Understanding the sediment sources from mineral composition at the lower reach of Rupnarayan River, West Bengal, India – XRD-based analysis

Abstract

Sources of sediments have been identified through study of mineral composition of sediments in the lower reach of the Rupnarayan River, West Bengal, India by X-ray diffraction (XRD) technique to understand the causes and mechanisms of sedimentation. Collected sediment samples are washed by hot and distilled water, dried and disaggregated manually with a mortar and pestle. Sediment samples are scanned at 7°–45°2θ interval by XPERT-PRO diffractometer. Diffractograms generated from XRD analysis reveals that the entire reach under study shows the dominance of minerals including quartz, illite, chlorite, chloritoid, anatase, goethite, oligoclase, sillimanite and corundum, having their origin in the upper and middle catchment with little contribution from lower catchment and river banks. Statistical test indicates that except tourmaline and anatase, all the minerals show steady trend in concentration in sediments. PCA reveals that five Eigen values account for 82.092% of the total variation of the distribution of minerals. There is no conspicuous trend in the spatial distribution of the minerals in the study area. The minerals drained from upper catchment are caught up in the estuary and again redistributed upstream by stronger flood tide. This leads to an unsystematic and irregular distribution of minerals in the study area.