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

2020 ◽  
Author(s):  
Amina Khaled ◽  
Minghui Zhang ◽  
Pierre Amato ◽  
Anne-Marie Delort ◽  
Barbara Ervens
Keyword(s):  
Organic Compounds ◽  
Dicarboxylic Acids ◽  
Water Soluble ◽  
Chemical Mechanism ◽  
Multiphase System ◽  
Cloud Droplets ◽  
Volatile Organic ◽  
Sensitivity Studies ◽  
Model Cloud ◽  
Acetic Acids

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 ≤ KH(eff) [M atm−1] ≤ 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 (

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

2021 ◽  
Vol 21 (4) ◽  
pp. 3123-3141 ◽  
Author(s):  
Amina Khaled ◽  
Minghui Zhang ◽  
Pierre Amato ◽  
Anne-Marie Delort ◽  
Barbara Ervens
Keyword(s):  
Cloud Condensation Nuclei ◽  
Liquid Water Content ◽  
Water Soluble ◽  
Chemical Mechanism ◽  
Multiphase System ◽  
Bacterial Cells ◽  
Model Sensitivity ◽  
Cloud Droplets ◽  
Sensitivity Studies ◽  
Organic Gases

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.

scholarly journals Aircraft observations of water-soluble dicarboxylic acids in the aerosols over China

2016 ◽  
Author(s):  
Yan-Lin Zhang ◽  
Kimitaka Kawamura ◽  
Ping Qing Fu ◽  
Suresh K. R. Boreddy ◽  
Tomomi Watanabe ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Organic Compounds ◽  
Aqueous Phase ◽  
Dicarboxylic Acids ◽  
Liquid Water Content ◽  
Water Soluble ◽  
Aircraft Observations ◽  
Volatile Organic ◽  
Intercontinental Transport ◽  
Surface Measurements

Abstract. Vertical profiles of low molecular weight dicarboxylic acids, related organic compounds and SOA tracer compounds in particle phase have not yet been simultaneously explored in East Asia, although there is growing evidence that aqueous phase oxidation of volatile organic compounds may be responsible for the elevated organic aerosols (OA) in the free troposphere. Here, we found consistently good correlation of oxalic acid, the most abundant organics globally, with its precursors as well as biogenic-derived secondary OA (SOA) compounds in Chinese tropospheric aerosols by aircraft measurements. Anthropogenically derived dicarboxylic acids (i.e., C5 and C6 diacids) at high altitudes were 4–20 times higher than those from surface measurements and even occasionally dominant over oxalic acid at altitude higher than 2 km, which is in contrast to the predominance of oxalic acid previously reported globally including the tropospheric and surface aerosols. This indicates an enhancement of tropospheric SOA formation from anthropogenic precursors. Furthermore, oxalic acid-tosulfate ratio maximized at altitude of ~2 km, explaining aqueous-phase SOA production that was supported by good correlations with predicted liquid water content, organic carbon and biogenic SOA tracers. These results demonstrate that elevated oxalic acid and related SOA compounds from both the anthropogenic and biogenic sources may substantially contribute to tropospheric OA burden over polluted regions of China, implying aerosol-associated climate effects and intercontinental transport.

scholarly journals Aircraft observations of water-soluble dicarboxylic acids in the aerosols over China

2016 ◽  
Vol 16 (10) ◽  
pp. 6407-6419 ◽  
Author(s):  
Yan-Lin Zhang ◽  
Kimitaka Kawamura ◽  
Ping Qing Fu ◽  
Suresh K. R. Boreddy ◽  
Tomomi Watanabe ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Organic Compounds ◽  
Aqueous Phase ◽  
Dicarboxylic Acids ◽  
Liquid Water Content ◽  
Water Soluble ◽  
Aircraft Observations ◽  
Volatile Organic ◽  
Intercontinental Transport ◽  
Surface Measurements

Abstract. Vertical profiles of dicarboxylic acids, related organic compounds and secondary organic aerosol (SOA) tracer compounds in particle phase have not yet been simultaneously explored in East Asia, although there is growing evidence that aqueous-phase oxidation of volatile organic compounds may be responsible for the elevated organic aerosols (OA) in the troposphere. Here, we found consistently good correlation of oxalic acid, the most abundant individual organic compounds in aerosols globally, with its precursors as well as biogenic-derived SOA compounds in Chinese tropospheric aerosols by aircraft measurements. Anthropogenically derived dicarboxylic acids (i.e., C5 and C6 diacids) at high altitudes were 4–20 times higher than those from surface measurements and even occasionally dominant over oxalic acid at altitudes higher than 2 km, which is in contrast to the predominance of oxalic acid previously reported globally including the tropospheric and surface aerosols. This indicates an enhancement of tropospheric SOA formation from anthropogenic precursors. Furthermore, oxalic acid-to-sulfate ratio maximized at altitudes of  ∼  2 km, explaining aqueous-phase SOA production that was supported by good correlations with predicted liquid water content, organic carbon and biogenic SOA tracers. These results demonstrate that elevated oxalic acid and related SOA compounds from both the anthropogenic and biogenic sources may substantially contribute to tropospheric OA burden over polluted regions of China, implying aerosol-associated climate effects and intercontinental transport.

scholarly journals Aerosol mass yields of selected biogenic volatile organic compounds – a theoretical study with nearly explicit gas-phase chemistry

2019 ◽  
Vol 19 (22) ◽  
pp. 13741-13758
Author(s):  
Carlton Xavier ◽  
Anton Rusanen ◽  
Putian Zhou ◽  
Chen Dean ◽  
Lukas Pichelstorfer ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Gas Phase ◽  
Organic Compounds ◽  
Chemical Mechanism ◽  
Biogenic Volatile Organic Compounds ◽  
Gas Phase Chemistry ◽  
Mass Load ◽  
Volatile Organic ◽  
Phase Chemistry ◽  
Good Agreement

Abstract. In this study we modeled secondary organic aerosol (SOA) mass loadings from the oxidation (by O3, OH and NO3) of five representative biogenic volatile organic compounds (BVOCs): isoprene, endocyclic bond-containing monoterpenes (α-pinene and limonene), exocyclic double-bond compound (β-pinene) and a sesquiterpene (β-caryophyllene). The simulations were designed to replicate an idealized smog chamber and oxidative flow reactors (OFRs). The Master Chemical Mechanism (MCM) together with the peroxy radical autoxidation mechanism (PRAM) were used to simulate the gas-phase chemistry. The aim of this study was to compare the potency of MCM and MCM + PRAM in predicting SOA formation. SOA yields were in good agreement with experimental values for chamber simulations when MCM + PRAM was applied, while a stand-alone MCM underpredicted the SOA yields. Compared to experimental yields, the OFR simulations using MCM + PRAM yields were in good agreement for BVOCs oxidized by both O3 and OH. On the other hand, a stand-alone MCM underpredicted the SOA mass yields. SOA yields increased with decreasing temperatures and NO concentrations and vice versa. This highlights the limitations posed when using fixed SOA yields in a majority of global and regional models. Few compounds that play a crucial role (>95 % of mass load) in contributing to SOA mass increase (using MCM + PRAM) are identified. The results further emphasized that incorporating PRAM in conjunction with MCM does improve SOA mass yield estimation.

Interactions and implications of halogens and VOCs on tropospheric oxidant cycles in the remote atmosphere

2020 ◽  
Author(s):  
Eric C. Apel
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Model Development ◽  
Tropospheric Chemistry ◽  
Chemical Mechanism ◽  
Chemical Production ◽  
Four Seasons ◽  
The Pacific ◽  
Volatile Organic ◽  
Remote Troposphere

&lt;p&gt;Reactive halogens have wide-ranging consequences on tropospheric chemistry including ozone destruction, HOx and NOx partitioning, oxidization of volatile organic compounds (VOCs) and initiation of new particle formation. Of particular note and importance, the tropospheric Ox loss due to halogens is estimated to be between 10-20% globally, and up to 50% in some local marine environments. In this work, we include a state-of-the-art coupled halogen and VOCs chemical mechanism into the CAM-Chem global model. Complementing the model development and providing the opportunity to test the model are recent results from the NASA Atmospheric Tomography (ATom) experiment. &amp;#160;ATom was conducted with a heavily instrumented NASA DC-8 aircraft over the course of two and a half years, transecting the lengths of the Pacific and Atlantic Oceans during four seasons, constantly profiling from the surface (200 m) to the upper troposphere/lower stratosphere (12000 m). The ATom payload included instruments that measured both inorganic halogens and organic halogen-containing very short-lived substances (VSLS), as well as those that measured additional volatile organic compounds (VOCs), including hydrocarbons and oxygenated VOCs (OVOCs), both of which react with halogens. Modeled BrO is sensitive to the inclusion of reactions between Br and OVOCs, particularly the aldehydes, which rapidly convert Br to HBr, a far less reactive form of Br&lt;sub&gt;y&lt;/sub&gt;. These reactions can have large implications in the remote troposphere where the ATom measurements have revealed significant emissions and chemical production of low molecular weight aldehydes over the remote marine environment. A version of CAM-chem, updated to include aldehyde emissions from the ocean to close the gap between models and measurements, is used in these analyses. Comparisons between measured and modeled halogen containing species, both organic and inorganic, is presented along with a summary of the implications of our findings on the overall budgets of tropospheric halogens and ozone.&lt;/p&gt;

scholarly journals On the effects of hydrocarbon and sulphur-containing compounds on the CCN activation of combustion particles

2005 ◽  
Vol 5 (3) ◽  
pp. 2599-2642 ◽  
Author(s):  
A. Petzold ◽  
M. Gysel ◽  
X. Vancassel ◽  
R. Hitzenberger ◽  
H. Puxbaum ◽  
...  
Keyword(s):  
Volatile Organic Compounds ◽  
Gas Turbine ◽  
Sulphuric Acid ◽  
Organic Compounds ◽  
Operating Conditions ◽  
Water Soluble ◽  
Data Set ◽  
Combustion Particles ◽  
Volatile Organic

Abstract. The European PartEmis project (''Measurement and prediction of emissions of aerosols and gaseous precursors from gas turbine engines'') was focussed on the characterisation and quantification of exhaust emissions from a gas turbine engine. A comprehensive suite of aerosol, gas and chemi-ion measurements were conducted under different combustor operating conditions and fuel sulphur concentrations. Combustion aerosol characterisation included on-line measurements of mass and number concentration, size distribution, mixing state, thermal stability of internally mixed particles, hygroscopicity, cloud condensation nuclei (CCN) activation potential, and off-line analysis of chemical composition. Modelling of CCN activation of combustion particles was conducted using microphysical and chemical properties obtained from the measurements as input data. Based on this unique data set, the role of sulphuric acid coatings on the combustion particles, formed in the cooling exhaust plume through either direct condensation of gaseous sulphuric acid or coagulation with volatile condensation particles nucleating from gaseous sulphuric acid, and the role of the organic fraction for the CCN activation of combustion particles was investigated. It was found that particles containing a large fraction of non-volatile organic compounds grow significantly less at high relative humidity than particles with a lower content of non-volatile OC. Also the effect of the non-volatile OC fraction on the potential CCN activation is significant. While a coating of water-soluble sulphuric acid increases the potential CCN activation, or lowers the activation diameter, respectively, the non-volatile organic compounds, mainly found at lower combustion temperatures, can partially compensate this sulphuric acid-related enhancement of CCN activation of carbonaceous combustion aerosol particles.

scholarly journals Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part A): tropospheric degradation of non-aromatic volatile organic compounds

2002 ◽  
Vol 2 (6) ◽  
pp. 1847-1903 ◽  
Author(s):  
S. M. Saunders ◽  
M. E. Jenkin ◽  
R. G. Derwent ◽  
M. J. Pilling
Keyword(s):  
Volatile Organic Compounds ◽  
Organic Compounds ◽  
Good Description ◽  
Field Studies ◽  
Companion Paper ◽  
Chemical Mechanism ◽  
North West ◽  
Radical Intermediates ◽  
Volatile Organic ◽  
Master Chemical Mechanism

Abstract. Kinetic and mechanistic data relevant to the tropospheric degradation of volatile organic compounds (VOC), and the production of secondary pollutants, have previously been used to define a protocol which underpinned the construction of a near-explicit Master Chemical Mechanism. In this paper, an update to the previous protocol is presented, which has been used to define degradation schemes for 107 non-aromatic VOC as part of version 3 of the Master Chemical Mechanism (MCM v3). The treatment of 18 aromatic VOC is described in a companion paper. The protocol is divided into a series of subsections describing initiation reactions, the reactions of the radical intermediates and the further degradation of first and subsequent generation products. Emphasis is placed on updating the previous information, and outlining the methodology which is specifically applicable to VOC not considered previously (e.g. a- and b-pinene). The present protocol aims to take into consideration work available in the open literature up to the beginning of 2001, and some other studies known by the authors which were under review at the time. Application of MCM v3 in appropriate box models indicates that the representation of isoprene degradation provides a good description of the speciated distribution of oxygenated organic products observed in reported field studies where isoprene was the dominant emitted hydrocarbon, and that the a-pinene degradation chemistry provides a good description of the time dependence of key gas phase species in a-pinene/NOX photo-oxidation experiments carried out in the European Photoreactor (EUPHORE). Photochemical Ozone Creation Potentials (POCP) have been calculated for the 106 non-aromatic non-methane VOC in MCM v3 for idealised conditions appropriate to north-west Europe, using a photochemical trajectory model. The POCP values provide a measure of the relative ozone forming abilities of the VOC. Where applicable, the values are compared with those calculated with previous versions of the MCM.

Sign in / Sign up

Export Citation Format

Share Document