ACETONE AND ACETALDEHYDE EXCHANGE ABOVE A MANAGED TEMPERATE MOUNTAIN GRASSLAND

BACKGROUND

Lukas Hörtnagl1, Ines Bamberger2, Martin Graus2*, Taina M. Ruuskanen2**, Ralf Schnitzhofer2, Armin Hansel2, and Georg Wohlfahrt1

1 Institute of Ecology, University of Innsbruck, Austria | 2 Institute of Ion Physics and Applied Physics, University of Innsbruck, Austria * current address: Chemical Sciences Division, NOAA Earth System Research, Laboratory, Boulder, CO, USA ** current address: Division of Atmospheric Sciences , University of Helsinki, Finland

Volatile organic compounds (VOCs) have received increasing attention in the past two decades due to their role in atmospheric chemistry 1. Plants emit a wide spectrum of biogenic VOCs to the atmosphere, and although anthropogenic sources can dominate in urban areas, terrestrial vegetation is the main source on a global scale 2. In the past, most studies focused on hydrocarbon compounds such as isoprenoids, but recently there is a growing interest in a small group of biogenic oxygenated VOCs 3 (BOVOCs) which have been measured in surprising abundance throughout the remote troposphere 4. BOVOCs include three compounds: methanol, acetaldehyde and acetone. Their combined biogenic source strength amounts to around 268 Tg C y-1, which is about half the source strength of isoprene. Previous studies have shown that land ecosystems can act both as sources and sinks for all three species 5,6,8.

Acetaldehyde and acetone fluxes were measured above a managed, temperate mountain grassland in Stubai Valley (Tyrol, Austria) during two growing seasons (2008 and 2009). Half-hourly flux values were calculated by means of the disjunct eddy covariance method using 3-dimensional wind-data of a sonic anemometer and mixing ratios of both species measured with a proton-transfer-reaction-mass-spectrometer (PTR-MS).

Largest perturbations of the exchange of acet- aldehyde and acetone were caused by the cutting of the meadow, causing half-hourly peak emissions of 12.1 nmol m-2 s-1 for acetaldehyde and 10.1 nmol m-2 s-1 for acetone (Fig. 1,2,5). During most of the two-year investigation period no clear diurnal cycles could be observed, both species exhibiting close-to-zero or noisy fluxes. However, both species exhibited a clear diurnal cycle during certain time periods: Distinct emissions of acetaldehyde and acetone were observed in October 2008 (Fig. 3), with emission rates of up to 3.7 nmol nmol m-2 s-1 for acetaldehyde and and up to 3.2 nmol nmol m-2 s-1 for acetone. Uptake of both acetaldehyde and acetone could be observed in late May 2009 (Fig. 3), with rates up to 1.8 and 2.1 nmol nmol m-2 s-1, respectively. The reason for this clear emission/uptake has yet to be explained, a statistical analysis using ancillary data like soil water content yielded no satisfying results. However, in May 2009 the concentrations of both acetaldehyde and acetone showed highly-significant, negative correlations with their respective fluxes and compensation points of 0.3 and 1.2 ppb, respectively.

General Assembly Vienna | Austria | 03 – 08 April 2011

METHODS

ACETALDEHYDE FLUXES

ACETONE FLUXES

Two years of acetaldehyde and acetone fluxes. One spike represents one half-hour of flux data, height and direction show magnitude of emission or uptake. Circled red numbers mark periods that are shown in detail in various figures.

1st cut 2008

2nd cut 2008

May 2009: uptake!

1st cut 2009

2nd cut 2009

3rd cut 2009

fertilization

October 2008: constant emission

FIGURE 1

has a lifetime of less than one day and plays an important role as a precursor of ozone, peroxyacetylnitrate 7 and hydrogen radicals 4 and is considered a hazardous air pollutant. The global source is dominated by atmospheric production (< 60 % 8), but plants represent a non-negligible source (~ 10 % 8). During periods of high soil water content when the roots are oxygen limited acetaldehyde is produced through oxidation of ethanol which is transported from the roots to the leaves 9. Production of acetaldehyde has also been reported during light-dark transitions by a pyruvic acid overflow mechanism 10. Dry deposition to land has been reported before 11, but is considered a minor sink on a global scale.

ACETALDEHYDE stays considerably longer in the atmosphere than acetaldehyde with a lifetime of 53 days and is a major source of PAN and hydrogen oxide radicals . Land ecosystems can act both as major sources and sinks, whereby pathways from which acetone emissions can arise are currently poorly understood 3. Acetone is produced as a byproduct from the cell walls from cyanogenic plants and was reported to be light dependent 13.

ACETONE

Daily average acetaldehyde and acetone flux measurements during the vegetation periods 2008 and 2009 at the study site Neustift. Grey vertical lines represent management events. ⇢

FIGURE 2

Average diurnal cycles in October 2008 and May 2009 during undisturbed conditions (not influenced by management events). ⇣

FIGURE 3

FIGURE 4

Cumulative carbon fluxes of acetaldehyde and acetone (data gaps shorter or equal to two hours were filled with interpolated values). Grey vertical lines represent management events. ⇣

FIGURE 5 The effect of cutting and fertilization on acetaldehyde and acetone exchange. Symbols represent one half-hour of data. ⇢

RESULTS & DISCUSSION

12:00

0:00

24:00

12:00

0:00

24:00

REFERENCES: 1 Chameides W.L., Lindsay R.W., Richardson J., Kiang C.S., 1988. The role of biogenic hydrocarbons in urban photochemical smog: Atlanta as a case study. Science 241, 1473-1475.| 2 Guenther A., Hewitt C.N., Erickson D., et al., 1995. A global model of natural volatile organic compound emissions. J. Geophys. Res. 100, 8873-8892. | 3 Fall R., 2003. Abundant oxygenates in the atmosphere: A biochemical perspective. Chem. Rev. 103, 4941-4951. | 4 Singh H., Chen Y., Staudt A., Jacob D., Blake D., Heikes B., Snow J. 2001. Evidence from the pacific troposphere for large global sources of oxygenated organic compounds. Nature 410, 1078-1081. | 5 Millet D.B., Jacob D.J., Boersma K.F., et al., 2008. New constraints on terrestrial and oceanic sources of atmospheric methanol. Atmos. Chem. Phys. 8, 6887-6905. | 6 Jacob D.J., Field B.D., Jin E.M., Bey I., Li Q., Logan J.A., Yantosca R.M., 2002. Atmospheric budget of acetone. J. Geophys. Res. 107, doi:10.1029/2001JD000694. | 7 Roberts J.M. 1990. The atmospheric chemistry of organic nitrates. Atmos. Environ. 24A, 243-287. | 8 Millet D.B., Guenther A., Siegel D.A., et al., 2010. Global atmospheric budget of acetaldehyde: 3-D model analysis and constraints from in-situ and satellite observations. Atmos. Chem. Phys. 10, 3405-3425. ^| 9 Copolovici L., Niinemets Ü., 2010. Flooding induced emissions of volatile signalling compounds in three species with differing waterlogging tolerance. Plant Cell Environ. 33, 1582-1594. | 10 Karl T., Curtis A., Rosenstiel T., Monson R., Fall R., 2002a. Transient releases of acetaldehyde from tree leaves – products of a pyruvate overflow mechanism? Plant Cell Environ. 25, 1121-1131. | 11 Asensio D., Penuelas J., Prieto P., Esiarte M., Filella I., Llusia J., 2008. Interannual and seasonal changes in the soil exchange rates of monoterpenes and other VOCs in a Mediterranean shrubland. Eur. J. Soil Sci. 59, 878-891. | 12 Kirstine W., Galbally I., Ye Y., Hooper M., 1998. Emission of volatile organic compounds (primarily oxygenated species) from pasture. J. Geophys. Res. 103, 10605-10619.

www.biomet.co.at

Visit us: