城区与县区不同空气质量下碳组分污染特征对比分析

为对比城区与相邻县区不同空气质量下的碳组分污染特征,分别在成都市和仁寿县采集霾期及非霾期PM_(2.5)有效样品共计88个,确定其相应质量和各碳组分浓度[有机碳(OC)、元素碳(EC)和二次有机碳(SOC)等],并进行各碳组分之间的相关性及主成分分析.结果表明,不同空气质量下的城区污染物浓度均高于县区.OC和EC密切相关,非霾期的相关性系数较霾期大.与城区相比,霾期县区的SOC/PM_(2.5)较大,说明其受二次有机物污染更为明显;但城区非霾期二次气溶胶占比明显高于霾期,表明霾期的一次排放是城区大气污染的主要原因.燃煤、机动车排放和生物质燃烧均是两个区域PM_(2.5)的主要来源.     

上海霾与非霾期间大气颗粒物光学特性垂直分布特征和质量浓度对比研究

采用美国国家航空航天局的云-气溶胶激光雷达红外开拓者卫星搭载的正交极化云-气溶胶激光雷达数据产品,包括消光系数、光学厚度、总后向散射系数、体积退偏比和色比,结合地面监测的颗粒物质量浓度,分析上海大气相对湿度小于80%霾发生期间气溶胶光学属性的垂直分布特征和颗粒物质量浓度变化,并与非霾期间进行比较.结果表明:霾期间532 nm和1064 nm消光系数在垂直高度上(海拔:0~10 km)均大于非霾期间,且大多数霾期间颗粒物在整层大气的光学厚度大于非霾期间.在近地面,霾期间大气颗粒物散射能力大于非霾期间.各垂直高度层,霾与非霾期间小粒径和规则气溶胶占主导地位.霾期间近地面大粒径颗粒物在霾期间所占比例大于非霾期间;2.0~4.0 km高度层,霾和非霾期间细颗粒所占比例接近;4.0~10.0 km高度层,霾期间细颗粒气溶胶所占比例大于非霾期间.PM1、PM2.5和PM10质量浓度在霾期间均大于非霾期间,且霾期间细颗粒物所占比例明显增加.颗粒物质量浓度和比值PM1/PM2.5和PM2.5/PM10分别随霾污染程度的加重而升高.冬季颗粒物质量浓度最高,主要来自细颗粒物的贡献;而春季PM10质量浓度高于其它季节.     

厦门市冬春季灰霾期间大气PM10中多环芳烃的污染特征及来源分析

采集了厦门市冬春季(2008-12-04～2009-03-20)湖里工业区和大嶝岛旅游区大气PM10样品,用GC-MS定量了PM10负载的19种多环芳烃(PAHs),并结合采样期间气象资料对灰霾期和非灰霾期多环芳烃的差异特征进行对比分析.结果表明,冬春季采样期内,厦门市大气PM10中PAHs的浓度变化范围为12.93～79.27 ng.m-3,平均42.28 ng.m-3,比2004年冬季增长近3倍.灰霾期间PM10中PAHs总的质量浓度明显高于非灰霾期,并且灰霾期间低分子量组分菲、荧蒽和芘的质量分数显著下降,高分子量组分苯并[b]荧蒽、苯并[k]荧、苯并[a]芘、苝、茚并[1,2,3-cd]芘、苯并[ghi]苝和晕苯的质量分数相对升高.采用特征化合物比值、主成分分析与多元线性回归对来源与贡献率进行了分析和估算.灰霾期间识别出3类污染源:机动车尾气排放+天然气燃烧、煤燃烧和焦炉排放,其贡献率分别为62.7%、28.1%和9.2%;非灰霾期间同样识别出这3类污染源,其贡献率分别为48.6%、36.9%和14.5%.表明厦门市冬春季灰霾期间PM10中PAHs受本地源排放影响相对较多,非灰霾期间受北方燃煤长距离传输影响更显著.     

Role of secondary aerosols in haze formation in summer in the Megacity Beijing

A field experiment from 18 August to 8 September 2006 in Beijing, China, was carried out. A hazy day was defined as visibility < l0 km and RH (relative humidity) < 90%. Four haze episodes, which accounted for ~ 60% of the time during the whole campaign, were characterized by increases of SNA (sulfate, nitrate, and ammonium) and SOA (secondary organic aerosol) concentrations. The average values with standard deviation of SO₄^2 −, NO₃⁻, NH₄⁺ and SOA were 49.8 (± 31.6), 31.4 (± 22.3), 25.8 (± 16.6) and 8.9 (± 4.1) μg/m³, respectively, during the haze episodes, which were 4.3, 3.4, 4.1, and 1.7 times those in the non-haze days. The SO₄^2 −, NO₃⁻, NH₄⁺, and SOA accounted for 15.8%, 8.8%, 7.3%, and 6.0% of the total mass concentration of PM₁₀ during the non-haze days. The respective contributions of SNA species to PM₁₀ rose to about 27.2%, 15.9%, and 13.9% during the haze days, while the contributions of SOA maintained the same level with a slight decrease to about 4.9%. The observed mass concentrations of SNA and SOA increased with the increase of PM₁₀ mass concentration, however, the rate of increase of SNA was much faster than that of the SOA. The SOR (sulfur oxidation ratio) and NOR (nitrogen oxidation ratio) increased from non-haze days to hazy days, and increased with the increase of RH. High concentrations of aerosols and water vapor favored the conversion of SO₂ to SO₄^2 − and NO₂ to NO₃⁻, which accelerated the accumulation of the aerosols and resulted in the formation of haze in Beijing.     

Chemical and optical properties of aerosols and their interrelationship in winter in the megacity Shanghai of China

A field campaign on air quality was carried out in Shanghai in winter of 2012. The concentrations of NO, NO₂, NO_x, SO₂, CO, and PM_2.5 increased during haze formation. The average masses of SO₄^2-, NO₃^- and NH₄⁺ were 10.3, 11.7 and 6.7 μg/m³ during the haze episodes, which exceeded the average (9.2, 7.9, and 3.4 μg/m³) of these components in the non-haze days. The mean values for the aerosol scattering coefficient (b_sp), aerosol absorption coefficient (b_ap) and single scattering albedo (SSA) were 288.7, 27.7 and 0.91 Mm^-1, respectively. A bi-peak distribution was observed for the mass concentrations of CO, NO, NO₂, and NO_x. More sulfate was produced during daytime than that in the evening due to photochemical reactions. The mass concentration of NH₄⁺ achieved a small peak at noontime. NO₃^- showed lower concentrations in the afternoon and higher concentrations in the early morning. There were obvious bi-peak diurnal patterns for bsp and bap as well as SSA. bsp and bap showed a positive correlation with PM_2.5 mass concentration. (NH₄)₂SO₄, NH₄NO₃, organic mass, elemental carbon and coarse mass accounted for 21.7%, 19.3%, 31.0%, 9.3% and 12.3% of the total extinction coefficient during non-haze days, and 25.6%, 24.3%, 30.1%, 8.1% and 8.2% during hazy days. Organic matter was the largest contributor to light extinction. The contribution proportions of ammonium sulfate and ammonium nitrate to light extinction were significantly higher during the hazy time than during the non-haze days.     

Characteristics of secondary inorganic aerosol and sulfate species in size-fractionated aerosol particles in Shanghai

Sulfate, nitrate and ammonium(SNA) are the dominant species in secondary inorganic aerosol, and are considered an important factor in regional haze formation. Size-fractionated aerosol particles for a whole year were collected to study the size distribution of SNA as well as their chemical species in Shanghai. SNA mainly accumulated in fine particles and the highest average ratio of SNA to particulate matter(PM) was observed to be 47% in the fine size fraction(0.49–0.95 μm). Higher sulfur oxidation ratio and nitrogen oxidation ratio values were observed in PM of fine size less than 0.95 μm. Ion balance calculations indicated that more secondary sulfate and nitrate would be generated in PM of fine size(0.49–0.95 μm). Sulfur K-edge X-ray absorption near-edge structure(XANES) spectra of typical samples were analyzed. Results revealed that sulfur mainly existed as sulfate with a proportion(atomic basis) more than 73% in all size of PM and even higher at 90% in fine particles. Sulfate mainly existed as(NH4)2SO4 and gypsum in PM of Shanghai. Compared to non-haze days, a dramatic increase of(NH4)2SO4 content was found in fine particles on haze days only, which suggested the promoting impact of(NH4)2SO4 on haze formation. According to the result of air mass backward trajectory analysis, more(NH4)2SO4 would be generated during the periods of air mass stagnation. Based on XANES, analysis of sulfate species in size-fractionated aerosol particles can be an effective way to evaluate the impact of sulfate aerosols on regional haze formation.     

阴霾天气PM_(10)的微观特征及生物活性研究

利用高分辨率场发射扫描电镜(FESEM)、图像分析技术(IA),对北京市2004年12月一次严重的阴霾天气条件下采集的PM10(指空气动力学直径小于10μm的颗粒物)的微观形貌、粒度分布、主要颗粒物类型进行了分析,并运用质粒DNA评价法对阴霾和非阴霾天气条件下的PM10样品的生物活性进行了对比研究。结果表明,阴霾天气时PM10样品中以粒度较小的烟尘及其集合体为主,且多呈湿状,含有较多的二次颗粒物,并发现了残余的有机液滴颗粒。质粒DNA实验的结果显示,阴霾天气PM10样品的水溶和全样样品的TD20值(造成20%DNA破坏时所需要的样品剂量)分别为93μg.ml-1和50μg.ml-1,而同一月份非阴霾天气条件下PM10样品的水溶和全样样品的TD20值分别为200μg.ml-1和160μg.ml-1,表明阴霾天气PM10样品比非阴霾天气样品具较强的生物活性,即对人体健康存在着潜在的危害。且无论是阴霾还是非阴霾天气条件下的PM10的全样样品均较水溶样品具更大的生物活性。     

Chemical characterization of size-resolved aerosols in four seasons and hazy days in the megacity Beijing of China

Size-resolved aerosol samples were collected by MOUDI in four seasons in 2007 in Beijing. The PM₁₀ and PM_1.8 mass concentrations were 166.0 ± 120.5 and 91.6 ± 69.7 μg/m³, respectively, throughout the measurement, with seasonal variation: nearly two times higher in autumn than in summer and spring. Serious fine particle pollution occurred in winter with the PM_1.8/PM₁₀ ratio of 0.63, which was higher than other seasons. The size distribution of PM showed obvious seasonal and diurnal variation, with a smaller fine mode peak in spring and in the daytime. OM (organic matter = 1.6 × OC (organic carbon)) and SIA (secondary inorganic aerosol) were major components of fine particles, while OM, SIA and Ca^2 + were major components in coarse particles. Moreover, secondary components, mainly SOA (secondary organic aerosol) and SIA, accounted for 46%–96% of each size bin in fine particles, which meant that secondary pollution existed all year. Sulfates and nitrates, primarily in the form of (NH₄)₂SO₄, NH₄NO₃, CaSO₄, Na₂SO₄ and K₂SO₄, calculated by the model ISORROPIA II, were major components of the solid phase in fine particles. The PM concentration and size distribution were similar in the four seasons on non-haze days, while large differences occurred on haze days, which indicated seasonal variation of PM concentration and size distribution were dominated by haze days. The SIA concentrations and fractions of nearly all size bins were higher on haze days than on non-haze days, which was attributed to heterogeneous aqueous reactions on haze days in the four seasons.     

西安市一次霾过程中气溶胶垂直分布特征及气象要素影响

为探讨西安市典型霾过程中的气溶胶垂直分布特征和气象要素影响,利用地面空气质量数据、CALIPSO卫星激光雷达资料以及气象要素资料,并结合HYSPLIT后向轨迹模式、天气形势分析、相关性分析等,对西安市2016年12月17-21日霾过程依据RH（相对湿度）进行干霾、湿霾和雾霾的划分,并分析不同阶段的气溶胶垂直分布特征.结果表明:前期干霾阶段,西北沙尘的输送使得高空气溶胶退偏比和色比较大,以沙尘型气溶胶为主;中期湿霾阶段,RH的增大使得低层细粒子增多,消光系数达1.7 km-1,以污染型气溶胶为主;后期干霾阶段时,低层大气中非球形粗粒子增多,以混合型气溶胶占主导.气象要素对霾过程影响较大,静风、高湿、"双逆温"效应不利于颗粒物的清除,逆温强度的变化与污染物的消长具有一定的滞后一致性.RH和ρ（PM）共同影响能见度变化,RH高于80%时,能见度由RH主导,相关系数达到-0.871;RH低于80%的污染阶段,ρ（PM）对能见度起主导作用,相关系数达0.85以上.研究显示,不同霾阶段气溶胶垂直分布特征差异较大,气象要素对霾过程的消长有重要影响.      

Progressively narrow the gap of PM2.5 pollution characteristics at urban and suburban sites in a megacity of Sichuan Basin, China

Nowadays, the fine particle pollution is still severe in some megacities of China, especially in the Sichuan Basin, southwestern China. In order to understand the causes, sources, and impacts of fine particles, we collected PM_2.5 samples and analyzed their chemical composition in typical months from July 2018 to May 2019 at an urban and a suburban (background) site of Chengdu, a megacity in this region. The daily average concentrations of PM_2.5 ranged from 5.6-102.3 µg/m³ and 4.3-110.4 µg/m³ at each site. Secondary inorganics and organic matters were the major components in PM_2.5 at both sites. The proportion of nitrate in PM_2.5 has exceeded sulfate and become the primary inorganic component. SO₂ was easier to transform into sulfate in urban areas because of Mn-catalytic heterogeneous reactions. In contrast, NO₂ was easily converted in suburbs with high aerosol water content. Furthermore, organic carbon in urban was much greater than that in rural, other than elemental carbon. Element Cr and As were the key cancer risk drivers. The main sources of PM_2.5 in urban and suburban areas were all secondary aerosols (42.9%, 32.1%), combustion (16.0%, 25.2%) and vehicle emission (15.2%, 19.2%). From clean period to pollution period, the contributions from combustion and secondary aerosols increased markedly. In addition to tightening vehicle controls, urban areas need to restrict emissions from steel smelters, and suburbs need to minimize coal and biomass combustion in autumn and winter.     

西安市秋冬季不同空气质量下可培养微生物气溶胶浓度和粒径分布

利用Anderson空气微生物采样器对西安市2014年9月~2015年1月间可培养微生物气溶胶进行采样、培养,分析不同空气质量下其浓度与粒径变化特征,并对其与颗粒污染物(PM_(2.5)、PM_(10))、气象参数(温度、相对湿度)和其它气态污染物(NO_2、SO_2、O_3)进行主成分+多元线性回归分析.结果显示,可培养细菌和真菌气溶胶浓度范围分别为97~1 909CFU·m~(-3),92~1 737 CFU·m~(-3).随空气污染程度加深,两种微生物气溶胶浓度均呈现增加趋势;细菌气溶胶粒径分布向粗颗粒偏移;而真菌气溶胶在低污染时呈正态分布,高污染时粒径峰值向细颗粒偏移.主成分分析结果显示,可培养微生物气溶胶主要与灰霾、太阳辐射和相对湿度有关.多元线性回归结果表明,细菌气溶胶与灰霾呈显著正相关(P0.05),与太阳辐射呈不显著负相关,与湿度呈不显著正相关;真菌气溶胶与灰霾、太阳辐射和相对湿度均呈不显著正相关.研究结果可以为评估微生物气溶胶所引起的环境与健康效应提供基础数据.     

华北平原灰霾天气下大气气溶胶的单颗粒分析

为分析灰霾期间单颗粒气溶胶化学组成和混合状态,于2014年12月9日—2015年1月10日,使用单颗粒气溶胶质谱仪（SPAMS）表征华北平原郑州市中牟县的气溶胶颗粒.结果表明:灰霾期（H1:20141213T19:00—20141215T10:00;H2:20150102T10:00—20150106T03:00）和清洁期（C1:20141215T18:00—20141217T18:00;C2:20141231T16:00—20150101T20:00）大气颗粒物种类相同,主要分为有机碳（OC）、元素碳（EC）、生物质燃烧颗粒（BB）、元素碳有机碳（ECOC）、钾二次颗粒（K-Secondary）、矿尘（Dust）以及重金属颗粒（HM）7类.C1时间段,ECOC颗粒占比最高,占总颗粒数的49.8%;其次是OC和EC颗粒物,二者分别占总颗粒数的16.5%和10.8%.H1时间段,K-Secondary颗粒的占比（31.3%）最高;其次是OC和EC颗粒,二者分别占总颗粒数的23.1%和20.2%.清洁期与灰霾期质谱差分结果表明,清洁期颗粒物中含有C₃H+、C₄H₃+、C₅H₃+等有机碳碎片峰,而灰霾期颗粒物中NO₃-、HSO₄-、NO₂-等组分的信号强度显著大于清洁期.混合状态分析表明,从清洁期到灰霾期的过程中,主要颗粒物与NO₃-和HSO₄-的混合程度显著增强.清洁期与灰霾期单颗粒化学组成与混合状态的对比分析表明,清洁期新鲜排放的含碳气溶胶在灰霾期不断老化,单颗粒中二次无机组分增加,气溶胶整体老化严重.此外,灰霾期（H2）EC颗粒占总颗粒数的比例增至18.1%,并且与NO₃-、HSO₄-二次组分的混合状态增强,使平均能见度降低为4.0 km.研究显示,郑州大气能见度主要受化学组分、颗粒物混合状态和污染物质量浓度的影响.      

Pollution characteristics and health risk assessment of polycyclic aromatic hydrocarbons and nitrated polycyclic aromatic hydrocarbons during heating season in Beijing

Polycyclic aromatic hydrocarbons(PAHs) and their nitrated derivatives(NPAHs) attract continuous attention due to their outstanding carcinogenicity and mutagenicity. In order to investigate the diurnal variations, sources, formation mechanism, and health risk assessment of them in heating season, particulate matter(PM) were collected in Beijing urban area from December 26, 2017 to January 17, 2018. PAHs and NPAHs in PM were quantitatively analyzed via gas chromatography-mass spectrometry(GC-MS). ...     

南京冬季气溶胶消光特性及霾天气低能见度特征

利用2015年1月气溶胶散射和吸收系数、PM_2.5质量浓度、大气能见度以及常规气象观测数据,分析了南京冬季大气气溶胶散射系数与吸收系数的变化特征,给出了散射系数与吸收系数对大气消光的贡献,以及能见度与PM_2.5质量浓度和相对湿度的关系.结果表明,观测期间南京大气气溶胶的散射系数和吸收系数分别为(423.4±265.3) Mm^-1和(24.5±14.3) Mm^-1,对大气消光的贡献分别为89.2%和5.2%,表明大气消光主要贡献来自于气溶胶的散射.散射系数与PM_2.5相关性较好(R²=0.91),能见度随PM_2.5质量浓度呈指数下降,也与相对湿度保持一定负相关性.能见度均值为4.3km,且连续出现能见度不足2km的低能见度天气,霾天气下消光系数和PM_2.5质量浓度大幅超过非霾天气,最高值分别达到1471.2Mm^-1和358 μg/m³,霾天气下能见度的降低来自颗粒物与相对湿度的共同影响.     

南京地区一次灰霾天气的微脉冲激光雷达观测分析

利用微脉冲激光雷达(MPL)对2012年10月南京地区的一次灰霾天气进行了不间断观测,结合地面气象要素和PM10、PM2.5质量浓度资料分析了此次污染过程颗粒物质量浓度、气象要素、气溶胶垂直方向光学特性和混合层高度(MLH)日变化趋势以及相关性并与11月11~12日非灰霾天气做了消光系数和MLH的比较.结果表明,本次灰霾天气颗粒物浓度与近地面消光系数日变化较相似,基本上呈现夜间高午后低的趋势;灰霾期间MLH峰值滞后于地面温度峰值2h,MLH与PM2.5呈现负相关关系,两者相关系数为-0.57;霾天MLH远低于非灰霾天;霾期间近地面消光系数大部分时刻大于1.0km-1,远大于非霾日0.1~0.25km-1范围的消光系数.     

基于地面微脉冲激光雷达的上海冬季霾强度及高度分析

利用2009—2013年冬季地面气象观测数据筛选出非霾和不同强度霾的影响时次,采用能见度与消光系数的定量关系和冬季波长系数对微霾冲激光雷达反演修正得到的气溶胶消光系数,分析了上海地区气溶胶在垂直高度上的集中范围,当地面出现轻微霾、轻度霾、中度霾、重度霾时气溶胶分别主要集中于近地面0.81、0.49、0.41、0.40 km以下,非霾时气溶胶主要集中在近地面1.35 km以下;在此基础上,根据判别不同强度霾的能见度标准和能见度与消光系数的定量关系,将能见度换算为消光系数,再对微脉冲激光雷达反演消光系数进行修正,从而判断高空霾的强度及所处的高度;另外还探讨了云对产生重度霾的影响、降水与中度霾和重度霾的关系以及颗粒物质量浓度与不同强度霾的关系,发现48.53%的重度霾是受云影响而产生的,37.11%中度霾发生前后伴有降水现象,51.14%的重度霾发生前后伴有降水现象,非霾、轻微霾,轻度霾、中度霾、重度霾期间的颗粒物浓度和细颗粒物占的比例依次增大.     

Particle number concentration, size distribution and chemical composition during haze and photochemical smog episodes in Shanghai

The aerosol number concentration and size distribution as well as size-resolved particle chemical composition were measured during haze and photochemical smog episodes in Shanghai in 2009. The number of haze days accounted for 43%, of which 30% was severe （visibility 〈 2 km） and moderate （2 km 〈 visibility 〈 3 km） haze, mainly distributed in winter and spring. The mean particle number concentration was about 17,000/cm3 in haze, more than 2 times that in clean days. The greatest increase of particle number concentration was in 0.5-1μm and 1-10 μm size fractions during haze events, about 17.78 times and 8.78 times those of clean days. The largest increase of particle number concentration was within 50-100 nm and 100-200 nm fractions during photochemical smog episodes, about 5.89 times and 4.29 times those of clean days. The particle volume concentration and surface concentration in haze, photochemical smog and clean days were 102, 49, 15 μm3/cm3 and 949, 649, 206 μm2/cm3, respectively. As haze events got more severe, the number concentration of particles smaller than 50 nm decreased, but the particles of 50-200 nm and 0.5-1μm increased. The diurnal variation of particle number concentration showed a bimodal pattern in haze days. All soluble ions were increased during haze events, of which NH4, SO24- and NO3 increased great/y, followed by Na＋, IC, Ca2＋ and CI-. These ions were very different in size-resolved particles during haze and photochemical smog episodes.     

干热河谷林地燥红土固碳特征及"新固定"碳表观稳定性

全球气候变化背景下,森林土壤固碳能力及所固定碳的稳定性受到极大关注.基于土壤密度分组和酸水解技术,对比研究了1991年营造的大叶相思(Acacia auriculiformis)林不同阶段(1991、1997、2003和2010年)土壤及其物理和生化组分中有机碳密度.结果表明,造林19 a后林地表层(0～15 cm)和亚表层(15～30 cm)土壤有机碳密度分别为1.40 kg.m-2和0.99kg.m-2.研究期内(1991～2010年)表层和亚表层土壤平均固碳速率分别为37.89 g.(m2.a)-1和16.84 g.(m2.a)-1,且土壤呈现加速固碳特征.2003年林地表层重组有机碳分配比例为71.44%,显著高于2010年(67.99%).2003年林地表层或亚表层轻组顽固性碳指数显著高于重组,但均随林龄的增加而降低,尤其是轻组顽固性碳指数.2003～2010年间燥红土"新固定"碳中57%～70%受物理保护,33%～49%为生化稳定性碳.研究揭示出干热河谷人工林燥红土具备较大的固碳能力.受物理保护碳的生化稳定性低于非保护碳,其稳定性均随林龄的增加而降低.     

北京市2014年10月重霾污染特征及有机碳来源解析

2014年10月北京市出现了多次重霾天气,与此同时,通过全国秸秆燃烧卫星遥感监测发现,北京周边河南、河北等地区恰存在一定规模的秸秆燃烧活动. 对2014年10月4—27日北京市大气PM_2.5中的水溶性离子、金属、OC(有机碳)、EC(元素碳)和有机物示踪物等化学成分进行了分析,对霾天和非霾天PM_2.5中化学成分进行了比较,并使用CMB(化学质量平衡)模型对PM_2.5中有机物的来源进行了解析,采用后向轨迹模拟和卫星遥感图像定量评估生物质燃烧(秸秆燃烧等)对重霾污染的影响. 结果表明:霾天ρ(PM_2.5)〔(229.0±96.3)μg/m3〕是非霾天的5.0倍,水溶性离子总质量浓度〔(125.3±59.3)μg/m3〕是非霾天的6.5倍,ρ(SO₄2-)、ρ(NO₃-)和ρ(NH₄+)分别是非霾天的6.1、8.6和7.1倍,ρ(OC)〔(81.8±39.5)μg/m3〕是非霾天的7.8倍,ρ(EC)〔(6.7±3.4)μg/m3〕是非霾天的4.2倍;霾天生物质燃烧的示踪物——左旋葡聚糖和K+的质量浓度平均值分别是非霾天的9.1和3.3倍. 生物质燃烧、机动车排放以及二次污染物对有机细颗粒物的贡献率分别为18.9%、36.9%和41.9%;二次细颗粒物质量浓度增加了1倍左右;气象条件同样在很大程度上促进了霾的形成. 常规的源解析方法仅可对生物质燃烧的一次污染贡献进行定量,但对重霾污染贡献的全面评价尚需进一步探讨.      

广州秋季灰霾污染过程大气颗粒物有机酸的污染特征

收集广州秋季一个灰霾过程大气颗粒物昼夜样品,进行了26种脂肪酸和8种二元羧酸的定量分析(GC/MS).结果表明,大气脂肪酸和二元羧酸的污染水平较高.灰霾与非灰霾期间脂肪酸和二元羧酸浓度之比分别为1.9和2.5.污染上升过程脂肪酸和二元羧酸晚上浓度(653 ng.m-3)高于白天浓度(487 ng.m-3),而在污染降低过程,白天脂肪酸和二元羧酸浓度(412 ng.m-3)要高于晚上浓度(336 ng.m-3).采样期间二元羧酸和脂肪酸日均值浓度总体上与颗粒物和碳质组分的变化趋势一致.脂肪酸和二元羧酸与有机碳比值大体上与颗粒物污染成反比,比值随着大气颗粒物的增加而降低,27号晚上之后,随着颗粒物的降低而开始增加,说明有机酸主要以直接排放为主,而灰霾对有机酸的富集有明显抑制作用.基于特征比值法(C3/C4)及相关性分析,表明秋季灰霾污染过程脂肪酸和二元羧酸都是以一次排放为主.