Munger, James William (1989) The chemical composition of fogs and clouds in southern California. Dissertation (Ph.D.), California Institute of Technology. http://resolver.caltech.edu/CaltechETD:etd-02132007-152409
Fogs and clouds are frequent occurrences in Southern California. Their chemical composition is of interest due to their potential role in the transformation of sulfur and nitrogen oxides to sulfuric and nitric acid and in the subsequent deposition of those acids. In addition, cloud and fog droplets may be involved in the chemistry of low-molecular-weight carboxylic acids and carbonyl compounds.
The major inorganic species in cloud and fogwater samples were NH+, H+, NO-, and SO[2-]. Concentrations in fogwater samples were 1-10 x 10[-3] M; pH values ranged from [~]2 to 6. Nitrate usually exceeded sulfate. Acidity depended on the availability of NH from agricultural operations. Stratus cloudwater had somewhat lower concentrations; pH values were in the range 3 - 4. The major factors accounting for variation in fog- or cloudwater composition were the preexisting aerosol and gas concentrations and variations in liquid water content. Deposition and entrainment or advection of different air masses were also important during extended cloud or fog episodes.
The droplet size dependence of cloudwater composition was investigated on one occasion in an intercepted coastal stratus clouds. The observations were consistent with the hypothesis that small droplets form on small secondary aerosol composed of HSO, HNO and their NH[4+] salts, while large droplets form on large sea-salt and soil-dust aerosol. Species that can exist in the gas phase, such as HCl and HNO, may be found in either droplet-size fraction.
Concentrations of S(IV) and CHO in the range 100 - 1000 µM were observed in fogwater from urban sites in Southern California. Lower concentrations were observed in stratus clouds. The high levels of S(IV) and CHO were attributed to the formation of hydroxymethanesulfonate (HMSA), the S(IV) adduct of CHO. Direct measurement of HMSA in fogwater samples from Bakersfield, CA were made by ion-pairing chromatography. Glyoxal and methyiglyoxal were observed at concentrations comparable to CHO in fogwater samples from Riverside, CA and in stratus cloudwater samples from sites along the Santa Barbara Channel.
|Item Type:||Thesis (Dissertation (Ph.D.))|
|Subject Keywords:||acid fog, stratus, cloudwater scavenging,cloudwater chemistry|
|Degree Grantor:||California Institute of Technology|
|Division:||Engineering and Applied Science|
|Major Option:||Environmental Science and Engineering|
|Thesis Availability:||Public (worldwide access)|
|Defense Date:||25 July 1988|
|Author Email:||jwmunger (AT) seas.harvard.edu|
|Default Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Imported from ETD-db|
|Deposited On:||12 Mar 2007|
|Last Modified:||03 Aug 2015 16:43|
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