In order to analyze and control air pollutant emissions effectively, on the basis of comprehensive consideration of three different pollution sources of industrial sulfur dioxide, industrial nitrogen oxides, and industrial smoke and dust, the Tapio decoupling model and LMDI decomposition model with six decomposition variables are constructed to compare the effects of socioeconomic factors on industrial air pollutant emissions in 11 cities in Zhejiang Province during 2006–2017. Then, a decoupling effort model is developed to analyze the effectiveness of the decoupling efforts taken at city level. This study found that (1) during the period of 2006–2017, the air pollutant emission reduction work in Zhejiang Province achieved remarkable results. More specifically, economic scale effect and population effect are the main factors for the increase of air pollutant emissions. And, the energy emission intensity effect and technological progress are the main driving forces for the reduction of three atmospheric pollutants, followed by the reduction effect of industrial structure and energy structure. (2) The environmental pollution problems of different air pollution sources in different cities are heterogeneous. (3) Eleven cities in Zhejiang Province have made significant decoupling efforts on the emission of three kinds of air pollutants, but there are some differences in the trend of the decoupling effort index of different pollution sources in different cities. In the future, illustrating by the example of Zhejiang, we should implement a “common but different” emission reduction strategy and emphasize pollutant emissions control during energy use in the efforts of further promoting the reduction of air pollutants.

Digital imaging using conventional camera, mobile phone camera, or computer scanner can be a convenient and low-cost approach for the highly sensitive assessment of hexavalent chromium in natural and waste waters. An aliquot sample containing Cr(VI) is reacted with diphenylcarbazide to yield a characteristic violet color. Image analysis of the violet-colored product gave the red, green, and blue (RGB) intensities that are converted into ten uniform and non-uniform color spaces and two color difference parameters, which are used and compared here, for the first time, as analytical signaling tools for the assessment of hexavalent chromium. Many of the acquired signals displayed outstanding analytical performance and statistically surpassed the regularly used RGB signals and competed well with signals of a sophisticated Shimadzu 1650 PC spectrophotometer. The sensitivity and simplicity and low cost of this strategy make it an outstanding competitor for commercial hexavalent chromium analyzers and advanced spectrophotometers. Graphical abstract

In this study, a photocatalytic fuel cell (PFC) based on immobilized zinc oxide (ZnO) on carbon felt photoanode and activated carbon flakes as cathode was designed for the treatment of azo dye, reactive red 120 (RR120) containing wastewater and simultaneous electricity generation. Under light irradiation, generated electron-hole pairs at the photoanode travel via the external circuit to the cathode, thus generating electricity. This was the first attempt where activated carbon flakes were applied as cathode material in PFC. This study examined the influence of parameters such as light irradiation, cathode material, initial dye concentration, supporting electrolytes, pH and concentration of oxidizing agent and hydrogen peroxide (H₂O₂) on the efficiency of PFC to degrade azo dye of RR120 while generating electricity. Complete decolourization of up to 50 mg/L of RR120 dye was achieved but increased dye concentration significantly reduced the PFC efficiency. The PFC efficiency improved using an amalgamation of supporting electrolytes, pH and oxidizing agent at optimum levels, achieving total dye removal and producing a maximum power density of 18.58 mW/cm².

The present study was the first trial to use the adsorptive capacity of the rice husk to reduce the toxicological impacts of the iron and aluminum oxides nanoparticles on Oreochromis niloticus. The fish groups were subjected to a sub-lethal concentration (10 mg/l) of both metal oxides nanoparticles (in single and combined doses) with and without rice husk water treatment for 7 days. The bioaccumulation of iron and aluminum metals showed a significant increase (p < 0.05) compared with the control groups. The results revealed a tissue-specific distribution pattern as following: liver > kidney > gills > skin > muscles for iron and liver > gills > kidney > skin > muscles for aluminum. Moreover, the bioaccumulation potency of iron was greater than that of aluminum in all studied tissues. Both studied nanoparticles caused a decrease in the red blood cells count, hemoglobin content, hematocrit values, and mean corpuscular hemoglobin concentration, with an obvious increase in mean corpuscular volume and mean corpuscular hemoglobin. While all those parameters were restored more or less to that of control groups after rice husk water treatment. The histological studies of the gills, liver, and kidneys showed different histopathological alterations ranging from compensatory histological changes in the rice husk–treated groups to severe histopathological damage in the untreated groups. Based on the all studied biomarkers, the rice husk is a good absorbent for both studied nanoparticles individually or combined.

The carbon stored as soil organic carbon (SOC) and tree biomass is typically the highest carbon pool of the forest and is impacted by degradation and deforestation. The impact of “C” stocks on climate change at different altitudes can have vital implications for the conservation and management of “C” sinks. This study was undertaken in subtropical belt of Tehri Garhwal, Uttarakhand, India, to understand the carbon-storing potential of Anogeissus latifolia tree and its soil properties in three altitudes, i.e., lower (LA: 790–824 m), middle (MA: 825–960 m), and upper (UA: 1168–1212 m), which provide fuel, fodder, and small timber for life support purposes. Results of the study suggested that soil moisture and pH increase with increasing depth and altitude, whereas SOC and soil nitrogen show reverse patterns. Moreover, bulk density (BD) does not follow any trend (i.e., BD increases with soil depth and altitude until 960 m and further decreases with an increase in altitude). Tree density, biomass, and carbon stock reported highest in MA compared with UA and LA because of dense forest and greater tree diameter. Looking into the soil carbon stock, nitrogen, C/N ratio (C/N: < 10), and climatic drivers supportive to microbial degradation, it is concluded that A. latifolia forest has played an important role in carbon reduction and mitigating climate change at regional and global levels. The study will help environmentalists, foresters, and policy-makers to stimulate the combined effect of degradation of forest species on climate change and socioeconomic development at regional and global scale.

Attributing to the booming industry, China has made huge economic achievements during recent decades/years. However, the issue of energy and environment has challenged the sustainable development of the industry a lot in China. Investigating the non-separable relationship among energy, capital, and CO₂ emission under natural and managerial disposability, this paper proposes two hybrid measure approaches to measure unified environmental efficiency of industry in China during 2011–2016. Besides, production efficiency, emission efficiency, damage to scale, and return to scale of 30 regions in China are calculated and recognized. The results show that (1) unified environmental efficiency of Chinese industry under natural disposability is higher than that under managerial disposability in early few years, but they are close to each other finally. (2) Unified environmental efficiency gaps among regions under natural disposability are wider than those under managerial disposability. Increasing capital investment and improving technology can help reduce efficiency gaps among regions. (3) It is available to increase production efficiency and reduce CO₂ emission by cutting down energy consumption for most regions; insufficient capital investment and poor production technology cause the decreasing return to scale and production efficiency.

In recent years, the concentration of aluminium in the Iskar River occasionally exceeds the environmental quality standard (EQS). The river and the Iskar Dam, build on the river, are the main drinking water source of Sofia city (Bulgaria), with population exceeding 1.2 million. The average concentrations of aluminium in the raw water entering the drinking water treatment plants of Sofia city—Bistritza and Pancharevo—in 2018 were 0.148 mg/L and 0.199 mg/L, respectively, which are very close to the limits set in Directive 98/83/EC. This study uses multifactorial analysis, taking into account the influence of the mineral and chemical composition of sediments of the Iskar Dam, the geological conditions at the dam’s catchment area, the relationship between the aluminium concentrations and precipitation in the region and also the relationship between the aluminium concentration and the turbidity at the inlet of the two treatment plants, to determine the origin of aluminium in the raw drinking water of Sofia city. The obtained linear regression models for the aluminium concentration and the turbidity at the inlet are significant (p ≤ 0.001) with coefficients of determination (R²) for DWTP–Bistritza and DWTP–Pancharevo of 0.54 and 0.51, respectively.

Hydraulic fracturing is used to enhance oil and gas extraction from tight shale formations and generates millions of gallons of wastewater which needs to be cleaned up prior to disposal or reuse. The current technologies used for the management of this wastewater present technical, economic, and environmental challenges. Hence, the main objective of this study was to examine the potential of algal remediation of hydraulic fracturing wastewater (PW) as an alternative method. Considering that PW contains very low concentration of the nutrients needed for algae growth PW supplemented with animal wastewater (AW-PW) was also examined. Biomass production capacity, average biomass productivity, and specific growth rate of the microalgae strain used in the study, Picochlorum oklahomensis, were 1.87 g L⁻¹, 268 mg L⁻¹ day⁻¹, and 0.35 day⁻¹, respectively, when grown in PW. Complete nitrate, ammonia, and phosphate removal could be achieved by growing algae in PW. Supplementation of PW with animal wastewater enhanced biomass production (1.87–2.40 g L⁻¹) and lipid content (15–25% wt) in the produced algal biomass. A mathematical model with a correlation coefficient of greater than 0.94 was developed to describe the growth kinetics of algae grown in AW-PW.

Anaerobic bioremediation of tetrachloroethylene (PCE) under high concentration conditions is difficult. Anaerobic dechlorination of PCE occurs with synergetic reactions, fermentation, and sulfate-reduction; however, the way in which high concentrations of PCE affects these reactions is still poorly understood. This study aims to elucidate how high concentrations of PCE affect fermentation and sulfate-reduction, as well as PCE dechlorination. Laboratory dechlorination tests were performed using a wide concentration range of PCE between 2 and 125 mg/L added to a microbial consortium that had been continuously cultivated in the laboratory and completely dechlorinated PCE for over 4 years. Fermentation of lactate, reduction of sulfate, and dechlorination of PCE were monitored in addition to microbial activities based on RNA. All three reactions, fermentation, sulfate-reduction, and PCE dechlorination were observed to be inhibited. The inhibition for fermentation, sulfate-reduction, and dechlorination occurred when PCE concentrations were higher than 125, 75, and 30 mg/L, respectively. The fermenter, Anaerotignum, and the sulfate-reducer, Desulfosporosinus, were active when the dechlorination was inhibited with 30 mg/L of PCE. These findings suggest that there is interference of PCE dechlorination, despite the occurrence of fermentation and sulfate reduction. Bioaugmentation with a PCE dechlorinator that is tolerant to high PCE concentrations can be a possible solution for bioremediation of PCE when its concentrations are greater than 30 mg/L.

The circular economy concept boosts the use of wastes as secondary raw materials in the EU renewable and sustainable framework. In wastewater treatment plants (WWTP), sludge is one of the most important wastes, and its management is being widely discussed in the last years. In this work, sewage sludge from WWTP was employed as raw material for producing activated carbon (AC) by physical-chemical activation. The prepared AC was subsequently tested for hydrogen sulphide removal in view of its further use in deodorization in a WWTP. The effects of the activation temperature and the chemical agent used (NaOH and KOH) during the activation process were studied. On the one hand, the characteristics of each AC fabricated were analysed in terms of BET (Brunauer-Emmett-Teller) surface area, pore and micropore volume, pore diameter, surface morphology and zeta potential. On the other hand, BET isotherms were also calculated. Finally, both the prepared AC and a commercial AC were tested for H₂S removal from a gas stream. Results demonstrated that the optimum physical and chemical activation temperature was 600 °C and 1000 °C, respectively, and the best activated agent tested was KOH. The prepared AC showed excellent properties (specific surface area around 300 m²/g) for H₂S removal, even better efficiencies than those achieved by the tested commercial AC.