2.2 Where, What, and When to Sample
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TABLE 2.2 PARAMETERS TO CONSIDER FOR POSSIBLE INCLUSION IN
SURFACE WATER ACIDIFICATION STUDIES
Parameter
Preferred Unit Importance
Rationale
ANC
μeq/L
High
ANC is the master acid-base
chemistry variable in aquatic
systems
pH
—
High
Biota respond strongly to pH
SO 4
2−
μeq/L
High
Usually the major acid anion from
atmospheric deposition
NO 3
−
μeq/L
High
Sometimes an important acid anion
Ca 2+
μeq/L
High
Usually the major base cation
Mg 2+
μeq/L
Moderate
Usually an important base cation
K +
μeq/L
Moderate
Base cation, usually in low
concentrations
Na +
μeq/L
Moderate
Indicator of road salt
contamination, geological
sources, or sea salt inputs
Cl −
μeq/L
Moderate
Indicator of road salt
contamination, geological
sources, or sea salt inputs
NH 4
+
μeq/L
Moderate
Potential indicator of agricultural
influence or anaerobic conditions
Specific
Cond.
μS/cm
Moderate
Useful in QA evaluation of internal
data consistency; potential general
screening variable to identify
waters with low ionic strength
DOC
μM
Variable
Indicator of organic acidity
Al m
μM
Variable
Used with Al o to estimate
potentially toxic Al i
Al o
μM
Variable
Used with Al m to estimate
potentially toxic Al i
Si
μM
Variable
Potential indicator of lake
hydrologic type and groundwater
inputs; may explain some patterns
in diatom presence and abundance
DIC
μM
Low
Used to estimate
HCO 3
− concentration
Total
dissolved F
μM
Low
Used for Al i speciation
cond. = conductance