Constraining the Impact of Bacteria on the Aqueous Atmospheric Chemistry of Small Organic Compounds

Fankhauser, Alison M.; Antonio, Dexter; Krell, Asher; Alston, Simone J.; Banta, Scott; McNeill, V. Faye

doi:10.1021/acsearthspacechem.9b00054

“…While phenol is not a major contributor to the WSOC content in cloud water (5-95 nM ) (Jaber et al, 2020) as compared to 10µm (Ervens et al, 2003b) (Löflund et al, 2002) (Sun et al, 2016) for formic and acetic acids respectively, its degradation processes in the atmosphere might be of interest due to its toxic properties. Overall, our results are in agreement with previous findings that neither chemical processes nor biodegradation are major WSOC 530 losses as compared to deposition (Ervens and Amato, 2020) (Fankhauser et al, 2019). However, in order to comprehensively describe the loss processes and time scales of organic degradation and residence time scales in the atmosphere, both chemical and biological processes should be considered.…”

Section: For Which Organics Is Biodegradation An Efficient Sink In Thsupporting

confidence: 92%

“…The metabolic activity of bacterial strains identified in cloud water (e.g. Pseudomonas, Sphingomonas) has been investigated in lab studies, and it was shown that they can biodegrade organics (e.g., malonate, succinate, adipate, pimelate, formaldehyde, methanol, acetate, formate, phenol and catechol (Delort et al, 2010) (Vaïtilingom et al, 2010(Vaïtilingom et al, , 2011(Vaïtilingom et al, , 2013 (Amato et al, 2007a) (Ariya et al, 2002) (Husárová et al, 2011) (Fankhauser et al, 2019) (Jaber et al, 2020). Based on comparisons of experimentally derived 60 biodegradation rates to chemical rates of oxidation reactions by radicals (e.g., OH, NO3) in the aqueous phase, it was concluded that they might be similar under some conditions, and that, depending on the abundance and metabolic activity of bacteria strains, oxidation and biodegradation processes of organics may compete in clouds.…”

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confidence: 99%

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Biodegradation by bacteria in clouds: An underestimated sink for some organics in the atmospheric multiphase system

Khaled¹,

Zhang²,

Amato³

et al. 2020

Preprint

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Abstract. Water-soluble organic compounds represent a significant fraction of total atmospheric carbon. The main oxidants towards them in the gas and aqueous phases are OH and NO3 radicals. In addition to chemical solutes, a great variety of microorganisms (e.g. bacteria, viruses, fungi) has been identified in cloud water. Previous lab studies suggested that for some organics, biodegradation by bacteria in water is comparable to their loss by chemical processes. We perform model sensitivity studies over large ranges of biological and chemical process parameters using a box model with a detailed atmospheric multiphase chemical mechanism and biodegradation processes to explore the importance of biodegradation of organics in the aqueous phase. Accounting for the fact that only a small number fraction of cloud droplets (~ 0.0001–0.001) contains active bacteria cells, we consider only a few bacteria-containing droplets in the model cloud. We demonstrate that biodegradation might be most efficient for volatile organic compounds (VOC) with intermediate solubility (~ 104 &leq; KH(eff) [M atm−1] &leq; 106, e.g., formic and acetic acids). This can be explained by the transport limitation due evaporation of organics from bacteria-free droplets to the gas phase, followed by the dissolution into bacteria-containing droplets. For non-volatile organics (NVOC), such as dicarboxylic acids, the upper limit of organic loss by biodegradation can be approximated by the amount of organics dissolved in the bacteria-containing droplets (

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“…The importance of biodegradation of CCN-derived compounds is limited by the number fraction of cloud droplets that contain bacteria. Malonate / malonic acid and succinate / succinic acid contribute on average to < 5 % to the total organic aerosol mass in ambient particles, e.g., Fu et al (2013) and Kawamura and Ikushima (1993). Their loss by chemical and biological processes will not affect the total carbon budget to a large extent nor the budget of the individual compounds.…”

Section: Ccn-derived Compoundsmentioning

confidence: 99%

Biodegradation by bacteria in clouds: an underestimated sink for some organics in the atmospheric multiphase system

Khaled

¹

,

Zhang

²

,

Amato

³

et al. 2021

View full text Add to dashboard Cite

Abstract. Water-soluble organic compounds represent a significant fraction of total atmospheric carbon. The main oxidants towards them in the gas and aqueous phases are OH and NO3 radicals. In addition to chemical solutes, a great variety of microorganisms (e.g., bacteria, viruses, fungi) have been identified in cloud water. Previous lab studies suggested that for some organics, biodegradation by bacteria in water is comparable to their loss by chemical processes. We perform model sensitivity studies over large ranges of biological and chemical process parameters using a box model with a detailed atmospheric multiphase chemical mechanism and biodegradation processes to explore the importance of biodegradation of organics in the aqueous phase. Accounting for the fact that only a small number fraction of cloud droplets (∼0.0001–0.001) contains active bacterial cells, we consider only a few bacteria-containing droplets in the model cloud. We demonstrate that biodegradation might be most efficient for water-soluble organic gases with intermediate solubility (∼104≤KH(eff) [M atm−1] ≤106, e.g., formic and acetic acids). This can be explained by the transport limitation due to evaporation of organics from bacteria-free droplets to the gas phase, followed by the dissolution into bacteria-containing droplets. For cloud condensation nuclei (CCN)-derived compounds, such as dicarboxylic acids, the upper limit of organic loss by biodegradation can be approximated by the amount of organics dissolved in the bacteria-containing droplets (<0.1 %). We compare results from our detailed drop-resolved model to simplified model approaches, in which (i) either all cloud droplets are assumed to contain the same cell concentration (0.0001–0.001 cell per droplet), or (ii) only droplets with intact bacterial cells are considered in the cloud (liquid water content ∼10-11 vol / vol). Conclusions based on these approaches generally overestimate the role of biodegradation, particularly for highly water-soluble organic gases. Our model sensitivity studies suggest that current atmospheric multiphase chemistry models are incomplete for organics with intermediate solubility and high bacterial activity.

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“…CC BY 4.0 License. et al, 2002;Fankhauser et al, 2019;Husárová et al, 2011;Vaïtilingom et al, 2010Vaïtilingom et al, , 2011Vaïtilingom et al, , 2013 have been measured in laboratory experiments. Comparison of such rates to those of chemical radical ( • OH 65 or NO3 • ) reactions in the aqueous phase show comparable rates of chemical and microbial processes under atmospherically relevant conditions.…”

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confidence: 99%

Biodegradation of phenol and catechol in cloud water: Comparison to chemical oxidation in the atmospheric multiphase system

Jaber¹,

Lallement²,

Sancelme³

et al. 2020

Preprint

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Abstract. The sinks of hydrocarbons in the atmosphere are usually described by oxidation reactions in the gas and aqueous (cloud) phases. Previous lab studies suggest that in addition to chemical processes, biodegradation by bacteria might also contribute to the loss of organics in clouds; however, due to the lack of comprehensive data sets on such biodegradation processes, they are not commonly included in atmospheric models. In the current study, we measured the biodegradation rates of phenol and catechol, which are known pollutants, by one of the most active strains selected during our previous screening in clouds (Rhodococcus enclensis). For catechol, biodegradation transformation is about ten times faster than for phenol. The experimentally derived biodegradation rates are included in a multiphase box model to compare the chemical loss rates of phenol and catechol in both the gas and aqueous phases to their biodegradation rate in the aqueous phase under atmospheric conditions. Model results show that the degradation rates in the aqueous phase by chemical and biological processes for both compounds are similar to each other. During daytime, biodegradation of catechol is even predicted to exceed the chemical activity in the aqueous phase and to represent a significant sink (17&#8201;%) of total catechol in the atmospheric multiphase system. In general, our results suggest that atmospheric multiphase models may be incomplete for highly soluble organics as biodegradation may represent an unrecognized efficient loss of such organics in cloud water.

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Constraining the Impact of Bacteria on the Aqueous Atmospheric Chemistry of Small Organic Compounds

Cited by 16 publications

References 63 publications

Biodegradation by bacteria in clouds: An underestimated sink for some organics in the atmospheric multiphase system

Biodegradation by bacteria in clouds: An underestimated sink for some organics in the atmospheric multiphase system

Biodegradation by bacteria in clouds: an underestimated sink for some organics in the atmospheric multiphase system

Biodegradation of phenol and catechol in cloud water: Comparison to chemical oxidation in the atmospheric multiphase system

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