Sampling - Field Sampling: Principles and Practices in Environmental Analysis - page 137

samples are also shown. In the lower right-hand corner, the sampling site is designated by
two sets of three numbers. These are the last three digits of the longitude and latitude
positions. The whole position is N39 26.456 and W83 48.157. Only the three last digits
need be shown, however, because the first four digits do not change throughout the field.
This designation lacks the initials of the person doing the sampling and does not give the
location in the project notebook in which a description of the sampling site is located.
The next sampling site is labeled by the sampler's initials and the page in the project
notebook on which the samples are described. This is sufficient if the project notebook
page also gives the position in the field using longitude and latitude. The initials of the
person doing the sampling and six numbers representing the latitude and longitude
location of the sampling site identify the next sample. In the last case, the operator's
initials, the page number in the project notebook (13b), and the longitudes and latitude
position are given.
In this last case the full project notebook designation plus the longitude and latitude
may be too big to fit on the map, and an abbreviated form may be called for. For
example, sample designation AC13b579190 might be simplified to AC13b579 or simply
13b. This may seem awkward, but is both invaluable as work continues and time-saving.
In all of the above situations, a second set of samples taken from a similar
uncontaminated soil in a similar location is needed as a comparison and control. It is
important in taking this sample that it comes from a field that has not been (and is not
now) contaminated by any process, especially in relationship to contamination occurring
at the field of concern. Again, both surface and subsurface samples are needed for
comparison.
5.15. DETERMINING SAMPLES SITES
Random places to be sampled can be obtained by throwing darts at a map of a field and
seeing where they land. In the case of field sampling, we could, for instance, take the
field shown in Figure 5.2, enlarge it, and throw darts at it. Each place a dart lands would
be a place at which a sample would be taken. Note that if this were done no distinction
would be made between different soil types. Another way would be to assign a number to
all possible sample locations in a field and randomly pick and sample these locations.
Because there are an infinite number of possible locations, this is not a practical
approach. Neither of these procedures is typically used in field sampling.
Another approach would be to pick a spot at the edge of a field as a starting point for
sampling. For example, point A in Figure 5.1 is chosen as the starting point. Two
randomly picked numbers are used to represent paces west and north. (Random number
generation will be covered in Chapter 6.) The respective paces are taken and a sample
obtained. This is then repeated to obtain a second sample. If only positive random
numbers are possible, then sampling would proceed north and west across the field,
leaving many portions of the field unsampled. If, on the other hand, both negative and
positive numbers are used, a more random sampling covering more of the field would
occur.
Although the above cases are statistically valid, they are not generally useful or