ALGAL BIODIVERSITY BASED RECONSTRUCTION OF THE PAST LOCAL AND REGIONAL ENVIRONMENTAL CONDITIONS OF RIVER YAMUNA IN DELHI REGION

Abstract

River Yamuna is one of the most essential river of India originating from the Yamunotri glacier in Himalayas from a height of 6387 meters and travelling a total length of 1,376 kilometres before it merges in river Ganga. A majority of population depends on river Yamuna for their daily needs. Yamuna enters in Delhi at Palla village covering a stretch of 48 kilometres. This is where it receives huge amount of pollutants as sewage and industrial disposals. However, it is assumed that river Yamuna was clean and in good health during earlier times. Therefore, the present research is the first attempt to study the paleolimnological conditions of river Yamuna using river bed sediments for radioactive Carbon-14 dating and using diatom diversity as an indicator of paleolimnological conditions . Two sites were selected for the research work, SITE A Palla village of Delhi where Yamuna enters in Delhi and SITE B was near Okhla barrage which is present almost at the last stretch of Yamuna in Delhi. SITE A, Palla village is present far from urban population of Delhi and surrounded by agricultural fields while Okhla barrage is located in vicinity of a outsized human population where it receives a massive amount of pollution through sewage and industrial wastes. A total of 18 river sediment samples were taken at different depths from both the sites in which 9 samples were from SITE A and 9 samples from SITE B. Diatoms have been an essential component of paleolimnological assessments for a variety of reasons, which includes their well-preserved siliceous frustules, their ability to respond swiftly to variations in the environment and their distribution among a varied range of water quality gradients. Therefore, diatom assemblage of particular vi sediment from river bed was used to reveal ecological conditions of a particular time frame observed by radiocarbon 14C analysis. A total of 31 species of diatom was observed from the riverbed sediments. Each sample revealed almost different diversity of diatoms. The ecological indicators like pH, trophic state, Nitrogen uptake, oxygen and moisture requirements which are very unique for every diatom taxa were used to reveal environmental conditions of the river Yamuna in prehistoric times using the sediments collected from river bed. Other experiments like SEM-EDAX, CHNS analysis, XRD and XRF analysis were also performed to study the geochemical nature of sediments. Different elements like Si, O, Al, Nb were recorded from river sediments by EDAX analysis, while CHNS analysis helped in analyzing the concentrations of Carbon, Hydrogen, Nitrogen and Sulphur. The nature of mineral composition is studied with the help of XRD which revealed Quartz as the major mineral present at both the Sites. XRF revealed most of the oxides, trace elements and some heavy metals from the riverbed sediments. Various oxides and trace elements which are found in XRF analysis are Al2O3, CaO, Fe2O3, K2O, MgO, Na2O, P2O5, SiO2, TiO2, Th, MnO, Sc, V, Cr, Co, Ni, Cu, Zn, Rb, Sr, Zr, Ba, Pb. The correlation of these oxides and trace metals is an efficient way to study chemical nature of river Yamuna sediments. Paleolimnological and geochemical data revealed from sediments could be of great significance for understanding complex nature of river sediments components, diatom diversity and ecology and hence in conservation of river.