Matter riverine particulate

Increased erosion due to forest clear-cutting and widespread cultivation has increased riverine suspended matter concentrations, and thus increased the riverine particulate-P flux. Dams, in contrast, decrease sediment loads in rivers and therefore diminish the phosphorus flux to the oceans. However, increased erosion below dams... 

The data presented in Tables 2-5 are updated as much as possible, with many of the references postdate the late 1980s. Notable exceptions are riverine particulate matter chemistry (Table 2), some references in Table 3, and references concerning the geochemical properties of the six heavy metals discussed in this chapter. There appears to be no recent publication that updates the worldwide average for riverine particulate matter trace metal chemistry (Martin and Whitfield, 1981 Martin and Windom, 1991). This is supported by the fact that two recent references (Li, 2000 Chester, 2000) concerning marine chemistry still refer to this 1981 publication. As for references in Table 3, there is a very limited data available concerning the pathways of heavy-metal transport to lakes. Some of the important works have been considered and... 

The Cu concentration of crustal rocks (32 34 p,g g ) is approximately equivalent to that for average soils (25 4 p,g g ). However, as the earth material is weathered and transported to streams-lakes-shaUow marine sediments there is a minimal enrichment in Cu concentration (39 = 34 = 43 p,g g ) (Table 4). And, as for Pb-Zn-Cd, riverine particulate matter is greatly enriched (100p,gg ) relative to the other sedimentary materials. While the Pb-Zn-Cd concentrations of deep-sea clay are enriched 1.5 times that of the continental sedimentary materials, Cu is enriched approximately five times. The substantial enrichment of Cu in oceanic pelagic clay relative to terrestrial earth materials is due to the presence of ubiquitous quantities of ferromanganese oxides in surficial ocean sediments (Drever, 1988). 

The Ni concentration of crustal rocks (58 53 p,g g ) is substantially greater than the average world soils (23 3 p,g g ), but essentially equal to continental sedimentary materials (49 13 p,gg ). Riverine particulate matter (90p,gg ) is nearly twice the Ni concentration of these continental sedimentary materials and deep-sea clay is nearly three times (230 p-g g ) that concentration. As noted for Cu, the substantial Ni enrichment of deep-sea clays is due to the presence of ferromanganese micronodules in the oxidized surficial sediment column (Drever, 1988). 

Geochronology of terrestrial or subaquatic deposited riverine particulate matter... 

In the past, numerous studies have been performed on dated sediment systems in order to reconstruct historical inputs of organic and inorganic contaminants. Most of these investigations have analysed contaminated sediment cores derived from two different depositional areas coastal zones as the final sedimentation area of riverine particulate matter (e.g. Fox et al., 2001, Venkatesan et al., 1999, Winkels et al., 1998, Latimer and Quinn, 1996, Gustafsson et al., 2001), and lacustrine systems (e.g. Reiser et al., 1997, Van Metre et al., 1997, Sanders et al., 1992, Eisenreich et al., 1989). 

This simple two component model for the Fe isotope composition of seawater does not consider the effects of the Fe isotope composition of dissolved Fe from rivers or from rain. Although the dissolved Fe fluxes are small (Fig. 19) the dissolved fluxes may have an important control on the overall Fe isotope composition of the oceans if they represent an Fe source that is preferentially added to the hydrogenous Fe budget that is ultimately sequestered into Fe-Mn nodules. In particular riverine components may be very important in the Pacific Ocean where a significant amount of Fe to the oceans can be delivered from rivers that drain oceanic islands (Sholkovitz et al. 1999). An additional uncertainty lies in how Fe from particulate matter is utilized in seawater. For example, does the solubilization of Fe from aerosol particles result in a significant Fe isotope fractionation, and does Fe speciation lead to Fe isotope fractionation ... 

Figure 9.20. Schematic diagram of fluxes and processes evaluated for the global cycle of an element. Rj, Rp, Sp, Dp, H

Table 4.3 Concentrations of major elements in continental rocks and soils and in riverine dissolved and particulate matter. 

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... 

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