Size-resolved aerosol water-soluble ions at a regional background station of Beijing, Tianjin, and Hebei, North China

The characteristics of water-soluble ions in size-resolved particulate matter were investigated usingion chromatography at Shangdianzi,a regional background station of Beijing,Tianjin,and Hebei.Seasonal total concentrations of ions(Na~+,Mg~(2+),K~+,Ca~(2+),NH_4~+,Cl~-,SO_4~(2-) and NO_3~-) were75.5±52.9 μg/m~3 in spring,26.5±12.3μg/m~3 in summer,22.7±20.4μg/m~3 in autumn,and31.1±23.9 μg/m~3 in winter,respectively.The secondary ions(NO_3~-,SO_4~(2-) and NH_4~+),mainly associated with fine particles,accounted for 84.2%in spring,82.1%in summer,81.5%in autumn and 76.3%in winter of all ions.Strong correlations were found between NH_4~+ and SO_4~(2-)(r=0.95,p0.01) as well as NH_4~+ and NO_3~-(r=0.90,p0.01) in fine particles;while in coarse particles,correlations between Mg~(2+) and NO_3~-(r=0.80,p0.01),and Ca~(2+) and NO_3~-(r=0.85,p0.01) were found.The concentrations of Na~+,K~+,Mg~(2+),Ca~(2+),NH_4~+,Cl~-,NO_3~-,and SO_4~(2-) were 2.02,0.81,0.36,1.65,9.58,4.01,18.9,and 18.4 μg/m~3 in particulate matter from southeast-derived air masses,which were typically 1.58-3.37 times higher than in northwest trajectories.Thus,concentrations of water-soluble ions at this background station were heavily influenced by regional transport of serious pollution derived from biomass burning,coal combustion,industrial and vehicle exhaust emissions from Beijing,Tianjin,and Hebei.     

Characteristics of the water-soluble components of aerosol particles in Hefei, China

Size-classified daily aerosol mass concentrations and concentrations of water-soluble inorganic ions were measured in Hefei,China,in four representative months between September 2012 and August 2013.An annual average mass concentration of 169.09μg/m~3 for total suspended particulate(TSP)was measured using an Andersen Mark-II cascade impactor.The seasonal average mass concentration was highest in winter(234.73μg/m~3)and lowest in summer(91.71μg/m~3).Water-soluble ions accounted for 59.49%,32.90%,48.62%and 37.08%of the aerosol mass concentration in winter,spring,summer,and fall,respectively,which indicated that ionic species were the primary constituents of the atmospheric aerosols.The four most abundant ions were NO_3~-,SO_4~(2-),Ca~(2+) and NH_4~+.With the exception of Ca~(2+),the mass concentrations of water-soluble ions were in an intermediate range compared with the levels for other Chinese cities.Sulfate,nitrate,and ammonium were the dominant fine-particle species,which were bimodally distributed in spring,summer and fall;however,the size distribution became unimodal in winter,with a peak at 1.1–2.1μm.The Ca~(2+) peak occurred at approximately 4.7–5.8μm in all seasons.The cation to anion ratio was close to 1.4,which suggested that the aerosol particles were alkalescent in Hefei.The average NO_3~-/SO_4~(2-)mass ratio was 1.10 in Hefei,which indicated that mobile source emissions were predominant.Significant positive correlation coefficients between the concentrations of NH_4~+ and SO_4~(2-),NH_4~+ and NO_3~-,SO_4~(2-)and NO_3~-,and Mg~(2+) and Ca~(2+) were also indicated,suggesting that aerosol particles may be present as(NH_4)_2SO_4,NH_4HSO_4,and NH_4NO_3.     

华南地区大气气溶胶中EC和水溶性离子粒径分布特征

利用1988~2010年在华南地区广州、深圳、海口等多地采得的126组样品,初步分析了华南地区不同时段不同地区和水溶性离子成分的浓度变化及其粒径分布特征.结果表明:各站的AEC(等效元素碳)浓度和水溶性无机离子浓度差异较大,Na+和Cl-基本表现为海岛站点>海岸站点>乡村站点>城市站点,其余主要离子成分和AEC则表现为城市站点>乡村站点>海岸站点>海岛.城市站点、乡村站点、海岸站点和海岛站点AEC质量浓度在不同年段随粒径分布的变化趋势比较一致的,基本呈双峰结构,主峰主要位于0.43~0.65mm,次峰主要位于4.7~5.8mm.根据各离子的粒径分布的相似性可以将各种离子的垂直分布形态分为3类:二次离子(SO42-、NO3-和NH4+)呈现明显的三峰分布形态;F-、Ca2+、Mg2+、Na+和Cl-呈双峰分布形态;K+和AEC呈单峰分布形态,主峰位于细粒子模态.各成分浓度随高度的变化则呈现不同的变化规律.降水对气溶胶粒子的清除作用是显著的,尤其是粒径大于1μm的颗粒,而1.1~2.1μm的粒子段是降水清除的关键区.局地污染中,AEC质量浓度随粒径的分布呈现出了很明显的“单峰”结构,且主要集中在次微米段粒径范围内.     

民用煤排放PM2.5中碳组分与水溶性离子特征

研究4种典型民用煤燃烧排放PM_2.5中的碳组分以及水溶性离子含量特点,并通过PAM-OFR(潜在气溶胶质量-氧化流动反应器)模拟了大气老化过程(2d)对煤球与烟煤燃烧PM_2.5中碳组分与水溶性离子含量的变化影响。结果表明,烟煤燃放PM_2.5中碳组分含量最高,达到57.96%,其EC含量是其他煤种的4.3~9.6倍。民用煤燃烧产生PM_2.5中水溶性离子以Na⁺与SO₄^2-为主,其在总水溶性离子中占比合计约47%~76%。经历了大气老化试验后,煤球与烟煤燃烧排放PM_2.5中NH₄⁺和NO₃^-离子含量大幅增加,与之相比,TC占PM_2.5比例分别下降了12.03%与19.99%。     

Insights into measurements of water-soluble ions in PM2.5 and their gaseous precursors in Beijing

To better understand the characteristics and transformation mechanisms of secondary inorganic aerosols, hourly mass concentrations of water-soluble inorganic ions (WSIIs) in PM_2.5 and their gaseous precursors were measured online from 2016 to 2018 at an urban site in Beijing. Seasonal and diurnal variations in water-soluble ions and gaseous precursors were discussed and their gas-particle conversion and partitioning were also examined, some related parameters were characterized. The (TNH₃) _Rich was also defined to describe the variations of the excess NH₃ in different seasons. In addition, a sensitivity test was carried out by using ISORROPIA II to outline the driving factors of gas-particle partitioning. In Beijing, the relative contribution of nitrate to PM_2.5 has increased markedly in recent years, especially under polluted conditions. In the four seasons, only a small portion of NO₂ in the atmosphere was converted into total nitrate (TNO₃)_, and more than 80% of TNO₃ occurred in the form of nitrate due to the abundant ammonia. The concentration of total ammonia (TNH₃) was much higher than that required to neutralize acid gases, and most of the TNH₃ occurred as gaseous NH₃. The nitrous acid (HONO) concentration was highly correlated with NH₃ concentration and had increased significantly in Beijing compared with previous studies. The total chloride (TCl) was the highest in winter, and ε(Cl^?) was more sensitive to variations in the ambient temperature (T) and relative humidity (RH) than ε(NO₃^?).     

Pollutants identification of ambient aerosols by two types of aerosol mass spectrometers over southeast coastal area, China

Two different aerosol mass spectrometers, Aerodyne Aerosol Mass Spectrometer(AMS) and Single Particle Aerosol Mass Spectrometer(SPAMS) were deployed to identify the aerosol pollutants over Xiamen, representing the coastal urban area. Five obvious processes were classified during the whole observation period. Organics and sulfate were the dominant components in ambient aerosols over Xiamen. Most of the particles were in the size range of 0.2–1.0 μm, accounting for over 97% of the total particles measured by both instruments.Organics, as well as sulfate, measured by AMS were in good correlation with measured by SPAMS. However, high concentration of NH4+was obtained by AMS, while extremely low value of NH4+was detected by SPAMS. Contrarily, high particle number counts of NO3-and Clwere given by SPAMS while low concentrations of NO3-and Cl-were measured by AMS. The variations of POA and SOA obtained from SPAMS during event 1 and event 2 were in accordance with the analysis of HOA and OOA given by AMS, suggesting that both of AMS and SPAMS can well identify the organic clusters of aerosol particles. Overestimate or underestimate of the aerosol sources and acidity would be present in some circumstances when the measurement results were used to analyze the aerosol properties, because of the detection loss of some species for both instruments.     

Characteristics of mass distributions of aerosol particle and its inorganic water-soluble ions in summer over a suburb farmland in Beijing

Agricultural activity is one of the most important sources of aerosol particles. To understand the mass distribution and sources of aerosol particles and their inorganic water-soluble ions in a suburb farmland of Beijing, particle samples were collected using a microorifice uniform deposit impactor (MOUDI) in the summer of 2004 in a suburb vegetable field. The distribution of the particles and their inorganic water-soluble ions in the diameter range of 0.18–18 μm were measured. The dominant fine particle ions were SO₄ ²⁻, NO₃ ⁻, and NH₄ ⁺. The association of day-to-day variation of the concentration of these ions with temperature, humidity, and solar radiation suggested that they are formed by the reaction of NH₃ released from the vegetable field with the acid species produced from photochemical reactions. Fine particle K⁺ is likely from vegetation emission and biomass burning. Coarse particles like Ca²⁺, Mg²⁺, NO₃ ⁻, and SO₄ ²⁻ are suggested to come from the mechanical process by which the soil particle entered the atmosphere, and from the reaction of the acid species at the surface of the soil particle. The results show that fertilizer and soil are important factors determining the aerosol particle over agricultural fields, and vegetable fields in suburban Beijing contribute significantly to the aerosol particle. Translated from Environmental Science, 2006, 27(2): 193–199 [译自: 环境科学]     

北京城区大气干沉降的水溶性离子特征

为了解北京城区大气干沉降中水溶性离子的化学组成与时间变化特征,连续进行了4年多的干沉降采样与分析.结果表明,在222个有效干沉降样品中,存在不同程度的阴离子缺失. SO42-与Ca2+分别是含量最丰富的阴、阳离子组分,其次是NO3-和NH4+. SO42-、NO3-和NH4+呈现相似的季节变化特征,即其浓度在夏季最高,冬季最低. 干沉降基本呈中性,其pH值月变化幅度小,但季节变化明显,夏季低而春季高.     

青岛大气气溶胶水溶性无机离子的粒径分布特征

为了解大气颗粒物中水溶性离子的来源及环境效应,利用安德森采样器连续采集青岛近海2008年1~12月大气颗粒物分级样品,用离子色谱法分析其中主要的水溶性离子,并讨论其粒径分布特征.结果表明, NH4+、K+、Cl-、NO3-、PO43-、SO42-主要存在于粒径小于2.1μm的细粒子中,Na+、Mg2+、Ca2+、F-则主要存在于粒径大于2.1μm的粗粒子中.各离子的粒径分布存在明显的季节变化.NH4+、K+和SO42-四季均主要分布于细粒子中,而Mg2+和Ca2+则主要分布在粗粒子中,两者均在3.3~4.7μm出现峰值;Na+在春、夏、秋3个季节主要存在于粗粒子中,集中分布在3.3~7.0μm粒径范围内,而在冬季则集中分布于0.43~1.1μm且细粒子含量高于粗粒子;春季Cl-在粗粒子中分布较多,尤以2.1~3.3μm范围内的最为突出,而其他3个季节均是细粒子比例明显偏高;NO3-春、夏两季在粗、细粒子中的含量各占50%,秋、冬季节均为细粒子占多数;PO43-夏季只出现在0.65~1.1μm以及>11μm的粒径范围内,粗粒子占95%,其他3个季节则是细粒子含量较高;春季F-在3.3~4.7μm出现峰值,夏季各粒径均未检出,而秋、冬两季粗、细粒子各占50%.K+、NH4+、F-、Cl-、NO3-、SO42-和PO43-受供暖期燃煤取暖的影响较大.K+和NH4+在供暖期和非供暖期峰值均出现在0.43~0.65μm粒径范围;F-供暖期在0.43~0.65μm和3.3~4.7μm粒径段出现峰值;供暖期Cl-的峰值出现在0.43~0.65μm粒径段,而在非供暖期,则出现在2.1~3.3μm的粗粒径段;SO42-和NO3-在供暖期和非供暖期的峰值均出现在0.43~0.65μm和3.3~4.7μm粒径段;供暖期PO43-的最大峰值出现在0.43~0.65μm粒径段,而在非供暖期其最大峰值出现在3.3~4.7μm粒径段.     

Chemical characteristics and sources of water-soluble organic aerosol in southwest suburb of Beijing

PM_2.5 filter sampling and components measurement were conducted in autumn and winter from 2014 to 2015 at a suburban site(referred herein as "LLH site") located in the southwest of Beijing.The offline aerosol mass spectrometry(offline-AMS) analysis and positive matrix factorization(PMF) were applied for measurement and source apportionment of watersoluble organic aerosol(WSOA).Organic aerosol(OA) always dominated PM_2.5 during the sampling period,especially in winter.WSOA po...     

济南市秋季大气颗粒物中水溶性离子的粒径分布研究

为了解济南市大气颗粒物的粒径分布特征,于2009年10月利用多级撞击式颗粒物采样器(MOUDI)进行了大气颗粒物采集,采用离子色谱仪分析了其中水溶性离子浓度.结果表明,SO42-、NO3-、NH4+和Ca2+是主要的水溶性离子,浓度总和约占总水溶性离子浓度的92%.SO42-、NO3-、NH4+、K+和Cl-浓度随时间变化较为显著,浓度变化主要原因是受风速以及气流来源方向的影响.SO42-和NH4+主要集中在细粒子中,其浓度呈单模态分布,随着颗粒物中含量的升高其峰值从0.32~0.56 μm粒径段逐渐移动到1~1.8 μm粒径段.NO3-浓度呈双峰分布,细粒子中的NO3-随着浓度的升高峰值从0.56~1μm粒径段移动到1~1.8μm粒径段,粗粒子中的峰值出现在3.2~5.6μm粒径段. NH4+可以完全中和细粒子中的SO42-和NO3-,在细粒子中主要以(NH4)2SO4和NH4NO3的形式存在.     

Size distributions of aerosol and water-soluble ions in Nanjing during a crop residual burning event

To investigate the impact on urban air pollution by crop residual burning outside Nanjing, aerosol concentration, pollution gas concentration, mass concentration, and water-soluble ion size distribution were observed during one event of November 4-9, 2010. Results show that the size distribution of aerosol concentration is bimodal on pollution days and normal days, with peak values at 60-70 and 200-300 nm, respectively. Aerosol concentration is 10⁴ cm^-3. nm^-1 on pollution days. The peak value of spectrum distribution of aerosol concentration on pollution days is 1.5-3.3 times higher than that on a normal day. Crop residual burning has a great impact on the concentration of fine particles. Diurnal variation of aerosol concentration is trimodal on pollution days and normal days, with peak values at 03:00, 09:00 and 19:00 local standard time. The first peak is impacted by meteorological elements, while the second and third peaks are due to human activities, such as rush hour traffic. Crop residual burning has the greatest impact on SO₂ concentration, followed by NO₂, O₃ is hardly affected. The impact of crop residual burning on fine particles (< 2.1 μm) is larger than on coarse particles (> 2.1 μm), thus ion concentration in fine particles is higher than that in coarse particles. Crop residual burning leads to similar increase in all ion components, thus it has a small impact on the water-soluble ions order. Crop residual burning has a strong impact on the size distribution of K⁺, Cl^-, Na⁺, and F^- and has a weak impact on the size distributions of NH₄⁺, Ca²⁺, NO₃^- and SO₄^2-.     

哈尔滨道路附近大气可吸入颗粒物浓度及其成份分析

采集了2005年8月具有代表性的道路附近空气中可吸入颗粒物(PM10),分析了PM10中的离子、重金属及碳成分含量。结果表明,哈尔滨市道路附近PM10离子组分中SO42-、NH4+、Ca2+浓度较高,其主要来源于交通尘污染;富集因子法表明元素Cr、Zn和Pb来源于人为污染;EC/TC大于0.36,主要来自于汽车尾气等一次污染源的排放。     

秋季南通近海大气气溶胶水溶性离子粒径分布特征

2012年10~11月在南通近海设立观测点,利用Anderson分级采样器采集大气气溶胶样品,用离子色谱仪(Metrohm IC)分析其中10种水溶性离子组成.结果表明,南通秋季近海PM10和PM2.1中水溶性离子浓度分别为59.70,45.96mg/m3.PM2.1中主要离子质量浓度排列依次为SO42->NO3->NH4+>Ca2+. SO42-,NO3-和NH4+占PM10中离子浓度的80%以上,二次离子为近海区域气溶胶的主要成分.SO42,NH4+和NO3-均表现出单峰型分布,峰值区间均为0.43~1.1mm,Ca2+,Na+和Cl-表现为双峰型.Ca2+高浓度峰值出现4.7~5.8mm粒径段内;Na+和Cl-峰值出现在0.43~1.1mm和3.3~5.8mm内,但最大峰值浓度区间不一致.PM10中nss-SO42-/SO42-比值均高于90%,陆地源对近海硫酸盐的影响显著.nss-SO42-/NO3-的比值在<2.1μm的粒径段内均大于1,表明该区域固定源是大气细粒子中离子的重要贡献源,但移动源对粗粒子的影响值得重视.个例分析显示,稳定的天气系统,高污染排放内陆地区的污染物传输,是造成10月27日的严重污染过程的主要原因.     

Seasonal variations and size distributions of water-soluble ions in atmospheric aerosols in Beijing, 2012

The characteristics of water-soluble ions in airborne particulate matter in Beijing were investigated using ion chromatography. The results showed that the total concentrations of ions were 83.7 ± 48.9 μg/m³ in spring, 54.0 ± 17.0 μg/m³ in summer, 54.1 ± 42.9 μg/m³ in autumn, and 88.8 ± 47.7 μg/m³ in winter, respectively. Furthermore, out of all the ions, NO₃⁻, SO₄^2 − and NH₄⁺ accounted for 81.2% in spring, 78.5% in summer, 74.6% in autumn, and 76.3% in winter. Mg^2 + and Ca^2 + were mainly associated with coarse particles, with a peak that ranged from 5.8 to 9.0 μm. Na⁺, NH₄⁺ and Cl⁻ had a multi-mode distribution with peaks that ranged from 0.43 to 1.1 μm and 4.7 to 9.0 μm. K⁺, NO₃⁻, and SO₄^2 − were mainly associated with fine particles, with a peak that ranged from 0.65 to 2.1 μm. The concentrations of Na⁺, K⁺, Mg^2 +, Ca^2 +, NH₄⁺, Cl⁻, NO₃⁻ and SO₄^2 − were 2.69, 2.32, 1.01, 4.84, 16.9, 11.8, 42.0, and 44.1 μg/m³ in particulate matter (PM) on foggy days, respectively, which were 1.4 to 7.3 times higher than those on clear days. The concentrations of these ions were 2.40, 1.66, 0.92, 4.95, 17.5, 7.00, 32.6, and 34.7 μg/m³ in PM on hazy days, respectively, which were 1.2–5.7 times higher than those on clear days.     

武汉市大气PM2.5中水溶性离子污染特征及来源

于2016年8月—2017年4月采集了武汉市PM2.5样品,使用离子色谱法分析了PM2.5中的水溶性离子(F-、Cl-、SO2-4、NO-3、Na+、NH+4、K+、Mg2+、Ca2+),并研究其污染特征及来源.结果表明,武汉市PM2.5质量浓度变化范围为24.8～215.7μg·m-3,均值为(81.3±38.1)μg·m-3.9种水溶性离子的年均质量浓度占PM2.5质量浓度的29.3%,其中,SO2-4、NO-3、NH+4(三者合称SNA)为主要的水溶性离子,SNA占PM2.5质量浓度的23.3%～32.0%.硫氧化率(SOR)和氮氧化率(NOR)年均值分别为0.4、0.1,说明武汉市大气存在较强的SO2向SO2-4、NO2向NO-3转化的二次过程.观测期间,武汉市的细颗粒物整体呈弱碱性.Ca2+与Mg2+,以及NH+4与NO-3、SO2-4等均有显著相关性,NH+4、NO-3、SO2-4主要以(NH4)2SO4和NH4NO3的形式存在.武汉市全年NO-3/SO2-4比值为0.9,表明固定源贡献相对较大.主成分分析结果表明,武汉市大气PM2.5中水溶性离子主要来自于燃煤及机动车排放、工业生产、扬尘等.     

大气气溶胶碳质组分在线分析仪的研制和应用

大气气溶胶碳质组分主要包括有机碳(Organic Carbon,OC)和元素碳(Elemental Carbon,EC),是大气细粒子的重要组成部分,对大气环境及人体健康具有非常重要的意义.针对目前商品化碳质气溶胶在线分析仪存在的一些问题,研制出大气气溶胶碳质组分在线分析仪(PKUOCEC),实现了对OC和EC的小时浓度测量.仪器同时采用热分解-光学透射(Thermo Optical Transmission,TOT)法和热分解-光学反射(Thermo Optical Reflection,TOR)法分离OC和EC,检测限为0.29μg·m-3(以C计)(采样时间40 min,采样流量8 L·min-1),测量范围最大值为211.50μg·m-3(以C计),可以满足不同环境的大气观测要求.于2016年1月23—31日采用该仪器对北京怀柔大气进行监测,并与商品化在线碳质气溶胶分析仪(RT-4 OCEC,Sunset Lab Inc.)和多角度吸收光度计(5012 MAAP,Thermo Scientific)进行比对.结果显示,PKU-OCEC测得的TC(Total Carbon,TC=OC+EC)和OC浓度均与Sunset-OCEC对应结果显著相关(TC:r=0.986,OC:r=0.984;p0.01),说明两台仪器测量结果具有很好的一致性;Sunset-OCEC测得的EC数据有39.39%低于0.013μg·m-3(以C计),剔除该部分异常值后,其测得的EC数据与PKU-OCEC数据的线性拟合方程由CEC_Sunset=0.9278×CEC_PKU!0.0704(TOT法)和CEC_Sunset=0.9476×CEC_PKU!0.2665(TOR法)变为CE C_Sunset=0.6810×CEC_PKU+1.2842(TOT法)和CEC_Sunset=0.7035×CEC_PKU+1.1179(TOR法),新的方程产生较大正截距,说明Sunset-OCEC的检测限偏高;PKUOCEC测得的EC数据与MAAP测得的BC数据显著相关,其线性拟合度(R2=0.8868(TOT法)、R2=0.8614(TOR法))大于Sunset-OCEC与MAAP的拟合度(R2=0.8047);PKU-OCEC分析仪TOT法和TOR法测得的OC浓度相当(COC_TOR=0.9963×COC_TOT,R2=0.9959).综合结果表明,PKU-OCEC分析仪测量数据可靠,运行稳定且操作简便,可以用于各种环境条件下的大气监测.     

北京市延庆区PM2.5中主要水溶性无机离子特征及来源解析

对2017年6月—2018年5月北京市延庆区大气PM2.5样本进行采集,分析了PM2.5中9种水溶性无机离子的污染特征,并利用SPSS软件进行来源解析。结果表明:延庆区大气PM2.5中总水溶性无机离子平均浓度为28.0 μg∕m 3,其中,S O 4 2 - 、N O 3 - 和N H 4 + 是最主要的水溶性无机离子,合计占比为82.1%。受天气影响,N O 3 - 和S O 4 2 - 浓度均表现为秋高冬低,N H 4 + 浓度为秋高夏低;受冬季气象条件和施工影响,Ca 2+、Mg 2+、Na +浓度冬季最高。根据电荷平衡分析,春季PM2.5中阴、阳离子基本达到平衡状态,夏、秋季呈弱酸性,冬季呈弱碱性;PM2.5中硫氧化率(SOR)、氮氧化率(NOR)的均值分别为0.53和0.27,大气中存在明显的二次转化过程;N O 3 - ∕S O 4 2 - 为1.66,说明机动车尾气排放源对PM2.5中水溶性无机离子贡献较大;根据N H 4 + 与S O 4 2 - 、N O 3 - 、Cl -的相关性分析,PM2.5中N O 3 - 和S O 4 2 - 以(NH4)2SO4、NH4HSO4、NH4NO3以及HNO3形式存在。利用SPSS软件进行皮尔森相关性分析,PM2.5中N O 3 - 、S O 4 2 - 、N H 4 + 两两相关性强,说明二次反应显著;Ca 2+、Mg 2+、Na + 两两相关性强,说明其污染来源可能相同;Cl -与K +相关性强,说明大气中Cl -主要以KCl的形式存在。利用因子分析模块进行主成分分析,发现延庆区主要污染源为生物质燃烧、扬尘污染和机动车尾气排放。     

Analysis of the origin of peak aerosol optical depth in springtime over the Gulf of Tonkin

By aggregating MODIS(moderate-resolution imaging spectroradiometer) AOD(aerosol optical depth) and OMI(ozone monitoring instrument) UVAI(ultra violet aerosol index)datasets over 2010–2014, it was found that peak aerosol loading in seasonal variation occurred annually in spring over the Gulf of Tonkin(17–23°N, 105–110°E). The vertical structure of the aerosol extinction coefficient retrieved from the spaceborne lidar CALIOP(cloud-aerosol lidar with orthogonal polarization) showed that the springtime peak AOD could be attributed to an abrupt increase in aerosol loading between altitudes of 2 and 5 km.In contrast, aerosol loading in the low atmosphere(below 1 km) was only half of that in winter. Wind fields in the low and high atmosphere exhibited opposite transportation patterns in spring over the Gulf of Tonkin, implying different sources for each level. By comparing the emission inventory of anthropogenic sources with biomass burning, and analyzing the seasonal variation of the vertical structure of aerosols over the Northern Indo-China Peninsula(NIC), it was concluded that biomass burning emissions contributed to high aerosol loading in spring. The relatively high topography and the high surface temperature in spring made planetary boundary layer height greater than 3 km over NIC. In addition, small-scale cumulus convection frequently occurred, facilitating pollutant rising to over 3 km, which was a height favoring long-range transport. Thus, pollutants emitted from biomass burning over NIC in spring were raised to the high atmosphere, then experienced long-range transport, leading to the increase in aerosol loading at high altitudes over the Gulf of Tonkin during spring.     

利用气体-气溶胶在线测量技术研究乌鲁木齐颗粒物水溶性组分与气体污染

将气体-气溶胶收集装置与离子色谱联用技术（GAC）应用于冬季重污染地区乌鲁木齐,对当地大气中痕量气体与气溶胶中的水溶性组分进行了为期2周的在线测量,并结合膜采样结果、PM10质量浓度及气溶胶消光系数等数据初步分析了污染物的变化规律与重污染成因.结果表明,GAC测得的氯盐、硝酸盐、硫酸盐与膜采样方法测得的相应组分数值显著正相关,相关系数分别为0.92(p<0.0001)、0.89(p<0.0001)、090 (p<0.0001).乌鲁木齐大气污染极其严重,氯盐、硫酸盐和二氧化硫浓度都非常高,这在其他地区较为罕见;二氧化硫、氯盐、硝酸盐与硫酸盐分别呈现不同的日变化规律;整个采样期间出现了1次极端污染天气,API值达到500,该日硫转化率（SOR）和氮转化率（NOR）的小时平均值最高达到0.69与0.36,说明二次转化也可能是形成重污染天气的主要原因.高浓度的PM10对能见度影响极大,PM2.5中的氯盐与气溶胶消光系数的相关系数最大,硫酸盐与硝酸盐次之,而硫酸盐、硝酸盐、氯盐这3种盐类对PM10的贡献依次递减.