Summary: We are concerned with conditional stability for an inverse problem of deciding source terms \(f(x)\) in a 1D advection-dispersion equation \[ \frac{\partial c}{\partial t}-D_L\frac{\partial^2c}{\partial x^2}+u \frac{\partial c}{\partial x}=\alpha(t)f(x) \] by final observations \(c(x,T)=c_T(x)\), \(0\leq x\leq\ell\). The inverse problem here is based on a mathematical model derived from a real world case in a geological region in Shandong province, China. With an integral identity and analysis for a normal Sturm-Liouville problem, conditional stability for the inverse problem is proved.