Raman and FTIR Spectroscopic Evaluation of Clay Minerals and Estimation of Metal Contaminations in Natural Deposition of Surface Sediments from Brahmaputra River

Abstract

This study demonstrates the compositional and structural analysis of surface sediments in natural depositional environment of the Brahmaputra River using X-ray fluorescence, Raman spectroscopic and Fourier transform infrared spectroscopic techniques. The main peaks in the Raman and infrared spectra reflected Al-OH, Al-O and Si-O functional groups in high frequency stretching and low frequency bending modes. The Raman and infrared spectra reveals the nature of clay (kaolinite) associated with quartz. The infrared spectra are indicative to the weathered metamorphic origin of the silicate minerals. The relative distributions of the contaminations in the sediment are: Si > Al > Fe > Mg > Ca > K > Ti > Mn > Cr >Ni > Zn > Cu > Co. The metal contaminations in the sediments are investigated by calculating the enrichment factor, contamination factor, geo-accumulation index and pollution load index. The relative distributions of the contamination among the samples are: Cu > Si > Mn > Mg > Ni > Cr > Ti > Al > Co > Pb > K > Ca > Zn. The investigating factors suggest the significant contamination in the sediment is due to Cu. The strong positive correlation among Al, Fe, Mg and K suggests association of sediments with clay. The elemental correlation is indicative to the metamorphosed pyrophanite (MnTiO3) deposition.