This paper presents an experimental study of suspended particle transport through sand layer using a new self-developed sand layer transportation-deposition testing system, and the study aims to identify the effects of temperature on the transport of suspended particles through porous medium. Four typical temperatures (5 °C, 15 °C, 25 °C, and 35 °C) were considered in our study, and the experiments were conducted under four size compositions and three flow velocities (1.5 cm/s, 0.2 cm/s, and 0.04 cm/s). The tests were conducted using quartz sand as the porous medium and quartz powder as particles to monitor the change in turbidity under the different conditions. The breakthrough curves were analyzed, and the results demonstrated that changes in temperature can affect the breakthrough curves, especially at the peak. The influence is particularly significant under lower flow velocities and for smaller particles. In regard to the influence factors on the transport process, water viscosity and adsorption effect can be regarded as promoting factors, while kinetic energy of particles can be classified as constraining factors.

In this study, organoclay and clay-biopolymer composites were evaluated for the adsorption process of an anionic red dye, Allura Red (AR), in aqueous solution. For this purpose, the cationic exchange capacity (CEC) of a natural bentonite was calculated, and it was modified with the cationic surfactant hexadecyltrimethylammonium bromide (OB). Furthermore, a commercial montmorillonite modified with dimethyldialkyl ammonium (OM) was also employed. These organo-modified clays were used for the synthesis of two series of composites, with alginate as the polymer matrix, and were identified as OBC and OMC, respectively; composites were obtained in the wet (W) and dry (D) states. The adsorbent materials were characterized by means of infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and dispersive energy spectroscopy (EDS). Afterwards, kinetics and isotherms studies were performed in batch systems, with dye solutions of different concentrations, without pH adjustment. Some parameters were evaluated, such as the variation of the pH value of the solution and the concentration of the dye with the organoclays and composites. Chemisorption was considered as the main mechanism that follows the adsorption processes of AR. Results demonstrated that the pseudo-second order was the kinetics model that best described the adsorption process of the AR dye, with both, hydrated and dry composites. Finally, the Freundlich and the Langmuir–Freundlich isotherms were the best models that described the hydrated and dry composites behavior, respectively.

Oleaginous microalgae and yeast are the two major propitious factories which are sustainable sources for biodiesel production, as they can accumulate high quantities of lipids inside their bodies. To date, various microalgal and yeast species have been exploited singly for biodiesel production. However, despite the ongoing efforts, their low lipid productivity and the high cost of cultivation are still the major bottlenecks hindering their large-scale deployment. Co-culturing of microalgae and yeast has the potential to increase the overall lipid productivity by minimizing its production cost as both these organisms can utilize each other’s by-products. Microalgae act as an O₂ generator for yeast while consuming the CO₂ and organic acids released by the yeast cells. Further, yeast can break complex sugars in the medium, which can then be utilized by microalgae thereby opening new options for copious and low-cost feedstocks such as agricultural residues. The current review provides a historical and technical overview of the existing studies on co-culturing of yeast and microalgae and elucidates the crucial factors that affect the symbiotic relationship between these two organisms. Furthermore, the review also highlighted the advantages and the future perspectives for paving a path towards a sustainable biodiesel product.

Nowadays, widespread application of engineered nanoparticles (ENPs) inevitably leads to their release into the environment. Soils are regarded as the ultimate sink for ENPs. The study on mobility of ENPs in soils is important in the assessment of potential risks related to their toxicity. The behavior of ENPs is dependent not only on parameters of soil but also on exposure scenarios, namely, the amount of ENPs trapped in soil. In the present work, the mobility of cerium dioxide nanoparticles (nCeO₂) in soils at different exposure scenarios has been studied. The relationship between mobility of nCeO₂ and their concentration in soil in the range from 1 to 1000 μg g⁻¹ is evaluated. It is shown that the mobility of nCeO₂ decreases with decreasing their concentration in soil and attains the minimum value at the concentration of nCeO₂ below 10 μg g⁻¹. In relative terms, only about 0.1–0.2% of nCeO₂ at their concentration in soil 10–1000 μg g⁻¹ are mobile and can migrate in soil profile under saturated conditions. The major portion of nCeO₂ (about 99.8%) remains immobile in soil. Evidently, the vertical transport of nCeO₂ in soil profile should depend on volume of released suspensions. In the case of small or moderate wet deposition, nanoparticles will accumulate in upper soil horizons, where biological activity is highest, and affect the soil inhabitants (plant roots, earthworms, insects, microorganisms, etc.).

Soil washing is an effective technology for the remediation of soils contaminated with various metals. However, the bioavailability of residual metals in soils and soil properties can be changed during the washing processes. In this study, we used four amendments to revitalize mixed chelator (MC)–washed soils (WS). These amendments included zeolite, CaCO₃, biochar, and chicken manure. Results showed that inorganic amendments reduced the available Cd and Zn concentrations, while organic amendments, particularly chicken manure, reduced the Pb bioavailability in WS. The combination of 0.2% CaCO₃ and 2% chicken manure amendments reduced the Cd, Pb, and Zn bioavailability by 45.8%, 77.8%, and 15.0% compared with the control treatment, respectively. The inorganic amendments should increase the seed germination rate of Chinese cabbage (Brassica rapa L.). However, the shoot growth decreased significantly. The combination of amendments cannot increase the seed germination but can significantly increase the shoot growth of Chinese cabbage compared with the control. The combination of amendments enhanced the fertility of WS, particularly available P and exchangeable K, which may improve plant growth. These results suggested that the combination of amendments, especially CaCO₃ (0.2%) and chicken manure (2%), can be used to revitalize MC-WS.

As a result of the widespread use of antibiotics, a large amount of excretions from human and animals, containing antibiotic residues, is discharged into aquatic environments, leading to potential adverse effects on the ecosystems’ health. These residues’ impact on seasonally ice-covered rivers remains under investigated. To understand the environmental fate of antibiotics with high-detection frequencies and concentration levels, sulfamethoxazole, lincomycin, and florfenicol were used as models in the present study. A Level IV fugacity model was established and applied to a seasonally ice-covered river receiving municipal wastewater treatment plant (WWTP) effluents, the Songhua River in Northeast China. Model validation and sensitivity analysis suggested that the fugacity model could successfully simulate the monitoring concentration within an average difference of one logarithmic unit. The advection process played a major role in the transport and attenuation of the antibiotics in the ice-covered river receiving WWTP effluents. The scenario simulation indicated that increasing the targeted antibiotic concentrations in WWTP effluents to μg L⁻¹ could keep the targeted antibiotic concentrations higher than 10 ng L⁻¹ in the receiving river from the WWTP discharge source to 25 km downstream. This finding also demonstrates that the depth of water and ice, as well as flow velocity, play key roles in the fate of antibiotics in the ice-covered river receiving WWTP effluents. To our best knowledge, this is the first major study to combine experimental investigation with modeling to explore the environmental behaviors and fate of antibiotics in such a river.

The objective of this article is to describe the effect of precipitation and temperature on the drought characteristics of Yunnan province in China. The rainfall and temperature data from 10 national meteorological stations in Yunnan province during 1969 to 2018 were used to investigate the spatial and temporal evolution of drought in Yunnan province and the difference of drought index based on Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) at nearly 50a different time scales. The results showed that Yunnan province had a frequent alternation of drought and flood, and the larger the time scale, the gentler the SPI and SPEI changes. The recent 50a drought mainly occurred in 1980–1982, 1988–1990, 2003–2007, and 2010–2015, and there was continuous drought and the duration was prolonged. The changes of SPI and SPEI showed a downward trend in different seasons. The linear slopes of SPI and SPEI in spring, summer, autumn, and winter were − 0.0064, − 0.0088, − 0.0057 and − 0.0.0111, respectively, and the drought trend was the most serious in winter. Continuous spring drought occurred in 2009–2010 and 2012–2014. The SPEI values in 2009–2010 and 2012–2014 were − 0.80, − 0.64, − 0.75, − 1.23, and − 1.17, respectively. The spatial distribution of drought frequency in Yunnan province was greatly different, and its distribution rule was more in the north and east, less in the south and west. The drought frequency in Zhaotong (northeast Yunnan) was the highest at 36.53%, the drought frequency in Deqin and Lijiang (northwest Yunnan) were 33.11% and 33.28%, and the drought frequency in Kunming (central Yunnan) Lincang, Lancang, and Simao (southwest Yunnan) were 29.35%, 30.73%, 32.77%, and 28.35%, respectively. This study provided a scientific basis for revealing the spatial and temporal variation rules, evolution trends, regional drought, and drought impact assessment and risk management of drought in Yunnan province.

The indirect carbon emission embodied in the intermediate input is also an important indicator of assessing a producer’s carbon emissions. Structural analysis of indirect carbon emissions is helpful to understand the responsibilities between producers and pay efforts to key areas. The aim of this study is to analyze indirect carbon emissions embodied in intermediate input between sectors and explore the distribution structure of indirect carbon emissions flow network (namely, ICEFN). Based on the modified input-output model and complex network theory, this study constructed four directed and weighted ICEFNs with 28 sectors from 1997 to 2012. The results show that indirect carbon emissions between sectors are significantly higher than direct carbon emissions, accounting for nearly 70% of the total carbon emissions of China. Second, we analyzed the embodied carbon emission intensity (namely, ECI) of each sector. Although the ECI has been decreasing over time, the decrease has increasingly diminished, which indicates that the additional carbon emission reductions are more difficult. Third, we identified the key sectors which play different roles in the ICEFNs. Meanwhile, we studied the key paths which show more closed relationships between some sectors in ICEFNs. Finally, based on the above analysis, we made policy recommendations.

Previous studies have demonstrated the side effects of tooth whiteners on the gastric mucosa. However, the impact of dental bleaching products on the liver, kidney, and heart remains obscure. The present study investigated the toxic potential of 35% carbamide peroxide (CPO) containing tooth whitening product (TWP) on the liver, kidney, heart, and stomach of mice, pointing to the role of oxidative stress and inflammation. Mice received 250 or 500 mg/kg body weight CPO-TWP orally for 3 weeks and samples were collected for analyses. Both doses of CPO-TWP induced a significant increase in circulating liver, kidney, and heart function markers. CPO-TWP-administered mice showed several histological alterations and a significant increase in liver, kidney, heart, and stomach lipid peroxidation levels along with diminished glutathione, superoxide dismutase, and catalase. In addition, administration of CPO-TWP provoked anemia, leukocytosis, and a significant increase in circulating levels of pro-inflammatory cytokines. In conclusion, exposure to 35% CPO-TWP induced functional, histological, and hematological alterations, oxidative stress, and inflammation in mice. Therefore, the frequent use of tooth bleaching agents should be monitored very carefully to avoid the application of excess amounts as well as the intake.

Biological reduction is an effective method for removal of perchlorate (ClO₄⁻), where perchlorate is transformed into chloride by perchlorate-reducing bacteria (PRB). An external electron donor is required for autotrophic and heterotrophic reduction of perchlorate. Therefore, plenty of suitable electron donors including organic (e.g., acetate, ethanol, carbohydrate, glycerol, methane) and inorganic (e.g., hydrogen, zero-valent iron, element sulfur, anthrahydroquinone) as well as the cathode have been used in biological reduction of perchlorate. This paper reviews the application of various electron donors in biological perchlorate reduction and their influences on treatment efficiency of perchlorate and biological activity of PRB. We discussed the criteria for selection of appropriate electron donor to provide a flexible strategy of electron donor choice for the bioremediation of perchlorate-contaminated water.