Carbonaceous aerosol is one of the most abundant components(20-80%) of atmospheric fine particulates(PM2.5) [1] and substantially affects both climate and human health. Based on their optical properties, carbonaceous ...
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Carbonaceous aerosol is one of the most abundant components(20-80%) of atmospheric fine particulates(PM2.5) [1] and substantially affects both climate and human health. Based on their optical properties, carbonaceous aerosols can be classified as organic carbon(OC) or elemental carbon(EC). In general, EC is a primary pollutant derived exclusively from the incomplete combustion of fossil fuels and biomass burning, whereas OC is a complex mixture of primary and secondary organic aerosols(POA and SOA, respectively). Compared with other methods, such as the use of the OC/EC ratio only, radiocarbon(14C) analysis facilitates the direct differentiation of modern carbon sources from fossil fuel sources [2, 3]. To date, many 14 C studies have focused on the amount of total carbon(TC) in aerosols [4-6], and only a few studies have separately analyzed both OC and EC due to limitations of the technique, the bulk samples required, and the high cost for 14 C measurement. Furthermore, due to their ambiguous artificial boundary, the identification of the individual OC and EC fractions in carbonaceous aerosols is depends significantly on the method [7]. Because EC is emitted into the atmosphere solely from either fossil fuel combustion or biomass burning as primary particles, a clear distinction of the EC source between these two sources can be achieved [8, 9]. As a result, the use of a combination of OC/EC separation and 14 C analysis for the identification of the source, regardless of whether its origin is fossil or non-fossil, is more effective than the analysis of the 14 C in the TC. Due to the rapid economic growth and high population density in China, the aerosols and their precursor emissions have drawn significant attention in recent decades. As one of the three largest economic hubs in China, the Yangtze River Delta(YRD) experiences serious air pollution but fewmonitoring station of 14C-related studies. Ningbo Atmospheric Environmental Observatory(NAEO), where close to the
Real-time measurements of non-refractory submicron aerosols(NR-PM1) were conducted using an aerodyne mass spectrometry(Q-AMS) at the summit of Mount Tai(1534m above sea level)in Shandong province, locates in the cente...
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Real-time measurements of non-refractory submicron aerosols(NR-PM1) were conducted using an aerodyne mass spectrometry(Q-AMS) at the summit of Mount Tai(1534m above sea level)in Shandong province, locates in the center of the Central East China(CEC) region, from June 2010 to January 2012, as a part of National basic research project monitoring campaign. The mass concentrations and size distributions of non-refractory submicron particle(NR-PM1) species(i.e., sulfate, nitrate, ammonium, chloride, and organics) were measured in situ at 5-min time resolution. Overall, 146 days valid data was obtained during the whole campaign, which covers four different seasons. The average total mass concentration of NR-PM1 was 42.9 g m-3, with 31%sulfate, 32% organics, 19% nitrate and 18% ammonium. The average mass concentration of NR-PM1 is highest(59.9 g m-3) in summer and lowest(31.9 g m-3) in spring. Species occupied different percentages in different seasons, sulfate in summer, Organics in fall and winter, while nitrate dominants the NR-PM1 in spring respectively. To investigate the size-resolved mass concentrations of aerosol chemical components from different sources, seven air masses were clustered based on the 72 hours back trajectory with HYSPLIT model. Cluster I, IV and V with short pathway represent the local and regional sources, and the concentrations from these clusters were higher than that from cluster III and VI which originated from remote and clean North-West sources. According to the results of diurnal cycles for chemical species in NR-PM1 higher at noon and lower at midnight from seven clusters, it was concluded that the site was controlled under the transitions between PBL and FT at daytime and nighttime. The size distributions of chemical species were different from different air masses, cluster I, II, IV, V and VII showed same shape with accumulation mode(500-600nm), the concentration at nighttime is lower than at daytime. For cluster VI and III, it demonstra
Aqueous-phase reactions of organic compounds are an important source of secondary organic aerosol(SOA)(Ervens 2011). Laboratory studies focused mostly on small aldehydes such as glyoxal(De Haan 2009;Tan 2009) as precu...
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Aqueous-phase reactions of organic compounds are an important source of secondary organic aerosol(SOA)(Ervens 2011). Laboratory studies focused mostly on small aldehydes such as glyoxal(De Haan 2009;Tan 2009) as precursors, and on pinene oxidation products(Lee 2011). We showed experimental results of aqueous-phase reactions of a semi-volatile and slightly water soluble methoxy-phenol from biomass burning, vanillin(C8H8O3). Reactions were performed in a vessel(Lee 2011) with UV(254 nm) irradiation under two conditions:(1) photochemical oxidation with H2O2 as an OH radical source;and(2) direct photolysis without H2O2 added. Solution of the resulted products, as well as the ammonium sulfate added(Lee 2011), was atomized continuously and dried before on-line analyses. An Aerodyne High-resolution Time-of-Flight Aerosol Mass Spectrometer(HR-To F-AMS) was used to measure the dried particle compositions, and a Hygroscopic Tandem Differential Mobility Analyzer(HTDMA) and a Cloud Condensation Nuclei counter(CCNc) were used to determine the particle growth factor and CCN activity respectively. Withou UV irradiation, most of vanillin evaporated to the gas phase during drying and gave negligible organic mass in particles(Figure 1, before time < 0 min). A large amount of SOA was formed and retained after reactions under both conditions, although products might be different under these two conditions according to HR-To F-AMS characterization(Figure 1). Off-line analyses by liquid chromatography-mass spectrometry(LC-MS) and gas chromatography-mass spectrometry(GC-MS) also confirmed that the product identities from these two conditions are different. Organic mass first increased rapidly and then decreased under condition(1), but kept increasing slowly under condition(2), as shown in Figure 1A and 1C, respectively. It was found that the degree of oxygenation of products from condition(1) first increased and then decreased, suggesting a competition between functionalization and fragme
珠江三角洲(PRD)近年来面临着越来越严重的大气污染问题,其中大气颗粒物污染问题尤为突出。为了解珠三角地区细颗粒物的长期变化趋势,本文收集2000-2010年文献中珠三角地区细颗粒物的相关数据,总结细颗粒物的质量浓度和化学组分长期变化特征,及其与污染源排放的关系。结果发现,2000-2010年珠三角地区细颗粒物质量浓度先上升后下降,2004-2005年浓度最高,达到85μg/m3,整体呈下降趋势,从2000年的49μg/m3下降到2010年的37μg/m3,11年的平均质量浓度为59.1μg/m3。细颗粒物中的含碳物质OC和EC变化趋势与PM2.5相同,先上升后下降,整体呈下降趋势,2004年含碳物质质量浓度达到最高值,分别为19.4和12.4μg/m3。主要是因2004年广州市灰霾天数达到131天,为近十年来灰霾天数最多年份,佛山市2004年能见度较其他年份也有所下降,2004年珠三角地区空气污染严重,污染物浓度较高(黄健,等,2008;陈欢欢,等,2010;陈慧娴,2011)。分析PM2.5与化学组分的相关性发现,PM2.5与OC、EC相关性最高,达到0.575和0.553。细颗粒物中的水溶性离子SO42-、NO3-和NH4+均呈上升趋势,分别从2000年的10.2、1.5和2.9μg/m3上升到2010年的12.2、6.4、5.3μg/m3,平均质量浓度分别为12.2、3.4、4.3μg/m3。由于城市化的发展,珠三角地区工业烟尘、粉尘的直接排放量虽大幅度减少,但是SO2和NOx等二次粒子的前体物排放量仍然很大,且O3浓度不断增加,大气氧化性增强,有利于无机二次颗粒物的生成(Wang et al.,2003;Zhang et al.,2004;Zheng et al.,2010),珠三角地区细颗粒物的无机二次污染日趋严重。珠三角地区细颗粒物中SO42-、NO3-、NH4+、OC和EC所占百分比分别为24%、6%、8%、21%和11%,共占细颗粒物百分达到70%,其中SO42-和OC贡献所占百分比最高。珠三角地区OC/EC比值主要介于2-5之间,表明珠三角地区二次有机碳的生成比较显著。通过对PRD不同功能区的细粒子颗粒物进行分析发现,道路和工业区细颗粒物质量浓度最高,可达到90μg/m3,城市和近郊约为60μg/m3,背景点浓度最低为38μg/m3。水溶性离子SO42-、NO3-和含碳物质均为工业区最高,城市和近郊次之。而NH4+为近郊浓度最高,工业区和道路反而较低,主要与近郊区的农业活动有关。通过分析水溶性离子与污染源的相关性发现,SO42-与电力消费量达到显著相关(α=0.05,R=0.626),火力发电燃煤产生的SO2通过化学反应产生SO42-对于细颗粒物中的SO42-有重要贡献。NO3-与机动车保有量(α=0.05,R=0.663)、电力消费(α=0.05,R=0.625)达到显著相关,机动车尾气和火电厂排放的NO x通过光化学反应生成的NO3-是大气中NO3-的重要来源(Zheng et al.,2009);NH4+与农业化肥施用量(R=0.699)达到显著相关,说明农业活动排放的NH3对于NH4+有重要影响(Zheng et al.,2012)。总体来说,珠三角地区细颗粒物二次污染问题突出,细粒子污染与珠三角地区不断增强的大气氧化性有关外,与工业、机动车尾气排放有很大关系,因此改善珠三角地区的细颗粒物污染问题,控制其前体物的排放是关键因素之一。
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