We study interfacial mass transfer between two immiscible fluids in porous media augmented with bulk reactions. A closed-form analytic approximation derived through Laplace transformation is represented for Darcy-Brinkman flow in the presence of first-order bulk reactions represented by the Damkohler number (Da). By comparing the residues of all the singularities, it is shown that the main contributor to the solution is the simple pole of the equations. We show that the solution holds for a range of , where Pe is the P,clet number. By determining the bulk flow mass transfer coefficient, we verify our approximation compared to the previous studies and show acceptable conformity of the solutions. We find that the results are applicable for potential bulk reactions, such as biodegradation, in a typical groundwater system.