The ultraviolet absorption characteristics of Vellar Estuary

Abstract

The distribution of organic matter in the surface and bottom waters of the Vellar Estuary, Tamil Nadu, India at different locations was determined during the post-monsoon season (1980) from UV-absorption spectra. The integrated UV-absorption spectra of the surface water at 250 and 350 nm revealed high values (1161 units) at the marine zone and low values (860 units) in the fresh water zone indicating that the DOM originates from both areas. The bottom water showed higher integrated UV-absorption only in the middle region of the estuary. Higher UV-absorbance was noticed at 225 than at 250 nm. Further the ratio between 225, 250, 300 and 350 nm revealed an increase towards the short wavelength (225 nm) without much alterations in the values at 250, 300 and 350 nm. The relationship between salinity and UV-characteristics was studied to assess the sources of dissolved organic matter. The nature of UV-absorbance of the culture medium of Unialgal Aphanocapsa sp. Oscillatoria sp. and Phormidium sp. was also investigated for comparison