Persistence of dissolved organic matter in lakes related to its molecular characteristics

• Published in: Nature geoscience Vol. 8; no. 6; pp. 454 - 457
• Main Authors: Kellerman, Anne M., Kothawala, Dolly N., Dittmar, Thorsten, Tranvik, Lars J.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.06.2015; Nature Publishing Group
• Subjects: 704/158/2445; 704/158/2449; 704/158/2459; 704/158/47; Aquatic environment; Aromatic compounds; Carbon; Chemistry; Dissolved organic matter; Earth science; Earth Sciences; Earth System Sciences; Environmental conditions; Fourier transforms; Geochemistry; Geology; Geophysics/Geodesy; Hydrology; Lakes; letter; Mass spectrometry; Molecular weight; Optical properties; Oxidation; Scientific imaging; Water analysis; Sweden
• ISSN: 1752-0894; 1752-0908; 1752-0908
• DOI: 10.1038/ngeo2440

Organic matter’s molecular structure has been thought to influence its decomposition. Analyses of dissolved organic carbon in Swedish lakes found that aliphatic and N-containing compounds persisted, while oxidized aromatic compounds were lost. Whether intrinsic molecular properties or extrinsic factors such as environmental conditions control the decomposition of natural organic matter across soil, marine and freshwater systems has been subject to debate 1 , 2 , 3 . Comprehensive evaluations of the controls that molecular structure exerts on organic matter’s persistence in the environment have been precluded by organic matter’s extreme complexity 4 . Here we examine dissolved organic matter from 109 Swedish lakes using ultrahigh-resolution mass spectrometry and optical spectroscopy to investigate the constraints on its persistence in the environment. We find that degradation processes preferentially remove oxidized, aromatic compounds, whereas reduced, aliphatic and N-containing compounds are either resistant to degradation or tightly cycled and thus persist in aquatic systems. The patterns we observe for individual molecules are consistent with our measurements of emergent bulk characteristics of organic matter at wide geographic and temporal scales, as reflected by optical properties. We conclude that intrinsic molecular properties are an important control of overall organic matter reactivity.