Carboxylic acids, sulfates, and organosulfates in processed continental organic aerosol over the southeast Pacific Ocean during VOCALS-REx 2008
Carboxylic acids, sulfates, and organosulfates in processed continental organic aerosol over the southeast Pacific Ocean during VOCALS-REx 2008
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DOI：
10.1029/2009jd013276
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发表时间：
2010-07-02
影响因子：
4.4
通讯作者：
Bates, T. S.
中科院分区：
文献类型：
--
作者：
Hawkins, L. N.;Russell, L. M.;Bates, T. S.
在NOAA R/V罗纳德H号上收集了亚微米颗粒。2008年10月和11月在东南太平洋海洋边界层进行的VAMOS海洋-云-大气-陆地研究区域实验（VOCALS-REx）期间。该区域气溶胶的特点是颗粒数少（150-700 cm-3），主要是硫酸根离子，浓度为0.9 +/- 0.7 μ g m-3，有机物质量为0.6 +/- 0.4 μ g m-3，没有可测量的硝酸根离子和低铵离子浓度。亚微米有机气溶胶功能群和微量元素的测量表明，大陆流出的人为排放是东南太平洋的有机质量（OM）的主要来源，额外的，较小的贡献，有机质量的主要海洋来源。这一大陆来源得到了OM和氡之间相关性的支持。饱和脂肪族C-CH（烷烃）占OM的41 +/- 27%。在与酮羰基、碳酸盐和钾内部混合的单个颗粒中观察到羧酸COOH（OM的32 +/- 23%）。仅在最高有机物和硫酸盐浓度以及最低铵浓度期间观察到有机硫酸盐COSO 3（OM的4 +/- 8%），这与拟定替代化合物的硫酸环氧化物水解一致（e.例如，在一个实施例中，异戊二烯氧化产物）或来自实验室研究的反应性乙二醛摄取机制。这种相关性表明，在高硫酸盐，低铵的条件下，在大气中形成的有机硫酸盐化合物有助于气溶胶OM的显着部分（大陆气团高达13%）。有机羟基C-OH组成20 +/- 12%的OM和高达50%的远程海洋OM和氡呈负相关，表明海洋来源。正矩阵因子分解（PMF）分析的双因子解导致一个因子由有机羟基（> 70质量%）主导，另一个因子由饱和脂肪族C-CH（烷烃）和羧酸（一起，90质量%）主导，分别被确定为海洋因子和燃烧因子。与MODIS气溶胶光学厚度估算的浓度相比，研究区域的颗粒浓度测量结果表明，大陆外流导致MBL颗粒浓度升高到背景水平（小于300 cm（-3））的2倍，远离海岸和高达10倍的背景水平在海岸。沿海化石燃料燃烧和海洋来源的含氧有机气溶胶的存在下，在含氧分数和氧碳比（O/C）沿着该地区的主要有机颗粒源的流出的变化不大。
Submicron particles were collected on board the NOAA R/V Ronald H. Brown during the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment (VOCALS-REx) in the southeast Pacific marine boundary layer in October and November 2008. The aerosol in this region was characterized by low numbers of particles (150-700 cm(-3)) that were dominated by sulfate ions at concentrations of 0.9 +/- 0.7 mu g m(-3) and organic mass at 0.6 +/- 0.4 mu g m(-3), with no measurable nitrate and low ammonium ion concentrations. Measurements of submicron organic aerosol functional groups and trace elements show that continental outflow of anthropogenic emissions is the dominant source of organic mass (OM) to the southeast Pacific with an additional, smaller contribution of organic mass from primary marine sources. This continental source is supported by a correlation between OM and radon. Saturated aliphatic C-CH (alkane) composed 41 +/- 27% of OM. Carboxylic acid COOH (32 +/- 23% of OM) was observed in single particles internally mixed with ketonic carbonyl, carbonate, and potassium. Organosulfate COSO3 (4 +/- 8% of OM) was observed only during the periods of highest organic and sulfate concentrations and lowest ammonium concentrations, consistent with a sulfuric acid epoxide hydrolysis for proposed surrogate compounds (e. g., isoprene oxidation products) or reactive glyoxal uptake mechanisms from laboratory studies. This correlation suggests that in high-sulfate, low-ammonium conditions, the formation of organosulfate compounds in the atmosphere contributes a significant fraction of aerosol OM (up to 13% in continental air masses). Organic hydroxyl C-OH composed 20 +/- 12% of OM and up to 50% of remote marine OM and was inversely correlated with radon indicating a marine source. A two-factor solution of positive matrix factorization (PMF) analysis resulted in one factor dominated by organic hydroxyl (>70% by mass) and one factor dominated by saturated aliphatic C-CH (alkane) and carboxylic acid (together, 90% by mass), identified as the marine and combustion factors, respectively. Measurements of particle concentrations in the study region compared with concentrations estimated from MODIS aerosol optical depth indicate that continental outflow results in MBL particle concentrations elevated up to 2 times the background level (less than 300 cm(-3)) away from shore and up to 10 times the background level at the coast. The presence of both coastal fossil fuel combustion and marine sources of oxygenated organic aerosol results in little change in the oxygenated fraction and oxygen to carbon ratio (O/C) along the outflow of the region's dominant organic particle source.