Unfortunately there doesn't appear to be a simple plug in formula to determine how many decades, centuries or millennia before all the free phase and residual DNAPL are finally, fully dissolved. Keep in mind the term DNAPL can also be referred to as "free phase" DNAPL when it has pooled on some sort of low permeability surface such as clay or even a silt aquitard. The term "residual" DNAPL refers more to long strings of DNAPL or even simply separated areas of pore spaces with the water in the pore spaces replaced with tiny chlorobenzene droplets. This residual DNAPL is also a long term source area of eventually dissolved chlorobenzene.
While concentrations of chlorobenzene in the groundwater can be low such as 100, 200 or even a thousand parts per billion (ppb.) nevertheless they are all greater than the Ontario Drinking Water Standard (ODWS) for chlorobenzene of 80 ppb.. Nearer to the DNAPL source areas concentrations however can exceed 1% of the Solubility of chlorobenzene in water which could be as high as 4,300 ppb in either pure lab water or less in already contaminated groundwater.
I expect that some sort of mathematical calculations showing the total number of kilograms of chlorobenzene dissolved within the aquifer is possible. That quantity could then be compared to the thousands upon thousands of gallons of chlorobenzene discharged by Uniroyal into the natural environment. Of course please don't waste my time with any calculations whatsoever done by Lanxess or GHD personnel. "You can't fool all the people all the time.".
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