APPARENT PARTITION-COEFFICIENTS OF 15 CARBONYL-COMPOUNDS BETWEEN AIR AND SEAWATER AND BETWEEN AIR AND FRESH-WATER - IMPLICATIONS FOR AIR SEA EXCHANGE

Apparent partition coefficients (K*, in M/atm) of 15 carbonyl compounds between water and air were determined as a function of temperature, salinity, and pH, using a bubble column technique. Values for K* decrease with increasing carbon number of alkanals; e.g., at 25 °C apparent partition coefficients between air and seawater range from 3710 for formaldehyde and 13.1 for acetaldehyde to 0.181 for decanal. Where overlap exists, our data are in good agreement with literature values. log K* was found to be highly temperature dependent, varying linearly with 1/T for all compounds studied. The salinity effect on K* increases with increasing molecular weight; K* (seawater)/K* (freshwater) ratios range from close to 1 for formaldehyde and acetaldehyde to less than 0.3 for nonanal and decanal. The effect of pH in the range of 4-8 on K* was found to be negligible. This study presents the most complete data set of carbonyl partition coefficients to date and should facilitate modeling of exchange of these compounds between gas and aqueous phases. Some implications of our results for air–sea exchange of carbonyl compounds are discussed. © 1990, American Chemical Society. All rights reserved.