Seawater, surfactant activity

There are two different classes of surface-active materials in seawater, those that are naturally present and those that have been added to the oceans by man s activities. Most of the analytical methods proposed for use in seawater actually measure the anthropogenic input, and attempt as much as possible to eliminate interferences from naturally occurring compounds. Yet sea foam was known to exist long before detergents. It is to be expected that both kinds of surfactants would be concentrated at the air-sea interface. 

It has been reported for both anionic [14,20,28] and non-ionic surfactants [2,15,23] that sorption increases with the number of carbon atoms in the hydrophobic chain (Table 5.4.5). The sorption coefficient of LAS in activated sludges [22] increases by 2.8 times with each methylene group, and a similar variation has been observed for river and marine sediments (Table 5.4.5). The partition coefficients obtained for the marine medium are slightly higher than those for river sediment, as a consequence of the higher ionic strength of seawater [14]. 

Studies of the effect of surface active materials on gas exchange have shown that natural surfactants present in seawater have a first-order effect on gas transfer [49-51] see reviews by Frew [52] and Asher [53]. In general, direct inhibition due to added resistance of adsorbed films does not appear to be important for limiting gas transfer in natural waters but, rather, hydrodynamic effects involving changes in near surface turbulence, and damping of waves are... 

---