介质阻挡放电协同光催化降解硫化氢废气

恶臭是一种感觉公害,极大地危害着人们的身体健康和生活的安宁舒适,其中含硫恶臭气体是最为典型的一类,目前恶臭物质的治理问题成为一项重要的任务.为了达到理想的去除效果,该文在传统的介质阻挡放电技术上,协同由2种不同基体上沉积有纳米二氧化钛的催化剂降解硫化氢废气,分别采用单独DBD放电、协同催化的一段式、两段式系统研究了不同参数(输入电压、气体流量、初始浓度)对硫化氢废气降解效率的影响,并对比研究了在单独低温等离子技术及其协同催化剂的情况下,反应系统中臭氧、二氧化氮浓度的变化,对降解途径进行了分析讨论.结果 表明:随输入电压增大,以及在污染气体初始浓度和流量较小时,反应器对硫化氢气体的去除效率增大;协同催化剂的反应系统中硫化氢去除效果明显增强,且副产物减少.     

Spatiotemporal variations of ambient air pollutants and meteorological influences over typical urban agglomerations in China during the COVID-19 lockdown

To investigate the air quality change during the COVID-19 pandemic, we analyzed spatiotemporal variations of six criteria pollutants in nine typical urban agglomerations in China using ground-based data and examined meteorological influences through correlation analysis and backward trajectory analysis under different responses. Concentrations of PM_2.5, PM₁₀, NO₂, SO₂ and CO in urban agglomerations respectively decreased by 18%–45% (30%–62%), 17%–53% (22%–39%), 47%-64% (14%–41%), 9%–34% (0%–53%) and 16%-52% (23%–56%) during Lockdown (Post-lockdown) period relative to Pre-lockdown period. PM_2.5 pollution events occurred during Lockdown in Beijing-Tianjin-Hebe (BTH) and Middle and South Liaoning (MSL), and daily O₃ concentration rose to grade Ⅱ standard in Post-lockdown period. Distinct from the nationwide slump of NO₂ during Lockdown period, a rebound (～40%) in Post-lockdown period was observed in Cheng-Yu (CY), Yangtze River Middle-Reach (YRMR), Yangtze River Delta (YRD) and Pearl River Delta (PRD). With slightly higher wind speed compared with 2019, the reduction of PM_2.5 (51%–62%) in Post-lockdown period is more than 2019 (15%–46%) in HC (Harbin-Changchun), MSL, BTH, CP (Central Plain) and SP (Shandong-Peninsula), suggesting lockdown measures are effective to PM_2.5 alleviation. Although O₃ concentrations generally increased during the lockdown, its increment rate declined compared with 2019 under similar sunlight duration and temperature. Additionally, unlike HC, MSL and BTH, which suffered from additional (> 30%) air masses from surrounding areas after the lockdown, the polluted air masses reaching YRD and PRD mostly originated from the long-distance transport, highlighting the importance of joint regional governance.     

Influence of particle size on the aggregation behavior of nanoparticles: Role of structural hydration layer

More and more attention has been paid to the aggregation behavior of nanoparticles, but little research has been done on the effect of particle size. Therefore, this study systematically evaluated the aggregation behavior of nano-silica particles with diameter 130–480 nm at different initial particle concentration, pH, ionic strength, and ionic valence of electrolytes. The modified Smoluchowski theory failed to describe the aggregation kinetics for nano-silica particles with diameters less than 190 nm. Besides, ionic strength, cation species and pH all affected fast aggregation rate coefficients of 130 nm nanoparticles. Through incorporating structural hydration force into the modified Smoluchowski theory, it is found that the reason for all the anomalous aggregation behavior was the different structural hydration layer thickness of nanoparticles with various sizes. The thickness decreased with increasing of particle size, and remained basically unchanged for particles larger than 190 nm. Only when the distance at primary minimum was twice the thickness of structural hydration layer, the structural hydration force dominated, leading to the higher stability of nanoparticles. This study clearly clarified the unique aggregation mechanism of nanoparticles with smaller size, which provided reference for predicting transport and fate of nanoparticles and could help facilitate the evaluation of their environment risks.     

Identification of close relationship between atmospheric oxidation and ozone formation regimes in a photochemically active region

Understanding ozone (O₃) formation regime is a prerequisite in formulating an effective O₃ pollution control strategy. Photochemical indicator is a simple and direct method in identifying O₃ formation regimes. Most used indicators are derived from observations, whereas the role of atmospheric oxidation is not in consideration, which is the core driver of O₃ formation. Thus, it may impact accuracy in signaling O₃ formation regimes. In this study, an advanced three-dimensional numerical modeling system was used to investigate the relationship between atmospheric oxidation and O₃ formation regimes during a long-lasting O₃ exceedance event in September 2017 over the Pearl River Delta (PRD) of China. We discovered a clear relationship between atmospheric oxidative capacity and O₃ formation regime. Over eastern PRD, O₃ formation was mainly in a NO_x-limited regime when HO₂/OH ratio was higher than 11, while in a VOC-limited regime when the ratio was lower than 9.5. Over central and western PRD, an HO₂/OH ratio higher than 5 and lower than 2 was indicative of NO_x-limited and VOC-limited regime, respectively. Physical contribution, including horizontal transport and vertical transport, may pose uncertainties on the indication of O₃ formation regime by HO₂/OH ratio. In comparison with other commonly used photochemical indicators, HO₂/OH ratio had the best performance in differentiating O₃ formation regimes. This study highlighted the necessities in using an atmospheric oxidative capacity-based indicator to infer O₃ formation regime, and underscored the importance of characterizing behaviors of radicals to gain insight in atmospheric processes leading to O₃ pollution over a photochemically active region.     

Synthesis and evaluation of cationic flocculant P(DAC-PAPTAC-AM) for flocculation of coal chemical wastewater

In this study, a high-efficiency cationic flocculant, P(DAC-MAPTAC-AM), was successfully prepared using UV-induced polymerization technology. The monomer Acrylamide (AM): Acryloxyethyl Trimethyl ammonium chloride (DAC): methacrylamido propyl trimethyl ammonium chloride (MAPTAC) ratio, monomer concentration, photoinitiator concentration, urea content, and cationic monomer DAC:MAPTAC ratio, light time, and power of high-pressure mercury lamp were studied. The characteristic groups, characteristic diffraction peaks, and characteristic proton peaks of P(DAC-MAPTAC-AM) were confirmed by fourier transform infrared spectroscopy (FTIR), X-Ray diffraction (XRD), ¹H nuclear magnetic resonance spectrometer (¹H NMR), and scanning electron microscopy (SEM). The effects of dosage, pH value, and velocity gradient (G) value on the removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol by poly aluminum ferric chloride (PAFC), P(DAC-MAPTAC-AM), and PAFC/P(DAC-MAPTAC-AM) in the flocculation treatment of coal chemical wastewater were investigated. Results showed that the optimal conditions for the flocculation of coal chemical wastewater using P(DAC-MAPTAC-AM) alone are as follows: dosage of 8–12 mg/L, G value of 100–250 s ^? 1, and pH value of 4–8. The optimal dosage of PAFC is 90–150 mg/L with a pH of 2–12. The optimal dosage for PAFC/P(DAC-MAPTAC-AM) is as follows: PAFC dosage of 90–150 mg/L, P(DAC-MAPTAC-AM) dosage of 8–12 mg/L, and pH range of 2–6. When P(DAC-MAPTAC-AM) was used alone, the optimal removal efficiencies of turbidity, COD, ammonia nitrogen, and total phenol were 81.0%, 35.0%, 75.0%, and 80.3%, respectively. PAFC has good tolerance to wastewater pH and good pH buffering. Thus, the flocculation treatment of coal chemical wastewater using the PAFC/P(DAC-MAPTAC-AM) compound also exhibits excellent resistance and buffering capacity.     

Isolation and characterization of a strain with high microbial attachment in aerobic granular sludge

Aerobic granule is a special microbial aggregate associated with biofilm structure. The formation of aerobic granular sludge is primarily depending on its bacterial community and relevant microbiological properties. In this experiment, a strain with high microbial attachment was isolated from aerobic granular sludge, and the detailed characteristics were examined. Its high attachment ability could reach 2.34 (OD_600nm), while other low attachment values were only around 0.06-0.32, which indicated a big variation among the different bacteria. The strain exhibited a very special morphology with many fibric fingers under SEM observation. A distinctive behaviour was to form a spherical particle by themselves, which would be very beneficial for the formation and development of granular sludge. The EPS measurement showed that its PN content was higher than low attachment bacteria, and 3D-EEM confirmed that there were some different components. Based on the 16S rRNA analysis, it was identified to mostly belong to Stenotrophomonas. Its augmentation to particle sludge cultivation demonstrated that the strain could significantly promote the formation of aerobic granule. Conclusively, it was strongly suggested that it might be used as a good and potential model strain or chassis organism for the aerobic granular sludge formation and development.     

铝穹顶储罐雷击损伤及燃爆风险研究

针对铝穹顶储罐雷击问题,开展了回击后长持续时间雷电流分量作用下的铝合金板烧蚀损伤试验研究,分析了铝穹顶储罐损伤及油气燃爆风险。结果表明:当直流分量为164 C时,2 mm铝板发生穿孔,铝穹顶储罐存在雷击燃爆风险;当直流分量≤157 C时,未穿孔,背面温度最高为480℃,存在燃爆风险,铝穹顶储罐存在雷击燃爆风险;当直流分量196 C时,4 mm铝板发生穿孔;当直流分量为196 C时,6 mm铝板未发生穿孔,背面温升为125℃,小于205℃,铝穹顶储罐不存在雷击燃爆风险。     

基于SOA和O3生成潜势的杭州市PM2.5和O3协同控制

2019年3月1日～2019年5月31日期间采用Syntech Spectras GC955在线气相色谱仪对杭州市大气环境中挥发性有机物（VOCs）进行了在线连续监测,分析了VOCs体积分数的组成特征、 PM_2.5和O₃协同控制的优控VOCs物种和VOCs特征污染物比值.结果表明,烷烃是VOCs体积分数中最重要的组分,贡献了62.40%. C2～C6的烷烃、苯系物、乙烯和乙炔是VOCs关键物种.烯烃和芳香烃是OFP的主要贡献组分,贡献率分别为41.35%和37.50%.芳香烃是SOA的主要贡献者,贡献率超过90%.低碳的烷烃、低碳烯烃和苯系物是OFP的关键贡献物种,控制好甲苯、间/对-二甲苯和邻-二甲苯这3种苯系物,是O₃和PM_2.5协同控制的关键.采样点大气中VOCs除了受机动车尾气的影响外,溶剂使用等工业排放的影响也较为显著.     

不同粒径聚乙烯微粒对大型溞的生物毒性效应

微塑料污染已经受到了国内外研究者的广泛关注,但研究热点多集中于海洋微塑料及其生物学效应,对淡水生物潜在影响的研究还很有限。本文选择淡水模式动物大型溞（Daphnia magna）作为受试生物,以2 μm、20 μm和50 μm聚乙烯微粒（polyethylene,PE）作为研究对象,探讨不同尺度微塑料对大型溞的急性活动抑制效应。结果表明,3种粒径的微塑料均可被大型溞摄入,并在肠道中积累,造成大型溞的活动抑制,并可能影响其脂类代谢;水中高浓度的PE微粒可粘附在大型溞体表,限制其活动,影响其摄食。在5~80 mg/L浓度范围内,2 μm PE微粒对大型溞的抑制率呈现线性增长趋势（96 h的EC₅₀为50.86 mg/L）;而20 μm和50 μm的PE微粒的抑制率随暴露浓度的增加呈现倒"U"形曲线。暴露48 h后,3种PE微粒的LOEC值分别为60、20和5 mg/L,即随粒径增大,毒性效应增加。粒径大小是影响大型溞摄入和积累微塑料的重要因素之一。本文结果为深入理解微塑料对淡水浮游动物的毒性效应提供了基础数据和理论依据。     

Numerical Simulation of Light/Dark Cycle Frequency of Microalgae Fluid in a Helical Tubular Photobioreactor for Carbon Dioxide Capture

In the present study, three-dimensional numerical simulations are conducted on hydrodynamics and light-intensity distribution of microalgae fluid flow in a helical tubular photobioreactor for CO₂ capture. The effect of incident direction of the light illumination is discussed and the light/dark cycle frequency experienced by the microalgae fluid in the cross-section of the photobioreactor is investigated. The simulation results reveal the steadily nonhorizontal and unsymmetrical Dean roll-cells of the microalgae fluid flow in the cross-section of the helical tube. The external light projecting onto the helical tubular photobioreactor from the center is a better way for microalgae cultivation. The light/dark cycle frequency of the microalgae fluid flow is calculated based on the light-intensity distribution inside the photobioreactor. The light/dark cycle frequency keeps constant for the same stream trace of the microalgae flow while varies with different flow regions. Meanwhile, the light/dark cycle frequency increases with the increase in microalgae fluid velocity. The suitable demarcation between the light and the dark zone depends on the shape and the location of the Dean roll-cells.