Environmental Engineering Reference
In-Depth Information
Description of Sampling Equipment and Methods
for In-Tank D-1 Standard Sampling
Water Column Sampler
In order to obtain an integrated sample from the whole water column, a water
column sampler may be lowered at best to the bottom of the tank or to the deepest
point accessible. During lowering the water column sampler, water will enter the
sampler from an opening at the top. The water will be proportionally sampled from
the entire water column provided the sampler is lowered with a constant speed
through the water column. As a relatively low water volume needs to be sampled,
i.e., ca. 50 ml, the water column sampler may need to be lowered down only once.
Point-Source Sampler
To take salinity samples from different depths, a point-source sampler has to be
lowered three times to different depths, i.e., the surface, somewhere in the middle of
the water column, and possibly close to the tank bottom or to the deepest accessible
point. Each time the valve of the sampler is opened, which is done by pulling the
rope connected to a valve at the bottom of the sampler, the water can enter the sam-
pler. The valve can be closed again when the rope is relaxed, and then the sampler
is pulled up. We recommend that the three samples from different depths are mixed
and one salinity value is measured. As relatively low water volumes have to be
sampled, i.e., ca. 50 ml, the point-source sampler may need to be lowered only once
per each desired sampling depth, all together three times.
Pump
A pump can be used to receive an integrated sample from three different water
depths or even from the whole water column. The pump itself, or the suction open-
ing of the hose connected to the pump, may be lowered to three desired water
depths, i.e., the surface, somewhere in the middle of the water column, and possibly
close to the tank bottom or to the deepest point accessible. From each depth water
can be pumped up. Alternatively, when lowering the pump or the suction opening of
the hose, water may be pumped up constantly from the top surface water to the
deepest point accessible. In this approach the limiting factor to be considered to
retrieve a sample is the pumping head. As relatively low water volumes are to be
sampled, i.e., ca. 50 ml, only a very short pumping time is needed to get a sample
from each of the three desired water depths. This is the same in case the water is
pumped up is constantly when lowering the pump to the deepest point accessible in
the tank.
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