Question

Small fish in an m-cresol contaminated lake acquire an m-cresol concentation of 0.1 ppm in their fatty tissue. If their fatty tissue behaves similarly to octanol with respect to m-cresol partitioning, what is the probable approximate concentration of m-cresol in the lake water?

Answer 1

The above question is an example of calculating the concentration of m-cresol in water from the octanol water partition co-efficient (Log Pow), assuming that the concentration of cresol in octanol is 0.1 ppm i.e. 0.1 mg/L.

The concentration of m-cresol in octanol is equivalent to the concentration of m-cresol in the fatty tissue of small fish in the m-cresol contaminated lake.

Authoritative sources like the US (EPA) mention the Log Pow, (sometimes also known as Kow) of m-cresol to be 1.95

So, as per the formula;

Log Pow = Log (concentration of solute in solvent/concentration of solute in water)

As we know,

Log Pow = 1.95

concentration of solute in solvent = 0.1 ppm = 0.1 mg/L

concentration of solute in water is to be calculated

Since Log is on either side, it will get cancelled

Thus, 1.95 = 0.1/x

Therefore, x = 0.1/1.95

                     X = 0.0512 mg/L

Thus, the probable approximate concentration of m-cresol in the lake water is 0.0512 ppm or 0.0512 mg/L.