Atypical behaviour of dissolved silicate in the Cochin backwater and Periyar river

Abstract

Dissolved silicate was determined for 1 y (1982-83) covering a wide range of salinity from the estuarine mouth to the fresh water region. Silicate concentration ranged between 0.03 and 4.75 mgl/1. Silicate-salinity relationship was linear and inverse in the salinity ranges 0-5 x 10/3 and 5-35 x 10/3. Since variability in the distribution of silicate explained by the significant linear regression model was small in the subranges of salinity 5-20 and 20-30 x 10/3, a curvilinear regression model was fitted and it gave a good fit at 5% level (P 0.05). The expected removal of silicate at salinity range 0-5 and 5-35 x 10/3 given by linear relationship was 28.8 and 51.1% respectively. In 5-20 and 20-30 x 10/3 salinity the expected removal as given by curvilinear relationship was 31.94 and 6.068% respectively