A Framework for Representing Biodegradation in Atmospheric Multiphase Models
Abstract
Biodegradation is a key process in natural ecosystems through which microorganisms recycle organic matter. Cloud water can host metabolically active microorganisms, opening the possibility that biodegradation contributes to atmospheric processing of organics. However, the extent to which microbial activity occurs in the atmosphere and modifies carbon budgets, and the parameters that control the rates, remain poorly constrained. We present a framework to quantify the key parameters of biodegradation of six major cloud-water organics (methanol, ethanol, formaldehyde, acetaldehyde, formic and acetic acids) and for unspecified organics. Using a multiphase box model, we perform sensitivity analyses to evaluate the dependence of biodegradation rates on bacterial abundance (N bact ), Henry's law constants (K H(ef f ) ) and biodegradation rate constants (k bact ). Biodegradation scales proportionally with N bact , while fits indicate weaker sensitivities to K H,eff and k bact with slopes of 0.89 and 0.39 in log-log space, respectively. Biodegradation of compounds with K H > 10 5 M atm -1 and/or k bact > 2 × 10 -13 L cell -1 s -1 is limited by insufficient substrate replenishment in bacteria-containing droplets. Biodegradation rates normalized by cell concentration are consistent in magnitude with values reported for other aqueous environments, resulting in an effective rate constant of k bact,DOM ∼ 10 -13 L cell -1 s -1 for dissolved organic matter (DOM). Comparison of predicted biodegradation rates with atmospheric chemical loss processes and biodegradation in other aquatic environments indicates that atmospheric biodegradation may be a significant sink for some individual compounds (C 2 H 5 OH, HCOOH, CH 3 COOH) but generally represents a minor sink (< 1%) under the conditions explored. Overall, the empirical relationships and sensitivities derived here provide a framework for implementing biodegradation in atmospheric multiphase models of different complexity, enabling assessment not only of its contribution to atmospheric carbon cycling but also of how environmental conditions may affect microbial functioning of the airborne portion of Earth' microbiome.
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BibTeX
@misc{nunezlopez2026framework,
title = {{A Framework for Representing Biodegradation in Atmospheric Multiphase Models}},
author = {Leslie Nuñez-López and Pierre Amato and Barbara Ervens},
howpublished = {HAL},
year = {2026},
month = sep,
doi = {10.5194/egusphere-2026-5013},
url = {https://hal.science/hal-05762894v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A Framework for Representing Biodegradation in Atmospheric Multiphase Models
AU - Leslie Nuñez-López
AU - Pierre Amato
AU - Barbara Ervens
PY - 2026
DA - 2026/09/04
PB - HAL
DO - 10.5194/egusphere-2026-5013
UR - https://hal.science/hal-05762894v1
AB - Biodegradation is a key process in natural ecosystems through which microorganisms recycle organic matter. Cloud water can host metabolically active microorganisms, opening the possibility that biodegradation contributes to atmospheric processing of organics. However, the extent to which microbial activity occurs in the atmosphere and modifies carbon budgets, and the parameters that control the rates, remain poorly constrained. We present a framework to quantify the key parameters of biodegradation of six major cloud-water organics (methanol, ethanol, formaldehyde, acetaldehyde, formic and acetic acids) and for unspecified organics. Using a multiphase box model, we perform sensitivity analyses to evaluate the dependence of biodegradation rates on bacterial abundance (N bact ), Henry's law constants (K H(ef f ) ) and biodegradation rate constants (k bact ). Biodegradation scales proportionally with N bact , while fits indicate weaker sensitivities to K H,eff and k bact with slopes of 0.89 and 0.39 in log-log space, respectively. Biodegradation of compounds with K H > 10 5 M atm -1 and/or k bact > 2 × 10 -13 L cell -1 s -1 is limited by insufficient substrate replenishment in bacteria-containing droplets. Biodegradation rates normalized by cell concentration are consistent in magnitude with values reported for other aqueous environments, resulting in an effective rate constant of k bact,DOM ∼ 10 -13 L cell -1 s -1 for dissolved organic matter (DOM). Comparison of predicted biodegradation rates with atmospheric chemical loss processes and biodegradation in other aquatic environments indicates that atmospheric biodegradation may be a significant sink for some individual compounds (C 2 H 5 OH, HCOOH, CH 3 COOH) but generally represents a minor sink (< 1%) under the conditions explored. Overall, the empirical relationships and sensitivities derived here provide a framework for implementing biodegradation in atmospheric multiphase models of different complexity, enabling assessment not only of its contribution to atmospheric carbon cycling but also of how environmental conditions may affect microbial functioning of the airborne portion of Earth' microbiome.
ER -