Environmental Engineering Reference
In-Depth Information
problems from transport. When this is completed the raw data are processed and
documented. Finally, the results from all the tests performed are considered together as a
whole. Complex matrices and difficult testing problems can all require a combination of
methods and analytical procedures to arrive at the final analytical report, so it is
important that all the data from a field or project be considered together as a whole at
some point.
Considering all data as a whole is also a form of error check; for example, checking for
impossible numbers or for sample mismatch of fractions between lab groups. At this
point the fundamental question asked in the beginning must again be considered in the
light of whether or not the data answer the original question posed by the client. If so, the
process is complete; if not, the process must continue until the original question has been
answered to everyone's satisfaction.
10.1.
DETERMINING THE PROBLEM
Problem determination is a fundamental part of the sampling and testing process and
there are multiple aspects to be considered. Since all of the aspects of these two activities
can have a dramatic impact on not only the nature of the sampling event but also the
sample analysis, it is a very good idea to spend time at the beginning asking simple and
basic questions. What does the client want, and what is the question that is being asked?
This could be as simple as what the pH and total organic carbon (TOC) level of a
groundwater sample is, or as complex as what all the compounds and concentration levels
are of all contamination in a soil or water sample.
After the original question is posed it is time to determine the limits of the testing and
sampling process by asking yet more questions. The limiting factors for the selection of
an analytical method will often be the amount of sample available for sampling and
subsequent analysis, and the form or state of the sample to be analyzed. The nature of the
sample taken will determine many of the procedures for the sampling event, as well as
sample transport, storage, and preparative process and many of the analytical methods
and procedures.
As an example of the importance of the sample characteristics the first question asked
would be the physical state of the sample to be taken; that is, is it a solid, liquid, or gas?
Is the sample homogeneous throughout the field to be sampled? Will the sample be able
to be taken in such a way as to maintain homogeneity during transport and sample
preparation and analysis? These questions all have distinct and far-reaching effects upon
the sampling process and the sample taken (e.g., the process and container used to take
and transport an air sample will be much different in form and type from that used to
obtain a solid or liquid sample).
The three generally found phases of natural matter on the Earth are gas, liquid, and
solid, each having its own sampling techniques and requirements, and each of which will
be discussed separately. The fourth phase of matter, plasma, is not usually seen outside
an extreme laboratory environment, and while it can be a part of some of the analytical
methods [i.e., inductively coupled plasma (ICP) analysis] it is really not a state of matter
that can be sampled, much less transported or stored. For these reasons it is outside the
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