Dissolved load

Geochemical studies of sulfate ia streams have beea approached ia various ways. For example. Ref. 17 is a review of Hterature oa sources of sulfate ia the dissolved loads of streams, especially ia areas where developmeat effects are likely to be stroag. It was coacluded that for North America as much as 60% of the average yield of sulfate carried to the ocean is related to human activities. This study assigned a higher proportion of the total yield of sulfate ia European streams to human sources, but for other continents it was thought the effects of human activities to be relatively minor. 

Their contribution to the total dissolved load in rivers can be estimated by considering the mean composition of river water and the relative importance of various rocks to weathering. Estimates (18) indicate that evaporites and carbonates contribute approximately 17% and 38%, respectively, of the total dissolved load in the wodd s rivers. The remaining 45% is the result of the weathering of siUcates, underlining the significant role of these minerals in the overall chemical denudation of the earth s surface. 

The material transported by rivers consists of dissolved ions (dissolved load), sediment suspended in the flow (suspended load), and sediment transported along the bed of the river (bedload). The total load and the proportion of the load represented by these phases varies widely among rivers in different environments. In particular, climate, topography, and erosion influence the amount and composition of riverine sediment loads. 

Table 8-5 Proportion of total load represented by dissolved load for large rivers. (Data from Summerfield, 1991)...

The most stable minerals are often physically eroded before they have a chance to chemically decompose. Minerals that decompose contribute to the dissolved load in rivers, and their solid chemical-weathering products contribute to the secondary minerals in the solid load. The secondary minerals and the more stable primary minerals are the most important constituents of clastic sedimentary rocks. Consequently, the secondary minerals of one cycle of erosion are... 

Meybeck, M. (1987). Global chemical weathering of superficial rocks estimated from river dissolved loads. Am.. Sci. 287, 401-428. 

Stallard, R. F. and Edmond, J. M. (1981). Geochemistry of the Amazon 1. Precipitation chemistry and the marine contribution to the dissolved load at the time of peak discharge. /. Geophys. Res. 86, 9844-9858. 

Figure 23. Relationship between ( Ra/ Ra) ratios and Sr/ Sr isotopic ratio in the dissolved load of the Ganges main stream and its tributaries. Radium data from Sarin et al. (1990), Sr data from Palmer and Edmond (1992).

Figure 24. Drawing of the continuous leaching model used by Vigier et al. (2001) to estimate the residence time of particles in the soils of the Mackenzie Basin, and the related equations. This model assumes that particles are continuously leached in the soil before leaving to the river. Dissolved load of the river integrates the present leaching of the whole soil profile. 238, 234, 230 and 226 are the leaching coefficients of h and Tla nuclides, respectively, and x is the duration of the chentical...

Walling DE (1984) Dissolved loads and their measurements. In Hadley RF, Walling DE (eds) Erosion and sediment yield some methods of measurements and modeling. Geo Books, London, 111-177... 

Keywords Carbonate dissolution, Dissolved flux, Dissolved load, Ebro River basin, Evaporite dissolution, Long-term fluxes... 

Dissolved Load Variation with the River Discharges. 105... 

Dissolved Load Fluxes at the Ebro Basin Scale. 106... 

The EC (pS cm-1) and the TDS (mg L ) both reflect the water ionic content, i.e. the dissolved load also called water salinity. The EC, easily obtained compared to chemical data, is thus widely documented in the CHEBRO database (n = 2,860 versus 999 complete major element analyses). These two parameters (EC and TDS) are linked by a linear relation TDS (mg L ) = b EC (pS cm-1), with a mean b factor 0.54 < b < 0.96 according to water types and range of salinity [21, 22], The linear relations between TDS and EC were calculated for each monitoring station, b factor ranging from 0.713 (Arga) and 0.86 (Aragon), whereas the Ebro River stations present less variability (0.774—0.798) with R2 always better than 0.72, all the relations are summarised in Table 1. These relations are very similar to that defined for the whole Ebro basin with b = 0.81 [23]. 

The main purpose of this work was to estimate, over a long time period (more than 20 years), the export fluxes for dissolved loads on the catchment scale of the Ebro River basin. Data were compiled from the databank of the Confederation Hidro-grafica del Ebro (CHE), the Spanish government agency in charge of managing... 

Stallard RF, Edmond JM (1983) Geochemistry of the Amazon. 2. The influence of geology and weathering environment on the dissolved load. J Geophys Res 88(C14) 9671-9688... 

Grosbois C, Negrel Ph, Fouillac C, Grimaud D (2000) Dissolved load of the Loire River chemical and isotopic characterization. Chem Geol 170 179-201... 

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