Characterization of Physicochemical Properties, Phosphorus Fractions and P Release of the EAA

Canal Sediments

Dr. Jaya Das

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

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

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?

Experiment - 1

P Release Potential of

Canal Sediments

Experiment - 2

Characterization of

Canal Sediments

Experiment - 3

Equilibrium Phosphorus

Concentration (EPC)

of Canal Sediments

Experiment 1 – Determination of

Phosphorus Flux from Canal Sediments of the Everglades Agricultural Area

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:

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

P Flux

Sediments

Each canal - 4 transects

Each transect - 3 cores

P Flux

Sediments

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

Results

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

P r

ele

ase (

mg

m-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

-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

P r

ele

ased

(m

g m

-2)

Time (days)

T1 T2

T3 T42nd 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

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

P r

ele

ase (

mg

m-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

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

P r

ele

ased

(m

g m

-2)

Time (days)

T1 T2

T3 T4

1st exchange

(0-28 days)

2nd exchange

(29- 56 days)

3rd exchange

(57 - 84 days)

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

P r

ele

ase (

mg

m-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

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

P r

ele

as

ed

(m

g m

-2)

Time (days)

T1 T2

T3 T4

2nd exchange

(29-56 days)

3rd exchange

(57-84 days)

1st exchange

(0-28 days)

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.

Experiment 2 - Characterization of the

Sediments of EAA Canals

Objectives

Determine the factors responsible for P release from

EAA canal sediments by:

Characterize EAA canal sediments

Physicochemical properties

P fractions

Inorganic minerals

Phosphorus

fractions

Physiochemical

properties:

Total P

%LOI

BD

pH

3 Main canals

Each canal: 4 transects

Each transect: 3 cores

Thermogravimetry

(TG)

X - Ray

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

Results

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

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

P C

on

cen

trati

on

(m

g k

g -1

)

KCl - P

NaOH - Pi

NaOH - Po

HCl - P

Residue - P

Miami Canal West Palm Beach Canal Ocean Canal

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%)

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

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 * 0.42 ns 0.47 ns

Correlation of P Release with Sediment Properties

0

5

10

15

20

25

30

35

40

T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4

Miami WPB Ocean

Perc

en

t W

eigh

t L

oss

(%

Wt

loss

)

%Wt loss-OM

%Wt loss-DO

%Wt loss-CA

Sediment Thermogravimetric Analysis

Miami Canal West Palm Beach Canal Ocean Canal

XRD Analysis – Miami Canal

0

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60

Inte

nsi

ty (

cou

nts

)

2θ

T1 T2

T3 T4

CA

AR

QZ

ARCA

QZSP

AR

CA

AR

CACA

AR

CA

AR

SP

Canals Minerals

Calcite Dolomite Aragonite Quartz Sepiolite Smectite Kaolinite Palygorskite

Miami √ √ √ √ √ - - -

WPB √ √ - √ √ √ √ √

Ocean √ √ √ √ √ - - -

XRD Analysis - EAA Main Canals

Different forms of carbonate minerals

Different Aluminosilicate minerals

No detectable P containing minerals

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?

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

KCl-P Ca/Mg-P Residue-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

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

Surface cross-section

sediment core from

WPB canal

Surface cross-section

sediment core from

Ocean canal

Intact cores showing subsurface carbonate

layers from WPB canal

Experiment 3 - Determination of EPC of EAA Canal Sediments

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

Objectives

To determine the EPC values of:

Miami canal

WPB canal

Ocean canal

Materials and Methods

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

Results

-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

P r

elea

se (

mg

m-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

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

P r

ele

ase

/ r

ete

nti

on

(m

g m

-2 d

-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)

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

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

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

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

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

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 Canals Lake Okeechobee

Main Canals

Farms

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

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.

West Palm Beach Canal

Questions?