Presampling - Field Sampling: Principles and Practices in Environmental Analysis - page 63

or a power station. (See Chapters 10 and 11.) Knowing what is around the field and other
possible sources of contamination will make discovering and understanding these sources
of confusion much easier.
As with all activities related to field sampling notes about this initial survey must be
put in the project notebook. All observations about the field need to be entered with
particular reference as to where the items of note are located in the field, and as indicated
above these observations are to be included on the appropriate maps of the field and their
positions marked using GPS.
3.6. FIELD HISTORY
After surveying the field the second thing to be put in the project book is a field history.
The best field history is one that includes all available information about the field use or
uses before its latest use and the use that has necessitated the sampling or cleanup. The
sources of this information will be owner records, along with deeds of sale and
municipal, county, state, and governmental records and any available GIS thematic maps.
In some cases it may also be valuable to talk with people living in and around the field
about what has happened there. Do not assume that an isolated field on a back road in the
country is not contaminated. I have seen hidden fields 20 miles from a city being used
clandestinely as dumpsites. Also, isolated areas on a farm might be used to dispose of
agricultural chemicals.
As indicated above, it is also a good idea to know what the areas around the site were
being used for historically. These surrounding areas can be a source of additional
contamination, (e.g., low-lying areas can become contaminated as water washes
contaminants or eroding soil from surrounding or neighboring fields into the area).
Field History in Relationship to Phosphate Content
I often work on projects in developing countries. One project involved a
search for a source of phosphate, which might have been used as fertilizer. I
was supplied five soil samples from an area, composed of several fields,
which were suspected to contain a phosphate rock deposit. Analysis of the
samples gave mixed results. Some samples had undetectable amounts of
phosphate, and other samples had moderate to high levels of phosphate.
In this case a lot of money would have been saved if a detailed history of
the fields had been obtained. A map showing the location of previous
activities in the fields and the sampling sites before detailed sampling and
analysis was done would also have been useful. It turned out that the samples
were taken from fields that had at one time been a village and at another time
a burial site. Soil samples that came from cooking fire sites showed moderate
levels of phosphate. Samples containing chips of bone showed high levels of
phosphate. Soil not contaminated with ash or bone had undetectable levels of
phosphate.