  In this paper, we address a time-dependent one-dimensional linear
advection-diffusion equation with Dirichlet homogeneous boundary conditions.
The equation is solved both analytically, using separation of variables, and
numerically, employing the finite difference method. The computational output
includes three dimensional (3D) plots for solutions, focusing on pollutants
such as Ammonia, Carbon monoxide, Carbon dioxide, and Sulphur dioxide.
Concentrations, along with their respective diffusivities, are analyzed through
3D plots and actual calculations. To comprehend the diffusivity-concentration
relationship for predicting pollutant movement in the air, the domain is
divided into two halves. The study explores the behavior of pollutants with
higher diffusivity entering regions with lower diffusivity, and vice versa,
using 2D and 3D plots. This task is crucial for effective pollution control
strategies, and safeguarding the environment and public health.
