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Exercise 7
sample and of being simple and relatively foolproof to operate. Available commercially in
several sizes, Van Dorn water samplers are
lowered slowly to the depth to be sampled. The
weighted messenger is dropped down the line to
trigger closure of the end cups. Horizontally
positioned Van Dorn samplers are also available
for sampling in sharply stratified layers, but these
tend to disturb the micro strata by their physical
movement. Battery-driven nonmetallic or peristaltic pumps also are available to sample at
specific depths.
Figure 7.1. The Van Dorn nonmetallic underwater sampler in the open position.