Copper speciation in the Stockholm Archipelago Kuria Ndung’u Applied Environmental Science Stockholm University

Acknowledgements Hans Borg Göran Lithner Jörgen Ek Karin Holm Britta Eklund Ken Bruland Matthew Hurst Kristen Buck Russ Flegal Kemikalieinspektionen-KEMI Naturvårdsverket 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 Cu 2+ Plankton Inorganic Complexes CuX i (e.g. CuCO 3 ) Organic Complexes CuL 1, CuL 2 ) Particulate-Cu Cu-P Adapted from Donat et al., 1994 Aquatic Cu speciation

Synthetic 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) ([M n+ ] >10 -7 M) 2. Voltammetry: Competing ligand equilibration Adsorptive cathodic stripping (CLE-CSV) Anodic stripping: DPASV-HMDE DPASV-GCDE 3. Others: Diffusive gradients in thin films (DGT) Chelating resins

Voltammetric speciation methods comparison Analytical method Basis of distinguishing species Species reactivitycomments Cu 2+ CuX CuL 1 CuL 2 CLE-CSVEquilibrium competition with added ligand labileCuL 1 & CuL 2 determinable depending on added ligand strength  CuL Best characterizati on of CuL (“carrying capacity”) DPASV-RGCDE Kinetics of CuL1 dissociation labileinertInert for k d < 1 s -1 DPASV-HMDElabileinertInert for k d < 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 Reference Station

SitedatepHSalinity (‰) DOC (  M) Cu tot (nM) S-79b29 Aug S-6729 Aug S-4029 Aug S-5029 Aug S-5520 Aug Reference station22 Aug Säck Harbor22 Aug Outside Bullandö22 Aug Bullandö Marina22 Aug Sampling sites: Ancillary data

Salinity, Cu and DOC gradient S79B S67 S55 S50 S57B S40

Bullandö Marina One of the biggest marinas in Sweden, ca berths

Ligand pool “carrying capacity” Reference station

Ligand pool “carrying capacity” Bullandö Marina

Summary

“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)

Cu speciation in the other marine waters Study areaDissolved Cu (  g/L)) Complexed Cu (% ) Reference Stockholm Archipelago >99.9 This study Gullmar Fjord >99.8 Croot, 2003 San Francisco Bay (California) >99.9 Buck & Bruland, 2005 Cape Cod (Massachusetts) < 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 Cu tot ) concentration of Cu complexing ligands buffers the [Cu 2+ ] to < 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