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