Potential of secondary aerosol formation from Chinese gasoline engine exhaust

Light-duty gasoline vehicles have drawn public attention in China due to their significant primary emissions of particulate matter and volatile organic compounds(VOCs). However,little information on secondary aerosol formation from exhaust for Chinese vehicles and fuel conditions is available. In this study, chamber experiments were conducted to quantify the potential of secondary aerosol formation from the exhaust of a port fuel injection gasoline engine. The engine and fuel used are common in the Chinese market, and the fuel satisfies the China V gasoline fuel standard. Substantial secondary aerosol formation was observed during a 4–5 hr simulation, which was estimated to represent more than 10 days of equivalent atmospheric photo-oxidation in Beijing. As a consequence, the extreme case secondary organic aerosol(SOA) production was 426 ± 85 mg/kg-fuel, with high levels of precursors and OH exposure. The low hygroscopicity of the aerosols formed inside the chamber suggests that SOA was the dominant chemical composition. Fourteen percent of SOA measured in the chamber experiments could be explained through the oxidation of speciated single-ring aromatics. Unspeciated precursors, such as intermediate-volatility organic compounds and semi-volatile organic compounds, might be significant for SOA formation from gasoline VOCs. We concluded that reductions of emissions of aerosol precursor gases from vehicles are essential to mediate pollution in China.     

Long-term effects of sliver nanoparticles on the abundance and activity of soil microbiome

正Silver nanoparticles(Ag NPs)are among the most extensively used engineered nanomaterials because of their wellestablished antimicrobial and unique physicochemical properties(Yin et al.,2015).Applications of AgNPs have now been     

Insights into the formation of secondary organic carbon in the summertime in urban Shanghai

To investigate formation mechanisms of secondary organic carbon(SOC) in Eastern China,measurements were conducted in an urban site in Shanghai in the summer of 2015. A period of high O_3 concentrations(daily peak 120 ppb) was observed, during which daily maximum SOC concentrations exceeding 9.0 μg/(C·m~3). Diurnal variations of SOC concentration and SOC/organic carbon(OC) ratio exhibited both daytime and nighttime peaks. The SOC concentrations correlated well with O_x(= O_3+ NO_2) and relative humidity in the daytime and nighttime, respectively, suggesting that secondary organic aerosol formation in Shanghai is driven by both photochemical production and aqueous phase reactions. Single particle mass spectrometry was used to examine the formation pathways of SOC. Along with the daytime increase of SOC, the number fraction of elemental carbon(EC) particles coated with OC quickly increased from 38.1% to 61.9% in the size range of 250–2000 nm, which was likely due to gas-to-particle partitioning of photochemically generated semi-volatile organic compounds onto EC particles. In the nighttime, particles rich in OC components were highly hygroscopic, and number fraction of these particles correlated well with relative humidity and SOC/OC nocturnal peaks. Meanwhile, as an aqueous-phase SOC tracer, particles that contained oxalate-Fe(III) complex also peaked at night. These observations suggested that aqueous-phase processes had an important contribution to the SOC nighttime formation. The influence of aerosol acidity on SOC formation was studied by both bulk and single particle level measurements, suggesting that the aqueous-phase formation of SOC was enhanced by particle acidity.     

关中典型城市及农村夏季PM2.5的化学组成对比

于2016年7~8月采集了陕西省西安市（城市）及蔺村（农村）夏季昼夜PM_2.5样品,分析其有机碳（OC）、元素碳（EC）和无机离子等化学组分的含量,探讨关中平原城市和农村地区PM_2.5的化学组成和来源的差异.结果表明,采样期间西安和蔺村的PM_2.5浓度分别为（49.7±22.8）和（62.6±14.2）μg/m³.西安PM_2.5中OC和EC的浓度[（6.5±2.5）μg/m³,（3.2±1.8）μg/m³]与蔺村[（6.8±1.8）μg/m³,（3.8±2.3）μg/m³]相当.西安OC/EC比值白天（2.6）高于夜晚（1.9）,蔺村反之（白天：1.6;夜晚：2.7）,主要是因为夜间城市地区重型卡车运输活动增强导致排放更多EC,而夜间农村地区人为活动较少导致EC排放显著降低.西安和蔺村无机离子总浓度分别为（20.2±14.6）和（30.1±10.5）μg/m³,占PM_2.5浓度的40.6%和47.6%.蔺村SO₄^2-的平均浓度高达19.0μg/m³,占PM_2.5浓度的30%以上,远高于西安（9.4μg/m³和18.9%）,主要与农村固体燃料（煤和生物质）使用有关.西安NO₃^-和Ca²⁺的浓度及其对PM_2.5的贡献、NO₃^-/SO₄^2-比值均明显大于蔺村,表明城市地区受机动车尾气和扬尘的影响更大.西安K⁺与Ca²⁺和Mg²⁺的相关性较强,而蔺村K⁺与EC的相关性显著强于西安,说明西安市区K⁺由粉尘源主导,而农村地区则主要来自生物质燃烧.     

有机物对SAD的影响及其数学模拟

通过血清瓶批式实验,研究了不同C/N下葡萄糖和乙酸钠对厌氧氨氧化耦合反硝化系统（SAD）污泥活性及脱氮性能的影响.耦合系统颗粒污泥为在亚硝态氮充足的UASB连续流反应器中培养得到,具有较高的厌氧氨氧化活性和反硝化活性.以葡萄糖为碳源,C/N分别为1,2,4时,厌氧氨氧化活性差异不大,反硝化活性逐渐增加,亚硝态氮最大降解速率分别为0.265,0.345,0.453kgN/（kgVSS·d）;以乙酸钠为碳源,C/N分别为1、2、4时,厌氧氨氧化活性和反硝化活性都无明显差别.相同C/N下,耦合系统以葡萄糖为碳源时的厌氧氨氧化活性较高,以乙酸钠为碳源时的反硝化活性较高.C/N分别为1,2,4时,以葡萄糖为有机物的氨氮最大降解速率分别为乙酸钠的1.15,1.19,1.58倍,以乙酸钠为有机物时反应的亚硝态氮最大降解速率分别为葡萄糖的1.89,1.48,1.15倍.实验的数学模拟结果表明,通过模型的模拟,能较为准确地预测实验过程中氮素的变化趋势,在C/N为1~4时耦合系统中颗粒污泥的厌氧氨氧化活性无较大变化.     

边际机会成本与自然资源定价浅析

采用边际机会成本理论,对自然资源定价的原理和方法进行阐述,并比较了各种方法在实际应用中的适用条件,以及相互之间的优劣,为自然资源开发中的环境损失估算提供理论支持.     

浅谈循环经济理念下工业固体废物资源化

探讨了从循环经济理论的角度论述了转变传统工业发展模式的必要性,分析了吉林省工业固体废物的现状、主要种类及其资源化的有效途径和具体措施,提出了循环经济在吉林省工业固体废物资源化方面的实践和集环境、社会、经济三大效益于一体的新思路.     

SF6绝缘设备的环保与经济运行维护

SF6气体作为一种优秀灭弧介质在高压灭弧领域得到了十分广泛的应用.同时,SF6气体的一些弊端,如泄漏对人体与环境的影响也体现出来,通过介绍SF6气体的环保要求和运行、检测、维护及未来的发展方向.使得其在环境保护的前提下,在电力系统得到更加广泛的应用.     

地理变异系数法和Fisher最优分割法在环境空气监测优化布点中的应用

在环境空气监测点位优化中,为反映优化后点位的整体代表性,需要在允许的测定误差内以最少的测点反映区域内较长时期的整体污染水平、污染分布状况和污染趋势.本文以博山城区为例,利用地理变异系数法和Fisher最优分割法对所布设点位进行数理统计.该方法使用简便,分级自然,避免了诸多人为因素的影响,同时,优选结果具有较强的整体代表性.