A portable, four-wavelength, single-cell photoacoustic spectrometer for ambient aerosol absorption
A portable, four-wavelength, single-cell photoacoustic spectrometer for ambient aerosol absorption
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DOI：
10.1080/02786826.2017.1413231
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发表时间：
2018-01-01
影响因子：
5.2
通讯作者：
Smith, Geoffrey D.
中科院分区：
文献类型：
--
作者：
Al Fischer, D.;Smith, Geoffrey D.
气溶胶通过散射和吸收太阳辐射直接影响地球气候。虽然它们在地球大气中无处不在，但直接、原位、波长分辨的气溶胶光学特性测量仍然具有挑战性。因此，所谓的气溶胶直接效应是预测地球未来气候的最大不确定性之一，需要新的仪器来测量大气颗粒对阳光的吸收。我们已经开发了一种便携式，四波长，单池光声光谱仪，用于同时测量气溶胶在406，532，662和785 nm的吸收，通过一个内置的腔衰荡光谱仪在662 nm的额外消光测量。该仪器被称为MultiPAS-IV，结构紧凑，坚固耐用，功率要求低，并利用多通光学装置实现典型的检测限为0.6-0.7Mm（-1）的吸收（2 sigma，2分钟平均值）。用苯胺黑气溶胶进行的试验表明，与米氏理论计算的一致性在2%以内，与7波长的大气蒸发仪进行的比较表明，环境气溶胶（美国佐治亚州雅典）具有良好的相关性。我们展示了MultiPAS-IV的宽光谱覆盖范围和灵敏度的实用性，用于计算黑碳的吸收埃指数（AAE（BC），中位值0.70），并使用此值推导出棕碳对406 nm（43%）和532 nm（13%）处吸收的贡献及其波长依赖性（AAE（BrC）= 6.3）。版权所有（2018美国气溶胶研究协会
Aerosols directly affect Earth's climate by scattering and absorbing solar radiation. Although they are ubiquitous in Earth's atmosphere, direct, in situ, wavelength-resolved measurements of aerosol optical properties remain challenging. As a result, the so-called aerosol direct effects are one of the largest uncertainties in predictions of Earth's future climate, and new instrumentation is needed to provide measurements of the absorption of sunlight by atmospheric particles. We have developed a portable, four-wavelength, single-cell photoacoustic spectrometer for simultaneous measurement of aerosol absorption at 406, 532, 662, and 785nm, with an additional extinction measurement at 662nm via a built-in cavity ringdown spectrometer. The instrument, dubbed MultiPAS-IV, is compact, robust, has low power requirements, and utilizes a multipass optical arrangement to achieve typical detection limits of 0.6-0.7Mm(-1) for absorption (2 sigma, 2-min average). Tests with nigrosin aerosols show agreement with Mie theory calculations to within 2%, and comparison with a 7-wavelength aethalometer shows good correlation for ambient (Athens, GA, USA) aerosols. We demonstrate the utility of the broad spectral coverage and sensitivity of the MultiPAS-IV for calculating the absorption angstrom ngstrom exponent of black carbon (AAE(BC), median value of 0.70) in ambient aerosols and use this value to derive the brown carbon contributions to absorption at 406nm (43%) and 532nm (13%) and its wavelength dependence (AAE(BrC) = 6.3).Copyright (c) 2018 American Association for Aerosol Research