These factors can have opposite effects on Kkao/w and cancel each other out. Note that Ndabambi and Kwon 33 also reported Kkao/w values of 4.12-7.48 for C8-to C18-BACs measured using algal toxicity responses. These values are substantially higher than any of the other measurements and are not plotted in Figure . The Kkao/w values from Droge and Goss were measured using a column retention method with a water composition similar to that of the current study. However, their log Kkao/w values were ~1 log unit higher than our values. In the literature, a factor of ~5 difference in sorption capacity between kaolinite samples of different origin has been reported for nonionic surfactant, and the result of the current study shows an even larger difference. It is interesting to note that in ref 29, benzyltrimethylammonium (C1-BAC) had a log Kkao/w value only 0.2 lower than that of C6-BAC, even though C1-BAC is five C atoms shorter than C6-BAC. This result is also consistent with the notion that the alkyl chain must be long enough to interact optimally with the kaolinite surface.