Photochemical evolution of submicron aerosol chemical composition in the Tokyo megacity region in summer
Photochemical evolution of submicron aerosol chemical composition in the Tokyo megacity region in summer
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DOI：
10.1029/2007jd009493
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发表时间：
2008-07
影响因子：
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通讯作者：
T. Miyakawa;N. Takegawa;Y. Kondo
中科院分区：
文献类型：
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作者：
T. Miyakawa;N. Takegawa;Y. Kondo
[1]我们研究了东京大城市地区夏季亚微米气溶胶的化学转化。2004年夏季，在东京市区(35°39‘N，139°40’E)和崎玉(36°05‘N，139°33’E)郊区(顺风站点)安装了一台Aerodyne四极气溶胶质谱仪(AMS)。利用烷基硝酸盐与碳氢化合物比值和NOZ/NOY比值(NOZ定义为不包括氮氧化物(NOx)的总活性氮氧化物(NOY))，研究了光化学烟雾过程中亚微米级(PM1)气溶胶化学组成随时间的演化。在大多数老化空气中，在下风处观测到的光化学年龄约为12h。有机气溶胶(OA)和硫酸盐(SO42-−)是观测期间两个采样点PM1气溶胶的主要成分(分别为40-50%和20-30%)，其组分随NOZ/NOY比值变化不大。随着NOZ/NOY比的增加，OA和SO42-−与炭黑(BC)的质量比显著增加(分别为∼-3和∼-2的1倍)，表明这些化合物的二次生成对控制PM1质量浓度具有重要意义。我们还研究了AMS观测到的OA质谱线的光化学演化。有机化合物相对于BC质量的质荷比(m/z)峰一般随着NOZ/NOY比的增大而增大。对于不同的m/z峰，这些增加的趋势明显不同，这表明有机官能团的时间演化的复杂性。M/z 44和45峰是有机颗粒中羧基的良好标志，它们的增加幅度大于其他m/z峰，这表明在测量期间，羧基在几个小时的时间尺度上有效地形成。
[1] We investigate the chemical transformation of submicron aerosol in the Tokyo megacity region in summer. An Aerodyne quadrupole aerosol mass spectrometer (AMS) was deployed both at an urban site in Tokyo (35°39′N, 139°40′E) and a suburban site (downwind site) in Saitama (36°05′N, 139°33′E) in the summer of 2004. The temporal evolution of size-resolved chemical compositions of submicron (PM1) aerosols during photochemical smog episodes are investigated using the photochemical age derived from the combination of alkyl nitrate-to-hydrocarbon ratio and NOz/NOy ratio (where NOz is defined as the total reactive nitrogen oxides (NOy) excluding nitrogen oxides (NOx)). The photochemical age observed at the downwind site was about 12 h in most aged air. Organic aerosols (OA) and sulfate (SO42−) were major constituents of PM1 aerosols (40–50% and 20–30%, respectively) at both sites during the observation period and their fractions showed no large variation with the NOz/NOy ratio. Mass ratios of OA and SO42− to black carbon (BC) largely increased with the NOz/NOy ratio (by factors of ∼3 and ∼2, respectively), indicating the significance of secondary formation of these compounds in controlling PM1 mass concentrations. We also investigate the photochemical evolution of OA mass spectra observed by the AMS. The mass-to-charge ratio (m/z) peaks of organic compounds relative to BC mass generally showed an increase with the NOz/NOy ratio. These increasing trends vary significantly for different m/z peaks, suggesting the complexity of the temporal evolution of organic functional groups. The m/z 44 and 45 peaks, which are good markers of carboxylic groups in organic particles, showed larger increases than any other m/z peaks, suggesting an efficient formation of carboxylic functional groups on a timescale of hours during the measurement period.