A. Krishnakumar, V. Sobha and D. Padmalal
Abstract
Vellayani Lake with a water-spread area of about 5.5 km2 is the second largest freshwater lake in the Kerala State. The lake is located in the outskirts of the Thiruvananthapuram city and lies between North latitudes 8° 24' 90" and 8° 26'30" and East longitudes 76° 59' 08" and 76° 59' 47". It is getting polluted consequent to the discharge of toxic contaminants from urban and agricultural areas. Lake of adequate base-line information is one of the major constraints challenging conservation and efficient use of freshwater resources. So an attempt has been made in this paper to evaluate the status of nutrient elements like C, N, P and K as well as heavy metals like Fe, Mn, Zn, Cu, Cr, Pb and Cd in the surface sediments ofVellayani lake.The observed values of C-org. N, P and K status indicate that the lake is under stress consequent to urbanization and unscientific agricultural practices in the catchment areas of the lake.The concentration of C-org ranges from 0.84% to 2.53%.The ranges of N, P and K are: 0.22% - 1.18%, 0.14% - 0.36% and 0.01% - 0.12%, respectively.The study showed that nitrogen appeared to be associated with organic matter, whereas phosphorus has a strong affinity with Fe/Mn complexes.The average concentration of Fe, Mn, Zn, Cu, Cr, Pb, and Cd in the lake sediments are: 1.07%, 63.15 ppm, 66.35 ppm, 31.65 ppm, 3.55 ppm 1.27 ppm and 0.81 ppm, respectively.The heavy metals are trapped mainly within the finer fractions of the lake sediments.