Dissolved organic matter (DOM) is one of the Earth’s largest actively cycling pools of organic carbon and nutrients, impacting the cycling of biogeochemicals through terrestrial and aquatic ecosystems. DOM has many ecologically significant functions including: the absorption of UV light, influencing spectral quality, intensity, and penetration depth; the chelation of metals, influencing the ionic and pH balance; and the transport and bioavailability of organic contaminants. These functions are based in the chemical and physical properties of NOM, but more than half of the organic matter in natural waters is uncharacterized at the molecular level.
Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) has emerged as used in the characterization of humic substances from soils/sediments, and dissolved organic matter from freshwater and marine ecosystems. One major impact of FT-ICR MS on our understanding of natural organic matter has been a paradigm shift away from the view of humic substances and DOM as polymeric macromolecules to a model which describes recognizable biological molecules interacting via non-covalent bonding forces.
Results/Conclusions
[1] FT-ICR MS can provide molecular-level insight to ecosystem processes and disturbances (e.g. fire). This paper gives an overview of changes in DOM molecular composition caused by photochemical and biological decomposition, and during riverine transport. [2] We will give examples of promising future applications of FT-ICR MS such as the DOM-mediated transport and transformation of hydrophobic contaminants, and inferring the history/origin of water masses in the ocean. [3] Practical considerations for the use of FT-ICR MS in ecology research will be discussed. For instance, we have found that that no single ionization technique provides a complete picture of the complex mixture of molecules that compose natural organic matter. Thus, we provide a brief overview of three common atmospheric pressure techniques (electrospray ionization, photoionization, and chemical ionization) their operating principles, advantages, and disadvantages. [4] Finally we introduce the FT-ICR user facilities that are currently available for ecology research.