Understanding Plant and Microbial Interactions with Phosphorous in

Wetlands Lauren Sager and Marissa Detschel

Geochemistry

December 15, 2008

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

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

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

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

• 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

Overview of Biological Interactions in Eutrophic and Freshwater Environments

Florida Everglades

Images sources - Everglades aerial view: www.wwwalker.net/restudy/introd.htmLO: www.lakeokeechobee.org/core/popups/algae2_tn.jpgEAA: http://www.nicholas.duke.edu/wetland/graphics/Eaa1.jpgEPA: http://www.florida-tourist-attractions.com/images/EvergladesNationalPark1.jpg

Lake Okeechobee

Everglades Agricultural Area

Everglades Protection Area(includes Everglades

National Park)

From: www.wwwalker.net/restudy/introd.htm

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

Test Region

• Four North Test Cells for 32 months - high P (60-150 μg/L)

• Seven South Test Cells for 26 months - low P (30-50 μg/L)

• Cells contained 3 distinct plant communitiesFrom: www.garygoforth.net/STAs.htm

North test cells

South test cells

From: Gu and Dreschel, WETLANDS, vol. 28., no. 1, March 2008, pp. 81-91

Plant Communities

Images from: Gu and Dreschel, WETLANDS, vol. 28., no. 1, March 2008, pp. 81-91

Submerged Aquatic Vegetation (SAV)Cattails

Periphyton Stormwater Treatment area (PSTA)

Analysis

• Weekly grab samples taken from input and output cells

• Water temperature, pH, and dissolved oxygen measured in field

Results

Gu and Dreschel, WETLANDS, vol. 28., no. 1, March 2008, pp. 81-91

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: http://sofia.usgs.gov/virtual_tour/controlling/sta.html

• 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.

Chara sp. Algae

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:

HCaCOOHCOCa 23222

OHCOHCOH 223 2222

OHCOCaCOHCOCa 22332 2

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

32

223 2HCOCaOHCOCaCO

232232 COOOCHHCO

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° = -53.246 kcal/mol, K = 1039.03

3)(264102243 10)()(22610 HCOOHPOCaHOHHPOCaCO s

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)

PHREEQC Modeling: Effectiveness of P RemovalP P removed P removed

(molality) (PHREEQC analysis) (Gu and Dreschel, 2008)

Inflow 2.33E-06 NA NACattail 8.07E-07 65% 64%SAV 9.69E-07 58% 55%

Inflow 1.39E-06 NA NACattail 7.75E-07 44% 49%SAV 8.40E-07 40% 33%PSTA 5.81E-07 58% 59%

Table 2. Effectiveness of P removal by plant communities in Everglades

North Test Cells

South Test Cells

• Differences in P removed possibly due to presence of organic P in total P as reported by Gu and Dreschel (2008)

PHREEQC Modeling: Relationship Between CaCO3 and P

Table 3. Saturation indices of selected sedimentsSI of calcite SI of aragonite SI of hydroxyapatite

North Test Cells CaCO3 CaCO3 Ca5(PO4)3OH

Inflow 0.17 0.03 -0.84Cattail 0.13 -0.02 -2.42SAV 0.28 0.13 -0.98South Test CellsInflow 0.72 0.58 1.04Cattail 0.06 -0.09 -2.69SAV 0.33 0.19 -1.01PSTA 0.17 0.03 -2.12

• SI at inflow and outflow for all species points to loss of species from water in test cells

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

PHREEQC Modeling: Increase pH

0

1

2

3

4

5

6

7.6 7.8 8 8.2 8.4 8.6 8.8 9 9.2 9.4 9.6

pH

Sat

urat

ion

Inde

x

Calcite Aragonite Hydroxyapatite

B.

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

ReferencesCooke, 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), 81-91.

Lucas, William J. (1979) Alkaline Band Formation in Chara corallina: Due to OH- Efflux or H+ Influx? Plant Physiology 63:248-254.

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), 1319-1332.

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 andApplications. CRC Press, Florida.

Yang, X., Wu, X., Hao, H., and He, Z. (2008) Mechanisms and assessment of watereutrophication. J. Zheijang Uni. Sci. B. 9(3), 197-209.