The soil beneath an old dry cleaning facility has been contaminated with tetrachloroethylene

$($PCE$).$ A soil vapour study indicated that the soil air contained $1250$ ppmv of PCE.

$($a$)$ Estimate the PCE concentration in the soil water $($in mg$/$L$),$ assuming that sorption to soil is

negligible and that there is no free phase $($i$.$e$.$ no pure chemical PCE$).(5$ marks$)$

$($b$)$ Estimate the PCE concentration in the soil water $($in mg$/$L$)$ if free phase $($i$.$e$.$ pure chemical$)$ is

present. $(2$ marks$)$