Arsenic (As) is considered as one of the most hazardous elements found in the groundwater. It is present in water in both arsenate (As(V)) and arsenite (As(III)) forms. On exposure for a considerable length of time to water having As concentration above the maximum permissible limit of 10 μg/L, there is a serious threat of developing various health problems including cancer. There is frequent reporting about the development of different newer methods for the removal of arsenic from water. In this present approach, a low-cost product namely modified paddy husk ash (PHA) was used as an adsorbent for the adsorption of arsenic from water. The adsorbent is important from the point of its easy availability in the tropical paddy producing countries. For improved removal efficiency and disposal of spent adsorbent, the surface of the PHA was activated with an aluminum oligomeric solution called as hydroxyl-alumina. To understand the process, various techniques such as XRD, SEM–EDS, particle size determination, and zeta potential measurements were used and the effects like variation of adsorbent dose, pH, initial arsenic concentration, and contact time were studied. The Freundlich adsorption isotherm and pseudo-second-order kinetic models were found to be the best fitted adsorption isotherm and kinetic data models respectively thereby confirming the adsorption as a multilayer chemisorption process. Finally, the issue of disposal of the spent sludge through the successful formation of cement clinkers was studied.

Coal mine dust continues to be a health and safety issue in underground coal mines. Coal seam water infusion was developed and widely applied in European coal mines for dust control, and was also a common practice in most Chinese coal mines. This method typically involves the infusion of water into the coal seam to increase its moisture content, and therefore reduce dust generation during mining operations. With the availability of other dust control methods such as water spraying systems, the water infusion method has not been considered as a viable means for dust mitigation in modern mines. However, the increase in production output and the deployment of more powerful equipment for coal cutting and transport and intensive gas drainage practices mean that workers could be exposed to more dust contaminations. Whilst the mine operators are committed to suppress and dilute airborne dust particles using these passive measures, there is a need to critically examine and subsequently develop this proactive dust control technology for practical applications in Chinese coal mines. The paper provides a critical review of the water infusion technologies in view of its technological advances and practical application limitations. The methods of water infusion, mechanism of water flow in coal, the role of surfactants and the key parameters influencing the effect of water infusion on dust control are identified and discussed. Existing problems and prospects for water infusion are analysed.

Over the past decades, overall ecological conditions in the Caspian Sea have deteriorated. However, a comprehensive understanding of lake-wide spatial differences in anthropogenic pressures is lacking and the biological consequences of human impacts are poorly understood. This paper therefore aims at assessing the individual and combined effects of critical anthropogenic pressures on the Caspian Sea ecoregions. First, cumulative pressure scores were calculated with a cumulative environmental assessment (CEA) analysis. Then, the individual contribution of anthropogenic pressures was quantified. Finally, ecoregion-specific differences were assessed. The analyses show that both cumulative and individual pressure scores are unevenly distributed across the Caspian Sea. The most important individual pressures are invasive species, chemical pollution and poaching. This uneven distribution of pressure scores across Caspian Sea ecoregions creates new challenges for future conservation strategies, as different ecoregions usually require different conservation measures.

Water fluoridation is considered a cost-effective and practical method for controlling and preventing dental caries in the general population. The objective of this study was to evaluate the dental health status and risk indicators for dental caries in adult Brazilian Indians without exposition to dental caries–preventive effects of water fluoridation. Decayed (DT), missing (MT), and filled (FT) permanent teeth (DMFT), as well as plaque index, unstimulated salivary flow rate, salivary buffering capacity, and fasting blood glucose were examined in 225 adult Indians. Smoking habits and sociodemographic data were evaluated using a structured questionnaire. Drinking water samples from 10 Indian villages were analyzed for the natural fluoride concentration. The mean DMFT was 10.33 ± 6.91 (DT, 4.19 ± 3.99; MT, 4.99 ± 5.64; FT, 1.14 ± 1.75). DMFT index ≥ 9 was associated with age ≥ 35 years (p = 0.000), lower education (p = 0.03), and plaque index > 40% (p = 0.003). DT was associated only with plaque index (p = 0.03). MT was associated with age (p < 0.001) and plaque index (p = 0.01). FT was negatively associated with age (p = 0.02) and income (p = 0.02). Fluoride concentration varied from 0.01 to 0.07 mg/L and was not associated with dental health status (p ≥ 0.29). In conclusion, poorer dental health status was associated with older age, higher plaque index, and lower education and income levels. The fluoride level in the drinking water of Kiriri villages was lower than the level recommended for preventing dental caries. Water fluoridation may be recommended for this population.

Crop straw is an abundant renewable resource whose usage is limited due to its high cellulose, hemicellulose, and lignin contents. Here, Trichoderma viride, Saccharomyces cerevisiae, and Musca domestica were used to transform crop straws, and we investigated their impact on housefly rearing performance and optimized their utilization. The weights of cellulose, hemicellulose, and lignin in fermented crop straw diets significantly decreased after bioconversion by M. domestica larvae. The highest bioconversion rate was recorded in corn straw diet (16.19%), followed by wheat straw diet (10.31%) and wheat bran diet (8.97%). Similarly, high larval weight (yield) and pupation rate and fecundity and fertility rate were recorded in fermented crop straw diets composed of corn straw and wheat bran in 1:1 proportions. These results indicated that fermenting crop straw with T. viride and S. cerevisiae represented an efficient strategy that enhanced crop straw bioconversion and improved the rearing capacity of the housefly larvae. The resulting larvae could further be used as proteinaceous feed in poultry and aquaculture industries. Graphical abstract

China, the largest developing country, is the world largest cement producer and the largest cement-consuming nation. Although China’s cement output reached its peak in 2014, regions, i.e., Fujian and Yunnan provinces, were no peaking until 2016. At the same time, rare studies referred to China’s cement consumption and CO₂ emissions from the perspective of cement consumption at the provincial level. We developed the S-Logistic, polynomial model, and ARIMA model to study the peaking time of cement consumption at the provincial level, and we also projected China’s cement consumption and CO₂ emissions toward 2030. Meanwhile, the discrepancies of peaking time and cumulative cement consumption per capita (CCCPC) among provinces were also studied based on GDP per capita and urbanization rate (UR). The results are that the CCCPC respectively in the range of 22–34 ton, 18–25 ton, and 17–27 ton in the eastern, intermediate, and western zone when cement consumption reached its peak. We draw the following conclusions that the CCCPC in 2030 could reach ~ 43 ton and the projected cement consumption is ~ 1252.72 Mt, which accounts for 50% of that in 2017, and cement CO₂ emissions are at the range of 488.19–510.90 MtCO₂ in 2030. Furthermore, capacity replacement, controlling new capacity and eliminating backward capacity are significant of greenhouse gas emission reduction not only for China, but also for the global cement industry.

Mercury (Hg) is a complex and multifaceted global pollutant. Artisanal and small-scale gold mining activities are largely responsible for Hg contamination in developing countries, in many cases impacting areas of high biodiversity such as the Amazon. The aim of the study was to establish Hg exposure in indigenous citizens from the Tarapaca village, Cotuhe and Putumayo Rivers, at the Colombian Amazon. Total Hg (T-Hg) concentrations were measured employing a DMA-80 Hg analyzer. For that purpose, 190 hair samples were taken from volunteers living in different communities of Tarapaca. The overall mean T-Hg level for all samples was 10.6 ± 0.4 μg/g, with values ranging from 0.61 to 31.1 μg/g. The mean T-Hg level decreased in the order Puerto Huila > Puerto Ticuna > Ventura > Nueva Union > Buenos Aires > Santa Lucia > Puerto Nuevo > Caña Brava > Pupuña. Based on recommendations from the United States Environmental Protection Agency (US EPA), 99.5% of the samples exceeded the maximum level of 1.0 μg/g. Hg content in human hair was significantly associated with fish consumption (ρ = 0.253; p < 0.001). According to the health survey, at least 24.7% of the volunteers manifested some signs and symptoms of Hg poisoning. In short, these data support the extensive Hg exposure in the environment of the Colombian Amazon, a process that could be impacting the quality of life of its vulnerable indigenous groups. Immediate actions must be taken by competent authorities to protect these communities from Hg poisoning.

This research is conducted to improve the dispersion of MnOₓ–CeO₂ catalyst because manganese is easily aggregated during continuous thermal environment at operating temperature. Aggregated MnOₓ particles on the support can be a major reason to degrade the catalyst performance. Therefore, the improved dispersion of MnOₓ particles leads to the enhancement of the catalyst performance by utilizing hexagonal boron nitride (h-BN) which is well known as thermally stable material. Due to the dispersion of MnOₓ–CeO₂ with 5–20 nm particle size, h-BN-supported MnOₓ–CeO₂ catalyst shows the 93% efficiency in NOₓ removal at 200 °C. The structure and properties of MnOₓ–CeO₂/h-BN catalyst are characterized by X-ray diffraction, Fourier transform infrared spectroscopy spectra, and NH₃-temperature programmed desorption. Then, NOₓ removal efficiency of catalyst is evaluated on a fixed bed reactor and h-BN-supported catalyst, (Mn₀.₂–Ce₀.₁)/BN, increases NOₓ removal efficiency up to 20% at 200 °C in spite of 2/3 reduced content of MnOₓ–CeO₂ compared to no-supported catalyst (Mn₀.₃–Ce₀.₁₅).

Linda Gehrmann and Helena Bielak contributed equally to this work and are regarded as joint first authors.

This study evaluated the oxidation of toluene (TOL) by persulfate (PS) in aqueous solution in the presence of a Fe₃O₄-carbon black (CB) composite oxidant system generating sulfate radicals. The cytotoxic activity and oxidative stress generated by these materials were investigated in rat liver Clone 9 cells. The effects of various operating parameters including the pH and concentrations of PS, Fe₃O₄-CB, and TOL were evaluated to optimize the oxidation process. The results showed that Fe₃O₄-CB/PS achieved effective removal of TOL under acidic conditions. The TOL degradation efficiency was strongly pH-dependent, where pH 3.0 > 6.0 > 9.0. Additionally, the viability of Clone 9 cells exposed to 0–400 μg/mL Fe₃O₄-CB indicated that this material showed low cytotoxicity. A dichlorodihydrofluorescein diacetate assay performed to evaluate the generation of reactive oxygen species indicated that Fe₃O₄ showed relatively lower toxicity than CB in these cells. Therefore, the cytotoxicity of CB may involve the induction of oxidative stress and physical changes in cell morphology.