References

AMTD

Atmospheric Measurement Techniques Discussions

AMTD

1867-8610

Copernicus GmbH

Göttingen, Germany

10.5194/amtd-5-2703-2012

A disjunct eddy accumulation system for the measurement of BVOC fluxes: instrument characterizations and field deployment

Edwards

G. D.

¹ Martins

D. K.

² ⁵ Starn

³ Pratt

² Shepson

P. B.

² ⁴

Department of Chemistry, Eastern Michigan University, Ypsilanti, MI 48197, USA

Department of Chemistry, Purdue University, West Lafayette, IN 47907, USA

Department of Chemistry, West Chester University, West Chester, PA 19383, USA

Purdue Climate Change Research Center, Purdue University, West Lafayette, IN 47907, USA

now at: Department of Meteorology, Pennsylvania State University, University Park, PA 16802, USA

04 04 2012

5 2 2703 2746

This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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Biological volatile organic compounds (BVOCs), such as isoprene and monoterpenes, are emitted in large amounts from forests. Quantification of the flux of BVOCs is critical in the evaluation of the impact of these compounds on the concentrations of atmospheric oxidants and on the production of secondary organic aerosol. A disjunct eddy accumulation (DEA) sampler system was constructed for the measurement of speciated BVOC fluxes. Unlike traditional eddy covariance (EC), the relatively new technique of disjunct sampling differs by taking short, discrete samples that allows for slower sampling frequencies. Disjunct sample airflow is directed into cartridges containing sorbent materials at sampling rates proportional to the magnitude of the vertical wind. Compounds accumulated on the cartridges are then quantified by thermal desorption and gas chromatography. Herein, we describe our initial tests to evaluate the disjunct sampler including the application of using vertical wind measurements to create optimized sampling thresholds. Measurements of BVOC fluxes obtained from DEA during its deployment above a mixed hardwood forest at the University of Michigan Biological Station (Pellston, MI) during the 2009 CABINEX field campaign are reported. Daytime (09:00 a.m. to 05:00 p.m.) isoprene fluxes, when averaged over the footprint of the tower were 1.31 mg m−2 h−1 which is comparable to previous flux measurements at this location. Speciated monoterpene fluxes are some of the first to be reported from this site. Daytime averages were 26.7 μg m−2 h−1 for α-pinene and 10.6 μg m−2 h−1 for β-pinene. These measured concentrations and fluxes were compared to the output of an atmospheric chemistry model, and were found to be consistent with our knowledge of the variables that control BVOCs fluxes at this site.

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