An Eddy-Covariance System for the Measurement of Surface/Atmosphere Exchange Fluxes of Submicron Aerosol Chemical Species—First Application Above an Urban Area
An Eddy-Covariance System for the Measurement of Surface/Atmosphere Exchange Fluxes of Submicron Aerosol Chemical Species—First Application Above an Urban Area
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用于测量亚微米气溶胶化学物质表面/大气交换通量的涡流协方差系统——首次在城市地区上空应用
DOI：
10.1080/02786820802227352
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发表时间：
2008
影响因子：
5.2
通讯作者：
A. Guenther
中科院分区：
文献类型：
--
作者：
E. Nemitz;J. Jimenez;J. A. Huffman;I. Ulbrich;M. Canagaratna;D. Worsnop;A. Guenther
到目前为止，亚微米气溶胶化学成分（例如硝酸盐、硫酸盐或有机物）的表面/大气交换通量的微气象测量只能通过梯度技术进行。本文介绍了一种通过更直接的涡流协方差技术测量特定气溶胶通量的新颖装置。该系统基于 Aerodyne 四极杆气溶胶质谱仪 (Q-AMS)，以足够涡流协方差的时间分辨率对环境问题的气溶胶成分进行定量测量。 Q-AMS 控制软件经过修改，可最大限度地提高占空比和统计数据，并实现快速数据采集，与超声波风速计同步。基于 Q-AMS 的通量测量系统的检测限范围从 NO3 − 的 0.2 到类碳氢化合物有机气溶胶 (HOA) 的 15 ng m−2 s−1，估计精度约为 6 ng m−2 s−1，具体取决于气溶胶负荷。在常见的环境浓度下，系统能够解析< 1 mm s−1 的沉积速度值，足以测量植被的干沉积。该系统在美国科罗拉多州博尔德市的城市环境中进行了首次测试（2003 年 6 月 6 日至 20 日），揭示了 HOA 和 NO3− 排放的清晰昼夜模式（可能与交通有关），并表明在测量高度以下会快速产生中等含氧有机气溶胶，平均约占 HOA 排放量的 15%。 HOA 的平均排放因子为 0.5 g（kg 燃料）−1，与之前研究中发现的类似。对于 NO3 − ，估计排放因子为 0.09 g（kg 燃料）−1，这意味着在 45 m 测量高度以下，氧化了 0.5% 的交通产生的 NOx。相比之下，SO4 2− 通量平均下降，沉积速度随着摩擦速度从 0.4 mm s−1 增加到 4 mm s−1 而增加。
Until now, micrometeorological measurements of surface/ atmosphere exchange fluxes of submicron aerosol chemical components such as nitrate, sulfate or organics could only be made with gradient techniques. This article describes a novel setup to measure speciated aerosol fluxes by the more direct eddy covariance technique. The system is based on the Aerodyne quadrupole-based Aerosol Mass Spectrometer (Q-AMS), providing a quantitative measurement of aerosol constituents of environmental concern at a time resolution sufficient for eddy-covariance. The Q-AMS control software was modified to maximize duty cycle and statistics and enable fast data acquisition, synchronized with that of an ultrasonic anemometer. The detection limit of the Q-AMS based system for flux measurements ranges from 0.2 for NO3 − to 15 ng m−2 s−1 for hydrocarbon-like organic aerosol (HOA), with an estimated precision of around 6 ng m−2 s−1, depending on aerosol loading. At common ambient concentrations the system is capable of resolving deposition velocity values < 1 mm s−1, sufficient for measurements of dry deposition to vegetation. First tests of the system in the urban environment (6 to 20 June 2003) in Boulder, CO, USA, reveal clear diurnal, presumably traffic related, patterns in the emission of HOA and NO3 −, with indication of fast production of moderately oxygenated organic aerosol below the measurement height, averaging about 15% of the HOA emission. The average emission factor for HOA was 0.5 g (kg fuel)−1, similar to those found in previous studies. For NO3 − an emission factor of 0.09 g (kg fuel)−1 was estimated, implying oxidation of 0.5% of the traffic derived NOx below the measurement height of 45 m. By contrast, SO4 2− fluxes were on average downward, with deposition velocities that increase with friction velocity from 0.4 to 4 mm s−1.
影响因子：
158.5
作者：
DOCKERY, DW;POPE, CA;SPEIZER, FE
通讯作者：
SPEIZER, FE