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Published July 1989 | Published
Journal Article Open

Carboxylic acids and carbonyl compounds in southern California clouds and fogs


Formaldehyde, formate, and acetate have been determined in fog and cloudwater from several areas of southern California. Up to 190 μM formate and acetate was seen in high pH fog samples from the San Joaquin Valley. Formaldehyde concentrations as high as 500 μM were observed there. Organic acid concentrations were much lower at an acidic site along the margin of the valley. Fog from Riverside, CA had maximum concentrations of 1500 and 500 μM formate and acetate. The highest concentrations were observed in the samples with highest pH. Formaldehyde at Riverside was as high as 380 μM. Average formate and acetate concentrations in intercepted stratus clouds from the Santa Barbara Channel coast and San Pedro Hill were 20–60 μM and 10–30 μM, respectively. Formaldehyde concentrations in stratus clouds were 10–20 μM. Because the lifetime of a cloud or fog droplet is usually much longer than the characteristic time for interfacial mass transport, hydration or dissociation, droplets can be assumed to be in equilibrium with their surroundings. The product of aqueous-phase concentration and liquid water content in the cloud (fog) is nearly always much less than the predicted equilibrium partial pressure. Only the high pH fogs from the San Joaquin Valley have the potential to deplete the gas-phase reservoir of organic acid.

Additional Information

This journal is published under the terms of the Creative Commons Attribution 4.0 International (CC-BY 4.0) License. Manuscript received 16 November 1987; in final form 1 July 1988. This research was supported by a contract with the California Air Resources Board (contract #A4-075-32). We thank the California Air Resources Board, Avenue Cable TV of Ventura, the US Navy, the Federal Aviation Administration and Dr. R. Musselman of Univ. Calif. Riverside for the permission to use their facilities as sampling sites. This work would not have been possible without the field and laboratory assistance of C. Choy, G. Gibb, W. Chong, and A. Kaloustian.

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Published - MUNGER_et_al-1989-Tellus_B.pdf


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