Biogeochemical Cycling of Heavy Metals in Lake Coeur d'Alene Sediments

The Role of Indigenous Microbial Communities

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Project

Biogeochemical Cycling of Heavy Metals in Lake Coeur d'Alene Sediments: The Role of Indigenous Microbial Communities

Funding

U.S. National Science Foundation

Collaborators

Rajesh Sani (WSU), Tim Ginn (UCD), Nicolas Spycher (LBL), Sutapa Barua (MSU, James Moberly (WSU), Sema Sevinc Sengor (UCD), Eileen Belding (UCD), Kristen Curthoys (UCD), Chris Taylor (WSU)

Introduction

Mining of precious metals since the late 1800's has left Lake Coeur d’Alene (LCdA) sediments heavily enriched with toxic metals, including Cd, Cu, Pb, and Zn. During major flood runoff events, stream transport have distributed metal enriched sediment mainly from Bunker Hill Superfund mining site, located at the South Fork of Coeur d’Alene mining district. Heavy metals are highly toxic in the environment and their biogeochemical cycling in sediments of Lake Coeur d'Alene (LCdA) in Idaho is largely unknown. The objectives of this project are to 1) characterize the diversity of microorganisms in LCdA sediments using modern molecular biology techniques, 2) quantify the role of individual members of the microbial community in biogeochemical cycling of metals (Cu, Pb, and Zn), and 3) develop a dynamic numeric biogeochemical model of heavy metal cycling in sediment systems, calibrated to the unique environments of LCdA.

map and aerial view of research site

Project objectives are being achieved by sampling LCdA sediments and identifying microbial diversity based on both 16S rDNA and rpoB gene sequences. These molecular techniques greatly facilitate the study of microbes in their natural environments and will provide a rational platform to base observations of community response to toxic metal additions. Focused laboratory studies are underway to quantify the effects of toxic metals on microbial growth and inhibition for incorporation into the predictive model. The modeling effort is integrating for the first time to our knowledge, syntrophic consortium biotransformation dynamics, dose-dependent inhibition, and spatial and temporal dynamics of redox front formation under a diffusive transport regime. Although this is a relatively new project (started Aug 2004), results to date show detailed heavy metal contaminated sediment characterization, a sediment-simulating laboratory reactor, a model for Cu and Pb transport with multiple microbial trophic groups, and progress on sediment clone libraries for rpob and 16S rDNA community analysis.

Characterization of Lake Coeur d’Alene sediments

Sediment samples were collected from metal-contaminated regions surrounding Harrison, Idaho (N 47o28’ W 116o43'; Figure 1).  These sediment samples were characterized using X-ray fluorescence microscopy (XRF) to obtain total metal concentration (Table 1).  The data show the presence of high concentrations of metal and compare well with published literature values.

Table 1: Major elements and trace metals in sediment.  Copper lead and Zinc are highlighted.

Primary Sediment Constituents (% Mass)

Trace Elements

(mg/kg)

 SiO2 

60.78

 Zn

5647 

 FeO

12.09

 Pb

2796 

 Al2O3

7.41

 Ba

605 

 K2O  

1.83

 Zr

236 

 MnO  

1.251

 Ce

120 

 MgO  

0.92

 Cu

107 

 Na2O 

0.57

 Rb

74 

 CaO  

0.42

 Nd

34 

 TiO2 

0.401

 Y

34 

 P2O5 

0.106

 Sr

34 

Primary Sediment Constituents (%)

85.78

 V

34 

LOI (%)

9.29

 La

32 

Trace Element (%)

0.98

 Cr

28 

 

 

Ni

13 

Total

96.05

 Ga

13 

 

"This material is based upon work supported by the National Science Foundation under Grant No. 0628258."

"Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation."