Presampling - Field Sampling: Principles and Practices in Environmental Analysis - page 70

FIGURE 3.7 Sample containers. Front (from left to right)—paper, plastic, and
cloth bags. Back (from left to right)—glass bottle and glass gas
sample bottle.
When initially surveying the area and obtaining information (i.e., history) about a field,
its pedology * and previous use, crop production, manufacturing, storage, and so forth
should be gathered. The accuracy and precision of sampling is best when both of these
factors are considered together in developing a sampling plan rather than when one is
used alone.
The number of samples or cores taken, the size of the sampling pattern, and the depth
of sampling are all important in obtaining accurate results. Three to six mixed cores give
four to five times better analytical results than analyzing the cores individually. Smaller
sampling grids give significantly better agreement between samples than do larger grids.
This of course has practical limitations, particularly if the contaminated area or fields to
be sampled are large. Also, if the problem is not agreement between samples but finding
threshold values, this issue may be moot. Also, when sampling with depth recognizing
the importance of horizonation is critical.
* Pedology is the scientific study of soils, including horizon formation, texture, and structure soil
types.