Environmental Engineering Reference
In-Depth Information
The range of chemical and physical variables that could be measured in wetland
water is extensive and ultimately depends on the objectives of the study. Those
listed in Tables
6.1
and
6.2
were selected because they include those variables
commonly measured in wetland monitoring programs and because the methodol-
ogy for most involve basic equipment such as electronic water quality meters or
relatively simple wet chemistry procedures. A number of suppliers also offer
“environmental laboratory” kits that provide step-by-step methodology using
pre-packaged reagents for the analyses of a number of these variables in the field.
In most cases, the methods employed in these kits are derived from protocols
described in APHA, AWWA and WEF (
2005
) and listed in Table
6.2
. If water
quality monitoring data are to be used for regulatory purposes, attention should be
paid to whether analytical techniques are acceptable to state or federal regulatory
agencies. Some of the methods presented in Table
6.2
, such as those for nutrient
determinations, have also been adapted for laboratory-based autoanalyzers that
allow high through-put of samples.
Other water quality parameters such as forms of organic carbon and individual
anions and cations are also often measured in wetland studies but are not discussed
in detail here since current methods for their determination involve more expensive
types of instrumentation. This is also the case for metals and organic contaminants.
A general overview of this instrumentation is provided by Wetzel and Likens
(
2000
). APHA, AWWA and WEF (
2005
) also provide general overviews and
basic methodology for analyzing selected metals and organic contaminants includ-
ing collection and processing of samples.
In addition to the sampling considerations already discussed, other issues must
often be considered when collecting water quality data from surface waters includ-
ing wetlands. Electronic water quality meters can greatly enhance data collection
from the field, with some models allowing the determination of a number of
parameters at one time. However, if these instruments are to provide reliable
data, attention must be paid to their calibration and maintenance. Without proper
calibration, a water quality meter can become an expensive random number
generator. As such, all personnel using the device should become acquainted with
the manufacture-prescribed frequency for calibration and the calibration procedure.
Maintaining records on when the meter was calibrated and by whom is also an
important element for data quality assurance. Similarly, regular inspection of the
probes of the meter for damage or fouling can help ensure reliable output during
use. Measurements taken with a water quality meter often rely on the passage of
gasses or ions across an electrode membrane and it may be necessary to provide
gentle agitation of the probe to enhance this exchange. Some probes are fitted with
small impellers to maintain this water flow. In addition to the handheld water
quality meter, a range of other electronic devices are available to collect water
quality data from surface waters including temperature loggers and multi-parameter
sondes that can be left on site to facilitate data collection over longer time frames.
These instruments are particularly useful for characterizing diurnal patterns,
although their use may be limited in shallower wetlands.
When using a water quality meter to take measurements from the wetland water
column, care must be taken to avoid stirring bottom sediments or allowing the probe
