Flux estimates and OH reaction potential of reactive biogenic volatile organic compounds (BVOCs) from a mixed northern hardwood forest

Abstract

Diurnal branch-level emission rates of biogenic volatile organic compounds (BVOC) including isoprene, monoterpenes (MT), and sesquiterpenes (SQT) were determined at the University of Michigan Biological Station for the tree species red maple (Acer rubrum), red oak (Quercus rubra), paper birch (Betula papyrifera), white pine (Pinus strobus), and big tooth aspen (Populus grandidentata). These emission rates were combined with detailed biomass distribution and meteorological data and incorporated into the canopy model, model of emissions of gasses and aerosols from nature (MEGAN), for estimating whole-canopy fluxes of isoprene. The modeled half-hour fluxes ðmg C m À2 h À1 Þ and cumulative seasonal fluxes ðmg C m À2 Þ compared favorably with results from direct, canopy-level eddy covariance (EC) isoprene measurements; modeled cumulative seasonal flux deviated less than 30% from the EC results. Significant MT emissions were found from four of the five tree species. MT emissions from three of these were both light-and temperature-dependent and were approximately one order of magnitude greater than light-independent MT emissions. SQT emissions were identified from three of the five tree species. The model was modified to incorporate SQT and both light-dependent and light-independent MT emissions for determining fluxes. Isoprene comprised 495% of the total terpenoid flux with MT and SQT comprising 4% and 0.3%, respectively. The average cumulative fluxes (in mg C m À2 ) from June through September were 2490 for isoprene, 105 for MT, and 7 for SQT. A simple box model analysis was used to estimate the contribution of the isoprene, MT, and SQT emissions to the total OH reactivity. These results confirm that isoprene dominates OH reactions especially during daytime hours. Emissions of reactive MT and SQT increase the BVOC+OH reactivity, but are still lower than estimates of BVOC fluxes at this site necessary for affecting OH reactivity to the significant degree suggested by recent reports. r

Sesquiterpene Emissions from Pine Trees − Identifications, Emission Rates and Flux Estimates for the Contiguous United States

“…Emission studies were performed by enclosing individual branches of pine trees with lighttransparent Tedlar of Teflon bags. Detailed descriptions of the experimental protocol, materials used, flow conditions, removal of ozone in the purge and sample air, and monitoring of environmental data have been published previously (20)(21)(22)31) and are only summarized here. After installation of the enclosure, the branch was allowed to acclimate to the enclosure conditions for 0.5-1 day, which also allowed any potential disturbance-induced BVOC bursts to subside and be purged out of the enclosure before sampling began.…”

“…Both automated systems typically collected 10-12 emission samples per day over a 2-3 day period for each enclosure experiment. SQT were identified based on their mass spectra and by comparison of their chromatographic elution order (32); quantifications were achieved after determining the analyte recoveries and calibrating the GC/FID response with n-alkane (33) and SQT (21) (20).…”

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

“…Speciated monoterpene measurements at this field site have been infrequently reported in the literature. Branch enclosure measurements made by Ortega et al (2007) showed that the dominant light-dependent monoterpene emitted from all deciduous species was transocimene with conifers emitting α-pinene, β-pinene, camphene, d-limonene, and para-cymene, among other monoterpenes. Kim et al (2009) reported speciated monoterpenes from canister measurements taken in their 2005 study.…”

BVOC ecosystem flux measurements at a high latitude wetland site

“…Guenther et al, 1995;Lathière et al, 2006;Seco et al, 2007) with an associated strong impact on atmospheric chemistry. BVOC consume or produce tropospheric ozone, depending on atmospheric physicochemical conditions like the levels of NO x , and influence the levels of OH and hence methane lifetime (Derwent et al, 1995;Atkinson, 2000;Poisson et al, 2000;Ortega et al, 2007). BVOCs are also known to initiate and foster the production of secondary organic aerosols (SOA, Hoffmann et al, 1997;O'Dowd et al, 2002;Kulmala et al, 2004) that scatter and absorb radiation and act as cloud condensation nuclei.…”