02 Jun 2021

02 Jun 2021

Review status: this preprint is currently under review for the journal ACP.

Total organic carbon and contribution from speciated organics in cloud water: Airborne data analysis from the CAMP2Ex field campaign

Connor Stahl1, Ewan Crosbie2,3, Paola Angela Bañaga4,5, Grace Betito4, Rachel A. Braun1, Zenn Marie Cainglet4,5, Maria Obiminda Cambaliza4,5, Melliza Templonuevo Cruz4,6, Julie Mae Dado7, Miguel Ricardo A. Hilario4,8, Gabrielle Frances Leung4,9, Alexander B. MacDonald1, Angela Monina Magnaye7, Jeffrey Reid10, Claire Robinson2,3, Michael A. Shook2, James Bernard Simpas4,5, Shane Marie Visaga5,7, Edward Winstead2,3, Luke Ziemba2, and Armin Sorooshian1,8 Connor Stahl et al.
  • 1Department of Chemical and Environmental Engineering, University of Arizona, Tucson, Arizona, 85721, USA
  • 2NASA Langley Research Center, Hampton, Virginia, 23666, USA
  • 3Science Systems and Applications, Inc., Hampton, Virginia, 23666, USA
  • 4Air Quality Dynamics-Instrumentation & Technology Development Laboratory, Manila Observatory, Quezon City, 1108, Philippines
  • 5Department of Physics, School of Science and Engineering, Ateneo de Manila University, Quezon City, 1108, Philippines
  • 6Institute of Environmental Science and Meteorology, University of the Philippines, Diliman, Quezon City, 1101, Philippines
  • 7Regional Climate Systems Laboratory, Manila Observatory, Quezon City, 1108, Philippines
  • 8Department of Hydrology and Atmospheric Sciences, University of Arizona, Tucson, Arizona, 85721, USA
  • 9Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado 80521, USA
  • 10Marine Meteorology Division, Naval Research Laboratory, Monterey, California 93943, USA

Abstract. This work focuses on total organic carbon (TOC) and contributing species in cloud water over Southeast Asia using a rare airborne dataset collected during NASA’s Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex), in which a wide variety of maritime clouds were studied, including cumulus congestus, altocumulus, altostratus, and cumulus. Knowledge of TOC levels and their contributing species is needed for improved modeling of cloud processing of organics and to understand how aerosols and gases impact and are impacted by clouds. This work relies on 159 samples collected with an Axial Cyclone Cloud water Collector at altitudes of 0.2–6.8 km that had sufficient volume for both TOC and speciated organic composition analysis. Species included monocarboxylic acids (glycolate, acetate, formate, and pyruvate), dicarboxylic acids (glutarate, adipate, succinate, maleate, and oxalate), methanesulfonate (MSA), and dimethylamine (DMA). TOC values range between 0.018–13.660 ppm C with a mean of 0.902 ppm C. The highest TOC values are observed below 2 km with a general reduction aloft. An exception is samples impacted by biomass burning for which TOC remains enhanced as high as 6.5 km (7.048 ppm C). Estimated total organic matter derived from TOC contributes a mean of 30.7 % to total measured mass (inorganics + organics). Speciated organics contribute (on carbon mass basis) an average of 30.0 % to TOC in the study region, and account for an average of 10.3 % to total measured mass.

The order of the average contribution of species to TOC, in decreasing contribution of carbon mass, is as follows: acetate (14.7 ± 20.5 %), formate (5.4 ± 9.3 %), oxalate (2.8 ± 4.3 %), DMA (1.7 ± 6.3 %), succinate (1.6 ± 2.4 %), pyruvate (1.3 ± 4.5 %), glycolate (1.3 ± 3.7 %), adipate (1.0 ± 3.6 %), MSA (0.1 ± 0.1 %), glutarate (0.1 ± 0.2 %), maleate (< 0.1 ± 0.1 %). Approximately 70 % of TOC remains unaccounted for, thus highlighting the complex nature of organics in the study region; samples collected in biomass burning plumes have up to 95.6 % of unaccounted TOC mass based on the species detected. Consistent with other regions, monocarboxylic acids dominate the speciated organic mass (~75 %) and are about four times in greater abundance than dicarboxylic acids.

Samples are categorized into four cases based on back-trajectory history revealing source-independent similarity between the bulk contributions of monocarboxylic and dicarboxylic acids to TOC (16.03 %–23.66 % and 3.70 %–8.75 %, respectively). Furthermore, acetate, formate, succinate, glutarate, pyruvate, oxalate, and MSA are especially enhanced during biomass burning periods, attributed to peat emissions transported from Sumatra and Borneo. Lastly, dust (Ca2+) and sea salt (Na+/Cl) tracers exhibit strong correlations with speciated organics, thus supporting how coarse aerosol surfaces interact with these water-soluble organics.

Connor Stahl et al.

Status: open (until 28 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Connor Stahl et al.

Data sets

CAMP2Ex P-3 In-Situ Aerosol Data CAMP2Ex Science Team

CAMP2Ex P-3 In-Situ Cloud Data CAMP2Ex Science Team

Connor Stahl et al.


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Short summary
A total of 159 cloud water samples were collected and measured for total organic carbon (TOC) during the CAMP2Ex campaign. On average 30 % of TOC was speciated based on carboxylic/sulfonic acids and dimethylamine. Results provide a critical constraint on cloud composition and vertical profiles of TOC and organic species ranging from ~250 m to ~7 km and representing a variety of cloud types and air mass source influences such as biomass burning, marine emissions, anthropogenic activity, and dust.