An Eddy-Covariance System for the Measurement of Surface/Atmosphere Exchange Fluxes of Submicron Aerosol Chemical Species—First Application Above an Urban Area
Open Access
- 26 June 2008
- journal article
- research article
- Published by Informa UK Limited in Aerosol Science and Technology
- Vol. 42 (8), 636-657
- https://doi.org/10.1080/02786820802227352
Abstract
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.Keywords
This publication has 55 references indexed in Scilit:
- O/C and OM/OC Ratios of Primary, Secondary, and Ambient Organic Aerosols with High-Resolution Time-of-Flight Aerosol Mass SpectrometryEnvironmental Science & Technology, 2008
- Elemental Analysis of Organic Species with Electron Ionization High-Resolution Mass SpectrometryAnalytical Chemistry, 2007
- A mass spectrometric study of secondary organic aerosols formed from the photooxidation of anthropogenic and biogenic precursors in a reaction chamberAtmospheric Chemistry and Physics, 2006
- Measurements of Secondary Organic Aerosol from Oxidation of Cycloalkenes, Terpenes, and m-Xylene Using an Aerodyne Aerosol Mass SpectrometerEnvironmental Science & Technology, 2005
- Characterization of urban and rural organic particulate in the Lower Fraser Valley using two Aerodyne Aerosol Mass SpectrometersAtmospheric Environment, 2004
- A generalised method for the extraction of chemically resolved mass spectra from Aerodyne aerosol mass spectrometer dataJournal of Aerosol Science, 2004
- Aircraft‐based aerosol size and composition measurements during ACE‐Asia using an Aerodyne aerosol mass spectrometerJournal of Geophysical Research: Solid Earth, 2003
- Estimates of the Annual Net Carbon and Water Exchange of Forests: The EUROFLUX MethodologyAdvances in Ecological Research, 1999
- Vertical aerosol particle fluxes measured by eddy covariance technique using condensational particle counterJournal of Aerosol Science, 1998
- Numerical modeling of concentrations and fluxes of HNO3, NH3, and NH4NO3 near the surfaceJournal of Geophysical Research: Solid Earth, 1988