沈阳市挥发性有机物污染特征及反应活性

2019年对沈阳市大气挥发性有机物(VOCs)开展了为期l a的观测,并对得到的53种物种进行浓度特征以及反应活性的研究.结果表明,观测期间沈阳市VOCs平均浓度为65.33 μg·m-3,烷烃、烯烃和芳香烃质量分数分别为62.44％、16.52％和19.32％.浓度排名前10的物种主要是C3～C5的烷烃、烯烃和部分芳香烃,累计占VOCs总浓度的64.13％.大气中烷烃、烯烃和芳香烃浓度均表现为双峰型的日变化特征,峰值分别出现在06:00～08:00和19:00～20:00,最低点出现在14:00～15:00;月变化上,该地ρ(VOCs)分别在12月和5月达到最高值(136.44μg.m-3)和最低值(35.61 μg·m-3);VOCs表现出明显的季节变化特征,即冬季＞秋季＞夏季＞春季,且烷烃、烯烃和芳香烃均随季节表现出增加趋势.通过特征值甲苯/苯(T/B)研究发现,沈阳春季VOCs主要来源于交通源和采暖源,夏季主要来源机动车尾气以及溶剂挥发,秋冬季主要受生物质燃烧和煤燃烧等排放源的影响.通过对反应活性分析,燃烧源是沈阳市控制臭氧污染的关键,丙烯、乙烯和1-己烯是沈阳市大气VOCs中反应活性最高的物种.     

Characterization of odorous charge and photochemical reactivity of VOC emissions from a full-scale food waste treatment plant in China

Food waste treatment plants(FWTPs) are usually associated with odorous nuisance and health risks, which are partially caused by volatile organic compound(VOC) emissions. This study investigated the VOC emissions from a selected full-scale FWTP in China. The feedstock used in this plant was mainly collected from local restaurants. For a year, the FWTP was closely monitored on specific days in each season. Four major indoor treatment units of the plant, including the storage room, sorting/crushing room, hydrothermal hydrolysis unit, and aerobic fermentation unit, were chosen as the monitoring locations.The highest mean concentration of total VOC emissions was observed in the aerobic fermentation unit at 21,748.2–31,283.3 μg/m3, followed by the hydrothermal hydrolysis unit at 10,798.1–23,144.4 μg/m3. The detected VOC families included biogenic compounds(oxygenated compounds, hydrocarbons, terpenes, and organosulfur compounds) and abiogenic compounds(aromatic hydrocarbons and halocarbons). Oxygenated compounds,particularly alcohols, were the most abundant compounds in all samples. With the use of odor index analysis and principal components analysis, the hydrothermal hydrolysis and aerobic fermentation units were clearly distinguished from the pre-treatment units, as characterized by their higher contributions to odorous nuisance. Methanthiol was the dominant odorant in the hydrothermal hydrolysis unit, whereas aldehyde was the dominant odorant in the aerobic fermentation unit. Terpenes, specifically limonene, had the highest level of propylene equivalent concentration during the monitoring periods. This concentration can contribute to the increase in the atmospheric reactivity and ozone formation potential in the surrounding air.     

Characterization of odorous charge and photochemical reactivity of VOC emissions from a full-scale food waste treatment plant in China

Food waste treatment plants (FWTPs) are usually associated with odorous nuisance and health risks, which are partially caused by volatile organic compound (VOC) emissions. This study investigated the VOC emissions from a selected full-scale FWTP in China. The feedstock used in this plant was mainly collected from local restaurants. For a year, the FWTP was closely monitored on specific days in each season. Four major indoor treatment units of the plant, including the storage room, sorting/crushing room, hydrothermal hydrolysis unit, and aerobic fermentation unit, were chosen as the monitoring locations. The highest mean concentration of total VOC emissions was observed in the aerobic fermentation unit at 21,748.2–31,283.3 μg/m³, followed by the hydrothermal hydrolysis unit at 10,798.1–23,144.4 μg/m³. The detected VOC families included biogenic compounds (oxygenated compounds, hydrocarbons, terpenes, and organosulfur compounds) and abiogenic compounds (aromatic hydrocarbons and halocarbons). Oxygenated compounds, particularly alcohols, were the most abundant compounds in all samples. With the use of odor index analysis and principal components analysis, the hydrothermal hydrolysis and aerobic fermentation units were clearly distinguished from the pre-treatment units, as characterized by their higher contributions to odorous nuisance. Methanthiol was the dominant odorant in the hydrothermal hydrolysis unit, whereas aldehyde was the dominant odorant in the aerobic fermentation unit. Terpenes, specifically limonene, had the highest level of propylene equivalent concentration during the monitoring periods. This concentration can contribute to the increase in the atmospheric reactivity and ozone formation potential in the surrounding air.     

Effects of fuel reactivity and injection timing on diesel engine combustion and emissions

Recent strategies for simultaneously reducing NOx and soot emissions have focused on achieving nearly premixed, low-temperature combustion (LTC) in diesel engines. A promising approach in this regard is to vary fuel reactivity in order to control the ignition delay and optimize the level of premixing and reduce emissions. The present study examines such a strategy by performing 3-D simulations in a single-cylinder of a diesel engine. Simulations employ the state-of-the-art two-phase models and a validated semi-detailed reaction mechanism. The fuel reactivity is varied by using a blend of n-heptane and iso-octane, which represent surrogates for gasoline and diesel fuels, respectively. Results indicate that the fuel reactivity strongly influences ignition delay and combustion phasing, whereas the start of injection (SOI) affects combustion phasing. As fuel reactivity is reduced, the ignition delay is increased and the combustion phasing is retarded. The longer ignition delay provides additional time for mixing, and reduces equivalence ratio stratification. Consequently, the premixed combustion is enhanced relative to diffusion combustion, and thus the soot emission is reduced. NO_x emission is also reduced due to reduced diffusion combustion and lower peak temperatures caused by delayed combustion phasing. An operability range is observed in terms of fuel reactivity and SOI, beyond which the mixture may not be sufficiently well mixed, or compression ignited. The study demonstrates the possibility of finding an optimum range of fuel reactivity, SOI, and EGR for significantly reducing engine out emissions for a given load and speed.     

石灰石中微量杂质对其脱硫活性的影响研究

石灰石的活性对湿法烟气脱硫工艺具有重要意义。采用间歇式硫酸消溶的方法，分别研究了石灰石中各微量杂质浓度对石灰石活性的影响，就其影响结果及其影响机理进行了理论分析，并用拟合曲线的方法预测各种杂质成分的影响程度。结果表明，二氧化硅和氧化铁的含量在一定范围内能提高石灰石的活性，超过此范围将使其活性降低，而氧化镁的存在能大幅提高石灰石的活性，氧化铝对石灰石活性影响不大。     

2015年南京市城区挥发性有机物组成特征及大气反应活性

采用GC-FID自动在线监测系统对南京市2015年环境大气中56种VOCs开展了为期1a的连续观测.结果表明,南京市城区大气VOCs小时平均体积分数为（17.49±11.35）×10^-9,其中4月最高（22.21×10^-9）,7月最低（12.39×10^-9）,日均体积分数变化特征不明显.烷烃、烯烃、芳香烃和乙炔占比分别为56.51%、11.06%、24.62%和7.81%,丙烷（15.26%）、乙烷（14.14%）、乙炔（7.81%）、甲苯（6.97%）、正丁烷（6.23%）、乙烯（5.23%）、异丁烷（4.34%）、丙烯（4.13%）、异戊烷（4.12%）和间/对-二甲苯（4.06%）是含量最丰富的VOCs物种.T/B（甲苯/苯）均值为2.02,表明南京市城区大气VOCs主要受机动车尤其是汽油车排放的影响.E/E（乙烷/乙炔）均值为2.24,表明观测站点区域大气老化程度较严重.利用·OH消耗速率（L^·OH）和臭氧生成潜势（OFP）评估了大气VOCs的反应活性.南京市城区大气VOCs冬春季大气反应活性较夏秋季强.芳香烃和烯烃的活性最高,对L^·OH和OFP的贡献依次为46.96%和41.58%、33.73%和39.86%,丙烯、乙烯和二甲苯等苯系物是活性最高的VOCs物种.     

黄冈市大气挥发性有机物污染特征、来源及对臭氧生成的影响

基于黄冈市城区大气挥发性有机物（VOCs）离线采样数据和常规空气污染物、气象在线监测数据,分析了黄冈市大气VOC组分和体积分数特征,并利用正交矩阵因子分解（PMF）模型和耦合MCM机制的光化学反应箱式模型（PBM-MCM）分别分析了臭氧（O₃）污染高发期VOCs的来源及臭氧生成敏感性.结果表明,φ（TVOCs）平均值为（21.57±3.13）×10^-9,且呈现出冬春高、夏秋低的季节性特征,其中烷烃（49.9%）和烯烃（16.4%）的占比最大.PMF解析结果显示黄冈市大气VOCs主要来源为：燃料燃烧源（27.8%）、机动车排放源（19.9%）、溶剂使用源（15.7%）、工业卤代烃排放源（12.1%）、化工企业排放源（10.5%）、自然源（7.8%）和柴油车排放源（6.2%）.在人为源中,溶剂使用、燃料燃烧和化工企业排放的VOCs对大气环境中O₃生成的贡献较大,贡献了O₃生成的60.9%,故对O₃污染防控应优先管控这3种人为源.通过相对增量反应性（RIR）和经验动力学方法（EKMA）曲线分析,观测期间黄冈市O₃生成处于VOCs控制区,且间/对-二甲苯、乙烯、1-丁烯和甲苯等VOCs对O₃生成比较敏感,应重点削减以上VOCs的排放.     

Adaptation to a New Workplace According to Reactivity and Values-Motives Coherence at Work

A new workplace is a result of changing a work post or undertaking a new job. Direct indices of adaptation to this situation (average mood at the workplace and job satisfaction) and the indirect ones (costs like health complaints and the level of depressing or facilitating anxiety) are analysed with regard to reactivity and values-motives coherence at work. Sixty bank workers were investigated. The obtained results confirm that mood and costs depend on reactivity, but satisfaction with work depends on coherence. Only achievement values-motives coherence at work differentiates direct and indirect indicators of adaptation. Considering both kinds of variables modifies dependencies. Some theoretical and practical conclusions resulting from the research are included.