1. Determination of dissolved oxygen free CO2, total alkalinity, total hardness, calcium, magnesium, ammonia, nitrate and phosphorus

2. DISSOLVED GASES
The major gases dissolving - Nitrogen, Oxygen and Carbon dioxide and minor gases such as Helium and the inert gases-Neon, Argon, Krypton and Xenon
Gases present in water enters from the atmosphere; very rare gases come from radio active decay processes with in the sediment in the ocean
Dissolution of gases depends on
Temperature of the gas and the solution
Atmospheric partial pressure of the gas
Salt content of the solution
Biological activity

3. DISSOLVED OXYGEN
Oxygen - one of the most significant chemical substances in natural waters
Significant for metabolic processes as a regulator of both community and organisms
Oxygen acts as an indicator of water quality
The solubility of oxygen in water is increased by
lowering of the temperature
The solubility increases by more than 40%
as fresh water cools from 250 to 00 C
The oxygen saturation values at various temperatures are represented in nomogram

4. The solubility of each gas is independent of other gases in the mixture
Under standard conditions of pressure and temperature, the solubility of oxygen in water is over twice that of nitrogen and about 1/3 that of carbon dioxide
The solubility of oxygen decreases as the dissolved salts increases
At O0C, fresh water at saturation and salts contains slightly over 2.0 mg/l than the average sea water salty (35%) at 150C the difference is about 1.5 mg/l

5. The amount of dissolved oxygen in sea water varied between 0 and 12
The amount of dissolved oxygen in sea water varied between 0 and 12.6 mg/l
Oxygen in neutral waters may also be derived from photosynthetic activity by plants.
6C H20  C6H H20 + energy
Maximum production of oxygen during afternoon on clear day and minimum after dawn
Major sources of oxygen in water
The atmosphere
The Biological

6. FACTORS INFLUENCE THE CONCENTRATION OF OXYGEN
The volume percent of oxygen in the atmosphere i.e % value of 210 cc. of oxygen/l.0 gm. air.
This is some 25 times the conc. oxygen in he same volume, fresh water
The rate of atmospheric oxygen passes across the air-water surface
i) Wave action - more dissolution at higher wave action
ii) Partial pressure between air and water-At greater partial pressure greater dissolution
iii) Moritecatent of the gas (Less rapid dissolve)

7. Transport of by currents
Major consumer of oxygen is animals and plants for respiratory and decomposition of organic materials
Oxidation process is the addition of oxygen to a substance
Reduction is the processes of removal of oxygen from the substance

8. CARBON DIOXIDE
It helps to buffer the environment –Important agent for acidity and alkalinity
Helps in biological productivity through photosynthesis
Help the seed germination in some plants and growth
Carbon dioxide readily reacts with document groups of
elements to produce many compounds
Carbon dioxide has very high solubility in natural water
Carbon dioxide is locked up in various combined forms especially in marine water – Bivales, corabonate etc.,

9. SOURCE OF CO2 IN NATURAL WATERS:
Bacterial decomposition of organic matter.
Respiration by animals and plants.
Rain water
Chemical reactions
Ground water
Atmospheric direct supply
CO2 in natural water is 35 – 40 atom; reaches 200 ppm or more.
Calcium and magnesium carbonate precipitated as Marl highly saline lakes carbonate conc. may be 8500 ppm
The pH of sea water usually ranged between 8.00 and 8.3 due to bicarbonate system

10. OTHER GASES
Methane (CH4)
Methane is an organic gas widely called Marsh Gas common in many alkaline lakes, ponds and swamps especially during summer season
Chemically CH4 gas produced due to decomposition of organic substances
It occurs in aquatic environments under anaerobic conditions