Organic Matter DOM

There are two basic approaches used to characterize seawater DOM (Benner, 2002). The first of these is to directly analyze bulk compositions (e.g., elemental or isotopic compositions) or individual compounds in the sample without concentration. This approach requires high-sensitivity methods for either broad biochemical types (e.g., total amino acids or carbohydrates) or individual compounds, often by either spectroscopic or chromatographic methods coupled to electrochemical or mass spectro-metric detectors. The latter type of molecular-level analyses are now feasible for measuring individual amino acids (Lindroth and Mopper, 1979), sugars (Skoog et al., 1999), and amino sugars (Kaiser and Benner, 

2000) in less than 10 ml of seawater. The great information potential of organic compounds as source and reaction indicators, coupled with continued development of more sensitive and selective measurement methods based on mass spectrometric and electrochemical detection, suggests that direct molecular measurements will continue to grow in application. 

The second basic approach to characterizing seawater DOM is to concentrate a fraction of the total mixture by chemical or physical means into either dry powder or concentrated solution. The solution can be analyzed using a wide array of methods (e.g., elemental analysis, biomarker analysis, mass, or nuclear magnetic resonance spectrometry) to which these isolates are amenable. 

The stability of the organic components of surface seawafer samples is more questionable, buf can be fesfed over time for a wide variefy of molecule classes. 

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F g- 15-15 Schematic representation of Fe and organic matter interactions in an estuary. POM = particulate organic matter DOM = dissolved organic matter PIM = particulate inorganic matter. 

The degradation of DEHP is directly related to releasable TOCw, perhaps the presence of TOCw improved the solubility and microbial degradability under thermophilic conditions in several studies [61, 62], Bauer and Herrmann [18] revealed that the elution of DEHP from MSW was facilitated by the presence of dissolved organic matter (DOM) even under anaerobic conditions. 

Haitzer, M., Hoss, S., Traunspurger, W., Steinberg, C. (1999) Relationship between concentration of dissolved organic matter (DOM) and the effect of DOM on the bioconcentration of benzo[a]pyrene. Aqua. Toxicol. 45, 147-158. 

Fluorescence analysis of dissolved organic matter (DOM) in landfill... 

Poerschmann, J., Kopinke, F-D. (2001). Sorption of very hydrophobic organic compounds (VHOCs) on dissolved hymic organic matter (DOM). 2. Measurement of sorption and application of Flory-Huggins concept to interpret the data. Environ. Sci. Technol., Vol. 35, p. 1142. 

The biogeochemical cycling of POM in the oceans. All of the trophic levels contribute to the POM pool. For the sake of clarity, only the macrozooplankton source is connected to this pool via an arrow. Also shown are the pools of (1) dissolved organic matter (DOM),... 

Sorption of Neutral Compounds to Dissolved Organic Matter (DOM)... 

It would lie far beyond the aim of this chapter to introduce the state-of-the art concepts that have been developed to quantify the influence of colloids on transport and reaction of chemicals in an aquifer. Instead, a few effects will be discussed on a purely qualitative level. In general, the presence of colloidal particles, like dissolved organic matter (DOM), enhances the transport of chemicals in groundwater. Figure 25.8 gives a conceptual view of the relevant interaction mechanisms of colloids in saturated porous media. A simple model consists of just three phases, the dissolved (aqueous) phase, the colloid (carrier) phase, and the solid matrix (stationary) phase. The distribution of a chemical between the phases can be, as first step, described by an equilibrium relation as introduced in Section 23.2 to discuss the effect of colloids on the fate of polychlorinated biphenyls (PCBs) in Lake Superior (see Table 23.5). 

Gerecke, A. C., S. Canonica, S. R. Muller, M. Scharer, and R. P. Schwarzenbach, Quantification of dissolved organic matter (DOM) mediated phototransformation of phenylurea herbicides in lakes , Environ. Sci. Technol., 35, 3915-3928 (2001). 

Recent investigations provide new insight on the structural chemistry of dissolved organic matter (DOM) in freshwater environments and the role of these structures in contaminant binding. Molecular models of DOM derived from allochthonous and autochthonous sources show that short-chain, branched, and alicyclic structures are terminated by carboxyl or methyl groups in DOM from both sources. Allochthonous DOM, however, had aromatic structures indicative of tannin and lignin residues, whereas the autochthonous DOM was characterized by aliphatic alicyclic structures indicative of lipid hydrocarbons as the source. DOM isolated from different morphoclimatic regions had minor structural differences. 

Bacterial break-down of the remaining phytoplankton, faeces and POM occurs after the filter-feeders have filtered out their ration. In addition the dissolved organic matter (DOM), which cannot be utilised directly by filter-feeders, is converted to bacterial production. Thus bacterial consumption of each component is represented by ... 

Sorption coefficients quantitatively describe the extent to which an organic chemical is distributed at equilibrium between an environmental solid (i.e., soil, sediment, suspended sediment, wastewater solids) and the aqueous phase it is in contact with. Sorption coefficients depend on (1) the variety of interactions occurring between the solute and the solid and aqueous phases and (2) the effects of environmental and/or experimental variables such as organic matter quantity and type, clay mineral content and type, clay to organic matter ratio, particle size distribution and surface area of the sorbent, pH, ionic strength, suspended particulates or colloidal material, temperature, dissolved organic matter (DOM) concentration, solute and solid concentrations, and phase separation technique. 

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