Energy stocks have become an essential segment of the investment portfolios of both households and institutional investors. This study investigates the dynamic aspect of evolving weak-form efficiency in six energy stock markets: those of the United States (US), Canada, China, Australia, India, and Saudi Arabia. The generalized autoregressive conditionally heteroskedastic in the mean GARCH-M(1,1) method is applied, alongside the state-space time-varying approaches with the Kalman filter estimation, to detect the evolving efficiency for periods ending in November 2019. The empirical results reveal that the studied markets undergo various extents of time-varying efficiency, containing periods of efficiency enhancement as well as periods of deviation from efficiency. Meanwhile, the 2007–2009 global financial crisis and the 2015 changes in the energy sector—in addition to other contemporaneous crises—have a profound influence on the timeline of market efficiency evolution. Overall, all of the markets gradually became more efficient, apart from India’s energy market as a result of the current energy crisis in India. Amid the energy markets explored in this study, the US energy market was found to be the most efficient.

The Campo and Km 119 rivers are sources of irrigation and water supply for the city of Campo Mourão, State of Paraná, Southern Brazil. However, these rivers are under the influence of agricultural and urban activities, which compromise the quality of their waters. The present study evaluated the waters of these rivers in the vicinity of this municipality in two different hydrological periods of 2018 for physical and chemical parameters and potential cytotoxic, genotoxic, and toxic effects. Among the eight sites, in the dry and rainy periods, P1, P2, P3, P4, and P6—sites surrounded by agricultural activities, with nearby residences and with low and/or reduced riparian forest—presented a low concentration of dissolved oxygen and high concentration of nitrite, phosphate, and chlorine. The waters of P1, P2, P3, P4, and P6, in the two samplings, were cytotoxic to the root meristem cells of Allium cepa at 24 and 48 h of exposure, and toxic to Artemia salina nauplii at 24 h of exposure, with LC₅₀ < 100 ppm. The results characterize water contamination by pesticides and urban waste from stormwater drains and runoff from the urban area. Therefore, waters of the Campo and Km 119 rivers in the vicinity of the city of Campo Mourão demonstrate the potential to cause adverse effects to man and the aquatic ecosystem. These results represent an alert to the public authorities of Campo Mourão and the State of Paraná regarding the need to inspect the anthropic activities in that city in the vicinity of these rivers, and in the implementation of a management plan for the replacement of riparian forests in places close to urban area, in order to preserve the health of the population and the ecosystems that depend on these water resources.

This study focused on the permeability and structural evolution of impeded soil layers in landfill. A series of laboratory tests including a permeability test, X-ray diffraction, nuclear magnetic resonance, scanning electron microscopy, and laser particle size tests were conducted to analyze the permeability and microstructure characteristics of undisturbed silty clay polluted by landfill leachate. The hydraulic conductivities increased with time in the first 108 h. After 108 h, the hydraulic conductivities of undisturbed silty clay polluted by landfill leachate decreased. After 205 h, the changes in the hydraulic conductivity stabilized, and the hydraulic conductivity decreased with the increase of the concentration of leachate. The volume fractions of inter-particle and intra-aggregate pores were much higher than those of other pores. The optimal radius decreased as the concentration of leachate increased. The blockage of the pore channel and weakened permeability was caused by solid matter interception by the porous medium. As the height of the specimen increased, the volume fraction of coarse grain changed rapidly and sharply, and the volume fraction of fine grain changed slowly. The average particle size increased with increased specimen height and decreased as the leachate concentration increased. A comprehensive structural parameter (ζ) of undisturbed silty clay polluted by landfill leachate was obtained based on the test results. The equation of comprehensive structural parameter ζ of undisturbed silty clay polluted by leachate was established. These results can provide fundamental data for evaluating the stability of the underlying stratum of landfill sites.

Rhodamine B (RhB) is a cationic organic dye widely used industrially, mainly in the textile and food industries. Then, the work aims to study on the photocatalytic degradation of RhB dye, under UV and visible radiation, using photocatalyst silica-based materials synthesized by sol-gel route with different solvents (ethanol and n-propanol) and catalysts (C₁₂H₂₇N, HNO₃, NH₄OH, and NaOH) to the hydrolysis and condensation of tetraorthosilicate (TEOS). In addition, the effect of doping with silver nanoparticles (AgNPs) was evaluated on the photocatalytic activity. The samples were characterized by X-ray diffraction (XRD), diffuse reflectance spectroscopy (DRS), N₂ porosimetry, zeta potential measurements (ZP), and Fourier transform infrared spectroscopy (FTIR). To evaluate the photocatalytic activity, photocatalytic tests were carried out in a stirred batch reactor, with the photocatalyst in suspension, under ultraviolet and visible radiation, and the target molecule chosen was the Rhodamine B dye (RhB). The photocatalyst Si–HNO₃–AgNPs showed the best photocatalytic activity with a degradation of the RhB dye of 90.16% (k = 0.0198 min⁻¹, under ultraviolet radiation) and 82.79% (k = 0.0148 min⁻¹, under visible radiation), after 120 min of reaction; while under the same conditions, the commercial catalyst TiO₂ (P25) showed a degradation of 50.02% and 42.14%, respectively.

Mucosal surfaces are the first mechanical barrier preventing the entry of foreign particles into the organism. The study addresses the detection and analysis of metal-based solid particles in cytological mucus samples from the surface of human hypertrophic tissue in the inferior nasal turbinates in patients diagnosed with chronic rhinitis. Solid particles were characterized by scanning electron microscopy and Raman microspectroscopy; all the biological samples were also subjected to vibration magnetometry. Since the upper airways are the first part of the respiratory tract, which is exposed to inhaled particles, it can be assumed that inhaled particles may be partially deposited in this region. Scanning electron microscopy revealed the presence of metal-based solid particles/clusters in the majority of the analysed cytological mucus samples and also in hypertrophic tissues; in all groups, the particles were of submicron size. Raman microspectroscopy detected the presence of particles/clusters based on amorphous carbon, graphite, calcium carbonate, anatase and barite only in the hypertrophic tissue. The obtained results show that the composition of some of the solid particles (i.e. Ba, Zn, Fe and Ti) detected in the mucus from the surface of the hypertrophic tissues resembled the particles found in the hypertrophic tissue itself. It can be assumed that after the capture of the inhaled particles by the mucus, they penetrate into the deeper layers of tissue.

Microbiological, physical, chemical, cytotoxic, and genotoxic analyses of waters from ten tubular wells intended for irrigation of a community garden complex in the state of Piaui, northeastern Brazil, were carried out in two periods of 2018 (rainy and drought). All wells in both periods were contaminated with total coliforms, and wells P1, P3, P5, and P10 also had fecal coliforms. The waters, in the two collections performed, presented low concentration of dissolved oxygen, and nitrate and chlorine concentrations higher than allowed by law. Water from P1, P3, P5, and P10 were cytotoxic to root meristem cells of A. cepa in the two periods studied. However, no water sample was genotoxic to root meristems. The results show that the analyzed waters are contaminated with untreated effluents as well as with pesticides. Such conditions are pointed out because the rivers near these wells are degraded by human activities, and the gardens where the wells are found have ditches, sinks, and black cesspools for the disposal of sewage. In view of this, the intervention of the State Government in these places is necessary, since the evaluated wells irrigate community gardens in overcrowded poor neighborhoods, and from there comes part of the food of their residents. Another activity for the government is to put in place management plans for the restoration of rivers and the implementation of public sanitation in the neighborhoods where the wells are located.

How do Chinese provinces perform in their commitments to carbon emission responsibility? This study extends the carbon emission responsibility allotment proposed by Dietzenbacher et al. (Nat Commun 11:1130, 2020) to a national multi-region setting to analyze provincial, industrial, and bilateral trade emission responsibility allotment in China. This paper uses China’s latest multi-region input-output tables in 2012 and 2015, and finds that based on the total amount of ERA carbon emissions, the province with the largest carbon emission responsibility in 2012 is Shandong, followed by Jiangsu and Hebei. From the perspective of industry, the construction is the highest carbon emissions in each province, followed by general and specialist machinery. In the allocation of carbon emissions responsibility in 2015, the credit between Xinjiang and Jiangsu is the largest; Guangdong and Jiangsu have the largest penalty. Among total credits which the province’s trade with others, Xinjiang has the highest credit, followed by Shanghai and Jiangsu; among total penalties which the province trade with others, Guangdong Province is the largest penalty province, followed by Guangxi.

Microplastics (plastic particles < 5 mm) is a pollution of growing concern. Microplastic pollution is a complex issue that requires systematic attempts to provide an overview and avoid management solutions that have marginal effects or only move the pollution problem. Substance flow analysis (SFA) has been proposed as a useful tool to receive such an overview and has been put forward as valuable for substance management. However, as the research on microplastics has only emerged recently, detailed and reliable SFAs are difficult to perform. In this study, we use three SFA studies for three pollutants (cadmium, copper and pharmaceuticals) to compare flows and strategies to control the flows. This in order to seek guidance for microplastic management and evaluate potential strategies for controlling microplastics. The analysis shows that there has been rigorous control on different levels to abate pollution from cadmium, copper and pharmaceuticals, but where in the system the major control measures have been carried out differ. For microplastics, there are many potential solutions, both in terms of preventive actions and treatment depending on the type of source. When forming management plans for microplastics, the responsibility for each measure and the impact on the whole urban system should be taken into consideration as well as which receiving compartments are particularly valuable and should be avoided.

The simultaneous determination of major, trace, and rare earth elements in sediments requires the development of specific procedures to prevent interferences. A single digestion method adapted from the EPA method 3051A is proposed for the quantification of 42 elements in sediments by inductively coupled plasma techniques associated with optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS). A combination of different acids and microwave-assisted acid extraction following hot plate extraction was tested. Evaluation of applicability range, linearity, limits of detection and quantification, selectivity, repeatability, intermediate precision, and trueness showed the accurate determination of all elements. Selectivity, precision, and trueness values were below the criteria established by the laboratory. The applicability of the proposed method was tested in real sediment samples. For each element, difference between duplicates was lower than the corresponding repeatability limit, with the coefficients of variation ranging between 1.7 and 14%. These results point to the usefulness of this method in multi-element determination of major, minor, trace, and REE in sediment samples, showing its applicability in environmental studies related, namely to sediment characterization, monitoring programs, assessment of environmental impacts, sediment provenance, and post-depositional mechanisms. Graphical abstract

Wastewater pollution results in detrimental effects on ecosystems and poses human health hazards. As the human population and urbanization rates increase, so do abiotic and biotic contaminants such as Escherichia coli within natural waterways. For example, the Chicago River has been degraded by contaminants and untreated sewage from city occupants since the late 1700s. Surprisingly, water treatment of the Chicago River has not met EPA freshwater river standards for some time, creating a need for remediation alternatives. Such an alternative is mycoremediation, where fungi are used to degrade and remove water contaminants. To explore this alternative for bioremediation of contaminated waterways, this two-part study focused on the feasibility and time efficiency of mycoremediation of polluted waters through mycofiltration. In the lab-based experiment, known amounts of E. coli–inoculated water were processed through organic wheat straw with mycelia of Pleurotus ostreatus (oyster mushroom) to assess if these fungi were capable of E. coli removal and at what rates. The second part of the study replicated the lab-based experiment with water samples from the Chicago River. Results showed that mycelia treatments were able to remove significant amounts of E. coli in lab- and field-sampling-based settings (99.25% and 99.74% over 96 h respectively), and did so at higher rates within the initial 48 h. With a substantial E. coli reduction by fungal mycelia from initial colony counts over 96 h, our study demonstrated that mycoremediation may be a feasible and possible option for natural contaminant remediation.