Chemical Microscopy Studies of Chemical Microscopy Studies of Peat from the Arctic Coastal PlainPeat from the Arctic Coastal Plain

Thaw Lake Basin: Barrow, Alaska

Heidi Heidi BialkBialk GREF Presentation GREF Presentation June 2003 June 2003

Portage, Alaska

Introduction

qq Introduction IntroductionØ Background

qq Project Goals Project GoalsØ ObjectivesØ Hypotheses

qqq Experimental Methods Experimental Methods Experimental MethodsØ Sample Collection and Sample Preparation

qq Preliminary Results Preliminary ResultsØ Data Collection: XANES and MicroscopyØ Summary of Preliminary Results

qq Conclusions ConclusionsØ Future Directions

qq Acknowledgements Acknowledgements

OverviewOverview

Whale Bone: Barrow, Alaska

Background: Why the ArcticCoastal Plain?

q Soils of the tundra biome are estimated to contain 13%of the world soil C pool

qPotential impact of climate warming on carbonaccumulation in the arctic tundra has multiplescenarios.

qAn improved understanding of the chemical nature ofpeat is needed in order to better predict impacts ofclimate change.

Age Classification of BasinsAge Classification of Basins

Young Medium

Old Ancient

Arctophila fulva, Caliergon Eriophorum augustifolium

Carex aquatilus, Dichranum elongatum and Sphagnum Eriophorum vaginatum

Photos by Dr. Wendy Eisner

Background Cont’d: Landsat-7 Background Cont’d: Landsat-7 Imagery of the Coastal Plain Imagery of the Coastal Plain

http://k2.gissa.uc.edu/~weisner/thawpage_files/frame.htm

young

old

ancient

medium

Background Cont’dq There have been several studies on the

progression of events within the thaw lake cycle(Billings and Peterson., 1980; Eisner., 1998a; Eisner andPeterson., 1998b).

q CPMAS-NMR used as a tool to characterizewhole peat samples along with soluble extractsfrom the Arctic (Ping et al., 2001)

q Spectra do not reveal organic origins.q Our approach will be similar, focusing on whole

insoluble residues using synchrotron x-raybased methods that include microscopy.Øchemical imaging

Alaskan Railroad: Anchorage, Alaska

Project Goals

ObjectivesObjectives

q Bridge a gap in the current understandingof peat mats from the arctic coastal plainØQuantify fresh source material in peat mats and

assess the extent of decomposition

ØEstimate the amount of chemically identifiablecell wall material of the following origin:ü vascular plants through a chemical mapping based on lignin

ümoss, fungal, and microbial cell wall material

Dominant Vegetation

Permafrost

Active LayerPeat Core

Fresh Material ?

vascular avascular

-Fungi-Mosses-Microbial cell walls

Main Hypothesesq Chemical imaging will distinguish detritus

of a vascular origin vs. detritus of anavascular origin via a chemical mapping oflignin. (Kogel-Knaber., 2002)

q There are chemical characteristics of fungaland bacterial cell wall material that will allowfurther distinction of detritus origin.

q Chemical imaging will reflect an increase in thedegree of decomposition of detritus with depth.(Dai et al., 2001)

Dominant Vegetation

Permafrost

Active Layer Peat Core

Fresh Material ?

vascular avascular

-Fungi-Mosses-Microbial cell walls

Denali National Park, Alaska

Experimental Methods

Synchrotron X-ray Radiation:What is it?

SynchrotronX-ray

Analysis

Bulk XANES Mark II Grasshopper Port 103 Averages over an entire sample

Chemical MicroscopyMephistoSelective Electronic Imaging

Schematic of ChemicalMicroscopy (Mephisto)

DeStassio et al., 1998

Brief Overview of X-ray Absorption

Quantized photon at C-K edge

e-

sample

Total Electron Yield

X-ray Absorption:A Model Chemical Signature

Energy (eV)

4p

5p

6p

7p

Re

lati

ve In

ten

sity

Experimental Methods:Sample Collection and Preparation

Barrow, Alaska

Sample Collection: Vegetation

Eriophorum vaginatum(graminoid)

ancientRI Basin

Carex aquatilus (graminoid),Dichranum elongatum andSphagnum (mosses)

oldTC Basin

Eriophorum augustifolum(graminoid)

mediumGolf Course Basin

Arctophila fulva (graminoid),Caliergon (moss)

youngFootprint Lake Basin

Dominant Vegetation (other species present)

Age Lake Site

Table 1. Parent Vegetation from drained thaw lake basins in Barrow, Alaska, at 71 degrees N latitude

Sample Collection Cont’d

qMicrobial Cell WallIsolation (Dufrene et al.,1997; Dengis et al., 1995)

Ø Bacteria: Archaea

q Peat Cores

http://k2.gissa.uc.edu/~weisner/thawpage_files/frame.htm

Rationale for Sample Preparation

Quantized photon at C-K edge

e-

sample

Total Electron Yield

++

+

Sample Preparation

q Soft X-ray Analysis in Bulk Mode (Port 103)Ø Samples ground and embedded into indium foil

Ø Coated with a 7 angstrom Pt-Pd alloy film

Ø Eliminates charging

q Soft X-ray Analysis in Microscopic ModeØ Samples fixed in a Polybed-812 & Spurr’s carbon based

resin

Ø Sectioned to 8 micrometers to minimize sample charging

Ø Smooth sample required for quality imaging

Sample Preparation: MicroscopySample Preparation: Microscopy

Photo by Russ Spears

Denali National Park, Alaska

Preliminary ResultsPreliminary Results

280 285 290 295 300 305

Energy, eV

Inte

nsi

ty

Aspen Lignin Cellulose

Bulk Data Collection: XANESBulk Data Collection: XANESSpectra of Cellulose and LigninSpectra of Cellulose and Lignin

Alaskan Peat

280 285 290 295 300 305 310 315 320 325 330

Energy

Data Collection: XANES Spectrum of Data Collection: XANES Spectrum of Arctic Peat at the Carbon K-edge Arctic Peat at the Carbon K-edge

Carbon K-edge (Eriophorum Augustifolum)

280 285 290 295 300 305 310 315 320

Energy (eV)

Inte

nsity

Data Collection: XANES SpectrumData Collection: XANES Spectrumof of EriophorumEriophorum augustifolumaugustifolum at theat the Carbon K-edgeCarbon K-edge

280 285 290 295 300 305 310 315 320 325 330 80 285 290 295 300 305 310 315 32

Inte

nsit

y

Key Points from XANES Analysis Key Points from XANES Analysis

Energy (eV) Energy (eV)

Inte

nsi

ty

Inte

nsi

ty

Alaskan Peat Eriophorum Augustifolium

Sample Preparation: MicroscopySample Preparation: Microscopy

Photo by Russ Spears

Data Collection: PEEM MicroscopyData Collection: PEEM Microscopy

Data Collection: Soft X-ray Data Collection: Soft X-ray Microscopy of Isolated Peat Region Microscopy of Isolated Peat Region

at the Carbon K-edgeat the Carbon K-edge

- Peat- Resin

Summary of Preliminary Resultsq Bulk soft x-ray analysis at the carbon K-

edge distinguishes between fresh plantmaterial and peat.q Chemical microscopy is feasible due to a

chemical contrast between embeddingresin and peat.q Changes in methodology have improved

data quality.q Chemical microscopy will provide insight

into the nature of peat originating from thearctic coastal plain.

Mt. McKinley, Alaska

ConclusionsConclusions

Future Directions

q Complete bulk spectra of parentvegetation

q Collect bulk and microscopic imagesat various depth intervals along apeat core

q Utilize IR microscopy techniques

q Analyze and interpret spectra

Arctic Ocean

AcknowledgementsAcknowledgements

CollaboratorsCollaborators::-Dr. Bockheim (UW-Madison)-Dr. DeStassio (SRC)-Dr. Xiaoyan Dai (post-doc)-Brad Frazier (SRC)

Technical Support:Technical Support: -Dr. Kim Peterson (UA- Fairbanks) -Randy Massey (UW-Madison) -Dr. Russ Spears (UW-Madison) -Dan Wallace (SRC) -Adam Hitchcock (SRC)

FundingFunding::- Global Research Environmental Fellowship (GREF)

Other: Other: --Barrow Arctic Consortium Barrow Arctic Consortium (BASC)(BASC)

Background: How Do Thaw Lakes Form?Background: How Do Thaw Lakes Form?

Billings and Peterson, 1980.

Photo by Russ Spears

Sample Preparation:Sample Preparation:Chemical MicroscopyChemical Microscopy

Sample Collection

qPollen

Øproxy for vegetation used inpaleoecological research

ØEriophorum scheuzeri, Arctophila fulva,Carex aquatilus

Alaskan Peat

280 285 290 295 300 305 310 315 320 325 330

Energy

Data Collection: XANES Spectrum of Data Collection: XANES Spectrum of Arctic Peat at the Carbon K-edge Arctic Peat at the Carbon K-edge

Fresh Material?

Data Analysis: Peak Deconvolution

Xia et al., 2002

Relative Energy (eV)

Inte

nsi

ty

Data Analysis: Peak Assignmentswith Model Compounds

Vairavamurthy et al., 2002

Energy (eV)

Data Collection: Soft X-rayData Collection: Soft X-ray Microscopy of Isolated Peat Region Microscopy of Isolated Peat Region at the Nitrogen K-edge at the Nitrogen K-edge

Double Normalization

Intensity = {(Sample Unknown TEY)(Nickel Mesh)} {(Silicon Chip TEY)(Nickel Mesh)}

q Fungal Cell Walls

ØChitin

ØCellulose

ØPolysaccharides

ØAmino sugars

q Bacterial Cell Walls

Ø Lipids

Ø Lipopolysaccharides& polysaccharides

ØPeptidoglycan

ØAlkyl macromolecules

ØAmino sugars

üN-acetyl muramicacid

Potential Pitfalls

q Sample Collection

Ødecomposition may not necessarily increasewith depth due to fine root penetration of thepeat mat and cryoturbation

q Data Analysis

Ødifficulty in obtaining quality data, samplecharging may limit confidence in ourquantification

Other Methods in PeatCharacterization

q Amino sugar analysis (bacterial vs fungalcell wall contributions)

q Isomer analysis with GC/MS

q Sulfur XANES – distinguish bacterial cellwall material?

q Lignin extraction in a mix of humicextracts

Expected Results

q Relationship between amount of freshmaterial vs depth/age

Ø depth and age may not be linear

Ø fresh material vs time may be moreappropriate

Research Timetable

- Complete thesispublications anddefend thesis

-Chem. Microscopy ofPeat

- Pollen Isolation andAnalysis

-Write and submitpublication on thosefindings

- Continued analysis ofcore peat sample

-Cell Wall Isolation

- Soft X-rayspectroscopy ofparent vegetation andcell wall material

- Write NSF proposal

- Write and submitpublication on initialresults

2005 2004 2003