Wetland Biogeochemistry Techniques - Wetland Techniques - page 354

We have tried to emphasize field techniques. However, some of the techniques
have relatively standard laboratory components that are beyond the scope of this
chapter. In some cases the reader will be advised to check additional documents for
the laboratory techniques. In addition, there are a number of commercial labs or
university soil testing labs that will perform some of these assays at cost. In some
cases, both a field assay and a lab assay are available to measure the same process.
The field assay may be presented in this discussion, but the reader will be referred to
documentation that covers the lab assay if the latter is considered to be more
accurate.
7.2 Quality Control
7.2.1 Sample Collection
Many of the biogeochemical assays require collection of a field sample which is
subsequently analyzed in the laboratory. The quality of the lab data is inherently
limited by the quality of the field sample. Whether monitoring wetlands for
regulatory purposes or for research studies, it is important to have a sampling
program that employs proper field monitoring techniques and accurate laboratory
analytical procedures. There are many publications that outline the proper methods
for environmental monitoring. The National Wetlands Research Center ( http://
www.nwrc.usgs.gov ) of the United States (U.S.) Geological Survey is a great
source of information on wetland assessments. Many states have developed wetland
monitoring guidelines; therefore, it is important to check with each state's environ-
mental department for the most current monitoring strategies.
Samples collected for wetland assessment must be representative of the environ-
mental variability that occurs both spatially and temporally within an ecosystem.
The Environmental Monitoring Systems Laboratory of the U.S. Environmental
Protection Agency's Office of Research and Development has published a guideline
on soil sampling of any site under investigation (Mason 1992 ). Today, different
geostatistical evaluations are used to design the monitoring approach and to evaluate
the collected data in such a way as to minimize the inherent variability found
within soils. Random selection techniques should be used to determine the actual
location where the soil samples will be taken. Areas that should be considered before
sampling include (1) maximizing the accuracy and precision of collection;
(2) selecting sample locations that represent the wetland under study; (3) determin-
ing when, how often and how deep to sample; and (4) considering how the size of
the wetland will affect the accuracy of sampling. Many field guides describe how
these issues are addressed (Barth et al. 1989 ; Barth and Mason 1984 ; Brown 1987 ).
Collection and preservation of samples is dependent on the type of sample
required and on the analytical procedures that will be performed on the sample.
Each method of analysis requires specific collection methods, sampling containers