Presampling - Field Sampling: Principles and Practices in Environmental Analysis - page 57

3.3.1. Number Changes
Sometimes another sample number replaces the number given in the field when the
sample is processed for storage, shipping, or almost always, in the commercial
laboratory. Renumbering opens up the whole process to error and is not recommended. If,
however, it cannot be avoided it is strongly recommended that the original sample
number be kept on or with the sample even after a new number is given. In all these cases
a cross-reference list relating the two different numbers must be readily available and a
copy must be kept with the samples at all times.
Sample numbering and recording process mistakes will be made during the sampling.
Numbers will not be written legibly, or they will get erased or smeared and become
unreadable. To the extent possible every effort should be made to eliminate or limit these
types of errors. Using nonsmearing pens, using paper that can be written on when wet,
and putting the sample numbers on the sample containers in several places are all good
approaches to limiting these problems. It is far less expensive and less time consuming to
spend extra time on sample labeling than on taking another sample or assuming a
sample's identity [1].
One way to help minimize sample labeling errors is bar coding. There are software
programs, computers, and printers that can print bar codes on various media, including
labels of different sizes. Not only will bar codes help prevent mistakes in labeling, they
will also speed up sample handling, especially in maintaining the chain of custody. If bar
codes are used, a bar code for the sample needs to be in the project notebook in which the
sample is described (see Chapter 8 for more information on bar coding) [2].
A GPS unit will often be used in sampling a field. This will give the location of a
sample site and may even record a sample number to be associated with that site. Even in
this case it is important to have a project notebook to record these and other data about
the sample when the sample is taken. At the time of sampling this will seem to be
unnecessary repetition, while a week later it will be found to be an essential, time-saving
step.
3.4. MAPS
Maps are the heart of the sampling process and are essential for any successful sampling
program. There are many types of maps available; for example, surface, topographic, and
three-dimensional. Especially valuable are aerial photographs of the specific area to be
sampled. If they are not available there are both firms and computer programs that can be
called upon to produce the needed maps, aerial photographs, or both. Before doing
anything at a contaminated field it is essential to have several maps of different scales of
the area. One map should show the contaminated field and the surrounding areas. Several
maps showing details of the field itself will also be needed.
I would not, however, recommend producing a large number of very detailed and
expensive maps. What is needed are many simple maps of the area suitable for recording
data on. Each time some activity takes place on the field it needs to be recorded not only
in the project notebook but also on a field map, so that the location is precisely known.