The global impact of bacterial processes on carbon mass

Ervens, B.; Amato, Pierre

doi:10.5194/acp-20-1777-2020

“…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%

“…Marker compounds such as adenosine 5'-triphosphate (ATP) (Amato et al, 2007c) , rRNA 50 (Krumins et al, 2014) or mRNA (Amato et al, 2019) have been used to demonstrate metabolic activity in the atmosphere. Metabolic activity and cell generation of bacteria is likely restricted to the time cells spent in clouds due to the abundance of liquid water (Haddrell and Thomas, 2017) (Ervens and Amato, 2020); bacteria have been found to be dormant at lower relative humidity than in clouds (Kaprelyants and Kell, 1993).…”

Section: Introductionmentioning

confidence: 99%

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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“…57,58 However, once entered the atmosphere, OM undergoes complex changes; first, abiotically due to chemical reactions, e.g., with OH and NO 3 radicals, and also biologically by microbial degradation. 59,60 Latest studies revealed that airborne bacteria can survive in the atmosphere even in the harsh polar environments and are, similar to bacteria in seawater, metabolically active in the aqueous phase of clouds, as well as on the surface or in the bulk of aerosol particles. 59−63 However, airborne bacteria do not only degrade available OM, but they also release new organics, as it was shown for EPS in cloud water.…”

Section: Introductionmentioning

confidence: 99%

Aerosol Marine Primary Carbohydrates and Atmospheric Transformation in the Western Antarctic Peninsula

Zeppenfeld

¹

,

Pinxteren

²

,

Pinxteren

³

et al. 2021

ACS Earth Space Chem.

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We present ship-borne and land-based measurements of carbohydrate concentrations and patterns in (i) bulk seawater, (ii) sea surface microlayer (SML), and (iii) atmospheric size-resolved aerosol particles (0.05−10 μm) collected in the Western Antarctic Peninsula. In seawater, we find higher combined carbohydrates (CCHO) in both the particulate (PCCHO, 13−248 μg L −1 ) and dissolved (DCCHO, 14−294 μg L −1 ) phases than dissolved free carbohydrates (DFCHO, 1.0−17 μg L −1 ). Moderate enrichment factors are found in the SML samples (median EF SML = 1.4 for PCCHO, DCCHO, and DFCHO). In PM 10 atmospheric particles, combined carbohydrates (CCHO aer,PM10 0.2−11.3 ng m −3 ) were preferably found in particles of two size modes (0.05− 0.42 and 1.2−10 μm) and strongly correlated with Na + aer,PM10 and wind speed, hence suggesting oceanic emission as their primary source. In contrast to SML samples, very high enrichment factors for CCHO aer relative to the bulk water (EF aer ) were estimated for supermicron (20−4000) and submicron (40−167 000) particles. Notably, the relative atmospheric aerosol monosaccharide compositions strongly differed from the ones sampled in seawater. The prevalence of bacterial monosaccharides (muramic acid, glucosamine) in aerosol particles allows us to suggest a selective consumption and release of polysaccharides by bacteria in the atmosphere. Our results highlight the need to evaluate the role of different ecosystems as aerosol sources around Antarctica.

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“…Current atmospheric multiphase chemistry models include chemical mechanisms of different complexity with up to thousands of chemical reactions describing the transformation of inorganic and organic compounds, e.g., (Ervens et al, 2003a;Mouchel-Vallon et al, 2017;Tilgner et al, 2013;Woo and McNeill, 2015). However, they do not include the biodegradation of organics by bacteria despite the available data sets discussed above.…”

Section: A Khaled Et Al: Biodegradation By Bacteria In Cloudsmentioning

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

Self Cite

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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The global impact of bacterial processes on carbon mass

Cited by 19 publications

References 120 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

Aerosol Marine Primary Carbohydrates and Atmospheric Transformation in the Western Antarctic Peninsula

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

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