1. Lauren Sager and Marissa Detschel Geochemistry December 15, 2008
Understanding Plant and Microbial Interactions with Phosphorous in Wetlands
Lauren Sager and Marissa Detschel
Geochemistry
December 15, 2008

2. Outline Introduction - Water eutrophication
- Overview of biological interactions
- Florida Everglades and Stormwater Treatment Areas
- Study of Gu and Dreschel (2008)
- Effects of presence of Chara sp. algae
Objectives of PHREEQC analyses
Details of PHREEQC Analyses
Results and Discussion
Conclusions L

3. Water Eutrophication
Due to overloading of nutrients in water such as phosphorous and nitrogen
Causes:
Agricultural and domestic waste runoff
Effects:
Algal blooms – release toxins
Block sunlight from underwater plants
Shortage of drinking water due to poor water quality
Biological interactions M

4. Overview of Biological Interactions in Eutrophic and Freshwater Environments
The most important use for phosphorous and nitrogen in a bacterial or microbial cell is the production of genetic material.
Phosphorous is important in the production of energy, AMP, ADP, ATP...
Nitrogen is important in making DNA and RNA

5. Overview of Biological Interactions in Eutrophic and Freshwater Environments
Freshwater Environments – Many microorganisms, including Cyanobacteria, protozoa, Amoeba, and Diatoms, survive because the chemical levels are more balanced allowing for more life to exist.
Eutrophic Waters – Microorganisms not as diverse as in the freshwater environments and ones that live in eutrophic waters tend to be anaerobic ones that can do photosynthesis

6. Overview of Biological Interactions in Eutrophic and Freshwater Environments
Excessive nutrients  growth of plants and algae at alarming rates  growth of microorganisms, such as bacteria
Bacteria use oxygen during cellular respiration when they produce energy, depleting the oxygen that many fish need to survive, allowing a few or no fish species to be able to live

7. Florida Everglades Lake Okeechobee Everglades Agricultural Area
Everglades Protection Area
(includes Everglades
National Park)
Images sources -
Everglades aerial view:
LO:
EAA:
EPA:

8. Stormwater Treatment Areas
Constructed to remove P from Lake Okeechobee and Everglades Agricultural Area runoffs
Gu and Dreschel (2008) – study of P removal with STA-1W test cells
From:

9. Test Region Four North Test Cells for 32 months - high P (60-150 μg/L)
From: Gu and Dreschel, WETLANDS, vol. 28., no. 1, March 2008, pp
Four North Test Cells for 32 months - high P ( μg/L)
Seven South Test Cells for 26 months - low P (30-50 μg/L)
Cells contained 3 distinct plant communities
South test cells
From:

10. Plant Communities Cattails Submerged Aquatic Vegetation (SAV)
Periphyton Stormwater Treatment area (PSTA)
Images from: Gu and Dreschel, WETLANDS, vol. 28., no. 1, March 2008, pp

11. Analysis Weekly grab samples taken from input and output cells
Water temperature, pH, and dissolved oxygen measured in field

12. Gu and Dreschel, WETLANDS, vol. 28., no. 1, March 2008, pp. 81-91
Results
High alkalinity, high Ca, high P inflow and all lower outflow – indicates possible P sink inside test cells
Gu and Dreschel, WETLANDS, vol. 28., no. 1, March 2008, pp

13. Image: http://sofia.usgs.gov/virtual_tour/controlling/sta.html
Chara sp. Algae
Branched algae
H+ influx pump vs. OH- efflux pump:
 H+ Influx pump in the alkaline band of this plant would not function at a fast enough rate to keep the high pH needed.
 Much more evidence points to the idea of an OH- Efflux pump
Image:

14. Chara sp. Algae
How does this algae, specifically the alkaline band, function at low and high pH?
The alkaline band functions normally at a high pH.
At a low pH, many things have to occur in the cell to keep it functioning correctly:
Exterior cells of alkaline band don’t function at low pH, but inner cells function to maintain a high pH (up to 10.5) by excreting bases such as HCO3- and OH-, increasing the effects of a high pH and returning the exterior cells to their normal function.

15. Chara sp. Interactions
Calcareous plants (i.e. Chara) display alkaline and acidic surfaces (pH up to 10.5)
Formation of CaCO3 generates two protons at the alkaline surfaces
Protons are transported to acidic surfaces and combine with bicarbonate to form carbon dioxide
Resultant reaction:

16. Other Plant Interactions
P assimilation in stems, roots, and periphyton
CaCO3 precipitation due to photosynthesis – can increase water column pH up to 10
High Ca2+ + breakdown of HCO3- leads to CaCO3 precipitation

17. Coprecipitation of CaCO3 and HAP
High pH, Ca2+, and alkalinity levels  a significant portion of water column P coprecipitates with CaCO3
High levels of P, Ca2+, and pH  hydroxyapatite (HAP) forms from CaCO3
ΔGR° = kcal/mol, K =

18. PHREEQC Objectives
Gu and Dreschel (2008) did not use PHREEQC in their chemical analyses
Objectives: Confirm P removal efficiencies of Gu and Dreschel (2008) and investigate possibility of coprecipitation of CaCO3 and hydroxyapatite as a P sink in test cells using PHREEQC
Input average values from Tables 1 and 2 from Gu and Dreschel (2008)

19. PHREEQC Modeling: Effectiveness of P Removal
Differences in P removed possibly due to presence of organic P in total P as reported by Gu and Dreschel (2008)

20. PHREEQC Modeling: Relationship Between CaCO3 and P
SI’s decrease between input and output, indicating a loss of species in the test cells.
SI at inflow and outflow for all species points to loss of species from water in test cells

21. PHREEQC Modeling: Increase pH
Increase in pH due to presence of plants was modeled by mixing inflow aqueous solutions as reported by Gu and Dreschel (2008) with an aqueous solution with the same composition as inflow aqueous solutions but higher pH values up to 10.6

22. PHREEQC Modeling: Increase pH

23. Conclusions from PHREEQC Analysis
Plant varieties are effective at removing P from eutrophicated inflow water
SI’s of CaCO3 species and HAP decrease between inflow and outflow and increase while inside the test cells, interacting with plants – coprecipitation and/or P sink

24. References
Cooke, G.D., Welch, E.B., Peterson, S., and Nichols, S.A. (2005) Restoration and
Management of Lakes and Reservoirs, third edition. CRC Press, Florida.
Faure, G. (1998) Principles and Applications of Geochemistry, second edition. Prentice Hall, New Jersey.
Gu, B. and Dreschel, T. (2008) Effects of plant community and phosphorous loading rate on constructed wetland performance in Florida, USA. WETLANDS. 28(1),
Lucas, William J. (1979) Alkaline Band Formation in Chara corallina: Due to OH- Efflux or H+ Influx? Plant Physiology 63:
McConnaughey, T.A., LaBaugh, J.W., Rosenberry, D.O., Reddy, M.M., Schuster, P.F., and Carter, V. (1994) Carbon budget for a groundwater-fed lake: Calcification supports summer photosynthesis. Limnol. Oceanogr. 39(6),
Parkhurst, D.L. and Appelo, C.A.J. (1999) User’s Guide to PHREEQC (Version 2) – A Computer Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse Geochemical Calculations. Denver, Colorado.
Reddy, R., and DeLaune, R.D. (2008) Biogeochemistry of Wetlands: Science and
Applications. CRC Press, Florida.
Yang, X., Wu, X., Hao, H., and He, Z. (2008) Mechanisms and assessment of water
eutrophication. J. Zheijang Uni. Sci. B. 9(3),