Ethene, propene, butene and isoprene emissions from a ponderosa pine forest measured by relaxed eddy accumulation

Abstract

Abstract. Alkenes are reactive hydrocarbons that influence local and regional atmospheric chemistry by playing important roles in the photochemical production of tropospheric ozone and in the formation of secondary organic aerosols. The simplest alkene, ethene (ethylene), is a major plant hormone and ripening agent for agricultural commodities. The group of light alkenes (C 2 -C 4 ) originates from both biogenic and anthropogenic sources, but their biogenic sources are poorly characterized, with limited field-based flux observations. Here we report net ecosystem fluxes of light alkenes and isoprene from a semiarid ponderosa pine forest in the Rocky Mountains of Colorado, USA using the relaxed eddy accumulation (REA) technique during the summer of 2014. Ethene, propene, butene and isoprene emissions have strong diurnal cycles, with median daytime fluxes of 123, 95, 39 and 17 µg m −2 h −1 , respectively. The fluxes were correlated with each other, followed general ecosystem trends of CO 2 and water vapor, and showed similar sunlight and temperature response curves as other biogenic VOCs. The May through October flux, based on measurements and modeling, averaged 62, 52, 24 and 18 µg m −2 h −1 for ethene, propene, butene and isoprene, respectively. The light alkenes contribute significantly to the overall biogenic source of reactive hydrocarbons: roughly 18 % of the dominant biogenic VOC, 2-methyl-3-buten-2-ol. The measured ecosystem scale fluxes are 40-80 % larger than estimates used for global emissions models for this type of ecosystem.

Ecosystem‐Scale Measurements of Methyl Halide Fluxes From a Brackish Tidal Marsh Invaded With Perennial Pepperweed (Lepidium latifolium)

“…Through the use of the temperature modules from MEGAN, fitted parameters can be compared to other volatile organic compounds. Accordingly CH 3 Cl and CH 3 Br responses (slope β = 0.08 and β = 0.10) lie in between reports for ethanol ( β = 0.07) on the lower end and monoterpenes and the biogenic stress VOC ethene ( β = 0.11) on the higher end (Kaser et al, ; Rhew et al, ).…”

“…and are the mean temperatures during intervals of updraft and downdraft sampling. Following recommendations in Baker () and similar to recent REA installments (Rhew et al, ; Riederer et al, ), we discarded sampling during very low vertical wind speeds using a symmetrical deadband ( w 0 = 0.6 σ w ) around the mean wind velocity for each flux‐averaging interval, meaning that sampled air was only transferred into the reservoirs if | w ′| ≥ w 0 .…”

“…The physical apparatus for conditional air sampling consists of two subsystems: (1) an air segregator with remote controlled fast‐response valve switching between up‐, down‐, and neutral line, and (2) an air accumulation and reservoir system, equipped with vacuum pump for sample transfer and reservoir evacuation purposes (detailed plumbing diagram and flow description in supporting information Figure S1; the physical apparatus is described in detail in Rhew et al ().…”

The Interplay Between Ozone and Urban Vegetation—BVOC Emissions, Ozone Deposition, and Tree Ecophysiology

“…Their impact on air chemistry is generally assumed to be small since anthropogenic emissions are dominating the concentration of these compounds in urban areas by far (e.g., Costa and Baldasano, 1996;Cheng et al, 2010). However, alkanes and alkenes have been found as major emissions over many forests (Kourtchev et al, 2008;Halliday et al, 2015;Rhew et al, 2017); thus, at least the more reactive alkenes are assumed to play a significant role at larger to global levels (Goldstein et al, 1996;Rhew et al, 2017).…”

Acyl Peroxy Nitrates Link Oil and Natural Gas Emissions to High Ozone Abundances in the Colorado Front Range During Summer 2015

“…Oil and natural gas activities emit a range of alkanes and aromatic hydrocarbons (Gilman et al, 2013;Halliday et al, 2016;Pétron et al, 2012;Pétron et al, 2014;Thompson et al, 2014). Biogenic emissions from dispersed broadleaf trees throughout urban neighborhoods in the NFRMA contribute small amounts of isoprene, and needle-leaf forests in the Rocky Mountain foothills along the western edge of the NFRMA have been shown to emit small amounts of several alkene species (Rhew et al, 2017).…”