Transplants of the epiphytic lichen Parmelia sulcata were suspended in nylon bags within a rectangle of 15 km wide and 25 km long on a grid 2.5 km'2.5 km in the Sado estuary region. The transplants were oriented towards the wind (F) and opposing the wind (T) and were collected after 3, 6 and 9 months of exposure. Samples were analyzed by INAA and PIXE. Source identification was made by Monte Carlo Target Transformation Factor Analysis (MCTTFA) using three different combinations of data (all data, F data and T data). Five factors were identified for all the combinations performed. For two factors, F and T differentiation was observed.