Monitoring of environmental contamination by red mud and fly ash pollutants and its spectral reflectance of Koraput district, Odisha, India using Landsat-8 satellite image

Red mud & fly ash are industrial waste generated during the extraction of alumina from bauxite. Red mud is composed of various oxides including iron oxide in bulk which gives it red colour. On the other hand, Fly ash is grey in its colour with a very fine size and can be easily carried away by wind. Both red mud & fly Ash contain high concentrations of various elements including radioactive elements. Its composition depends upon the type of raw material used. It is disposed of into man made ponds, landfills etc. Due to its hazardous nature if not stored/disposed properly pose a serious environmental hazard. Hence its regular monitoring is needed. It can be made simple by use of satellite data which is freely available and systematic results can be generated. This study attempts to examine the spectral reflectance signature of the pollutants-Red mud and Fly ash & its feature extraction and also to analyse its contamination in the surrounding area of Aluminium Extraction Company and to the nearby water reservoir using multi-spectral Landsat-8 Satellite image by employing three supervised machine learning classifiers i.e., Maximum Likelihood (ML) classifier, Support Vector Machine (SVM) classifier and Artificial Neural Network (ANN) classifier, over the period from 2015 to 2023. The result obtained for five years reveals that SVM yielded better overall accuracy and kappa coefficients and its average value of classification outputs were 89.11% and 0.83 followed by Artificial Neural Network classifier with 83.19% & 0.74, whereas Maximum Likelihood classifier yielded lowest average value i.e. 82.68% & 0.76 respectively. The results obtained were carefully examined by comparing classification accuracies and then by visual analysis. From the analysis of spectral signature it was concluded that the nearby reservoir is contaminated by fly ash and also found widely spread in the nearby areas too. The results of the present study indicated that significant changes in terms of the wide spread of pollutants have occurred in the study region, which has degraded the environment a lot.