Analysis and Characterization of Dissolved Organic Matter in Ice Cores as Indicators of Past Environmental Conditions Using High Resolution FTICR-MS

Abstract:

With rapid changes in global temperatures, research aimed at better understanding past climatic events in order to predict future trends is an area of growing importance. Carbonaceous gases stored in ice cores are known to correlate with temperature change and provide evidence of such events. However, more complex forms of carbon preserved in ice cores such as dissolved organic matter (DOM) can provide additional information relating to changes in environmental conditions over time. The examination of ice core samples presents unique challenges including detection of ultra-low concentrations of organic material and extremely limited sample amounts.

In this study, solid phase extraction techniques combined with ultra-high resolution electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FTICR-MS) were utilized to successfully extract, concentrate and analyze the low concentrations of DOM in only 100 mL of ice core samples originating from various regions of Antarctica and Greenland. We characterize the DOM composition in each sample by evaluating elemental ratios, molecular formula distribution (CHO, CHON, CHOS and CHNOS) and compound class composition (lignin, tannin, lipid, condensed aromatic, protein and unsaturated hydrocarbon content). Upon characterization, we identified molecular trends in ice core DOM chemistry that correlated with past climatic events in addition to observing possible photochemical and microbial influences affecting DOM chemistry. Considering these samples range in age from 350-1175 years old, thus being formed during the Medieval Warm Period and Little Ice Age, we observed that DOM properties reflected anticipated changes in composition as influenced by warming and cooling events occurring during that time period.