Environmental Engineering Reference
In-Depth Information
and storage requirements. These requirements are designed so that no significant
changes in the composition of the sample occur before the tests are performed.
When sampling for organic compounds and trace metals, special precautions are
needed to ensure detection. Often these parameters are present at such low
concentrations, that they may be totally or partially lost if the proper procedures
are not used. Standard Methods for the Examination of Water and Wastewater
(Eaton et al.
2005
) is a comprehensive reference topic that covers all facets of water
and wastewater analytical techniques. Standard Methods is a joint publication of the
American Public Health Association, the American Water Works Association, and
the Water Environment Federation. The Soil Science Society of America (SSSA)
has published the topic series, Methods of Soil Analysis, containing the following
volumes: Part 1:
Physical and Mineralogical Methods
, Part 2:
Microbiological
and Biochemical Properties
,Part3:
Chemical Methods
,Part4:
Physical Methods
and Part 5:
Mineralogical Methods
. This series is one of the primary references on
methodology in soil science. Part 4 contains information on sampling procedures.
Another good reference on soil sampling is a SSSA Special Publication entitled
Soil Testing: Sampling, Correlation, Calibration, and Interpretation
(Brown
1987
).
Sampling plans determine the type of sample required for each particular
project. The objective of the sampling plan is to ensure that the number and type
of samples collected is representative of the “population” under study. The plan
designates how many samples are needed, the locations of the samples and the
sample depth at each location. The plan may include simple random samples,
stratified random samples, systemic samples, sub-sampling and composite samples.
The best plan must consider the overall cost and precision (lack of error) of
sampling.
Once in the field, it is important to document the sampling operation. Field log
books are used to record all information pertinent to field sampling such as: the
purpose for sampling; location of the sampling point; date and time the sample was
collected; name and address of field contact; procedure for field decontamination
of sampling tools between samples to prevent cross contamination, field measure-
ments, and any observations worth noting. A chain-of-custody record should also
accompany each sample or group of samples. This record includes: the sample
number; signature of the collector; date, time, and address of collection; sample
type; signatures of persons involved in the chain of possession; and inclusive dates
of possession. Once collected, most samples need to be kept on ice until delivered
to the analytical laboratory.
7.2.2 Quality Control and Detection Limits
Analytical laboratories have quality assurance and quality control plans that ensure
data accuracy and precision. Quality assurance (QA) is the system that uses
procedures and assessments that ensure reliable data. The plan ensures that the
best available sample preparation, handling, preservation and storage methods
