Results and Discussions
The reduction in pH vales during the Feb was due to the input of
fresh water in rainy season from rivers Kalanji, Arani, Swarnamukhi and small tributaries. The drainage basin of the lake and the Buckingham
canal as a part of the lake are influencing the pH parameter. The water exchange
between the lake and the Bay of Bengal is mostly takes place in the northern
part of the lake, just above the Satish Dhavan Space Centre.
The alkalinity ranges from 213 to 298 meg/L. This parameter is
also due to the fresh water intrusion by the rivers, rainwater and the
groundwater levels increase in the rainy seasons. Due to the precipitation of
the CaCo3 in the lake waters, there is a reduction of alkalinity in
the water. This calcium may come out in the summer due to the water
evaporation, thereby reducing the alkalinity. In summer there is a much shell
mining and processing in the surroundings of the lake. Sources
of Salinity in fresh water include urban and rural runoff from Industry,
sewage, agriculture and storm water. Cleaning of vegetation also causes the raising
the levels of salinity due to resultant rise in the water table.
The salinity in the lake ranges from 1.8 0/00
to 6.9 0/00 in the rainy season. The lowest salinity is
noted always in the rainy season due to the much fresh water mixing with the
lake water coming from the rivers and the water table rise. The dilution of fresh
water in the lake reduced the concentrations of Ca, Mg, Na and K ions in the post
monsoon. Areas within the tidal limit of rivers that
flow into the sea will experience fluctuations in salinity between low and high
Nitrate and the phosphate are very low even in the post monsoon.
As, generally, freshwater coming from the rivers brings the large quantities of
Nitrates and the phosphates. But, in the lake, the quantity is almost
negligible. The high levels of Nitrate
levels lead to lower the DO levels in the water, which may disrupt the entire
Phosphate level is from 0.6 to 0.7, which is constantly
distributed in the lake. Actually, phosphate is not toxic to plants and the
animals, but it is a plant nutrient, which stimulates the growth of aquatic
weeds and algae. This may cause lakes to become clogged and overrun with the
bushes and plants.
Silicate, generally has the tendency to get absorbed into the
suspended matter and co precipitate with humus substances and other materials.
The silica concentration was very less in the post monsoon ranging from 37 to
Arsenic and cadmium are the two trace metals found in the fresh
water as dissolved species and as adsorbed ions into particulates. Due to the
estuarine mixing, these tracing metals were flocculated forming aggregates. Thermal
power plant significantly, contributes these trace metals to the lake waters.
One of the authors is thankful to Dr. Veeraswamy, Assoc Prof for
his constructive discussion and Mr. Suresh, doing M.Tech in Biochemistry at Andhra
University for his help in the collection of Samples and Testing.