Gas‐phase chemistry dominates O₃ loss to a forest, implying a source of aerosols and hydroxyl radicals to the atmosphere

Abstract

Tropospheric ozone (O3) effectively deposits to forested ecosystems but the fate of O3 within the forest canopy is unresolved. We partitioned total measured ecosystem daytime O3 deposition to a ponderosa pine (Pinus ponderosa) forest into its major loss pathways; stomatal uptake, non‐stomatal surface deposition, and gas‐phase chemistry. Total O3 flux was dominated by gas‐phase chemistry during the summer and by stomatal uptake during winter. O3 loss due to gas‐phase chemistry was exponentially dependent on temperature, with the same functionality as biogenic hydrocarbon emissions, implicating reactions with biogenic hydrocarbons as the likely gas‐phase chemical O3 loss process within the canopy. The reaction of O3 with biogenically‐emitted hydrocarbons leads to both hydroxyl radical formation and secondary aerosol growth with important effects on atmospheric chemistry and climate.

Isoprene and monoterpene fluxes measured above Amazonian rainforest and their dependence on light and temperature

“…A large ecosystem-scale source of missing reactive volatiles has been previously suggested based on measurements of total ozone deposition fluxes to canopies of midlatitude forests [Mikkelsen et al, 2000;Fowler et al, 2001;Barr et al, 2003;Kurpius and Goldstein, 2003]. The highly reactive monoterpenes quantified in this study including terpinolene, trans-β-ocimene, and cis-β-ocimene (Figure 1) may contribute to this missing reactivity balance.…”

“…Within ecosystems, monoterpenes mediate plant-microbe [Dorman and Deans, 2000] and plant-insect [Beyaert and Hilker, 2014] interactions and protect photosynthesis during abiotic stress [Peñuelas and Llusià, 2002;Vickers et al, 2009]. Fueled by large total monoterpene emissions from forested ecosystems [Karl et al, 2002[Karl et al, , 2003[Karl et al, , 2004, atmospheric photochemical oxidation of monoterpenes generates low-volatility oxidation products that can partition to the particle phase [Yu et al, 1999;Fuentes et al, 2000;Kurpius and Goldstein, 2003;Mcfrederick et al, 2008;Martin et al, 2010]. These oxidation products, along with the oxidation products of isoprene (C 5 H 8 ), sesquiterpenes (C 15 H 24 ), and possibly higher-order terpenoids (C 20 H 32 and above), play important roles in the formation and growth of secondary organic aerosol (SOA) particles that can activate into cloud condensation nuclei [Claeys et al, 2004;Pöschl et al, 2010].…”

Ozone deposition into a boreal forest over a decade of observations: evaluating deposition partitioning and driving variables

“…The system, located at 23 m height above the ground on the top of a scaffolding tower, included an ultrasonic anemometer (Solent Research HS1199, Gill Ltd., Lymington, Hampshire, England) to measure the three wind velocity components and the sonic temperature, a closed-path infrared gas analyser (LI-6262, LiCor Inc., Lincoln, NE, USA) that measured the CO 2 and H 2 O concentrations, and a fast response chemiluminescence gas analyzer for the ozone concentration (LOZ-3 Ozone analyzer, Unisearch Associates Inc., Concord, Ontario, Canada). The calibration and maintenance procedures of the O 3 analyzer were described in detail by Keronen et al (2003). The data were sampled at 21 Hz and a 2-D rotation of sonic anemometer wind components (McMillen et al, 1998) and filtering to eliminate spikes were performed according to standard methods (Vickers and Mahrt, 1997).…”

“…The data were sampled at 21 Hz and a 2-D rotation of sonic anemometer wind components (McMillen et al, 1998) and filtering to eliminate spikes were performed according to standard methods (Vickers and Mahrt, 1997). The high-frequency flux attenuation was corrected by using empirical transfer functions and co-spectral transfer characteristics (Keronen et al, 2003;Rannik et al, 2004;Mammarella et al, 2009). …”

“…Several papers addressing the ozone deposition over pine forests (Goldstein et al, 2004;Holzinger et al, 2005Holzinger et al, , 2006 revealed the role of the chemical reactions with BVOC-s in ozone removal. Kurpius and Goldstein (2003) noted that lifetimes of many reactive terpenes can be less than a minute and significant part of ozone deposition into ecosystem was due to chemical loss in the canopy. Holzinger et al (2006) identified connection between monoterpene flux and nonstomatal ozone flux, further suggesting that large amounts of other substances reacting with ozone are released causing the observed correlation.…”