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An Eddy-Covariance System for the Measurement of Surface/Atmosphere Exchange Fluxes of Submicron Aerosol Chemical Species—First Application Above an Urban Area

Nemitz, Eiko; Jimenez, Jose L.; Huffman, J. Alex; Canagaratna, Manjula R.; Worsnop, Doug R.; Guenther, Alex B.. 2008 An Eddy-Covariance System for the Measurement of Surface/Atmosphere Exchange Fluxes of Submicron Aerosol Chemical Species—First Application Above an Urban Area. Aerosol Science and Technology, 42 (8). 636-657. 10.1080/02786820802227352

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Abstract/Summary

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 paper 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 NO−3 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 NO−3 , 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 NO−3 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, SO2− 4 fluxes were on average downward, with deposition velocities that increase with friction velocity from 0.4 to 4 mm s−1.

Item Type: Publication - Article
Digital Object Identifier (DOI): 10.1080/02786820802227352
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry > BG01 Measuring and modelling trace gas, aerosol and carbon > BG01.5 Aerosols
CEH Sections: Billett
ISSN: 0278-6826
Additional Keywords: aerosol
NORA Subject Terms: Atmospheric Sciences
Date made live: 24 Nov 2008 12:08
URI: http://nora.nerc.ac.uk/id/eprint/4696

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