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