Abstract
An intensive surface sediment survey was carried out over 24 locations from the upstream to downstream sections of two large rivers (Adyar and Cooum) in Chennai (India) during the February dry season of 2015. Trace element concentrations were assessed on a <63 µm fraction using the Geoaccumulation Index (Igeo) and the newly proposed Geochemical Urban Footprint Index (GUFI), which can be performed to determine the pollution status of any megacity river influenced by urban development. The sediment quality of Chennai’s rivers was also compared to worldwide megacity pollution using sediment quality guidelines (SQGs), and a new megacity pollution ranking was determined. The Igeo results indicate that the Chennai rivers studied are strongly to extremely polluted regarding trace element content of sediment. Silver (Ag), Cadmium (Cd) and Mercury (Hg) are the most significant tracers of urban contamination. Chromium (Cr) concentrations show an industrial contamination gradient in relation to levels of other trace elements (As, Cu, Ni, Pb, and Zn) at the Chennai megacity scale. The GUFI ranges from moderate to extreme contamination, particularly in the downstream stretches of the two rivers. This spatial trend is related to various point sources and identified at specific sampling stations, with a lack of identifiable buffer zones. According to the worldwide comparison of megacity pollution, Chennai is ranked in fifth position. The present position can be attributed to a number of explanations: a population explosion associated with the unplanned growth of the city and non-controlled point sources of pollution in Chennai’s waterways.
Highlights
Rapid urbanization and industrial development over the last four decades have resulted in some serious concerns about water bodies, in megacities [1,2,3,4,5,6]
The aim of the present study is to identify the present pollution status of Chennai megacity, along the two urban rivers, the Adyar and Cooum, and to identify the sources of trace elements and their transport along the river to the Gulf of Bengal
The minimum concentrations of trace elements Ag, Cd, Cu, Hg, Pb and Zn were always found in sediment samples collected at the most upstream stations (A1 and C1, Table 1)
Summary
Rapid urbanization and industrial development over the last four decades have resulted in some serious concerns about water bodies, in megacities [1,2,3,4,5,6]. Urban rivers have been associated with pollution because of the practice of discharging untreated domestic and industrial waste into rivers [7,8,9,10]. The presence of certain trace elements may highlight certain sources, for example, trace elements such as Ag, Cd, Cr, Cu, Hg, Ni, Pb and Zn from domestic and industrial effluents [17,18,19,20]. In Paris (Seine river basin, France), trace element concentrations in sediment varied by one order of magnitude
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
