Abstract: Pollutant dispersion problem in the atmosphere is a hard issue, because the atmosphere presents several stability conditions, implying different parameterisations for the atmospheric turbulence. In some practical situations, such as accident, it is important to have available a tool capable of identifying the pollutant source emission strength on the basis of measured concentrations only. % Therefore, the goal here is to identify the strength of pollutant sources knowing the ground level concentrations, where two different sources, linear and an areal, are simultaneously emitting. A Langrangian particle model, based on the Langevin equation, is used to simulate the forward problem, while the inverse problem is formulated as an optimization problem. Regularized solutions are searched, using the Tikhonov norm of second order, associated to the objective function. Two optimizers are employed to obtain inverse solutions: quasi-Newton method, and simulated annealing; a deterministic and stochastic approaches, respectively. Under certain conditions, the deterministic approach is unable to find a good inverse solution.