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Collaborative Research: Molecular Level Characterization of Organic Matter in Ice Cores using High-resolution FTICR mass spectrometry

Entry ID: hatcher_0739684

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Summary

Abstract: This award supports a project to fully develop the analytical protocols needed to exploit a relatively new technique for the analysis of soluble organic matter in ice core samples. The technique couples Electrospray ionization to high resolution Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICR-MS). We demonstrate that one can analyze a small volume (100 mL) of ice core ... melt-water with sufficient mass spectral sensitivity to describe the molecular composition of the DOM. Following method optimization a suite of ice core samples from several Antarctic and Greenland locations were examined to address several hypothesis driven research questions. DOM is thought to represent an assemblage of complex molecules that, among them, could contain proxies for climatological conditions of the past. Studies of the DOM in ice cores have recently taken on great importance, because they generally record past histories of atmospheric conditions at time of deposition. Several important questions related to developing a better understanding of the nature and paleo record of organic matter in ice cores are being addressed. The mass spectra of the ice core DOM consist of multitudes of peaks spanning the range of 200-700 m/z, and complexity is apparent from the detection of up to 20 peaks per nominal mass at nearly every mass throughout that range. A molecular formula calculator generates formula matches, from which van Krevelen plots are constructed. Analysis was conducted using ice core samples from 2 sites in Antarctica and 1 centralized region of Greenland (obtained from the National Ice Core Laboratory). Changes in the types and amounts of CHO-, CHOS-, CHON-, and CHONS-containing molecular formulae are observed. Samples at lower depth (i.e., younger in age) have higher O/C ratios than those at higher depth (i.e., older). There is little variation in the S/C ratios amongst samples, there was a notable difference in the N/C ratios between the Greenland and Antarctic samples. The nitrogen content was lower for Greenland samples relative to the Antarctic samples. The large datasets generated from the FTICR-MS analysis of DOM can make data mining difficult, and multivariate statistical analysis (such as principal component analysis, PCA) assists in the data interpretation.In general, the DOM in all of the ice cores is aliphatic in nature, as indicated by the vast majority of molecular formulas having H/C values greater than 1.5. However, there are many formulas with a low H/C (and thus high DBE), indicating the presence of some aromatic and condensed aromatic species. Based on the multivariate principal component analysis, the 2 Greenland samples are remarkably similar and dominated by CHO-only formulas, with less contribution from nitrogen- and sulfur-containing species. The Antarctic ice cores contain a much higher number of formulas containing nitrogen, but fewer containing sulfur. The deepest sample (from Siple Dome, aged at approximately 1000 years old) separates from the other younger ice core samples. This sample contains formulas with lower O/C ratios than the other samples’ molecular formulas.

Purpose: The intellectual merit of this work is that this analytical method provides a new understanding of the nature of organic matter in ice, leading to the discovery of multitudes of molecular species indicative of global change processes whose abundances can be compared with other change proxies. The studies are of an exploratory nature and potentially transformative for the field of ice core research ...

Related URL

Link: VIEW RELATED INFORMATION

Description: NSF Award #0739684

Location Keywords

CONTINENT > NORTH AMERICA > GREENLAND

CONTINENT > ANTARCTICA > ROSS ISLAND

Science Keywords

CRYOSPHERE > SNOW/ICE

PALEOCLIMATE > ICE CORE RECORDS

ATMOSPHERE > AEROSOLS

ISO Topic Category

CLIMATOLOGY/METEOROLOGY/ATMOSPHERE

Platform

COMPUTERS

LABORATORY

Instrument

MASS SPECTROMETERS

Project

NSF/OPP > Office of Polar Programs, National Science Foundation

Ancillary Keywords

ice cores

molecular

Originating Center

Department of Chemistry &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp; Biochemistry, Old Dominion University

Data Center

NSIDC Antarctic Glaciological Data Center

Data Center URL: http://nsidc.org/agdc/

Data Center Personnel
Name: NSIDC AGDC USER SERVICES Phone: +1 (303) 492-6199 Fax: +1 (303) 492-2468 Email: nsidc at nsidc.org Contact Address: National Snow and Ice Data Center CIRES, 449 UCB University of Colorado City: Boulder Province or State: CO Postal Code: 80309-0449 Country: USA

National Snow and Ice Data Center

Data Center URL: http://nsidc.org

Data Center Personnel
Name: NSIDC USER SERVICES Phone: +1 (303) 492-6199 Fax: +1 (303) 492-2468 Email: nsidc at nsidc.org Contact Address: National Snow and Ice Data Center CIRES, 449 UCB University of Colorado City: Boulder Province or State: CO Postal Code: 80309-0449 Country: USA