| There is currently little molecular level information available for dissolved organic matter (DOM). In this study, electrospray ionization mass spectrometry (ESI-MS) with ultra-high resolution has been used to study DOM at a molecular level.; High resolution mass spectra of DOM routinely contains several thousand peaks with a multitude of peaks in each nominal mass region. To study the spectra at the molecular level, the individual peaks need to be examined, a process that is arduous and time consuming. In this study, use of the van Krevelen diagram is demonstrated as an innovative graphical interpretation tool for ultra-high resolution mass spectrometric data of DOM. Plotting of ESI-FT ICR-MS data from DOM indicates that lignin or tannin type molecules compose the main portion of readily ionizable DOM molecules. In addition, many peaks corresponding to hydrogen deficient molecules are observed. These hydrogen deficient molecules found in DOM samples can be related to black carbon derived material.; The process of consumption and utilization of DOM by microorganisms is investigated by employing plug-flow thin film bioreactors and ultra-high resolution mass spectrometry of DOM from inflow and outflow water samples. It is shown that the DOM molecules are subject to modifications to lower molecular weight molecules by micro-organisms. Applying van Krevelen analyses for mass spectral data reveals that relative importance of the peaks with low H/C ratios (especially the peaks in the region that has been assigned to black carbon molecules) are generally increased from inflow to outflow water samples. This is consistent in two sets of bioreactor samples collected from two different locations.; The current study clearly demonstrates that the method employed in a significant "breakthrough" in the ability to recognize such a biologically refractory form of DOM. |
