Traps, Mistakes, and Errors - Field Sampling: Principles and Practices in Environmental Analysis - page 282

11.4. NOT ACCOUNTING FOR INPUTS, LOSSES, AND MOVEMENT
The level of a contaminant in water or soil will depend on the amount added to it, the
losses, and its movement through or out of the field. Although this seems simple and it is,
it is not the total story. It may be that the addition of a contaminant is a single, one-time
event. On the other hand, there may be a continuing addition of contamination. This can
be very confusing if the occurrence, source, and amounts of contamination being added
are not known.
Additions can be made by spillage, but may also be due to water invading the area or
by windborne material. A spill is likely to be known and may indeed be the reason for
sampling. However, if additional material is being brought into the area by water or wind
movement, it will make the sampling seem bad. Samples may show a continuing increase
in contamination when there is no additional spill. The movement of water onto an area
may be evident; however, the fact that it is carrying contaminant may not. On the other
hand, wind may not seem a possible source of contamination when, through the
deposition of airborne dust, it may well be. Analysis of water entering and air over a field
may be essential in understanding what is happening.
Losses of contaminant through percolation, leaching, and erosion may be evident and
measurable. Certainly there will be monitoring wells around the contaminated field, and
from the analysis of the water in these wells the movement of contaminant out of the field
will be known. However, erosion of contaminated soil may not be as easily identified. A
hectare furrow slice of soil weighs approximately 2,000,000 kg, and thus the loss of 500
kg of soil will not be observable. For this reason, losses from this source may go
unnoticed. Likewise, it may be that a small but significant amount of contaminant is
escaping into the atmosphere. This also may be missed.
Mass movement of soil (as in sliding down a hill) can cause movement of associated
contamination. This may mean that the area originally sampled no longer contains the
contaminant, thus requiring samples to be collected downhill from the original sampling
area. Sampling thus needs to follow the direction of the movement of the contaminated
medium. Failure to take this into account can result in an area being declared free of
contamination when all that has happened is that the contamination has moved to a new
location. This can come back to haunt both samplers and remediators.
11.5. PERSONNEL
Businesses will always prefer to hire the least expensive labor they can. Because field
sampling appears to be simple it seems reasonable to hire samplers who have little
education and no background in field sampling. This can and will lead to sampling
inconsistencies that will cause severe and sometimes costly or even deadly mistakes.
These mistakes will be made in six areas. The first and simplest is that the correct field
will not be found or the incorrect field will be sampled. The second set of mistakes will
occur in reading maps and judging distances. The third will occur because representative,
consistent, uniform samples will not be taken. Observing of environmental