Inverse transport problem of estimating point-like source using a Bayesian parametric method with MCMC

Recovering the origin of an incident after detection of a polluting substance in the environment is crucial to start the remediation procedures. The lack of observations, the measurement errors and the model uncertainties make the problem of source estimation an ill-posed inverse problem that requires regularization to determine a solution. The two most frequent methods of regularization are source parametrization and penalization of undesirable solutions. In this paper, the proposed approach combines both methods in order to obtain a strong regularization that is efficient in case of few and erroneous observations. Point sources with parametric temporal releases and parameter penalizations are incorporated in a Bayesian framework where observations and prior information are combined in a hierarchical probabilistic model and the posterior law is explored with a Markov Chain Monte Carlo sampling algorithm. Estimation of the source parameters is provided by the posterior mean and uncertainties are provided by the posterior variance. To validate the method, several simulated cases with different emission events are considered. Quality of the estimate as well as impact of source model errors are also investigated. Then, a comparison with two existing least squares methods is conducted, in various configurations of sensors and noise level. Finally, the behavior of the method is described on a strongly underdeterminate real case where only one sensor recorded the pollution.