Emissions of isoprenoids and oxygenated biogenic volatile organic compounds from a New England mixed forest

Abstract

Fluxes of biogenic volatile organic compounds, including isoprene, monoterpenes, and oxygenated VOCs measured above a mixed forest canopy in western Massachusetts during the 2005 and 2007 growing seasons are reported. Measurements were made using proton transfer reaction mass spectrometry (PTR-MS) and converted to fluxes using the disjunct eddy covariance technique. Isoprene was by far the predominant BVOC emitted at this site, with summer mid-day average fluxes of 5.3 and 4.4 mg m<sup>−2</sup> h<sup>−1</sup> in 2005 and 2007, respectively. In comparison, mid-day average fluxes of monoterpenes were 0.21 and 0.15 mg m<sup>−2</sup> h<sup>−1</sup> in each of these years. On short times scales (days), the diel pattern in emission rate compared well with a standard emission algorithm for isoprene. The general shape of the seasonal cycle and the observed decrease in isoprene emission rate in early September was, however, not well captured by the model. Monoterpene emission rates exhibited dependence on light as well as temperature, as determined from the improved fit to the observations obtained by including a light-dependent term in the model. The mid-day average flux of methanol from the canopy was 0.14 mg m<sup>−2</sup> h<sup>−1</sup> in 2005 and 0.19 mg m<sup>−2</sup> h<sup>−1</sup> in 2007, but the maximum flux was observed in spring (29 May 2007), when the flux reached 1.0 mg m<sup>−2</sup> h<sup>−1</sup>. This observation is consistent with enhanced methanol production during leaf expansion. Summer mid-day fluxes of acetone were 0.15 mg m<sup>−2</sup> h<sup>−1</sup> during a short period in 2005, but only 0.03 mg m<sup>−2</sup> h<sup>−1</sup> averaged over 2007. Episodes of negative fluxes of oxygenated VOCs, particularly acetone, were observed periodically, especially in 2007. Thus, deposition within the canopy could help explain the low season-averaged flux of acetone in 2007. Fluxes of species of biogenic origin at mass-to-charge (<i>m/z</i>) ratios of 73 (0.05 mg m<sup>−2</sup> h<sup>−1</sup> in 2005; 0.03 mg m<sup>−2</sup> h<sup>−1</sup> in 2007) and 153 (5 μg m<sup>−2</sup> h<sup>−1</sup> in 2007), possibly corresponding to methyl ethyl ketone and an oxygenated terpene, respectively, were also observed

Spatiotemporal Controls on Observed Daytime Ozone Deposition Velocity Over Northeastern U.S. Forests During Summer

“…In terms of ambient in‐canopy chemistry, NO concentrations are typically not high enough at Harvard Forest to impact ozone fluxes (Munger et al, ). The highly reactive BVOCs that impact observed ozone fluxes are generally not expected at Harvard Forest (McKinney et al, ) because the forest is mostly dominated by red oak, red maple, and eastern hemlock. However, red and white pines are ~20% of the trees in the flux tower footprint when wind comes from the northwest (NW), a dominant wind sector (Moody et al, ; Munger et al, ).…”

Ecosystem‐scale volatile organic compound fluxes during an extreme drought in a broadleaf temperate forest of the Missouri Ozarks (central USA)

“…Monoterpene mixing ratios reported in the literature from forests where isoprene is the dominant isoprenoid emitted were generally < 1 ppbv, somewhat lower than average mixing ratios described here. Maximum fluxes were also on the lower side of those at MOFLUX, approximately 0.5 mg m −2 h −1 (Karl et al ., ; Langford et al ., ; McKinney et al ., ; Misztal et al ., ), except for the Amazon (similar with up to 1.2 mg m −2 h −1 ; Karl et al ., ) and for an oak‐dominated forest in France that featured monoterpene fluxes below the detection limit (Kalogridis et al ., ). In European forests dominated by monoterpene emitters, monoterpene fluxes were in a range similar to the values in Missouri (maxima of 1 mg m −2 h −1 ; Rinne et al ., ; Davison et al ., ), while mixing ratios were either lower (0.3 ppbv; Davison et al ., ) or above (daytime mean of 2.1 ppbv and maxima around 2.5 ppbv; Seco et al ., 2011b) the values reported in this work.…”

“…Nevertheless, measured isoprene fluxes during T2 and Drought , although reduced, were still very similar to or higher than fluxes reported for many other forests in the world that were not subject to extreme drought (e.g. Karl et al ., , ; Langford et al ., ; McKinney et al ., ; Kalogridis et al ., ). Monoterpenes showed a similar behavior with reduced emission fluxes compared with the model during the strongest phase of the drought (Fig.…”

“…(; 53.3 mg m −2 h −1 ) are the highest ever reported for a forest canopy, surpassing fluxes of up to 30 mg m −2 h −1 previously reported from an oil palm plantation in Borneo (Misztal et al ., ). Other North American temperate forests with large components of isoprene‐emitting tree species showed lower fluxes, with maxima on the order of 13 mg m −2 h −1 (Baldocchi et al ., ; Fuentes et al ., ; McKinney et al ., ; see Potosnak et al ., for a discussion). The higher values at the MOFLUX site compared to other North American temperate forests are expected due to a higher fraction of isoprene emitters and higher temperatures.…”

Diel Variation of Biogenic Volatile Organic Compound Emissions- A field Study in the Sub, Low and High Arctic on the Effect of Temperature and Light

“…Thus, emission of BVOCs often peaks during midday and decreases with decreasing light and temperature (see e.g. McKinney et al [ 13 ]). The emission from arctic ecosystems, with low temperature, low foliar density and low solar angle, has been previously estimated to be minimal [ 14 ].…”