Coastal and estuarine sediment archives for flood-induced pollution in subtropic / tropic areas – a proof-of-concept study

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A precursory proof-of-concept study of the applicants focused on riparian wetlands of two river systems, the Adyar and Cooum rivers, affecting the urban area of Chennai (Tamil Nadu, India). The corresponding results pointed to three remarkable aspects: (i) The urban riverine floodplains in Chennai do not represent significant deposition systems for the riverine sediment-bound pollution; (ii) a broad spectrum of pollutants was detectable even though on a moderate to low concentration level and (ii) in particular for the organic contaminants, several source specific and, therefore, indicative compounds have been identified. However, the question on the major accumulation deposit for the especially urban waste emissions, that can act as sedimentary archive reflecting the pollution history, still remains.Therefore, this project consecutive proposal is intended to test estuarine and backwater systems of the same river systems as suitable major sediment accumulation areas. A first aim is the identification of appropriate sediment archives reflecting the flood/monsoon-driven flushing-out of pollutants at the Indian river systems towards the coastal systems. Here, the interaction of urban riverine systems with the estuarine and backwater areas is focused on. Secondly, a first pollution history using specific marker substances and elements reflecting the various emission sources discharging along the river’s course and in particular the urban area will be built up.Three different areas at the estuary and along the connected coastline will be sampled and tested for their potential to act as sedimentary long-term deposits of riverine discharge. These includes the estuarine area directly at the river mouths (floodplains and river islands), the nearshore areas as well as the backwater systems at Pulicat lagoon and Muttukadu connected to the river systems by the Buckingham canal.Finally, the geochemical comparison of estuarine, backwater and coastal core samples will test the ability to act as sedimentary archives and will reveal evidence for redeposition and accumulation processes of Adyar and Cooum derived particulate matter. The riverine pollution history with particular focus on the urban emissions of Chennai will be exemplarily reconstructed by quantitative analyses of indicator substances and elements in selected sediment cores.