Copper speciation in the Stockholm Archipelago Kuria Ndung’u Applied Environmental Science Stockholm University
Jan 03, 2016
Copper speciation in the Stockholm Archipelago
Copper speciation in the Stockholm Archipelago
Kuria Ndung’uApplied Environmental Science
Stockholm University
AcknowledgementsAcknowledgements
Hans Borg Göran Lithner Jörgen Ek Karin Holm Britta EklundKen BrulandMatthew HurstKristen BuckRuss Flegal
Kemikalieinspektionen-KEMINaturvårdsverket
European Copper Institute
Sensitive analytical techniques(AAS, ICP-OES/MS, ASV/CSV)
Clean techniques and reliable data(last ca. 20 yrs)
Ecotoxicologists: metal speciation
Speciation: Historical background
Trace metal clean sampling and analysis
Trace metal clean methods
Benoit, 1994
Dissolved Cd and Pb in river water
conventional
TM clean methods
Contamination artifacts have seriously compromised the reliability of many past and current analyses and in some cases, metals have been measured at 100 times their true concentration. Benoit et al., 1997
Anderson & Morel, 1978, Paquin et al., 2002
Free ion activity model (FIAM)
The Biotic Ligand Model
Paquin et al. 2002
Biotic ligands: Cell membrane
Sunda, 1988
Aquatic chemistry
Biological effects
Filter feeders
Cu2+
Plankton
Inorganic Complexes CuXi (e.g. CuCO3)
Organic ComplexesCuL1 ,CuL2)
Particulate-CuCu-P
Adapted from Donat et al., 1994
Aquatic Cu speciation
Synthetic ChelatorsSynthetic Chelators
EDTA
NTA
DTPA
Multiple sources: Soaps & detergents, water treatment, metal finishing and plating
Morel & Price, 2003
Natural Chelators
Speciation Techniques
1. Ion selective electrodes (ISE)([Mn+] >10-7 M)
2. Voltammetry:Competing ligand equilibrationAdsorptive cathodic stripping (CLE-CSV) Anodic stripping:
DPASV-HMDEDPASV-GCDE
3. Others: Diffusive gradients in thin films (DGT) Chelating resins
Voltammetric speciation methods comparisonAnalytical method
Basis of distinguishing species
Species reactivity comments
Cu2+
CuX
CuL1 CuL2
CLE-CSV Equilibrium competition with
added ligand
labile CuL1 & CuL2 determinable depending on added ligand strength CuL
Best characterization of CuL (“carrying capacity”)
DPASV-RGCDE
Kinetics of CuL1 dissociation
labile inert Inert for kd< 1 s-1
DPASV-HMDE labile inert Inert for kd< 0.1 s-1
Modified from Donat et al., 1994
Differential pulse anodic stripping voltammetry
DPASV: Titration of BA-30 (Dumbarton Bdge)
Hurst and Bruland, 2005
Sampling sites
S55
S50
S40
S79b
S67
S57b
Bullandö Marina
Outside marina
Säck harbor
Refer
ence
Sta
tion
Site date pH Salinity
(‰)
DOC (M)
Cutot (nM)
S-79b 29 Aug. 06 7.4 2.9 426 24
S-67 29 Aug. 06 7.9 4.3 388 22
S-40 29 Aug. 06 8.2 5.1 354 14
S-50 29 Aug. 06 8.5 6.0 330 8
S-55 20 Aug. 05 - 5.4 8
Reference station 22 Aug. 06 8.0 5.2 341 13.3
Säck Harbor 22 Aug. 06 8.1 5.4 363 14.2
Outside Bullandö 22 Aug. 06 8.0 4.9 370 16.4
Bullandö Marina 22 Aug. 06 8.0 4.9 367 49.7
Sampling sites: Ancillary data
Salinity, Cu and DOC gradient
S79B S67
S55S50
S57BS40
0.0
2.0
4.0
6.0
S79B S67 S40 S50 S55
Sampling site
DO
C (
mg/
L) &
Sal
inity
(‰
)
0.0
5.0
10.0
15.0
20.0
25.0
Cu
(nM
)
Salinity
(( DOC)mg/L
( Cu/nM
Bullandö Marina
One of the biggest marinas in Sweden, ca. 1400 berths
Ligand pool “carrying capacity”
Reference station
-15
-13
-11
-9
0 30 60 90 120
[Cu*T] (nM)
log
[Cu2+
] Minorganic complexation only
possible cyanobacteria toxicity threshold
ambient [Cutot] = 13.3 nM (0.84 g/L)
Ligand pool “carrying capacity”
Bullandö Marina
-15
-13
-11
-9
0 30 60 90 120
[Cu*T] (nM)
log
[Cu2+
] (
M)
inorganic complexation only
cyanobacteria toxicity threshold
ambient [Cutot]=49.7 nM (3.2 g/L)
SummaryOutside Bullandö Marina
-15
-13
-11
-9
0 20 40 60 80 100 120
[Cu*T] (nM)
log
[C
u2+
] (
M)
ambient [Cutot]=16.4 nM (1.04 g/L)
Säck natural harbor
-15
-13
-11
-9
0 30 60 90 120
[Cu*T] (nM)
log
[C
u2+
] (
M)
ambient [Cutot]=14.2 nM (0.90 g/L)
-15
-13
-11
-9
0 30 60 90 120
[Cu*T] (nM)
log
[C
u2+ ]
(M
)
[Cutot]=49.7 nM (3.2 g/L)
Bullandö marina Reference station
-15
-13
-11
-9
0 30 60 90 120
[Cu*T] (nM)
log [C
u2+ ] (
M)
ambient [Cutot]=13.3 nM (0.84 g/L)
“Cu concentration has doubled in the last decade”
…..In the water samples the copper concentrations have generally
doubled, while zinc concentrations have gone up with up to 6.5 times……(KEMI, 2006)
B
B
B
B
1993 2004 2004-2006 1993-20050.4
0.6
0.8
1
1.2
1.4
1.6C
u C
once
ntra
tion
(ng
/ml)
Year
EPA-1993
KEMI-2004
This study
Landsort Deep
IOW (HELCOM)
Cu speciation in the other marine watersStudy area Dissolved Cu
(g/L))
Complexed Cu (% )
Reference
Stockholm Archipelago
0.8-3.2 >99.9 This study
Gullmar Fjord
0.2-1.2
>99.8 Croot, 2003
San Francisco Bay(California)
1.1-3.2 >99.9 Buck & Bruland, 2005
Cape Cod(Massachusetts)
0.3-3.4 90-99< Moffett et al., 1997
Narragansett Bay(Rhode Island)
0.8 >99.9 Bruland et al., 2000
Conclusion More than 99.9 % of the total dissolved copper in the sites studied was organically complexed
The large excess (compared to Cutot) concentration of Cu complexing ligands buffers the [Cu2+] to < 10-12 M (< 0.1 ng/L) in all sites, an order of magnitude below the toxicity threshold for microorganisms
We need more detailed (both spatially and temporally)speciation studies on the Archipelago and the Baltic
Proper