Physicochemical uptake and release of volatile organic compounds by soil in coated-wall flow tube experiments with ambient air

Guo, Li; Cheng, Yafang; Kühn, U.; Xu, Rongjuan; Yang, Yudong; Meusel, Hannah; Ma, Nan; Wu, Yusheng; Ling, Meng; Williams, Jonathan; Hoffmann, Thorsten; Ammann, Markus; Pöschl, Ulrich; Shao, Min; Su, Hang

doi:10.5194/acp-2018-683

Cited by 1 publication

(1 citation statement)

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“…Together, the above analyses suggest a rapid in-canopy photochemical (rather than direct emission) HCOOH source: The HCOOH gradients do not match well with those for tracers of direct biogenic emissions (isoprene, monoterpenes, sesquiterpenes, methanol, and acetone) and instead strongly resemble those of oxidized VOCs whose main atmospheric source is thought to be secondary chemical production. Potential mechanisms for such a secondary HCOOH source are discussed in supporting information S2 (Crounse et al, 2012;Finlayson-Pitts et al, 2003;Jud et al, 2016;Li et al, 2018;Neeb et al, 1997;Paulot et al, 2009;Welz et al, 2014). A separate possibility is that the canopy source of HCOOH arises from direct emissions that are dissimilar from those of any available primary emission tracers (thus causing the poor correlations in Figure 4b).…”

Section: 1029/2018gl081526mentioning

confidence: 99%

Oxidation of Volatile Organic Compounds as the Major Source of Formic Acid in a Mixed Forest Canopy

Alwe

Millet

Chen

et al. 2019

Geophysical Research Letters

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Formic acid (HCOOH) is among the most abundant carboxylic acids in the atmosphere, but its budget is poorly understood. We present eddy flux, vertical gradient, and soil chamber measurements from a mixed forest and apply the data to better constrain HCOOH source/sink pathways. While the cumulative above‐canopy flux was downward, HCOOH exchange was bidirectional, with extended periods of net upward and downward flux. Net above‐canopy fluxes were mostly upward during warmer/drier periods. The implied gross canopy HCOOH source corresponds to 3% and 38% of observed isoprene and monoterpene carbon emissions and is 15× underestimated in a state‐of‐science atmospheric model (GEOS‐Chem). Gradient and soil chamber measurements identify the canopy layer as the controlling source of HCOOH or its precursors to the forest environment; below‐canopy sources were minor. A correlation analysis using an ensemble of marker volatile organic compounds suggests that secondary formation, not direct emission, is the major source driving ambient HCOOH.

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