TY  - JOUR
AB  - Ultrahigh resolution mass spectrometry of marine dissolved organic matter (DOM) has suggested the presence of many common molecular compositions throughout the open ocean. The majority of these supposedly ubiquitous molecules was concluded to represent the refractory marine DOM pool. This study demonstrates that 24 h of exposure of Atlantic and Pacific surface DOM to simulated sunlight causes phototransformation of about half of these supposedly refractory molecular compositions. It is suggested that these transformations are related to indirect photobleaching possibly involving reactive oxygen species (e.g. hydroxyl radicals), because very little change in the fluorescent component of the DOM (FDOM) was observed during the photo-degradation experiments. A significant decline in average mass with distinct decrease of average O/C ratios and concomitant increase of H/C ratios was observed. NMR spectra revealed a decrease in aromatic and olefinic unsaturation and the formation of a limited and near identical suite of oxygenated aliphatic compounds in both Atlantic and Pacific surface DOM. Their NMR characteristics indicated a mixture of about 10 polyols that are plausible products of convergent pathways of photochemical carbohydrate decomposition and oxidation of functionalized, branched aliphatic compounds. These prominent photochemical signature molecules amounted to -2% of total proton NMR integral and are expected to be quickly consumed by various microorganisms in the open ocean. These results may suggest a fast photo-induced large-scale cycling of DOM within the surface ocean dynamic equilibrium of photo- and bio-transformations.
AU  - Gonsior, M.*
AU  - Hertkorn, N.
AU  - Conte, M.H.*
AU  - Cooper, W.J.*
AU  - Bastviken, D.*
AU  - Druffel, E.*
AU  - Schmitt-Kopplin, P.
C1  - 31815
C2  - 34796
CY  - Amsterdam
SP  - 10-18
TI  - Photochemical production of polyols arising from significant photo-transformation of dissolved organic matter in the oligotrophic surface ocean.
JO  - Mar. Chem.
VL  - 163
PB  - Elsevier Science Bv
PY  - 2014
SN  - 0304-4203
ER  - 

TY  - JOUR
AB  - The investigation of marine dissolved organic matter (DOM) using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) requires the concentration and extraction of the DOM. Reactions between extraction solvent and DOM might influence data evaluation parameters, which are used to compare DOM of different origin. Potential reactions between methanol and solid-phase extracted marine DOM (SPE-DOM) and their influence on FT-ICR MS data were studied on a molecular level. For elemental formula assignments 9 isotopes were included in the evaluation, and different strategies based on isotope ratios and mass peak intervals were applied to achieve data sets of single assignments. DOM was eluted from the sorbent with methanol, methanol-C-13-D-4 and acetonitrile and stored at 20 degrees C and -20 degrees C. Under both storage conditions HID exchanges were detected. In addition, esterifications were detected in the extract stored at 20 degrees C. but did not result in significant differences in the mass peak magnitudes. Hence, no changes of the weighted average H/C and O/C ratios or other values such as Kendrick mass defect (KMD) and double bond equivalents (DBE) were observed. Acetonitrile was tested as an alternative solvent. Both, methanol or acetonitrile can be used to extract marine DOM from sorbents if samples are immediately stored at -20 degrees C after the SPE process. However, FT-ICR MS data of DOM samples extracted with different solvents showed substantial differences as expected and should not be directly compared.
AU  - Flerus, R.*
AU  - Koch, B.P.*
AU  - Schmitt-Kopplin, P.
AU  - Witt, M.*
AU  - Kattner, G.*
C1  - 6292
C2  - 28334
SP  - 100-107
TI  - Molecular level investigation of reactions between dissolved organic matter and extraction solvents using FT-ICR MS.
JO  - Mar. Chem.
VL  - 124
IS  - 1-4
PB  - Elsevier
PY  - 2011
SN  - 0304-4203
ER  -