Predicting the contents of BTEX and MTBE for the three types of tollbooth at a highway toll station via the direct and indirect approaches

This study was set out to assess the contents of five volatile organic compounds (VOCs), including BTEX (the acronym for benzene, toluene, ethylbenzene, and xylene) and methyl tertiary-butyl ether (MTBE), in three types of tollbooth (including the car lane/ticket-collecting, car lane/cash-collecting, and bus/truck lane tollbooths) at a highway toll station via the direct and indirect approaches. For the direct approach, VOC samples were collected from the breathing zone of booth attendants at all selected tollbooths during the three workshifts. For samples collected during the dayshift, we found VOC contents of BTEX and MTBE in both the car lane/ticket-collecting (=6.23, 21.93, 3.24, 8.56, and 5.63 ppb, respectively) and car lane/cash-collecting tollbooths (=5.98, 21.71, 3.25, 8.59, and 6.04 ppb, respectively) were quite comparable, but both were significantly higher than that in the bus/truck lane tollbooth (=3.13, 13.91, 2.05, 4.52, and 2.70 ppb, respectively). The same pattern can also be found for the other two workshifts. For the indirect approach, we conducted multivariate regression analyses to predict VOC contents for any given type of tollbooth by using the four independent variables of the vehicle flowrate, wind speed, relative humidity, and air temperature. We found that, except the vehicle flowrate, the other three factors did not have a significant effect on VOC contents in the three types of tollbooth. In addition, the magnitudes of the effect of the vehicle flowrate on VOC contents for the three types of tollbooth were: car lane/cash-collecting>bus/truck lane>car lane/ticket-collecting. All regression results yielded R²-values in the range of 0.41−0.74 indicating that the developed indirect approach was able to predict VOC contents for three types of tollbooth.     

Cr/γ-Al_2O_3对乙酸乙酯的催化燃烧

使用浸渍法制备不同负载量的Cr/γ-Al_2O_3催化剂,研究乙酸乙酯的催化燃烧.BET,XRD结果表明,Cr在γ-Al_2O_3上负载存在分散阈值效应,负载量在阈值以下时呈单层分散形式,在超过阈值时Cr形成结晶,实验测得单层分散阈值与理论计算一致.Raman结果表明Cr在单层分散时为Cr~(6+),而在非单层分散时为Cr_2O_3.催化乙酸乙酯燃烧的活性研究显示,阈值效应对催化活性有显著影响:催化活性在单层分散阈值时最好,此时活化能最高,指前因子最大.     

区域高时空分辨率VOC天然源排放清单的建立

将中尺度气象模式MM5应用于估算VOC天然源排放的研究,建立了高时空分辨率VOC天然源排放清单的估算方法.根据方法需要,确定了我国部分树木排放异戊二烯和萜烯的标准排放因子,各植被类型排放各种VOC的标准排放因子,以及各植被类型季节平均的叶生物量密度.应用该方法估算了华南地区满足区域空气质量数值模拟要求的高时空分辨率VOC天然源排放清单.结果表明,华南地区夏季典型日的VOC天然源排放总量约1.12×10⁴t,VOC排放速率具有明显的时空分布,其中地理分布取决于植被类型及其分布,日变化规律则依赖于太阳辐射和温度的高低.并讨论了VOC天然源排放估算过程中误差的来源     

一次污染物对臭氧生成的影响研究

利用OZIPR模式模拟研究一次污染物对φ(O₃)的影响,研究设计3组比较方案:VOC和NO_x初始浓度比,VOC和NO_x排放比以及VOC排放中各组分所占比例的变化对臭氧生成浓度的影响.结果表明:随着VOC与NO_x初始浓度比和排放比的增大,φ(O₃)增长速率提高,其最大值出现时间提前,并且呈现先上升后下降的变化规律.结合O₃等浓度线分析认为,深圳市O₃污染属于VOC敏感型,控制VOC是控制φ(O₃)的有效途径.改变VOC组分的研究表明,控制VOC排放时应重点控制含乙烯、二甲苯、三甲苯较多的污染源.      

Cyclohexane oxidation and carbon deposition over metal oxide catalysts

Catalytic activity of V, Mn, Ni, Cu, Zn, Mo, Zr and Ce oxides over an -alumina support was evaluated for cyclohexane oxidation under oxygen deficient conditions in order to understand the relation between carbon deposition and catalytic activity/selectivity. Carbon formation over the catalysts during the oxidation reaction was measured by means of Fourier transformed infrared spectroscopy (FTIR). Catalysts Mn/Al₂O₃ and Ce/Al₂O₃, which are selective for deep oxidation of cyclohexane, possessed relatively carbon free surfaces. The catalysts with relatively high carbon deposition (V, Ni, Cu, Zn, Mo and Zr) produced CO in addition to CO₂. Traces of formaldehyde were produced over the catalysts Mo and V.     

Advanced analytical determination of volatile organic compounds (VOC) and other major contaminants in water samples using GC-Ion Trap MS

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Characterization of VOC emissions from construction machinery and river ships in the Pearl River Delta of China

Speciated characterization of Volatile Organic Compounds (VOCs), including oxygenated VOCs (OVOCs), from construction machinery and river ships in China is currently lacking. In this regard, we conducted field measurement on speciated VOC (including OVOC) emissions from six construction machinery and five river ships in the Pearl River Delta (PRD) region to identify VOC emission characteristics. We noticed that OVOC emissions from construction machinery and ships accounted for more than 50% of the total VOC emissions, followed by alkenes, aromatics and alkanes. Formaldehyde and acetaldehyde were the most emission species, accounting for 61.8%-83.2% of OVOCs. For construction machinery, the fuel-based emission factors of roller, grader and pile driver were 3.12, 3.12 and 7.36 g/kg, respectively. With the rigorous restraint by the national emission standards, VOC emissions of construction machinery had decreased considerably, especially during stage Ⅲ. Ozone formation potential was also significantly reduced due to the significant decrease in emissions of OVOCs and alkenes with higher reactivity. For river ships, the fuel-based emission factors of cargo ships and speedboat were 1.46 and 0.44 g/kg, respectively. VOC emissions from construction machinery and river ships in Guangdong Province in 2017 were 8851.0 and 4361.0 ton, respectively. This study filled the knowledge gaps of reactive gas emissions from different kinds of non-road mobile sources over the PRD, and more importantly, highlighted the necessity in adding OVOC measurement to give a complete and accurate depiction of reactive gas emissions from non-road mobile sources.     

我国典型城市环境大气挥发性有机物特征比值

城市环境大气挥发性有机物(VOCs)比值能够提供有用信息.基于在我国典型城市进行的7次VOCs观测数据,利用正交最小二乘法(ODR)、线性拟合法等4种方法计算了VOCs组分比值,并探讨其在监测数据质量评估、来源诊断和光化学过程研究中的应用.结果显示:间,对-二甲苯与邻-二甲苯浓度在7次观测中均呈现非常好的相关性(r为0.975~0.997),且不同观测中比值接近(2.78~3.05),这一比值可以用来对城市大气VOCs(尤其是芳香烃)测量数据的可靠性进行评估.以甲苯/苯(T/B)和丙烷/乙烷(P/E)为例初步分析了我国不同城市大气VOCs来源的差异.上海和广州T/B最高,分别为2.37和1.78,高于隧道实验中T/B比值(1.52),说明还受到溶剂涂料等富含甲苯的排放源影响,北京夏季T/B与隧道实验接近,而成都、北京冬季和重庆T/B较低(0.744~1.36),说明受到生物质燃烧、煤燃烧等其他富含苯的排放源影响.P/E分析结果显示,广州P/E(1.27)显著高于其他数据集(0.270~0.645),与2010年广州部分公交车和出租车仍利用液化石油气(LPG)作为燃料有关.另外,基于邻-二甲苯/乙苯变化特征表征光化学反应程度,并初步估算出典型城市大气上午·OH暴露量为(2.70~4.45)×10~(10)molecule·cm~(-3)·s.     

Vehicular volatile organic compounds losses due to refueling and diurnal process in China: 2010–2050

Volatile organic compounds (VOCs) are crucial to control air pollution in major Chinese cities since VOCs are the dominant factor influencing ambient ozone level, and also an important precursor of secondary organic aerosols. Vehicular evaporative emissions have become a major and growing source of VOC emissions in China. This study consists of lab tests, technology evaluation, emissions modeling, policy projections and cost-benefit analysis to draw a roadmap for China for controlling vehicular evaporative emissions. The analysis suggests that evaporative VOC emissions from China's light-duty gasoline vehicles were approximately 185,000 ton in 2010 and would peak at 1,200,000 ton in 2040 without control. The current control strategy implemented in China, as shown in business as usual (BAU) scenario, will barely reduce the long-term growth in emissions. Even if Stage II gasoline station vapor control policies were extended national wide (BAU + extended Stage II), there would still be over 400,000 ton fuel loss in 2050. In contrast, the implementation of on-board refueling vapor recovery (ORVR) on new cars could reduce 97.5% of evaporative VOCs by 2050 (BAU + ORVR/BAU + delayed ORVR). According to the results, a combined Stage II and ORVR program is a comprehensive solution that provides both short-term and long-term benefits. The net cost to achieve the optimal total evaporative VOC control is approximately 62 billion CNY in 2025 and 149 billion CNY in 2050.