A few studies on volatile organic compound (VOC) emission inventories in coal resource-based cities have been reported, and previous emission inventories lacked verification. Herein, using Yangquan as a case study, emission factor (EF) method and “(tracer ratio) TR - positive matrix factorization (PMF)” combined method based on atmospheric data were used to establish and verify the VOC emission inventory in coal resource-based cities, respectively. The total VOC emissions in Yangquan were 9283.2 t [-40.0%, 62.1%] in 2018, with industrial processes being the major contributors. Alkanes (35.8%), aromatics (25.0%), and alkenes (19.8%) were the main compounds in the emission inventory. The verification results for both species emission and source structure were in agreement, indicating the accuracy of VOC emission inventory based on EF method to a certain extent. However, for some species (ethane, propane, benzene, and acetylene), the EF method indicated emissions lower than those obtained from the TR results. Furthermore, the summer-time emission contribution from fossil fuel combustion indicated by the EF method (23.4%) was lower than that obtained from the PMF results (38.4%). Overall, these discrepancies could be attributed to the absence of a coal gangue source in the EF method. The verification results determined the accuracy of the VOC emission inventory and identified existing problems in the estimation of the VOC emission inventory in coal resource-based cities. In particular, not accounting for the coal gangue emissions may result in an underestimation of VOC emissions in coal resource-based cities. Thus, coal gangue emissions should be considered in future research.

Volatile organic compounds (VOCs) emissions from the chimney of a prevailing domestic stove fuelled with raw bituminous coal were measured under flaming and smoldering combustion processes in a farmer's house. The results indicated that the concentrations of VOCs quickly increased after the coal loading and achieved their peak values in a few minutes. The peak concentrations of the VOCs under the smoldering combustion process were significantly higher than those under the flaming combustion process. Alkanes accounted for the largest proportion (43.05%) under the smoldering combustion, followed by aromatics (28.86%), alkenes (21.91%), carbonyls (5.81%) and acetylene (0.37%). The emission factors of the total VOCs under the smoldering combustion processes (5402.9 ± 2031.8 mg kg⁻¹) were nearly one order of magnitude greater than those under the flaming combustion processes (559.2 ± 385.9 mg kg⁻¹). Based on the VOCs emission factors obtained in this study and the regional domestic coal consumption, the total VOCs emissions from domestic coal stoves was roughly estimated to be 1.25 × 10⁸ kg a⁻¹ in the Beijing-Tianjin-Hebei region.

Although crop residue return increases upland soil emissions of nitrous oxide (N₂O), a potent greenhouse gas, the mechanisms responsible for the increase remain unclear. Here, we investigate N₂O emission pathways, gross nitrogen (N)-cycling rates, and associated N-cycling gene abundances in an upland soil following the addition of various organic material under aerobic incubation using a combination of ¹⁵N tracing technique, acetylene (C₂H₂) inhibition, and real-time PCR (qPCR) methods. Increased total N₂O emissions following organic material amendment was attributed to both increased nitrification-derived N₂O emissions, following increased ammonia-oxidizing bacteria (AOB)-amoA abundance, and denitrification-derived N₂O emissions, following increased nirS and decreased nosZ abundance. Increasing plant residue carbon (C)/N ratio decreased total N₂O emissions by decreasing the contribution of denitrification to N₂O emissions, potentially due to higher proportions of denitrified N emitted as N₂O than nitrified N emitted as N₂O. We further propose a novel conceptual framework for organic material input effects on denitrification-derived N₂O emissions based on the decomposable characteristics of the added organic material. For slowly decomposing organic materials (e.g., plant residue) with insufficient available C, NO₃⁻-N immobilization surpassed denitrification, resulting in gradual decrease in denitrification-derived N₂O emissions with an increase in mineralization of plant residue C losses. In contrast, available C provided by readily available C sources (e.g., glucose) seemed sufficient to support the co-occurrence of NO₃⁻-N immobilization and denitrification. Overall, for the first time, we offer a microbial process perspective of N₂O emissions following organic material input. The findings could facilitate the improvement of process-orientated models of N₂O emissions and the formulation of appropriate N₂O mitigation strategies for crop residue-amended soils.

Nitrogen cycling in coral reefs may be affected by nutrient availability, but knowledge about concentration-dependent thresholds that modulate dinitrogen fixation and denitrification is missing. We determined the effects of different nitrate concentrations (ambient, 1, 5, 10 μM nitrate addition) on both processes under two light scenarios (i.e., light and dark) using a combined acetylene assay for two common benthic reef substrates, i.e., turf algae and coral rubble. For both substrates, dinitrogen fixation rates peaked at 5 μM nitrate addition in light, whereas denitrification was highest at 10 μM nitrate addition in the dark. At 10 μm nitrate addition in the dark, a near-complete collapse of dinitrogen fixation concurrent with a 76-fold increase in denitrification observed for coral rubble, suggesting potential threshold responses linked to the nutritional state of the community. We conclude that dynamic nitrogen cycling activity may help stabilise nitrogen availability in microbial communities associated with coral reef substrates.

Calcium carbide residue (CCR) is generated from acetylene gas production, and it is highly alkaline and contains a very high amount of calcium. Nano silica (NS), on the other hand, is mostly used in combination with other pozzolanic materials in concrete to ignite the reactivity of the material and to improve the properties of the concrete. This study investigated the effect of CCR incorporated in concrete mixtures to partially replace cement content at 0 to 30% (interval of 7.5%). NS was used as an additive by weight of binder at levels 0 to 4% in increment of 1%. Thus, response surface methodology (RSM) was employed to investigate the effects of CCR and NS on the properties of the concrete, including compressive strength, flexural strength, splitting tensile strength, modulus of elasticity (MoE), and water absorption. The RSM was used for model development predicted concrete’s properties and carried out mixture multi-objective optimization by maximizing strengths, MoE, and minimizing water absorption. The results showed that using up to 15% CCR improved the strengths, MoE, and water absorption of the concrete. Adding up to 3% NS further enhanced the strengths, MoE, and water absorption significantly. The developed models for predicting the properties of the concrete using RSM were highly efficient with high degree of correlation. The optimization solutions indicated that the best optimum or best mix combination based on maximum strengths and MoE with minimum water absorption was achieved by replacing 10.6% cement with CCR and adding 1.95% NS by the weight of cementitious materials.

In the recent decades, most rivers and lakes in the Taihu Basin have experienced degradation from an excess of nutrients. The presence of the nitrogen in water contributes to the increase of eutrophication. The riparian zones are associated with these watercourses and can effectively reduce any excess nitrogen. Soil denitrification is the most significant process in the transfer of nitrogen, which migrates from the terrestrial to the aquatic ecosystem. The relationship between soil denitrification and soil characteristics is well documented. However, the degree of soil denitrification and the main impact factors during different processes within the riparian zones due to gradual changes in the surroundings are not well understood. The present study selected four types of riparian soils that are contained in three different watersheds. The soil denitrification potential was determined within these soils using the acetylene block technique. The results indicate that, among the local factors studied, the soil denitrification potential increased with the intensity of anthropogenic activities, which varied significantly within the basin. This variation indicated a trend in the soil denitrification potential: cropland > woodland > grassland > bareland. Results suggest that soil moisture, nitrate-nitrogen concentration, and microbial biomass carbon concentration are the dominant factors that influence the riparian soil denitrification potential in the Tiaoxi watershed, while soil organic matter is the major factor for soil denitrification potential in the Hexi watershed and nitrate-nitrogen concentration is the dominant factor in the Tianmuhu watershed.

In this paper, the effect of injection pressure on the performance, emission, and combustion characteristics of a diesel-acetylene fuelled single cylinder, four-stroke, direct injection (DI) diesel engine with a rated power of 3.5 kW at a rated speed of 1500 rpm was studied. Experiments were performed in dual-fuel mode at four different injection pressures of 180, 190, 200, and 210 bar with a flow rate of 120 LPH of acetylene and results were compared with that of baseline diesel operation. Experimental results showed that highest brake thermal efficiency of 27.57% was achieved at injection pressure of 200 bar for diesel-acetylene dual-fuel mode which was much higher than 23.32% obtained for baseline diesel. Carbon monoxide, hydrocarbon, and smoke emissions were also measured and found to be lower, while the NO ₓ emissions were higher at 200 bar in dual fuel mode as compared to those in other injection pressures in dual fuel mode and also for baseline diesel mode. Peak cylinder pressure, net heat release rate, and rate of pressure rise were also calculated and were higher at 200 bar injection pressure in dual fuel mode.

Glycerol, considered as a waste feedstock resulting from biodiesel production, has received much attention in recent years due to its properties, which offer to recover energy. The aim of this study was to investigate the use of a thermal water vapor plasma for waste (crude) glycerol conversion to synthesis gas, or syngas (H₂ + CO). In parallel of crude glycerol, a pure glycerol (99.5%) was used as a reference material in order to compare the concentrations of the formed product gas. A direct current (DC) arc plasma torch stabilized by a mixture of argon/water vapor was utilized for the effective glycerol conversion to hydrogen-rich synthesis gas. It was found that after waste glycerol treatment, the main reaction products were gases with corresponding concentrations of H₂ 50.7%, CO 23.53%, CO₂ 11.45%, and CH₄ 3.82%, and traces of C₂H₂ and C₂H₆, which concentrations were below 0.5%. The comparable concentrations of the formed gas products were obtained after pure glycerol conversion—H₂ 46.4%, CO 26.25%, CO₂ 11.3%, and CH₄ 4.7%. The use of thermal water vapor plasma producing synthesis gas is an effective method to recover energy from both crude and pure glycerol. The performance of the glycerol conversion system was defined in terms of the produced gas yield, the carbon conversion efficiency, the cold gas efficiency, and the specific energy requirements.

Ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) are crucial for N₂O emission as they carry out the key step of nitrification. Dicyandiamide (DCD) and acetylene (C₂H₂) are typical nitrification inhibitors (NIs), while the comparative effects of these NIs on N₂O production and ammonia oxidizers’ (AOB and AOA) growth are unclear. Four treatments including a control, urea, urea + DCD, and urea + C₂H₂ were set up to investigate their effect of inhibiting soil nitrification, nitrification-related N₂O emission as well as the growth of ammonia oxidizers with a fluvo-aquic soil using microcosms for 28 days. N₂O emission and net nitrification rate increased after the application of urea, but were significantly restrained in urea + NI treatments, while C₂H₂ was more effective in reducing N₂O emission and nitrification rate than DCD. The abundance of AOB, which was significantly correlated with N₂O emission and net nitrification rate, was more inhibited by C₂H₂ than DCD. Furthermore, the application of urea in all the soils had little impact on the AOA community, while obvious shifts of AOB community structure were found compared with the control. All AOB sequences fell within Nitrosospira cluster 3, and the AOA community was clustered to group 1.1b. Collectively, it indicated that application of urea combined with NIs (DCD or C₂H₂) could potentially alter N₂O emission, mainly through regulating the growth of AOB but not AOA in this fluvo-aquic soil.

Combination of ozone together with electrolysis (ozone-electrolysis) is a promising wastewater treatment technology. This work investigated the potential use of carbon nanotube (CNT)-based gas diffusion cathode (GDC) for ozone-electrolysis process employing hydroxyl radicals (·OH) production as an indicator. Compared with conventional active carbon (AC)-polytetrafluoroethylene (PTFE) and carbon black (CB)-PTFE cathodes, the production of ·OH in the coupled process was improved using CNTs-PTFE GDC. Appropriate addition of acetylene black (AB) and pore-forming agent Na₂SO₄ could enhance the efficiency of CNTs-PTFE GDC. The optimum GDC composition was obtained by response surface methodology (RSM) analysis and was determined as CNTs 31.2 wt%, PTFE 60.6 wt%, AB 3.5 wt%, and Na₂SO₄ 4.7 wt%. Moreover, the optimized CNT-based GDC exhibited much more effective than traditional Ti and graphite cathodes in Acid Orange 7 (AO7) mineralization and possessed the desirable stability without performance decay after ten times reaction. The comparison tests revealed that peroxone reaction was the main pathway of ·OH production in the present system, and cathodic reduction of ozone could significantly promote ·OH generation. These results suggested that application of CNT-based GDC offers considerable advantages in ozone-electrolysis of organic wastewater.