a$.$ Air$-$water interfacial area is an important hydrologic parameter. How does it affect in cleaning the contaminated soil and groundwater?

b$.$ Draw qualitatively the breakthrough curves for solute transporting in porous medium for the following conditions:

i$.$ Advective transport

ii$.$ Advective$-$dispersive transport

iii. Advective$-$dispersive$-$reactive transport

c$.$ A moist soil sample of $550$ cm$3$ was collected and dried in an oven at $105$C for $24$ hours. The weight of the dry soil was found $600$gm$.$ From the grain size distribution of the soil sample, the mean diameter was determined as d$50=0\mathrm{.}50$ mm$.$ Assuming the typical value of particle density for this soil sample, calculate the specific surface area per unit volume of porous medium.