Multispecies solute dispersion with variable porosity in semi-infinite saturated porous media

Multispecies solute dispersion with sequential first-order decay often occurs in contaminated geological formation with radioactive wastes and their biodegradation products. As a result, analytical result is an essential and effective means with a variability of applications, such as providing approximate analysis of contamination dispersion hazard scenarios, executing sensitivity analysis to exploring how various decay parameters affect the processes of contaminant transport. The main objective is to analyze solute dispersion for two-species solute migration model subject to uniform source concentration. The effect of linear isotherm, porosities, densities, and first-order decay terms is also analyzed for concentration distribution. For the prediction of solute dispersion, use solute included domain as a linear combination of the initial source concentration with zero-order production at initially. An exact solution is derived for unsteady-state two-species transport model with uniform dispersion coefficient for semi-infinite saturated geological formation. The concentration distribution pattern is depicted for the first and second species for a finite length of the domain in the presence and absence of species for different values of densities and variable porosities. The results showed that the contaminant concentration remained the same during the early period of injection for the first species, whereas for the second species, it attained its maximum level of concentration. Also, we found that beyond a certain distance, it attains the minimum level of concentration for both the first and second species. Results were compared with the existing research works and were shown noticeable good agreement between them.