The Everglades wetland is world renowned for its unique hydrogeology, flora and fauna and its scenic beauty. It is a 'World Heritage site' and an 'International Biosphere Reserve'. It's trophic status has come under threat from nutrient inputs from multiple sources. My research attempted to answer critical questions regarding the characteristics, behavior, transportability of sediments along with the flux and fate of Phosphorus in Everglades Agricultural Area canals.

1. Characterization of Physicochemical Properties,
Phosphorus Fractions and P Release of the EAA
Canal Sediments
Dr. Jaya Das

2.  Everglades Agricultural Area
(EAA)
 In South Florida - between
Lake Okeechobee and ENP
 280,000 ha of organic soils
 Sugarcane, vegetables, rice &
sod
 Annual 2 billion dollar industry
Introduction

3. Drainage
 Importance of drainage in EAA
 Flat topography
 Canals and pumps used irrigate and drain fields
 Agricultural drainage water - farm canals – main canals –
ecosystems in the south – Everglades National Park
(ENP)
 Drainage water contributes P

4.  Years of P loading
 Accumulation of P canal sediments
 Sediments as P sink or source
 Internal load of P
 Sediments can be transported
 Can act as P source wherever are transferred
 Concern for P limited ecosystem
Justification
 Important Questions:
 What are the P release/retention potential of the sediments?
 What are the factors responsible for P release/retention?
 What is the extent of P release/retention?

5. Experiment - 1
P Release Potential of
Canal Sediments
Experiment - 2
Characterization of
Canal Sediments
Experiment - 3
Equilibrium Phosphorus
Concentration (EPC)
of Canal Sediments

6. Experiment 1 – Determination of
Phosphorus Flux from Canal Sediments
of the Everglades Agricultural Area

7.  Miami canal
 West Palm Beach canal (WPB)
 Ocean canal
Objectives
 Identify P release potential of sediments in the
main drainage canals spread across the EAA:

8. Water
Sediment
Stopper
Air flow from pumps
 Incubation study
 Intact sediment cores
 Aerobic conditions
 Water from 0.007 mg
L-1 to 0.01 mg L-1 P
 3 exchanges (28 days
each)
 Soluble Reactive P
(SRP)
Materials and Methods

10. P Flux
Sediments
Each canal - 4 transects
Each transect - 3 cores

11. P Flux
Sediments

12. P Flux Calculations
 Ct = SRP concentration (mg L-1) at time t days
 Ct-1 = SRP concentration (mg L-1) at time t-1 days
 VT = The total volume (L) of the water column
 A = Column cross sectional area (m2)
 P released/retained = (Ct – Ct-1) * Vt
 P flux = P released or retained/Cross sectional area
[(Ct – Ct-1) * Vt]/A

13. Results

14. 0
20
40
60
80
100
120
0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28
Prelease(mgm-2)
Time (days)
T1 T2 T3 T4
1st exchange
(0-28 days)
2nd exchange
(29-56 days)
3rd exchange
(57-84 days)
P Release from Miami Canal from Exchanges
1, 2 and 3

15. -100
50
200
350
500
650
0 1 2 4 7 14 21 28 29 29 30 32 35 42 49 56 57 57 58 60 63 70 77 84
Preleased(mgm-2)
Time (days)
T1 T2
T3 T4
2nd exchange
(29- 56 days)
3rd exchange
(57 - 84 days)
1st exchange
(0-28 days)
 Highest P release T2 and T3 ~ total 625 mg m-2 P released
 Low P release – T1 & T4 ~ 200 – 325 mg m-2 P released
Cumulative P Release- Miami Canal

16. 0
10
20
30
40
0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28
Prelease(mgm-2)
Time (days)
T1 T2 T3 T4
1st exchange
(0-28 days)
2nd exchange
(29-56 days)
3rd exchange
(57-84 days)
P Release from WPB Canal from Exchanges
1, 2 and 3

17. Cumulative P Release - West Palm Beach
Canal
 P release in WPB canal < Miami canal
 P release in T1, T2 & T3 ~ 110 mg m-2
 P release in T4 ~ 35 mg m-2
-25
25
75
125
175
225
0 1 2 4 7 14 21 28 28 29 30 32 35 42 49 56 56 57 58 60 63 70 77 84
Preleased(mgm-2)
Time (days)
T1 T2
T3 T4
1st exchange
(0-28 days)
2nd exchange
(29- 56 days)
3rd exchange
(57 - 84 days)

18. 0
10
20
30
40
0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28 0 1 2 4 7 14 21 28
Prelease(mgm-2)
Time (days)
T1 T2 T3 T4
1st exchange
(0-28 days)
2nd exchange
(28-56 days)
3rd exchange
(57-84 days)
P Release from Ocean Canal from Exchanges
1, 2 and 3

19. Cumulative P Release - Ocean Canal
P release in Ocean canal <P release in Miami canal
 Comparable to P release in WPB canal
 P release ranges from 75 – 200 mg m2
-25
25
75
125
175
225
0 1 2 4 7 14 21 28 29 29 30 32 35 42 49 56 57 57 58 60 63 70 77 84
Preleased(mgm-2)
Time (days)
T1 T2
T3 T4
2nd exchange
(29-56 days)
3rd exchange
(57-84 days)
1st exchange
(0-28 days)

20. Conclusions
 P released was much lower in the third exchange
 P release from Miami canal > WPB and Ocean canal.
 More questions:
 What are the factors responsible
for P release from EAA canal
sediments?
 Canals are potential sources of P to the water column.
 Canals can sustain P release over a period of 84 days.

21. Experiment 2 - Characterization of the
Sediments of EAA Canals

22. Objectives
Determine the factors responsible for P release from
EAA canal sediments by:
 Characterize EAA canal sediments
 Physicochemical properties
 P fractions
 Inorganic minerals

23. Phosphorus
fractions
Physiochemical
properties:
Total P
%LOI
BD
pH
3 Main canals
Each canal: 4 transects
Each transect: 3 cores
Thermogravimetry
(TG)
X - Ray

24. 0.1 M NaOH
17 h
0.5 M HCl
24 h
Ashed @ 550oC
6 M HCl digestion
2 h
1 M KCL
HCl Pi
Ca and Mg-P
Residual P
P-recalcitrant organic
compounds/minerals
Sediment
NaOH-Pi
Fe/Al-P
NaOH-Po
Humic Fulvic P
Labile P
Wet sample equivalent of
0.3 g dry weight
Residue
Residue
Residue
Inorganic P Fractionation Scheme

25. Results

26. Selected Physicochemical Properties of EAA Canal
Sediments
Canal
Total P
mg kg-1
BD
g cm-3 %LOI pH
Miami 1430 a 0.26 b 26.1 ns 7.4 b
WPB 1130 a 0.22 b 26.7 7.4 b
Ocean 590 b 0.35 a 24.5 7.9 a

27. Sediment P Fractions
0
200
400
600
800
1000
1200
1400
1600
1800
T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4
Miami Canal West Palm Beach Canal Ocean Canal
PConcentration(mgkg-1)
KCl - P
NaOH - Pi
NaOH - Po
HCl - P
Residue - P
Miami Canal West Palm Beach Canal Ocean Canal

28. Sediment P Fractions
 HCl-Pi largest P fraction (50-80% of Total P)
 Residue-P next big P fraction (10-30% of Total P)
 KCl-Pi least P fraction (0.2-2% of Total P)
 NaOH-Pi and NaOH-Po (3-8% and 1-6%)

29. Canal Transect
Feox
mg kg-1
Alox
mg kg-1
Ca
mg kg-1
Mg
mg kg-1
Miami
T1 677 195 26000 1280
T2 661 170 17600 678
T3 906 124 8240 615
T4 606 123 24900 461
WPB
T1 62.6 23 1820 213
T2 489 98 18500 754
T3 971 122 7150 1240
T4 846 123 6530 796
Ocean
T1 385 99.4 22000 644
T2 169 59.9 31600 582
T3 330 122 20800 685
T4 248 59.3 32400 468
Amorphous Fe, Al and Extractable Ca and Mg of
Miami, WPB and Ocean Canal Sediments

30. Variables Total P KCl-P NaOH-Pi NaOH-Po HCl-Pi Residue-P
P
released
0.41** 0.33ns
0.004ns
0.25ns
0.25ns
0.04ns
BD %LOI pH
-0.28ns
0.29ns
-0.30ns
Fe Al Ca Mg
0.64* 0.64* 0.42ns
0.47ns
Correlation of P Release with Sediment
Properties

31. 0
5
10
15
20
25
30
35
40
T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4
Miami WPB Ocean
PercentWeightLoss(%Wtloss)
%Wt loss-OM
%Wt loss-DO
%Wt loss-CA
Sediment Thermogravimetric Analysis
Miami Canal West Palm Beach Canal Ocean Canal

32. XRD Analysis – Miami Canal
0
200
400
600
800
1000
1200
1400
0 10 20 30 40 50 60
Intensity(counts)
2θ
T1 T2
T3 T4
CA
AR
QZ
AR
CA
QZ
SP
AR
CA
AR
CA
CA
AR
CA
AR
SP

33. Canals
Minerals
Calcite Dolomite Aragonite Quartz Sepiolite Smectite KaolinitePalygorskite
Miami √ √ √ √ √ - - -
WPB √ √ - √ √ √ √ √
Ocean √ √ √ √ √ - - -
XRD Analysis - EAA Main Canals
 Different forms of carbonate minerals
 Different Aluminosilicate minerals
 No detectable P containing minerals

34. Conclusions
 P release was correlated with total P
 P release was correlated with Fe and Al oxides
 P fractions, BD, %LOI, pH not correlated with P release
 P release involves complex interaction of different
chemical and physical factors
 Other factors may be playing important roles generating
variability in P release are the spatial distribution of CaCO3
layers, the presence of shells, resuspension etc.
 More questions:
 What is the extent of P release from EAA canal
sediments?

35. Miami Canal
Fe3+-P
KCl-P
Ca/Mg-P
Residue-P
NaOH-Po
Aerobic
canal water
Aerobic
Sediment layer
Anaerobic
Sediment
layer
Limestone bedrock
• Reduction of Fe3+-
P in anaerobic layer
• Release of soluble
Fe2+-P along with
• Reprecipitation of
Fe3+-P in the aerobic
layer
Pi
Pi
Pi and
DOP
• Possible release of Ca/Mg P by
hydrolysis of organic acids or
• by chelation and release of P
• Microzones of low pH regions
due to respiration by macrophytes
• Mineralization
of organic P
Calcium
carbonate rock
fragments

36. KCl-P Ca/Mg-PResidue-P NaOH-Po
Aerobic
sediment layer
Anaerobic
sediment
layer
Limestone bedrock
Aerobic canal
water
•WPB
canal
shallower
than
Miami
canal
•Mean
canal
depth:
13ft
Layers of carbonates -
reduces P release
Fe3+-P
Pi
Pi
Pi and
DOP
WPB Canal

37. Aerobic canal
water
KCl-P Ca/Mg-P
Residue-P NaOH-Po
• Mechanical
barrier of
shells,
limestone
rocks
reduces P
release
Aerobic sediment
layer
Anaerobic
sediment layer
Limestone bedrock
• Shallower
than both
Miami and
WPB canal
• Mean
depth:
7.5 ft
Fe3+-P
Pi
Pi
Pi and
DOP
Ocean Canal

38. Surface cross-section
sediment core from
WPB canal
Surface cross-section
sediment core from
Ocean canal

39. Intact cores showing subsurface carbonate
layers from WPB canal

41. Experiment 3 - Determination of EPC of EAA
Canal Sediments

42. Justification
 Equilibrium Phosphorus Concentration (EPC)
 Extent of internal load
 P release when water column P concentration < EPC
 P retained when water column P concentration >EPC
 No P release/retention at EPC

43. Objectives
 To determine the EPC values of:
 Miami canal
 WPB canal
 Ocean canal

44. Materials and Methods

45. P release
Sediments
EPC
 5 different exchanges
 7 days each
 Spike concentrations of
0.007, 0.05, 0.13, 0.27 and
0.35 mg L-1 for exchanges 1,
2, 3, 4 and 5 respectively

46. Results

47. -50
-40
-30
-20
-10
0
10
20
30
40
50
0 2 4 7 7.5 9 11 14 14.5 16 18 21 21.5 23 25 28 28.5 30 32 35
Prelease(mgm-2)
Time (days)
T1 T2 T3 T4
1st exch. 2nd exch. 5th exch.3rd exch. 4th exch.
P: 0.007 mg L-1
Days: 0-7
P: 0.05 mg L-1
Days: 7-14
P: 0.13 mg L-1
Days: 14-21
P: 0.27 mg L-1
Days: 21-28
P: 0.35 mg L-1
Days: 28-35
P Release/Retention - Miami Canal

48. y = -13.53 x + 1.13
R² = 0.98
-3.5
-3.0
-2.5
-2.0
-1.5
-1.0
-0.5
0.0
0.5
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Prelease/retention(mgm-2d-1)
Spike concentration (mg L-1)
EPCw= 0.12 mg L-1
or 120 ppb
Miami
canal
EPC
(mg L-1 )
T1 0.12
T2 0.16
T3 0.12
T4 0.07
Equilibrium Phosphorus Concentration - Miami
Canal (Incubation Experiment)

49. EPCw(mg L-1 )
Miami canal WPB canal Ocean canal
T1 0.12 0.05 0.05
T2 0.16 0.09 0.13
T3 0.12 0.08 0.08
T4 0.07 0.02 0.07
Equilibrium Phosphorus Concentration
of EAA Canals

50. Miami canal WPB canal Ocean canal
EPCw
(mg L-1)
Water
column
SRP
EPCw
(mg L-1 )
Water
column
SRP
EPCw
(mg L-1 )
Water
column
SRP
T1 0.12 0.03 0.05 0.06 0.05 0.06
T2 0.16 0.03 0.09 0.06 0.13 0.07
T3 0.12 0.03 0.08 0.05 0.08 0.07
T4 0.07 0.05 0.02 0.06 0.07 0.06
Equilibrium Phosphorus Concentration
of EAA Canals: Incubation Experiment)
 EPCw from incubation experiment predicts
 P release from Miami canal T1, T2 and T3
 EPCw ~ SRP in WPB all transects and Ocean canal T1, T3 and T4
 P release in Ocean canal T2

51. Conclusions
 Miami canal and sections of Ocean canal can serve as P source to
the water column
 P in EAA canals sourced from both farms as well as by internal
loading
 This drainage water is treated for P by the Storm Treatment Areas
(STAs)
 The STAs undergo regular rehabilitation to maintain their P
removal capacity
 Management practices and regular monitoring in the main
canals particularly in Miami and sections of Ocean canal can help
reduce P load to the STAs

52. Overall Conclusions
 EAA main canal sediment properties
 Ocean canal
- Has higher mineral characteristics
- Higher pH (7.9), BD, lower total P
- Lower P storage 7.1 MT
- Area: 6.89x105 m2.
 Miami and WPB canal
- Lower pH (7.4), BD, higher total P
- Higher P storage 175 and 25.4 MT
- Area: 9.45x105 m2, 2.03x106 m2
 EAA canal sediment mineralogy
 No detectable P containing minerals in EAA canals
 Minerals identified were forms of carbonates and aluminosilicates
USGS maps

53.  P release from EAA main canals
 EAA canals can sustain P release over a period 84 days
 P release is correlated with total P and amorphous Fe and Al
 P fractions did not correlate with P release
 This internal P load varied from 0.1 to 0.8 MT
 A small fraction of total P load from EAA (129 MT) in 2009
 Resuspension can lead to 20 - 30 times more P release
 P transport to downstream ecosystems
 Canals will continue to transport P to the downstream ecosystem by
either P from farms/P release from canals and transport of
particulates
 STAs have to be rehabilitated to maintain their P retention capacity
Overall Conclusions
 Management and monitoring at both pre and post STAs are important
 Management of EAA main canals can be an important factor in meeting
the 0.01 mg L-1 nutrient criterion

54. P
enriched
water
P concentrations
to the STAs (ppb):
 STA 1E-182
 STA 1W-246
 STA 2-122
 STA ¾-96
 STA 5-254
 STA 6-264
STAs function by:
 P uptake
 Reduction of SRP
 Reduction of particulate P
by sedimentation
Out flow P concentrations
from STAs (ppb):
 STA 1E-21
 STA 1W-26
 STA 2-18
 STA ¾-13
 STA 5-56
 STA 6-93
Target concentration-10 ppb
 Periodic STAs maintenances
 Reduced inflow concentrations to
STAs
 Reduced load can enhance STA
performance
 Possibly can get outflow
concentrations closer to target
concentrations
 Prolong STA longevity
 Reduced cost for STA maintainance
STAs
WCAs and
Downstream P Limited
Ecosystems
Farm CanalsLake Okeechobee
Main Canals
Farms

55. Co-Advisors
Dr. Samira Daroub
Dr. George O’Connor
Committee members
Dr. Willie Harris
Dr. Patrick Inglett
Dr. Ion Ghiviriga
Group members
Dr. Timothy A. Lang
Dr. Manohardeep D. Josan
Dr. Olawale Oladeji
Dr. Jehangir Bhadha
Ms. Viviana Nadal
Ms. Irina Ognevich
Funding Agency
Everglades Agricultural Area-Environmental Protection District(EAA-EPD)
Acknowledgements

56. Acknowledgements
Thank you so much:
Thais, Ann, Chay, Kathy, Miguel, Rani, Gwen, Joan, Gaurav,
Hardev, Brandy, Sandy, Maria, Franciscka, Eva, David, Gary, Jose,
Amanda and everyone at EREC.

57. West Palm Beach Canal
Questions?