PHYSICO-CHEMICAL PARAMETERS OF LAKE

Temperature: It is an important factor for aquatic life as it regulates the maximum dissolved oxygen concentration of the water, controls the rate of metabolic activities, reproductive activities and therefore, life cycles. The temperature ranges between 19.90C to 24.20C.

Dissolved Oxygen: Dissolved oxygen (DO) is the most essential feature in aquatic system that helps in aquatic respiration as well as detoxification of complex organic and inorganic mater through oxidation. The presence of organic wastes imposes a very high oxygen demand on the receiving water leading to oxygen depletion with severe impacts on the water ecosystem. The effluentsalso constitute heavy metals, organic toxins, oils, volatile organics, nutrients and solids. The DO of the analysedwater samples varied between 0 to 14.52mg/l.
Table 1: Parameters monitored at site

Profuse growth coupled with the spread of aquatic plants lead to impairment of ecosystem’s functional abilities due to alterations in the food chain. Macrophytes hinder the sunlight penetration leading to anaerobic conditions with the lowered oxygen levels affecting aquatic life. Similarly algal blooms due to respiration would create  lowering of oxygen.  Persistence of anaerobic conditions with lower DO would create stressful conditions for fish, eventually leading to large scale mortality of aquatic life.
Table 2: Chemical Parameters of Water Analysis

pH: pH is a numerical expression that indicates the degree to which water is acidic or alkaline, with the lower pH value tends to make water corrosive and higher pH provides taste complaint and negative impact on skin and eyes. The pH was alkaline in the entire lake ranging from 8.8 to 10.3.
Total Dissolved Solids (TDS): TDS is a measure of the amount of material dissolved in water. This material can include carbonate, bicarbonate, chloride, sulfate, phosphate, nitrate, calcium, magnesium, sodium, organic ions, and other ions.TDS affect the water quality in numerous ways impacting the domestic water usage for cleaning, bathing etc as well as drinking purposes. Total dissolved solids originate from organic sources such as leaves, silt, plankton, industrial waste and sewage. Other sources come from runoff from urban areas, road salts used on street, fertilizers and pesticides used on lawns and farms (APHA, 1995). Surface as well as groundwater with high dissolved solids are of inferior flavor and induce an unfavorable physiological reaction to the dependent population. A limit of 500mg/l TDS is desirable for drinking waters. The TDS values in the samples analysed, ranged from 463to 1128 mg/l across all locations.
Chlorides: Chlorides are essentially potential anionic radical that imparts chlorosity to the waters. An excess of chlorides leads to the formation of potentially carcinogenic and chloro-organic compounds like chloroform, etc. Chloride values in samples ranged from 165to 372mg/l. Chloride values were high at inlets (treated and untreated water) and relatively lower at the outlet and the middle portion of Jakkurlake. A range of 250 mg/l is desirable according to IS 10500.
Sodium: Sodium (Na) is one of the essential cations that stimulates various physiological processes and functioning of nervous system, excretory system and membrane transport in animals and humans. Increase of sodium ions has a negative impact on blood circulation, nervous coordination, thence affecting the hygiene and health of the nearby localities. According to WHO guidelines the maximum admissible limit is 200 ppm. In this study the concentration of sodium ranged from 166- 290mg/l.
Potassium: Potassium (K) is an essential element for both plant and animal nutrition, and occurs in ground waters as a result of mineral dissolution, decomposing of plant materials and also from agricultural runoff. Potassium ions in the plant root systems helps in the cation exchange capacity to transfer essential cations like Ca and Mg from the soil systems into the vascular systems in the plants in replacement with the potassium ions. Incidence of higher potassium levels in soil system affects the solute transfer (active and passive) through the vascular conducting elements to the different parts of the plants. The potassium content in the water samples ranges between 37-80mg/l.
Alkalinity: Alkalinity is a measure of the buffering capacity of water contributed by the dynamic equilibrium between carbonic acid, bicarbonates and carbonates in water. Sometimes excess of hydroxyl ions, phosphate, and organic acids in water causes alkalinity. High alkalinity imparts bitter taste. The acceptable limit of alkalinity is 200mg/l as per IS 10500. The water samples analysedhad higher alkalinities (277-740 mg/l) values.
Total hardness: Hardness is the measure of dissolved minerals that decides the utility of water for domestic purposes. Hardness is mainly due to the presence of carbonates and bicarbonates. It is also caused by variety of dissolved polyvalent metallic ions predominantly calcium and magnesium cation although, other cations like barium, iron, manganese, strontium and zinc also contribute. In the present study, the total hardness ranged between 260 to 482mg/l. According to IS 10500 and WHO guidelines the desirable limit is 300 mg/l.
Calcium: Calcium (Ca) is one amongst the major macro nutrients which are needed for the growth, development and reproduction in case of both plants and animals. The presence of Ca in water is mainly due to its passage through deposits of limestone, dolomite, gypsum and other gypsiferous materials (Manivasakam, 1989). Caconcentration in all samples analysed periodically ranged between 59 to 185mg/l.
Nutrients (nitrates and phosphates): Nutrients essentially comprise of various forms of N and P which readily dissolve in solutions that are up-taken by microbes and plant root systems in the form of inorganic mineral ions. Accumulation of N as nitrates and P as inorganic P in aquatic ecosystems causes significant water quality problems due to higher net productivity. Together with phosphorus, nitrates in excess amounts in streams and other surface waters can accelerate aquatic plant growth causing rapid oxygen depletion or eutrophication in the water. Nitrates at high concentrations (10 mg/l or higher) in surface and groundwater used for human consumption are particularly toxic to young children affecting the oxygen carrying capacity of blood cells (RBC) causing cyanosis (methemoglobinemia). In the present study, nitrate values ranged from 0.7 to 1.28mg/l and phosphate values ranged between 0.3 to 1.86 mg/l. 
The process by which a body of water acquires a high concentration of nutrients, especially phosphates and nitrates is called as eutrophication. These typically promote excessive growth of algae. As the algae die and decompose, high levels of organic matter and the decomposing organisms deplete the water of available oxygen, causing the death of other organisms, such as fish.
COD and BOD: BOD and COD are important parameters that indicate the presence of organic content.

• Biochemical oxygen demand (BOD): Biochemical oxygen demand (BOD) is the amount of oxygen required by bacteria while stabilizing decomposable organic matter under aerobic conditions. Sources of BOD include leaves and woody debris; dead plants and animals; animal manure; effluents from pulp and paper mills, wastewater treatment plants, feedlots, and food-processing plants; failing septic systems; and urban storm water runoff.It is required to  assess  the  pollution  of  surface  and  ground  water  where  contamination  occurred  due  to disposal of domestic and industrial effluents. The BOD ranged between 19 and 53 mg/l.
• Chemical oxygen demand (COD): COD is important parameter that indicates contamination with organic wastes. Chemical oxygen demand (COD) determines the oxygen required for chemical oxidation of most organic matter and oxidizable inorganic substances with the help of strong chemical oxidant. COD test is helpful in indicating toxic conditions and the presence of biologically resistant organic substances. In this study the COD values ranged from 32-84 mg/l.