factors contributing to the internal loading of phosphorus from anoxic sediments in six maine (usa)...

FACTORS CONTRIBUTING TO THE INTERNAL LOADING OF

PHOSPHORUS FROM ANOXIC SEDIMENTS IN

SIX MAINE (USA) LAKES

Bjorn LakeDoctoral Student

Civil and Environmental EngineeringThe University of Maine

Research Goals

• Perform a sedimentary analysis on six lakes with varying trophic status using a common sequential extraction procedure.– Delineate P, Al, and Fe speciation in the

sediments– Decipher any temporal trends in sediment P, Al,

and Fe speciation– Determine any correlations/predictors that are

characteristic of lakes with internal P load

• Calculate sedimentary P-flux using publicly available water column data and bathymetric data from Maine DEP

Background

• How do lakes become anoxic?• What controls phosphorus availability?

• Why is phosphorus important?

Al(OH)X

Classic Model of P Sorption

Fe Fe 3+3+

Ferric ionFerric ion

Fe Fe 2+2+

Ferrous ionFerrous ion

Fe(OH)Fe(OH)XX

Iron HydroxideIron Hydroxide

SRPSRP

SRPSRP

Anoxic

Oxic

Study Lakes

• Highland Lake • Pennesseewassee

Lake• Salmon Pond• China Lake• Webber Pond• Cobbosseecontee

Lake

Hydrologic Characteristics

High P/ Low P

Max Depth

Mean Depth

Surface Area

Drainage Area/ Surface

Area

Flushing Rate

Perennial Inlets

Intermittent Inlets

m m ha yr-1China H 25.9 8.5 908 19.3 0.72 6 54Cobb H 30.5 11.3 2120 10.2 1.07 8 2High L 20.0 6.0 252 10.2 0.91 6 2Penn L 14.6 5.5 384 31.3 1.38 9 1Salm H 17.4 7.0 270 7.8 0.54 2 26Webb H 12.5 5.5 485 11.2 1.52 4 15

Lake

Sequential ExtractionSedimentSediment

ResidueResidue

ResidueResidue

ResidueResidue

Ca-PCa-PLabileLabile

NaOH-TPNaOH-TP NaOH-rPNaOH-rP NaOH-nrPNaOH-nrP- =

1 M NH4Cl @ pH 7

1 M NaOH

0.1 M Na2S2O4/NaHCO3

0.5 M HCl

1 M NaOHFe-PFe-PResidueResidue

ResidueResidue Refractory-PRefractory-P

Al-P Org./Bact.-P

Digestion

Extraction Results0 10 20 30 40 50 60 70

Hig

hlan

d

MayJulySept

Pen

n MayJulySept

Sal

mon May

JulySept

0 50 100 150 200 250

Chi

na

MayJulySept

Ext-P mol g-1

0 50 100 150 200 250

Cob

b MayJulySept

0 10 20 30 40 50 60 70

Web

ber

MayJulySept

NH4Cl-P

BD-P NaOH25-P

HCl-P NaOH85-P

0 100 200 300 400 500

Hig

hlan

d

MayJulySept

Pen

n MayJulySept

Sal

mon May

JulySept

0 200 400 600 800 1000

Chi

na

MayJulySept

Ext-Fe mol g-1

0 200 400 600 800 1000

Cob

b MayJulySept

0 100 200 300 400 500

Web

ber

MayJulySept

NH4Cl-Fe

BD-Fe NaOH25-Fe

HCl-Fe NaOH85-Fe

0 5 10 15 20 200 400 600 800 1000

Hig

hlan

d MayJulySept

Pen

n MayJulySeptS

alm

on MayJulySept

Chi

na

MayJulySept

Cob

b MayJulySept

Ext-Al mol g-1

0 5 10 15 20 200 400 600 800 1000

Web

ber May

JulySept

NH4Cl-Al

BD-Al NaOH25-Al

HCl-Al NaOH85-Al

Prerequisite 1

NaOH25-Al:[NH4Cl-Fe+BD-Fe]

0 1 2 3 4 5 6

SR

P [

NH

4C

l-P+

BD

-Fe]

0

20

40

60

80

100

HighlandPenneesseewasseeSalmonChinaCobbosseeconteeWebber

Prerequisite 2

March May July September November

NaO

H2

5-A

l:[N

H4C

l-P+

BD

-P]

25

75

125

300Highland Penneesseewassee Salmon China Cobbosseecontee Webber

Calculated P-Flux

Webb (11) Salm (8) China (15) Cobb (16) Penn (7) High (15)

P F

lux

(mg

m-2

d-1

)

0

2

4

6

8

Al:Fe vs. P Flux

NaOH25-Al:[NH4Cl-Fe+BD-Fe]

0 1 2 3 4 5 6

P F

lux

(mg

m-2

d-1

)

0

1

2

3

4

5

Cobbosseecontee

Webber

China

Salmon

Highland

Penneesseewassee

Conclusions

• Prerequisites for low P release NaOH-Al:[NH4Cl-Fe+BD-Fe] > 3* NaOH-Al:[NH4Cl-P+BD-P] > 25* [NH4Cl-P+BD-P]:TP < 0.1

• Other possible factors Alkalinity during summer Fe-flux during summer †

Quality of organic matter

* Kopačék et al. (2005)† Amirbahman et al. (2003)

Alkalinity

Webber

Salmon

China

PennHighCobb

0

2

4

6

8

10

12

14

16

0 50 100 150 200 250 300

Alkalinity

P F

lux

* Pearce (1999)

Fe-flux

Future Research

• What’s going on in Cobbosseecontee?

• What role does Org-P have in anoxic sedimentary P-flux?

• How accurate is water column data for calculating P-flux?

AcknowledgementsAcknowledgements

• Kyle CoolidgeKyle Coolidge• Advisory CommitteeAdvisory Committee

• Maine DEPMaine DEP• Environmental Chemistry LaboratoryEnvironmental Chemistry Laboratory

• National Science FoundationNational Science Foundation• NEAEBNEAEB