Sample Transport and Storage - Field Sampling: Principles and Practices in Environmental Analysis - page 208

Various paper forms will come with the shipping container and must be filled out and
enclosed with the samples when they are returned to the analytical laboratory. Typical
forms are shown and discussed in Chapter 10.
8.6. TRANSPORT OUT OF FIELD
Care must be taken in transporting samples out of the field to the field storage facility.
Samples should not be thrown in the back of a pickup and left for several days before
being placed in the field office storage facility. This is of particular importance, because
samples banging around in the back of a pickup are prone to both breakage and picking
up contamination, as well as being exposed to light and variations in temperature. Any of
these variations alone or in combination can cause changes in the component or
components of interest.
8.7. STORAGE
There will almost always be time between taking a field sample and its field laboratory
and final analytical laboratory analysis. This will require a secure sample storage area at
or near the field office and at the analytical laboratory. The preference is to have this be a
separate building or at least an area separated from most or all of the other activities
occurring at the field office. As discussed above, this area must be secure from intrusion
by animals and unauthorized intrusion by persons working in the field or in the field
office. It must also be free of possible contaminants. Using a room that has previously
been used for the storage of feed, fertilizer, insecticides, solvents, or some unknown
purpose is not acceptable. Equally important, the stored samples must not be located in a
way that allows materials from samples to contaminate either the office area or the
personnel working there.
The room should be both humidity- and temperature-controlled. In some instances this
will require only heating or cooling, while in others maintaining a constant temperature
may require both a heating and a cooling unit. Constant temperatures are often best
achieved by having a heater and a refrigeration unit working against each other. In high
humidity areas removing some humidity may also be advisable. Air conditioners will
condense moisture out of the air, but this water must be drained to the outside of the
storage room.
The storage room may need to have several sections or different areas, depending on
the storage requirements of the samples taken and the components of interest they
contain. Some samples may need to be stored at 4°C, while others may need to be kept at
−20°C. Yet others may need to be kept at room temperature. Also, some samples may
need to be stored dry, while others need to have the original moisture content maintained.
Ross and Bartlett [1] found that nitrate levels increased dramatically in forested
Spodosols stored at 3°C after only 24 hr. On the other hand, Martens and Suarez found
little change in selenium species in air-dried soil samples. They found significant changes
in selenium oxidation states of air-dried alfalfa (Medicago sativa), however [2].