Atmos. Chem. Phys. Discuss., 13, 24435-24480, 2013
© Author(s) 2013. This work is distributed
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Establishing the contribution of lawn mowing to atmospheric aerosol levels in American suburbs
R. M. Harvey, J. Zahardis, and G. A. Petrucci
1University of Vermont Department of Chemistry, 82 University Place, Burlington VT, USA

Abstract. Green leaf volatiles (GLVs) are a class of wound-induced volatile organic compounds emitted by several plant species. Turfgrasses emit a complex profile of GLVs upon mowing, as evidenced by the "freshly cut grass" smell, some of which are readily oxidized in the atmosphere to contribute to secondary organic aerosol (SOA). The contribution of lawn mowing-induced SOA production may be especially impactful at the urban/suburban interface, where urban hubs provide a source of anthropogenic oxidants and SOA while suburban neighborhoods have the potential to emit large quantities of reactive, mow-induced GLVs. This interface provides a unique opportunity to study aerosol formation in a multi-component system and at a regionally relevant scale. Freshly cut grass was collected from a study site in Essex Junction, Vermont and was placed inside a 775 L Teflon experimental chamber. Thermal desorption gas chromatography mass spectrometry (TD-GC/MS) was used to characterize the emitted GLV profile. Ozone was introduced to the experimental chamber and TD-GC/MS was used to monitor the consumption of these GLVs and the subsequent evolution of gas phase products while a scanning mobility particle sizer was used to continuously measure aerosol size distributions and mass loadings as a result of grass clipping ozonolysis.

Freshly cut grass found to emit a complex mixture of GLVs, dominated by cis-3-hexenyl acetate and cis-3-hexenol, which were released at an initial rate of 1.8 (±0.5) μg and 0.07 (±0.03) μg per square meter of lawn mowed with each mowing. Chamber studies using pure standards of cis-3-hexenyl acetate (CHA) and cis-3-hexenol (HXL) were found to have aerosol yields of 1.2 (±1.1)% and 3.3 (±3.1)%, respectively. Using these aerosol yields and the emission rate of these CHA and HXL by grass, SOA evolution by ozonolysis of grass clippings was predicted. However, the measured SOA mass produced from the ozonolysis of grass clippings exceeded the predicted amount, by upwards of ~ 150%. The ozonolysis of a mixture of CHA and HXL representative of environmental mixing ratios also failed to accurately model the SOA mass produced by grass clippings.

Aerial photographs and geospatial analysis were used to determine the turfgrass coverage in a suburban neighborhood, which was then used along with measured SOA production as a function of grass mowed to determine that lawn mowing has the potential to contribute 47 μg m−2 SOA to the atmosphere per mowing event by ozonolysis, which cannot be modeled solely by the ozonolysis of CHA, HXL or a representative mixture of the two.

Citation: Harvey, R. M., Zahardis, J., and Petrucci, G. A.: Establishing the contribution of lawn mowing to atmospheric aerosol levels in American suburbs, Atmos. Chem. Phys. Discuss., 13, 24435-24480, doi:10.5194/acpd-13-24435-2013, 2013.
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