Sampling - Field Sampling: Principles and Practices in Environmental Analysis - page 127

FIGURE 5.9 Numbering across the top for surface samples. Greek letters
designate subsurface samples.
should be sampled differently from a flat field. A river bottom sampling plan should be
different from sampling a plateau above a river.
In the case of a sloping field, the top, middle, and bottom of the field should be
designated as separate sampling areas. If grids are used, a horizontal grid line should
occur at the top and bottom of the slope, with additional grid lines in the middle as
needed. A field with little slope can be sampled without regard to slope. However, such
fields commonly contain depressional areas that collect water from surrounding fields.
These areas are thus typically higher in organic matter and should be sampled separately.
Other unusual areas may be encountered, and these should be sampled separately, or at
least the unusual characteristics should be noted in the project notebook.
Sampling must occur on both sides of rivers, as well as the bottom. This is especially
true if contamination of the surface or subsurface is of concern. Even though it will not
look like this can happen, over time all streams and rivers gradually work their way back
and forth across the river valley and can thus both move and bury contaminants [16].
5.12. OTHER SAMPLING STRATEGIES FOR DIFFERENT FIELD
SITUATIONS
5.12.1. The Grab Sample
In taking a grab sample, the question is what is being grabbed. Too often the grab sample
is obtained in the excitement of first visiting a contaminated site. It is often taken without
regard to its position in the contaminated area, the depth of sampling, the sampling tool,
the labeling, or the type of container, and with no specific idea about the conditions of
transport or analysis. For these and for safety reasons, grab samples are not advisable.
In addition, the grab sample is particularly inappropriate where contamination may