Estimating the direction of an unknown air pollution source using a digital elevation model and a sample of deposition

A new method is described for estimating the direction of an unknown air pollution source. A heterogeneous topographic exposure to the wind on the polluted surface is assumed. Hence, the method is applicable to mountainous or hilly areas. Estimators of the topographic exposure to wind are modelled using a digital elevation model for different hypothetical directions of wind using an azimuthal step. These estimators are correlated to soil pollution but any other relevant field sampling can be used. If significant, maximum positive correlation indicates the direction towards pollution source(s). When spatial sampling intensity is low, estimators of topographic exposure can be used to significantly improve spatial interpolation of measured values. The first application of the method were performed on a sample of heavy metals soil concentrations in the Risnjak National Park in Croatia. Maximum correlations between soil pollution and topographic exposure are obtained toward the west. This is the main direction of incoming cyclones and also the direction toward major industrial pollution sources. (C) 1999 Elsevier Science B.V. All rights reserved.