Environmental pollution is one of the most serious problems of the contemporary world. Chemical industry is one of the major sources of environmental pollutants. Human knowledge and experience is currently focused on the use of assessment methods and techniques before and during the onset of such activities. For instance, it is common to consider the integration of multiple constraining factors and also, taking into account their high complexity and the application of one of the various techniques of Multi-Criteria Decision Making. The purpose of this study is to determine the location of the least and most polluted areas from several sampling points on the Olt River, in Romania. In the investigations carried out, MCDM methods were used: AHP and TOPSIS and spatial analysis performed using GIS software. The first part of the paper presents a quantitative assessment of the pollution in each sampling using AHP method. In the second part, the most polluted and least polluted sampling points among those under consideration were determined by using TOPSIS. At the end of the work performed, a spatial analysis allowed for the development of representative maps of the studied area. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.