Assessment of WQ parameters
o Preparation for sampling and analysis
o Sampling
o Analysis at the site as needed
o Sample preservation at the site
o Lab analysis, in replicate
o Calculation of the final result
o Statistical treatment
o Interpretation of result/ judgment of WQ
Preparation for sampling and analysis
Before we’re going to analyze we have to have good idea about the sampling and analyzing process. We should know how many containers to be taken, what type of bottles to be taken, volume of sample that we need etc.
Before we’re going to analyze we have to have good idea about the sampling and analyzing process. We should know how many containers to be taken, what type of bottles to be taken, volume of sample that we need etc.
Ex: when we’re choosing the bottles or containers…
ü Pesticide analysis- must use a glass bottles
ü Metal ion analysis- must use plastic bottles because metal ions exchange Na+ ions with glass.
ü DO (Dissolved Oxygen) - fixing should be done at the site and necessary chemicals should be added at the site.
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| source:www.gov.mb.ca |
Sample we select should represent the entire water body (should represent the bulk). Therefore, depending on the type of WQ parameter to be measured the volume of the sample and pretreatment method should be decided.
1) Grab (catch) smaples
o Sample collected at a particular time and place
o Only recommended If the water body is completely uniform
o Not suitable for natural water bodies
2) Composite samples
o Combination of grab samples collected at the same sampling point at different times
o Only recommended of the level pollution is time dependent
o Recommended for industrial outlets
o Number of samples will depend on the
· Industrial process
· Which step uses more chemicals
· Idea of the amount of chemical used
· Number of shifts
3) Integrated samples
o Collection of grab samples from many different points at the same time
o These samples are recommended to investigate water pollution of a natural water body
EX:
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| Integrated Sampling in a Lake According to the above example, |
Level 1(Top surface)- 13 samples
Level 2(drop line1) - 9 samples
Level 3(drop line2) - 5 samples
Analise at the site as needed
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| Source: www.shorelinewa.gov |
Temperature, pH, conductivity, salinity color and tasty can be determined at the sampling site. If the measurements are taken at the site, no preservation requires. If measurements are done at a Laboratory, sample should be stored in a proper manner until the analysis is performed. In some cases special preservation methods are requires to maintain the pollution level unchanged.
WQ parameters will be discussed in next posts.............
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