrylamide, whereas higher reduction of 80–85% was observed for cells immobilized in 40% acrylamide after 10 days. At higher concentration of 10-μg/ml strontium, 62 to 71% reduction was observed with immobilized bacterial cells. Obtained results indicated that immobilized bacterial cells in hydrogels prepared by gamma irradiation were found to have significantly higher efficiency as compared to free cells for bioremoval of strontium ions.

Small-scale agriculture (SA) is regarded as unsustainability because of its low benefit. To protect traditional agricultural landscapes like terraces through SA will be difficult. However, in China, terraces are still maintained well by smallholders now. This study takes the family as a basic unit and SA in Hani terraced region as an object to explore its sustainability from the perspective of labor productivity (LP) through the questionnaire method. The findings are that peasant households work on both farm and non-farm jobs. They get a low income (3854.5 yuan RMB) from hybrid-rice-cropping and a high income (44,665.8 yuan RMB) from non-farm jobs but spend a small part of labors (34.23 person•days) in growing hybrid-rice and expended lots of labor (522 person•days) for non-farm jobs. In conclusion, LP of hybrid-rice-cropping is 1.32 times that of non-farm jobs for a household. The result shows SA in Hani terraced region has a higher return of labor investment than non-farm jobs. It is different from the common impression of the low benefit of SA and also explains why SA still continues to exist in the mountainous area in China now. However, SA in Hani terraced region also faces challenges with salary level rise of non-farm jobs and part-time farmers’ requirement for living quality improvement. In the future, promoting industrial integration development in this region to add local employment for improving farmers’ income is a feasible approach to protect terraced landscapes.