Very recently, in the air pollution modeling, the usual practice of neglecting the concentration correlation in the atmospheric photochemical reaction has been recognized as a source of serious error and it is shown that in the case of pure mixing (without chemical reaction) the concentration of air pollution decays in a natural manner but if the concentration selected is the chemical reactant of the first order, then the effect is that the decomposition of the concentration fluctuation is much more rapid (Kumar and Patel 1974, 1975; Patel 1974. 1976, 1983, 1984, 1992, 1998). Further the study of formation and destruction of photochemical smog is increasing at both small and large scales (Wanner et al., 1993) and also the transport of chemical species through the Planetary Boundary Layer (PBL) of the atmosphere is a key of global change problem (Lenschow and Hill 1989) and will have to be parameterized more reliably than in the past (Wyngaard 1990). So, it is important to study the various aspects of the concentration fluctuations (of air pollution) with chemical reaction. A model of the diffusion of concentration correlation of air pollution with chemical reaction in the convective Planetary Boundary Layer has been developed using the diffusion approximation of Leith (1968) and Panchev(1969). The general simplifying restrictions, under which the discussion has been carried out are as follows: (i) the turbulence and the concentration fields are homogeneous, (ii) the chemical reaction and the local mass transfer have no effect on the velocity field and (iii) the reaction rate and the diffusivity are constants. For the case of pure mixing (without chemical reaction) and the concentration replaced by temperature, the form of the spectra obtained here reduces to the form obtained by Panchev (1969). This study, also shows that, in the case of pure mixing, the concentration decays in a natural manner, but if the concentration selected is that of the chemical reactant, then the effect is that the dispersion of the concentration of air pollution is much more rapid