1 Biogeochemical Cycling of Cu Associated with Particulate Matter in Lake Superior Jaebong Jeong Environmental Engineering Michigan Technological University

2 Courtesy of Judy Budd, MTU KITES Project (Keweenaw Interdisciplinary Transport Experiment in Superior) Nearshore Offshore Keweenaw Current Cross-margin transport Thermal Bar (NOAA CoastWatch L. Superior Surface Temperature Imagery)

3 Houghton Keweenaw Peninsula Ontonagon Eagle Harbor Copper Harbor My project: Cu cycling associated with particles (SP and mine tailings). Freda and Redridge Portage Canal & Torch Lake Gay

4 Gay, MI Courtesy of Dave Bolgrien, EPA

5 Freda Old Smelter Site

6 Freda Stamp Sands

7 ]Copper (Cu) FCopper is a trace metal essential to healthy life of plants and animals (micro-nutrient). FThe elevated copper concentrations have toxic effects on animal and plant communities. ]Particulate matter (PM) FParticles play an important role in regulating trace metals (sink and source terms).  It is important to understand copper cycling associated with particles in this area.

8 Objectives ]Characterize the source sediments (Freda Stamp Sands, Ontonagon sediments, Wisconsin red clay). ]Investigate transport of suspended particles and sediments redistribution. ]Investigate the spatio-temporal patterns of dissolved Cu. ]Identify the factors controlling biogeochemical cycling of Cu.

9 Intensive Shipboard Sampling (1998~2000) The RV Laurentian (U of Michigan)

10 ]Sediment and Suspended Particles ]Total Suspended Particles (TSP): GFF filters ]Particle Size of Sediments: Sieve & Particle Counter ]Mineralogical Composition: XRD ]Chemical Composition: Chemical Extractions & ICP and AAS ]Organic Carbon and Nitrogen of Suspended Particles: TOCA ]Water ]Dissolved Cu: Ultraclean Technique (Teflon) ]Cu analysis: Atomic Absorption Spectrophotometer (AAS) ]Cations and Anions: Ion Chromatography ]Alkalinity: PC-Titrate TM Autotitrator ]CTD data: Conductivity, Temperature, Chlorophyll a, & Transmissivity Methodology

11 ON Transect CH Transect EH Transect HN Transect FR Transect Redridge Freda Ontonagon Eagle Harbor Copper Harbor Major Sampling Sites Ontonagon River sediments Freda stamp sands Wisconsin red clay Surface Sediment sampling Sites Core Sediment (MCA2)

12 Depth Profile of Cu in the Core Sediment  The background level of Cu is 0.1 mmol/g Sediment.  The Core Sediment shows the maximum Cu concentration at 2.5~3cm depth and slightly high Cu in the surface. [Cu] Tot (mmol/g sediment) Mean Mass Diameter (  m) MCA2-Cu MCA2-BG MCA2-Surf

13 Ontonagon Eagle Harbor Copper Harbor Longshore Transport ? Or Dissolution and Precipitation? Or Algae Uptake & Sink? MCA2 Redridge Freda Original dumping site of stamp sands

14 Characterization of Sediments  Glycerol-treated X-ray diffraction patterns of clay-size particles of the three source materials.

15 Mineralogical Composition  Ternary phase diagram (Illite-Smectite-Chlorite system) of clay minerals  Three sediment source materials (triangle) and near Freda lake sediments (circle) including a core sediment.

16 Longshore & Cross-margin Transport Longshore transport 7.06 (mg/g) Under water Back Ground Cu peak Surface Freda Stamp Sands Ontonagon River Sediments Settling Particles the HN transect Core Sediments Wisconsin red clay  Concentrations of total Cu in the different particles. Cross-margin transport Source MaterialsSettling Particles & Sediments In Lake Superior Total [Cu] (mg/g)

17 HN Transect Freda Ontonagon Eagle Harbor Copper Harbor Sediment Trap Samples Cross-margin Transport

18 Cu Concentrations in Surface Sediments North Entry Freda Redridge Grain Size of Sediments (  m) Freda North Entry Redridge Bathymetry (m) Redridge Freda North Entry Total Cu Concentrations Kraft (mg/kg) Our Data (mg/g)

19 How the contaminated sediments in neashore contribute the dissolved Cu concentrations in the water column? Contaminated Sediments with High Cu Normal Lake Sediments Dissolved Cu Concentrations ? Original Dumping Site

20 Spatial Variations of Dissolved Cu  Nearshore/offshore gradients in concentrations of dissolved Cu were found due to the dissolution of Cu-rich tailings and river inputs.  These values are low due to rapid mixing and dispersing. Transect

21 Nearshore/offshore gradients (HN Transect) What are the controlling factors for the gradients?

22 The Vertical Profiles of Dissolved Cu  Unlike Cu cycling in the Oceans, biological uptake and regeneration seem not to be the major processes of Cu cycling in L. Superior. Bruland, K. W., 1980 (North Pacific, Sept. 1977) Our data (L. Superior, Aug. 2000)

23 Cu:C ratios in Settling Particles  High Cu:C ratios in suspended particles give strong evidence that dissolved copper concentrations may be controlled by particles via sorption. Sunda and Susan 1995 Our data 2000 Sigg 1987 Shafer and Armstrong 1990 Log Cu:C

24 HN210, 2000 DCM and BNL Deep chlorophyll maximum (DCM) and Benthic nepheloid layer (BNL) are co- occur during summer due to biological activity and resuspension of sediments. HN 110, August 22, 1999 BNL DCM

25 Particle Scavenging Particulate Cu fractions are closely related to particle resuspension in the BNL. ON 210, August2000 Transmissivity/100 (%) Particulate Cu (F p, %) TSP

26 Conclusions (Particle Transport) ] Copper tailings are distinguishable from other sediment sources and usable as tracers for particle transport and sediment redistribution. ] The Keweenaw Current is responsible for the longshore transport of fine particles, whereas wave action causes the lateral transport of the coarse deposits along the shore. ] Bathymetry also plays an important role for movements of resuspendable sediments. ] Some cross-margin transport occurs as evidenced by Cu-rich particles in surface sediments and sediment traps in offshore stations.

27 Conclusions (Cu Cycling) ]Continuous dissolution of Cu from the Cu-rich mine tailings causes high Cu concentrations found in the nearshore zones. ]Tributaries containing high Cu concentrations contribute to spatial variation in dissolved Cu in the Ontonagon area. ]Uniform depth profile and high Cu:C ratios in the settling particles suggest that dissolved Cu is controlled by the suspended particles via sorption rather than biological activity. ]Also, physical processes (i.e., the fast mixing of the entire water body and transport by currents) appear to be significant factors regulating the dissolved copper.

28 Questions?