INTERSTITIAL WATER-SEDIMENT GEOCHEMISTRY OF P AND FE IN SEDIMENTS OF VEMBANAD LAKE, WEST-COAST OF INDIA

Sediment, interstitial water and overlying water (surface and bottom) samples from Vembanad lake, Kerala have been studied mainly for P, Fe and salinity. The southern sector with low interstitial water salinity (av. 1.39 x 10(-3)) is characterised by low sediment P (av. 33.08-mu-g.g-1) and Fe (av. 32.43 mg.g-1), while the northern high interstitial water salinity (av. 18.14 x 10(-3)) zone shows elevated levels of sediment P (86-mu-g.g-1) and Fe (av. 74.14 mg.g-1). On the other hand the concentrations of these elements in the interstitial water of southern and northern sectors show opposite trend to that in sediments. The respective averages of interstitial water P and Fe are 35.11-mu-g.l-1 and 58.04 mg.l-1 in the southern sector and 5.02-mu-g.l-1 and 5.08 mg.l-1 in the northern sector. The marginal variation observed in the concentration of P and Fe between surface and bottom waters as well as between southern and northern sectors is presumably due to the near fresh water (monsoon) character of the overlying waters during the study period (June 1989).