Geochemistry, mineralogy and nutrient concentrations of sediment of River Pampa in India during a massive flood event

Kerala, the southern state of India, was severely hit by a massive flood in August 2018 affecting millions of people causing loss to the state exchequer. The aim of this paper was to study the impacts of this flood on mineralogy, geochemistry (grain size, and heavy metal content) and nutrient content (organic carbon, total and available nitrogen, and phosphorus) of sediment of flood affected Pampa river, Kerala. The study indicates that this large-scale flood results in a considerable reduction in the heavy metals and nutrient concentration of sediment. Frequency histograms for most of the sediment particle size showed unimodal distribution curve with the dominance of sand particles which may be due to wash of fine size fraction like silt and clay during flood. FTIR study indicates that Pampa river sediment is dominant with quartz, orthoclase and microcline feldspar, and kaolinite, along with other trace minerals. SEM study also indicates that quartz is the common occurring mineral and its shape varies from highland to downstream due to transportation. Ratio of carbon to nitrogen and phosphorus particularly at downstream stations indicates the considerable influence of macrophyte which leads to accumulation of terrestrial organic matter. The cluster analysis results indicate that there were some similarity in origin and migration behaviour among these metals and nutrients of the sediments.