SMART Spectro 2 Operator’s Manual 04.16
9
CHEMICAL TESTING
WATER SAMPLING FOR CHEMICAL ANALYSIS
Taking Representative Samples
The underlying factor to be considered for any type of water sampling is whether or not the
sample is truly representative of the source. To properly collect a representative sample:
• Sample as frequently as possible.
• Collect a large sample or at least enough to conduct whatever tests are necessary.
• Make a composite sample for the same sampling area.
• Handle the sample in such a way as to prevent deterioration or contamination
before the analysis is performed.
• Perform analysis for dissolved gases such as dissolved oxygen, carbon dioxide, and
hydrogen sulfi de immediately at the site of sampling. These factors, as well as
samples for pH testing, cannot be stored for later examination.
• Make a list of conditions or observations which may aff ect the sample. Other
considerations for taking representative samples are dependent upon the
source of the sample. Taking samples from surface waters involves diff erent
considerations than taking samples from impounded and sub-surface waters.
Sampling of Open Water Systems
Surface waters, such as those found in streams and rivers, are usually well mixed. The
sample should be taken downstream from any tributary, industrial or sewage pollution
source. For comparison purposes samples may be taken upstream and at the source of
the pollution.
In ponds, lakes, and reservoirs with restricted fl ow, it is necessary to collect a number of
samples in a cross section of the body of water, and where possible composite samples
should be made to ensure representative samples.
To collect samples from surface waters, select a suitable plastic container with a tight
fi tting screw cap. Rinse the container several times with the sample to be tested, then
immerse the container below the surface until it is fi lled to overfl owing and replace the
cap. If the sample is not to be tested immediately, pour a small part of the sample out
and reseal. This will allow for any expansion. Any condition which might aff ect the sample
should be listed.
Sub-surface sampling is required to obtain a vertical profi le of streams, lakes, ponds, and
reservoirs at specifi c depths. This type of sampling requires more sophisticated sampling
equipment.
For dissolved oxygen studies, or for tests requiring small sample sizes, a Water Sampler
(LaMotte Code 1060) will serve as a sub-surface or in-depth sampler. This weighted
device is lowered to the sampling depth and allowed to rest at this depth for a few minutes.
The water percolates into the sample chamber displacing the air which bubbles to the
surface. When the bubbles cease to rise, the device has fl ushed itself approximately
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