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12.755 Lecture 05 Biogeochemical Aspects of Aluminum, Lead, Copper, Cadmium, and Zinc
12.755 Lecture 05Biogeochemical Aspects of Aluminum, Lead,
Copper, Cadmium, and Zinc
Readings
• L05, L06, L07 will all be posted shortly• Read Nealson, both Johnson papers (Mn L06, Fe L07) for Thursday• Browse Weber for Thursday• Read all Iron fertilization policy papers (esp Boyd 2009) for next
Tuesday• Also read Frew for next Tuesday
• Next Tuesday we will have a discussion on iron fertilization and climate mitigation after Phoebe Lam’s guest lecture.
Dust deposition is a key source for many metals (and macronutrients)Figure from Fung et al, 2000 GBC.
Also see work by Jickells, Duce, Mahowald, Sedwick, Sholkovitz, Church, Measures, Landing and others.
North Atlantic Aluminium DistributionsMeasures, Geotraces Document
PNAS 2009
Paytan et al is inconsistent with Mann et al.Prochlorococcus is more sensitive to copper than Synechococcus in careful laboratory studies
Species shift effects: the control decreases in chlorophyll by >3-fold, not a healthy experiment, light levels are highEukaryotes are increasing massively in cell number , known to be less sensitive to metal toxicity
Prochlorococcus doesn’t decrease in cell number but should be contributing a significant component of Chlorophyll, implying their pigment per cell has decreased significantly (which is a sign of stress).
Moffett et al., 1997, Limnol Oceanogr
Solubility of anthropogenic dust is much higher than natural dust
Sholkovitz, Sedwick, Church GCA 2009
Potential use of Vanadium as a proxy for iron solubility
Sholkovitz, Sedwick, Church GCA 2009
Summary and Future issues from Mahowald et al Annual Review Marine Science 2009
Correlations with Nutrients:Micronutrient influences on oceanographic distributions
Cadmium and Zinc: Oceanographic Observations:Nutrient-like profiles and correlations with phosphate or silicic acid
Boyle , Sclater and Edmond. 1976 On the Marine Geochemistry of Cadmium. Nature
Bruland , K. Knauer, Martin. 1978 Zn in Northeast Pacific Waters. Nature
Boyle 1988 Paleoceanography
Bruland , K. Knauer, Martin. 1978 Zn in Northeast Pacific Waters. Nature
ALMOST all lead data for the marine environment are inaccurate, contends Patterson1, because of gross contamination from faulty sampling and analytical procedures. Most marine chemists assume that similar problems are associated with other trace elements as well. Hence, clean sampling and analytical techniques have been adopted. These procedures, in conjunction with the improvement of analytical instrumentation, have resulted in reports on Cu, Ni and Cd (refs 2–4; 3, 5; and 3, 6–8 respectively) levels in seawater that are at least an order of magnitude lower than those previously thought to exist. We report here that Zn concentrations (10–600 ng l -1) are also considerably lower than previously published estimates of 1–30 g l -1 and that its vertical distribution (surface depletion, deep enrichment) is very similar to that of a major plant nutrient; that is, silicate.
Why is there a kink in the Cd:P relationship? An unresolved matter.
1. Analytical issues
2. Province differences, mechanism unknown (Atlantic is distinct, DeBaar 1994)
3. Biodilution effect of iron limitation on Cd:P (Lane, Cullen, Maldonado, 2009)
4. Zn biochemical substitution influences (Zn, Co, Cd interactions – Sunda and Huntsman 2000)
- Zn preference, as Zn becomes depleted, Cd uptake increases
- Zn abundance falls below ligand concentration
• Figure from DeBaar 1994
Zinc – correlates well with silicic acid But Zn is not particularly enriched in diatom frustrules
Nickel – nutrient like similar to phosphate, with caveats
Copper – “evidence of scavenging”There is clearly more to learn about copper scavenging
Nutrient like metals are strongly controlled by biological uptake and remineralization (diagonal vectors)
Metals with strong dust and scavenging show no correlation (vertical vectors)What controls the slope?
The hybrid-types can also have correlations: Co:P correlation exists - but only in surface waters due to scavenging.
(Saito et al., 2004 GBC; Noble et al., 2008 DSR; Saito et al in prep; Noble et al in prep).
Ross Sea of Antarctica
Phosphate (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Tot
al D
isso
lved
Cob
alt
(pM
)
0
20
40
60
80
100
Late Season (2005)Early Summer (2006)
South Atlantic
Phosphate (M)
0.0 0.5 1.0 1.5 2.0 2.5 3.0
Tot
al D
isso
lved
Cob
alt
(pM
)
0
50
100
150
200
250
Benguela Upwelling S.Atlantic Gyre
Downward scavenging vector evident when all depths are included
T5
Total Dissolved Cobalt (pM)
0 20 40 60 80
Dep
th (
m)
0
200
400
600
800
1000
1200
1400
1600
T6
Total Dissolved Cobalt (pM)
0 20 40 60 80
0
200
400
600
800
1000
1200
1400
1600
T7
Total Dissolved Cobalt (pM)
0 20 40 60 80
0
1000
2000
3000
4000
T8
Total Dissolved Cobalt (pM)
0 20 40 60 80
0
200
400
600
800
1000
1200
1400
1600
8-3910m
Phosphate (mol kg-1)
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5
To
tal D
isso
lved
Cob
alt (
pM)
0
10
20
30
40
50
608-100m
Phosphate (mol kg-1)
0.0 0.5 1.0 1.5 2.0
To
tal D
isso
lved
Cob
alt (
pM)
0
10
20
30
40
50
60
Data from Martin et al., 1989
Relative utilization of cobalt and phosphate ( Co vs PO4, mol mol-1)
Location Depth range
Co (pM) Co/P
mol mol-1
r2
South Atlantic (CoFeMUG)
0-200
0-100
7-130
7-37
46
300
0.85
Peru Upwelling Region (Saito, Moffett DiTullio, 2004)
8m 21-315 248 0.83
Equatorial Atlantic(Saito and Moffett, GCA 2002)
5m 5-87 560 0.63
NE Pacific(Martin et al., DSR, 1989)
50-150m 7.9-32 39.8 0.98
NE Pacific (Martin et al., DSR, 1989)
50-150m 28-40 35.5 0.99
NE Pacific(Martin et al., DSR, 1989)
8-50m 25-55 38.4 0.97
Central N Pacific (Saito et al., August 2003, unpublished)
15-150m 13-150 67 0.86
Ross Sea, Antarctica(Saito and Noble, 2006 unpublished)
10-300m 21-65 27 0.83
Biogeochemical Provinces for Cobalt (and Zn/Cd)?Co:P correlations in the upper water column are a global phenomenonBut have a much higher slope in surface waters of oligotrophic regions
cyanobacteria
cyanobacteria
cyanobacteria
Cd and Zn are used as paleotracers of phosphate and silica By analysis of Cd:Ca and Zn:Ca in foraminfera shells
(Figures by Boyle or Marchitto, see Boyle for development of Cd method; Marchitto et al. for Zn method; Boyle, Oppo, Curry, Elderfield, Rickaby, Marchitto and others for application).
