An underground storage tank $($volume $=1m^3)$ spills its contents of $1\mathrm{.}0kg$ of TCE in a $10m$ thick sand aquifer. The seepage velocity is $1\mathrm{.}0\frac{m}{?}$ day in the $x-$direction. The longitudinal dispersivity is $1\mathrm{.}0m,$ the transverse and vertical dispersivities are $0\mathrm{.}1m.($a$)$ Calculate the maximum concentration at a distance of $x=500m.$ Note: $y=z=0$ for maximum concentration. $($b$)$ If the contaminant was uniformly spilled over the $10m$ thickness of the aquifer, what is the maximum concentration at $x=500m,y=z=0,$ with vertical dispersion $=0.$ The effective porosity is $0\mathrm{.}2.$

The answer is: a$)2$ x $10-5$ kg$/$m$3,$ b$)2\mathrm{.}52$ x $10-4$ kg$/$m$3$