This study examines the effects of energy use, financial development, and globalization on carbon dioxide emissions for Asian countries comprising the panel data over the period 1990–2017. To account for cross-sectional dependence, Pesaran cross-sectional dependence test is used. The second-generation tests are used to determine the stationarity level of the variables. Furthermore, the Westerlund panel cointegration test confirms cointegration among the variables. For long-run association, fully modified ordinary least squares approach is used. The study also used Dumitrescu and Hurlin’s (Econ Model 29:1450-1460, 2012) panel causality test to explore the causal relationship among the variables. The results suggest that financial development contributes to carbon emissions, whereas globalization helps to mitigate emissions. As financial development deteriorates environmental quality, therefore, the government should monitor the disbursement of loans for research and development, green financing, and efficient products that reduce resource consumption and improves environmental quality. Financial development should not compromise environmental quality and endanger sustainability. Such findings show that both renewable energy industries and financial development in the Asian economies are not meeting the maturity level in terms of leading to changes in environmental quality. Furthermore, Asian countries should promote globalization to support the inflow of green technologies to enhance environmental quality.

Water quality is one of the most important indices for public health especially for drinking water consumptions. This study was conducted to survey the presence of heavy metals in drinking water resources of Iran using a systematic review and meta-analysis. The literature search was conducted in data bases of PubMed, Web of Science, EMBASE, Scopus, Google Scholar, and some Persian databases up to 31 July 2018. Of all the articles reviewed (1151 articles), 61 papers were eligible for systematic review. Results indicated variable heterogeneity between studies for different pollutants (I² between 0 and 100). A subgroup analysis was performed for three different types of water resources such as drinking water, groundwater, and surface water to find the possible source of the heterogeneity. The pooled mean concentration level of iron was the highest at 255.8 (95% CI = 79.48–432.13 μg/l) and vanadium the lowest at 3.21 (95% CI = 1.45–4.98 μg/l). The sequence of metal concentration (μg/l) in descending order is as follows: Fe (255.8) > B (159.81) > Al (158.5) > Zn (130.73) > As (85.85) > Mn (51.61) > Cu (47.98) > Se (42.68) > Pb (37.22) > Co (22.76) > Mo (18.92) > Ni (16.79) > Cr (13.47) > Hg (4.49) > Cd (4.19) > V (3.21). The mean pooled concentration level of Al, As, Se, Pb, and Cd was higher than the WHO guideline and Iran Standard, and the rest of the metals had lower mean pooled concentration level. Pb and Cd were the common heavy metals that existed in all subgroups. As a recommendation, the relationship assessment of water parameters and heavy metals could be addressed in future studies of Iran’s water resources.

Microfibers are now ubiquitous in the environment largely due to the widespread use of natural and synthetic textiles. Many enter aquatic systems through wastewater treatment plant (WWTP) effluent, surface water runoff, and atmospheric deposition, where they persist and may be ingested by filter-feeding organisms. In addition to causing physical damage (e.g., digestive and respiratory obstructions), microfibers are often carriers of chemical pollutants that may also harm biota. This exploratory study aimed to determine whether freshwater mussel (Margaritifera margaritifera L.) microfiber content varied between two rural tributaries of the Saint John River, whether microfiber content was related to WWTP discharge points or potential diffuse microfiber sources, and whether mussel size was associated with microfiber content. Mussels were collected both upstream and downstream of five WWTP discharge points and at 11 other points along two rivers within rural watersheds of maritime Canada. Microfiber content differed significantly between the two rivers; however, no trends were observed in microfiber content in relation to WWTP discharge points on either river. Smaller mussels contained significantly more microfibers than larger mussels, despite differences in mussel size ranges between tributaries. These results reveal a potential pathway for microfibers to enter aquatic food webs and highlight important implications for the use of freshwater mussels as bioindicators of microfiber contamination.

Rapid migration to cities and the increasing demand for housing negatively affect living areas. Furthermore, uncontrolled population growth, industrialization, urbanization, narrowing of urban areas, and expansion of cities cause physical boundaries. Urbanization growth and the cold climate restrict pedestrian mobility in the city. Therefore, hourly microclimate data of the city center streets were collected 1.5 m above ground level in the winter period of 2019–2020. Then, different landscape design scenarios on pedestrian roads were investigated extensively using the ENVI-met V.4.4.2 winter model to determine the outdoor thermal comfort level. The RayMan model was utilized to generate the sky view factor (SVF) and analyze the mean values of the microclimate data. The proposed landscape design scenarios were as follows; (1) hard-covered street, (2) complete street coverage with a canopy, (3) street coverage with a semi-canopy, (4) sage of a combination of different plant species (30% deciduous, 30% coniferous, 30% bush), and (5) usage of ornamental pools in streets. The time period when pedestrians used the outdoor space was taken into consideration in evaluating and interpreting the analysis results. The findings of this study generally indicated that the semi-open canopy design provided roads with high thermal comfort such that people can walk and cycle in winter time. In conclusion, the thermal comfort condition of a street design, which is important for achieving sustainable urbanization, can be changed by making appropriate plan decisions. The findings of this study will help improve the outdoor thermal comfort in the first stage of urban planning and landscape street design for more livable and effective cities. This study emphasizes that a multidisciplinary team should work together to establish a healthy, sustainable, and livable urbanized area with thermal comfort in the streets.

Treatment of aqueous leachate from acid mine tailings with pristine biochar (BC) resulted in the removal of more than 90% of the dissolved arsenic with an attendant rapid and sustained pH buffering from 3 to 4. Pine forest waste BC was transformed to a highly effective adsorbent for arsenic remediation of acid mine drainage (AMD) because the dissolved iron induced “activation” of BC through accumulation of highly reactive ferric hydroxide surface sites. Physicochemical properties of the BC surface, and molecular mechanisms of Fe, S, and As phase transfer, were investigated using a multi-method, micro-scale approach (SEM, XRD, FTIR, XANES, EXAFS, and STXM). Co-located carbon and iron analysis with STXM indicated preferential iron neo-precipitates at carboxylic BC surface sites. Iron and arsenic X-ray spectroscopy showed an initial precipitation of ferrihydrite on BC, with concurrent adsorption/coprecipitation of arsenate. The molecular mechanism of arsenic removal involved bidentate, binuclear inner-sphere complexation of arsenate at the surfaces of pioneering ferric precipitates. Nucleation and crystal growth of ferrihydrite and goethite were observed after 1 h of reaction. The high sulfate activity in AMD promoted schwertmannite precipitation beginning at 6 h of reaction. At reaction times beyond 6 h, goethite and schwertmannite accumulated at the expense of ferrihydrite. Results indicate that the highly functionalized surface of BC acts as a scaffolding for the precipitation and activation of positively charged ferric hydroxy(sulf)oxide surface sites from iron-rich AMD, which then complex oxyanion arsenate, effectively removing it from porewaters. Graphical abstract

The present investigation attempted to examine the defluoridation feasibility onto the extracted nanocellulose/PVA polymer composites. Nanocellulose were derived from sugarcane bagasse and blended with PVA (polyvinyl alcohol) polymer matrix. The defluoridation potential of nanocellulose/PVA was observed to be significantly dependent on the various operational factors including pH, time interval, etc. the Temkin isotherm (R² = 0.989) as well as the Langmuir isotherm equation (R² = 0.982) could well fit with the investigational data. Following the Langmuir isotherm, the maximum monolayer adsorption capacity for fluoride elimination at 25°C was obtained as 11.363 mg g⁻¹. The nature of rate-limiting steps involved in defluoridation process might be effectively predicted by pseudo-second-order kinetics. Values of thermodynamic state properties achieved as of the thermodynamic analysis showed that the defluoridation process was spontaneous, exothermic, and feasible. The diffusion and mass transfer study were estimated by following the Boyd’s model. Average effective diffusion coefficient (Dₑ) at various initial fluoride concentrations (4–10 mg L⁻¹) was obtained as 15.3343×10⁻⁷ m²s⁻¹ and the estimated magnitude of the mass-transfer coefficient (Kf) was 0.0346×10⁻⁹ m s⁻¹ (temperature = 298 K, C₀= 6 mgL⁻¹). An ANN (artificial neural network) model applied to optimize and simulate the defluoridation procedure. Furthermore, continuous flow column reactor was conducted to investigate the practical applicability of composites in the defluoridation process. The Yoon-Nelson and the Thomas model exhibited excellent conformity with the breakthrough curves. Nanocellulose/PVA satisfactorily eliminated fluoride from its aqueous solution and can be considered as a suitable bio-sorbent for defluoridation.

This study applied the techniques of high-resolution dialysis (HR-Peeper) and diffusive gradients in thin films (DGT) to explore the effects and the behind mechanism for inhibition phosphorus (P) releasing from sediments by nFe₃O₄ capping. The highest decreasing rates of SRP and labile P (i.e., 49% and 47%, respectively) and the decreased flux of SRP showed that nFe₃O₄ capping can successfully control sediment internal P release. Adsorption by Fe(III) hydroxides with the oxidation of Fe(II) was one of the reasons for the decrease of P concentrations in nFe₃O₄ capping sediments. This was supported by the increase of Eh and significant negative correlation between Eh with Fe(II) (soluble and labile Fe(II)) and P (SRP and labile P) and significant positive correlation between Fe(II) and P in sediments by nFe₃O₄ capping. An outer-sphere complex between positively charged nFe₃O₄ surface groups and P formation was the other reason to decrease the concentrations of P in the nFe₃O₄ capping sediments. This was supported by the decrease of pH value in sediments by the capping of nFe₃O₄. This study shows that nFe₃O₄, when used as capping agent, can effectively control the sediment internal P release, which is expected to be used as a potential material for repairing lake eutrophication.

In this work, TiO₂-based nanomaterials have been successfully synthesized by doping TiO₂ with Co, Mn, and Ni and by co-doping it with (P,Mo) or (P,W). The structural, optical, and morphological properties of the synthesized nanomaterials have been investigated using various techniques such as XRD, FTIR spectroscopy, UV-vis diffuse reflectance spectroscopy, XPS, and SEM-EDS. The obtained results showed that the crystalline structure of the doped TiO₂-based nanomaterials depends strongly on the nature of the doping ions. The obtained band gap energy of TiO₂ co-doped with (P,Mo) changes to a level below the band gap energy of TiO₂ anatase indicating a high ability to absorb visible light. The obtained photocatalytic activity results of methyl orange degradation showed that, under visible light, the mono-doping of TiO₂ with Co and its co-doping with (P,Mo) or (P,W) improve significantly the photocatalytic activity of TiO₂ in comparison with undoped TiO₂. The activity order obtained under UV-A irradiation for the used photocatalysts is TiO₂ > > 1%Ni-TiO₂ > 1%Co-TiO₂ > 30%(P,Mo)-TiO₂ ≈ 30%(P,W)TiO₂ > 1%Mn-TiO₂ while under visible light, it is 1%Co-TiO₂ > 30%(P,Mo)-TiO₂ > 30%(P,W)TiO₂ ≈ TiO₂ > 1%Ni-TiO₂ > 1%Mn-TiO₂. The high photocatalytic activity observed for these samples could be the result of a synergetic effect of the high visible light absorption capacity and the low recombination rate of photoexcited electrons and holes.

This study examines the association between air pollution and economic growth based on the idea of environment Kuznets curve (EKC) hypothesis which suggests an inverted U-shaped link between air pollution and economic growth in six different regions including Latin America and the Caribbean, East Asia and the Pacific, Europe and Central Asia, South Asia, the Middle East and North Africa, and Sub-Saharan Africa over the period 2000 to 2018. This regional classification is done to investigate the regional differences of the EKC relationship for carbon emissions. Models based on panel data econometric models are employed to obtain empirical results. Random effect and fixed effect models are used in the present study. A multivariate framework is used in which carbon dioxide emission, per capita gross domestic product, trade openness, foreign direct investment, primary school enrollment, financial development indicator, and institutional quality that is measured by six indicators are included. The result is that the EKC hypothesis is supported in all the abovementioned regions except in the Sub-Saharan Africa region. Thus, the hypothesis that different regions have dissimilar EKC relationships is supported through the results of this research study.

The aerobic granular sludge (AGS) process and microalgal-bacterial granular sludge (MBGS) process were comparably applied for municipal wastewater treatment in sequencing batch reactors with a height to diameter ratio of eight. For morphological appearances, the yellow aerobic granules were strip-shaped (4.0 mm × 0.62 mm) while the green microalgal-bacterial granules were elliptical-shaped (2.0 mm × 0.75 mm). The dominated rod-shaped bacteria (e.g., Acidobacteria and Bacteroidetes) and the slender configuration might be associated with the strip shape of aerobic granules under weak acid conditions. The nutrients removal performances by MBGS process were generally slightly better than AGS process. In addition, nutrients removal mechanisms were identified to elucidate how organics, ammonia, and phosphorus were removed by AGS process and MBGS process, respectively. Mass balance calculation estimated that MBGS process appeared to achieve much less CO₂ emission (5.8%) compared with AGS process (44.4%). Overall, it proved that MBGS process, with the merits of potentially low energy cost, limited CO₂ emission, and excellent performance, showed more prospects in municipal wastewater treatment than AGS process.