Water Chemistry Field Sampling
40
the charge balance. Some studies might choose to analyze silicon (Si) or total
fluoride (F), but these are often not needed for standard acid-base chemistry
assessment. The concentration of Si can be useful in evaluating the extent
of groundwater influence on surface water chemistry and in discriminating
between perched and flow-through seepage lakes. It can also provide useful information in interpreting diatom data because Si can be limiting to
diatom growth in some cases. Measurement of total dissolved F (fluorine)
is needed to calculate the speciation of Al i into various components, such
as Al(OH) 2+ , Al(OH) 2
+ , AlF 2+ , Al(F) 2
+ , Al 3+ , and so on. This can be important
because the Al-F species are thought to be less toxic to aquatic biota than
the Al-hydroxide species and Al 3+ .
Important parts of the water chemistry QA/QC evaluation can include
determination of the charge balance and comparison between measured and
calculated conductivity, sum of anions and sum of cations, and titrated and
calculated ANC. Charge balance calculations can also be used to determine
the charge density (organic anion concentration per mole of DOC) of DOC in
surface waters. To permit these QA/QC checks to be conducted, all parameters
listed in Table 2.2 are required except Si. Thus, the full list of parameters should
be analyzed if funding permits. It is possible to perform these evaluations
without a measurement of total dissolved F if one is willing to make certain
assumptions about the Al i speciation.
2.2.2.2 Eutrophication Studies
Eutrophication, or nutrient enrichment, is a potential consequence of N deposition to aquatic ecosystems that are N limited. However, many freshwater ecosystems are P limited and therefore would not be expected to increase primary
productivity in response to increased atmospheric inputs of N. Nevertheless,
there are many examples of freshwaters that appear to be N limited or N and
P colimited (e.g., Baron 2006, Elser et al. 2009). In such aquatic systems, atmospheric inputs of N would be expected to increase productivity or alter biological communities such as phytoplankton.
Atmospheric deposition of N may increase in the future in remote areas that
are situated downwind from centers of agricultural or human population growth.
Surface waters in such areas can be N limited. As a consequence, N additions
might contribute to nutrient enrichment, including changes in algal species distribution and abundance. In particular, high-elevation areas in the Sierra Nevada
and Rocky Mountains (and perhaps portions of the Cascade Mountains) are susceptible to such increases in nutrient N deposition (Fenn et al. 2003, Sickman et al.
2003b). In some areas, atmospheric N deposition has been linked with eutrophication of high-elevation lakes (cf., Melack et al. 1989, Sickman et al. 2003a).
Estuaries and near-coastal marine ecosystems are also susceptible to nutrient enrichment, especially from N. This is because estuarine and marine waters
40
the charge balance. Some studies might choose to analyze silicon (Si) or total
fluoride (F), but these are often not needed for standard acid-base chemistry
assessment. The concentration of Si can be useful in evaluating the extent
of groundwater influence on surface water chemistry and in discriminating
between perched and flow-through seepage lakes. It can also provide useful information in interpreting diatom data because Si can be limiting to
diatom growth in some cases. Measurement of total dissolved F (fluorine)
is needed to calculate the speciation of Al i into various components, such
as Al(OH) 2+ , Al(OH) 2
+ , AlF 2+ , Al(F) 2
+ , Al 3+ , and so on. This can be important
because the Al-F species are thought to be less toxic to aquatic biota than
the Al-hydroxide species and Al 3+ .
Important parts of the water chemistry QA/QC evaluation can include
determination of the charge balance and comparison between measured and
calculated conductivity, sum of anions and sum of cations, and titrated and
calculated ANC. Charge balance calculations can also be used to determine
the charge density (organic anion concentration per mole of DOC) of DOC in
surface waters. To permit these QA/QC checks to be conducted, all parameters
listed in Table 2.2 are required except Si. Thus, the full list of parameters should
be analyzed if funding permits. It is possible to perform these evaluations
without a measurement of total dissolved F if one is willing to make certain
assumptions about the Al i speciation.
2.2.2.2 Eutrophication Studies
Eutrophication, or nutrient enrichment, is a potential consequence of N deposition to aquatic ecosystems that are N limited. However, many freshwater ecosystems are P limited and therefore would not be expected to increase primary
productivity in response to increased atmospheric inputs of N. Nevertheless,
there are many examples of freshwaters that appear to be N limited or N and
P colimited (e.g., Baron 2006, Elser et al. 2009). In such aquatic systems, atmospheric inputs of N would be expected to increase productivity or alter biological communities such as phytoplankton.
Atmospheric deposition of N may increase in the future in remote areas that
are situated downwind from centers of agricultural or human population growth.
Surface waters in such areas can be N limited. As a consequence, N additions
might contribute to nutrient enrichment, including changes in algal species distribution and abundance. In particular, high-elevation areas in the Sierra Nevada
and Rocky Mountains (and perhaps portions of the Cascade Mountains) are susceptible to such increases in nutrient N deposition (Fenn et al. 2003, Sickman et al.
2003b). In some areas, atmospheric N deposition has been linked with eutrophication of high-elevation lakes (cf., Melack et al. 1989, Sickman et al. 2003a).
Estuaries and near-coastal marine ecosystems are also susceptible to nutrient enrichment, especially from N. This is because estuarine and marine waters