Dissolved organic carbon-water distribution

The early field studies revealed that elevated concentrations of fallout plutonium correlated with Increased concentrations of dissolved organic carbon. Experiments at Argonne National Laboratory corroborate this correlation the explanation Is probably that the organic compounds complex Pu(IV), and, hence, decrease the distribution ratio between water and sedlments(27). In these experiments the distribution ratio (Kj) between sediment and natural waters was measured as a function of DOC. Measurements of Kj In both field and laboratory experiments show an unmistakable effect of DOC upon the distribution ratio. Figure 4 shows the Inverse correlation between the K, of plutonium and concentration of DOC. 

Holten Liitzhoft, H.-C., Yaes, W. H. J., Freidig, A. P., Halling-Sorensen, B. and Hermens, J. L. M. (2000). 1-Octanol/water distribution coefficient of oxolinic acid influence of pH and its relation to the interaction with dissolved organic carbon, Chemosphere, 40, 711-714. 

All water sources may contain natural organic matter, but concentrations (usually measured as dissolved organic carbon, DOC) differ from 0.2 to more than 10 mg L l. NOM is a direct quality problem due to its color and odor, but more important are indirect problems, such as the formation of organic disinfection by-products (DBPs, e. g. M -halomethanes (THMs) due to chlorination), support of bacterial regrowth in the distribution system, disturbances of treatment efficiency in particle separation, elevated requirements for coagulants and oxidants or reductions in the removal of trace organics during adsorption and oxidation, etc. 

A subsurface peak in HgT was evident at 2-4 cm in most cores. A mechanistic explanation for this observation is not clear. Dissolved organic carbon (DOC) concentrations ranged from about 2.5 to 4 mg/L and generally increased with increasing depth of the core. Thus, a clear correlation was not seen between Hg and DOC (38). Similarly, there was no apparent relationship between dissolved Hg and dissolved Fe or Mn. The distribution of Hg in aqueous and solid phases is the net result of many geochemical processes (e.g., redox, complexation, and solubility). Information available to our group thus far cannot explain the observed subsurface peak in the pore-water Hg profile. 

FIGURE I Molecular weight distribution (thousands of daltons) of dissolved organic carbon in wet precipitation, throughfall, A and B horizon soil solution, and stream water at Hubbard Brook, New Hampshire. Source Adapted from McDowell (1982) and Cole et al. (1984). 

Kiichler, I.L., N. Miekeley, and B.R. Forsberg. 1994. Molecular mass distributions of dissolved organic carbon and associated metals in waters from Rio Negro and Rio Solimoes. Sci. Total Environ. 156 207-216. 

Burdige, D.J. and K.G. Gardner. 1998. Molecular weight distribution of dissolved organic carbon in marine sediment pore waters. Mar. Chem. 62 45-64. 

For air-water systems, this equation is known as Henry s law. For solids-water systems, the equilibrium constant is known as the partition coefficient (Ky) or distribution constant (KA). Partition coefficients are available for many organic chemicals from laboratory and field measurements. As organic carbon (OC) present in water (dissolved organic carbon, or DOC), sediment, or soil is the main sink for hydrophobic organic contaminants, the partition coefficients for these compounds are often adjusted (normalized) with respect to the organic carbon content of these compartments ... 

Figure 15.5 Downstream distributions of dissolved species between Vargem Grande and 6bidos the Brazilian Amazon. Distributions for each species are given for both rising-water and falling-water periods, with the particular concentration scale applicable to both periods. Aik = alkalinity, pC02 = dissolved CO2 gas, O2 = dissolved oxygen, PO4 = phosphate ion, DOC = dissolved organic carbon and NO3 = nitrate ion. Solid dashed and thick gray lines are as defined in Fig. 15.4. All units are pM except alkalimty, which is peq 1. ...

Figure 3. Dissolved organic carbon (DOC) size distribution of water samples taken at Volo Bog filtered immediately after sampling and after storage for three weeks before filtration.

Vertical distributions of dissolved Ba and total (dissolved+particulate) Pu, Am and Th in Framvaren Fjord all show increased concentrations with depth (Falkner etal., 1993 Roos etal., 1993). Ba cycling was dominated by its uptake into particulate matter associated with productivity in surface waters, followed by its regeneration at depth or in the sediments. Microbiological activity near the redox interface likely promotes the breakdown of settling particulate matter and the release of barite just above the 02/H2S interface (Falkner etal., 1993). Complex formation with dissolved organic carbon (DOC) is believed to be the main cause for the observed behavior of Pu, Am and Th (Roos etal., 1993). The distributions of these elements were not examined within the regions near the 02/H2S interface and the associated microbial layer. 

Cai, Y., Size distribution measurements of dissolved organic carbon in natural waters using ultrafiltration technique, Water Res., 33, 3056-3060, 1999. 

Starikova, N.D., 1970. Regularities of vertical distribution of dissolved organic carbon in marine waters and ground solutions of marine sediments. Okeanologiya, 10 988— 1000 (in Russian). 

FIGURE 17.23 Vertical distribution of dissolved organic carbon in soil pore water and water column at impacted and unimpacted sites in the WCA-2A of the Everglades. (Reddy, K. R., Unpublished Results, University of Florida.)... 

FIGURE 17.24 Spatial distribution of dissolved organic carbon of surface water in the Everglades. (From Osborne, 2005.)... 

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