Matter riverine organic

The amount of organic matter carried in particulate form by the Amazon depends largely on concentrations of total suspended particles (Fig. 15.7). The partitioning of riverine organic matter between fine particulate and dissolved forms as a function of fine suspended solids is illustrated in Fig. 15.14. The direct relationship of FPOM/DOC... 

Riverine fluxes. Approximately 0.2 Gt each of dissolved and particulate OC are carried from land to sea annually by rivers (Ludwig et al., 1996). Much of this riverine organic matter appears to be soil derived based on its chemical characteristics (Meybeck, 1982 Hedges et al., 1994), although autochthonous sources may be important for the dissolved fraction (Repeta et al., 2002). It is now recognized that, on a global basis, riverine... 

Marine scientists have long puzzled over the fate of riverine organic matter on entry to the ocean [69,71]. Isotopic studies indicate that the DOC in the open ocean is primarily of marine origin [142,143], although some terrestrial character would have been expected. Models have been used to evaluate the potential loss of organic matter in coastal regions. 

In nearly all industrialized, densely populated or agricultural stressed regions and countries (especially in North America and Europe) the riverine organic matter is superimposed by huge anthropogenic emissions as described above. 

The most striking characteristic of the dissolved humic substances is their chromophoric nature. As part of the DOM, they impart a yellow-brown cast to marine and freshwaters and, hence, are part of the CDOM pool. Terrestrial hiunic substances compose a significant fraction of the riverine DOM entering the ocean. In seawater, humic substances compose 5 to 15% of the HMW DOM. Differences exist in the bulk properties of marine and terrestrial humic substances. These are summarized in Table 23.6. They have been used to trace the fate of terrestrial organic matter in the ocean. 

Raymond, P. A., and J. E. Bauer. 2001. Riverine export of aged terrestrial organic matter to the North Atlantic Ocean. Nature 409 497-500. 

Smith, E. M., and Benner, R. (2005). Photochemical transformations of riverine dissolved organic matter Effects on estuarine bacterial metabolism and nutrient demand. Aquat. Microb. Ecol. 40, 37-50. 

Kaiser, E., Simpson, A. J., Dria, K. J., Sulzberger, B., and Hatcher, P. G. (2003). Solid-state and multidimensional solution-state NMR of solid phase extracted and ultrafiltered riverine dissolved organic matter. Environ. Sci. Technol. 37,2929-2935. 

Of the organic carbon entering the ocean, about 35% accumulated in marine sediments as organic carbon with a molar C/N/P ratio of about 250/20/1 (Mackenzie, 1981) the rest was respired and oxidized to CO2 and evaded the ocean. The nitrogen and phosphorus riverine fluxes of 1 and 0.045 x 1012 moles y1, respectively, represented the nutrient fluxes necessary to support the organic matter accumulation of 11.7 x 1012 moles C y1. 

Figure 8.6 Major sources of dissolved organic matter (DOM) to estuaries, primarily composed of riverine inputs, autochthonous production from algal and vascular plant sources, benthic fluxes, groundwater inputs, and exchange with adjacent coastal systems. (Modified from Hansell and Carlson, 2002.)...

---