segunda-feira, 17 de janeiro de 2011

Collecting water samples


The sampling consists on collecting samples to do a laboratorial analysis. The way how it is done is important. In our country there are rules to collect samples, which are defined by NP-409.
- Surface water: the samples collection should be done with special bottles, with an automatic opening.  
- Automatic collection: let the bottle suspended by a rope go down, until achieve the water surface, drop a meter of role fast, so that water can go into the bottle before it is carried by the river current. Repeat this procedure until the bottle is full.  
- Manual collection: take the bottle in the base (without taking off the stopper not to cause contamination) and submerge it with the opening turned down, doing oscillatory movements in the river current’s direction (if the place has a calm water, push the bottle ahead, parallel to the surface).

The collection must be done about 30 cm above the water surface and 20 m away from the river bank and in different spots, on the chosen places, for a correct representativeness. Then it must be sent, as fast as possible, to the laboratory.

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