Environmental Engineering Reference
In-Depth Information
Potential sources of variability to consider when monitoring
wetlands
Internal generation of solids occurs through fragmentation of
detritus and litter, algal cells, and bioturbation by fish and
invertebrates can further contribute to the concentration of
wetland TSS (USEPA
2008a
)
Wind-driven mixing of wetland water can cause suspension of
particulate material and result in elevated TSS. As such, land-
scape topography and wetland position on the landscape may
also lead to differences between wetlands
Parameter
General notes/reasons for measuring the parameter
Turbidity
Turbidity is a measure of water clarity and results from particulate
matter (living and non-living) and dissolved color. See addi-
tional discussion for total suspended solids (TSS)
Hydrology
:
See influences discussed for TSS, although color and dissolved
organic carbon in source water can influence turbidity readings
as well (Trebitz et al.
2007
)
Internal and other processes
:
See influences discussed for TSS. Biological activity and seasonal
variation of dissolved organic carbon in the wetland water
column (e.g. Waiser and Robarts
2004
) could also influence
turbidity readings
Trebitz et al. (
2007
) found that turbidity could serve as a possible
surrogate for total suspended solids, although state that deter-
mining water transparency through the use of a “Secchi trans-
parency tube” would also serve as a surrogate for TSS
Nutrients
Nutrients include the macronutrients (e.g., phosphorus, nitrogen,
sulphur, potassium, magnesium, and calcium) and
micronutrients or trace elements (e.g., iron, copper, silicon).
Nitrogen and phosphorous are often measured in routine water
quality monitoring since they may be limiting and so could have
a significant impact on productivity of the system. Nitrogen and
phosphorus can both occur in the water column as organic and
inorganic forms, with each having dissolved and particulate
fractions. Different fractions of phosphorous are also designated
based on reaction with molybdate (see Wetzel (
2001
) and
APHA, AWWA and WEF (
2005
) for a more extensive
description of these categories). Generally, the dissolved inor-
ganic forms (soluble reactive in the case of phosphorous) are
Hydrology
:
Recent precipitation events may result in increased nutrient loading
from overland flow while flooding from rivers may decrease or
increase nutrient loads them depending on the nutrient status of
the river (Weilhoefer et al.
2008
)
In seasonal wetlands, nutrient levels in the water column may
increase shortly after inundation due to release from sediments.
Nutrients may also increase during wetland drawdown due to
evapoconcentration
Internal processes
:
Seasonal variation in nutrient levels may occur due to temperature
effects on biota and nutrient fluxes influenced by changing
oxygen levels (Trebitz et al.
2007
; USEPA
2008a
)
