Bicarbonate amount from rivers

At steady state the rate of bicarbonate removal by CaCOs precipitation in the ocean is given by two times the flux of calcium from rivers, based on the river flow rate and Ca + concentration in Table 2.3. (This is an upper limit for the removal of HCOif by precipitation of CaCOs because a small amount of the Ca + from rivers is precipitated as anhydrite in the Mackenzie and Carrels mass balance, Table 2.4.)... 

Sedimentary lamination is also caused by the deposition of calcium carbonate and is important in most freshwater lakes where the clastic input from rivers is low. Carbonate deposits may be chemical or biogenic (see Box 1.1). As with phytoplanktonic production, the abiogenic (chemical) precipitation of calcium carbonate is seasonal, occurring during the warmer months. During this period carbon dioxide is removed from the water by planktonic photosynthesis, which causes water acidity to decrease and calcium carbonate to precipitate. From the equilibrium in Eqn 3.9c (Box 3.12) it can be seen that if the amount of C02(aq) decreases, more C02(aq) and carbonate are produced from bicarbonate, which increases the concentration of carbonate and promotes its precipitation. Subsequently, the water becomes more acidic and no longer supersaturated with respect to calcite (the main form of crystalline calcium... 

Seawater has nearly equal amounts of alkalinity and DIG because the main source of these properties is riverine bicarbonate ion, which makes equal contributions to both constituents. The processes of CaCOs precipitation, hydrothermal circulation, and reverse weathering in sediments remove alkalinity and DIG from seawater and maintain present concentrations at about 2 mmol (meq) kg . Reconciling the balance between river inflow and alkalinity removal from the ocean is not well rmderstood, and is discussed in much greater detail in Ghapter 2. 

Whereas the composition of dissolved main solid compounds in seawater is rather constant all over the oceans, the freshwater in the Baltic Sea outbalanced by river discharge is dominated by calcium bicarbonate. For this reason, significant anomalies are observed in Baltic waters from the standard composition of seawater (Nehring and Rohde, 1966), in particular in the brackish surface water, with amount increasing toward the eastern and northern margins of the Baltic Sea. Directly measured densities of Baltic water compared with density determined from the seawater equation of state with Baltic water salinity measured by chlorinity titration resulted in a deviation of up to 0.123 kg/m (Millero and Kremling, 1976). This may result in uncertainties in estimating the thermodynamic properties of Baltic water, for example, the vertical stability. 

Let us first look at the terrestrial waters, lakes, and rivers. The total amount of the terrestrial waters on the Earth is about 5 x lO kg. With a few exceptions like Great Salt Lake and Dead Sea (in Jordan/Israel), the terrestrial waters contain relatively low levels of dissolved ionic species (low salinity). Though it varies widely, the salinity of river waters has been estimated on average as about 100 ppm (that is, 100 g of ionic compounds of various kinds per 1 million grams (1 m volume) of water). On average, the contents of various elements (compounds) in rivers are HCOj" (bicarbonate anion) >Si(OH) (silicate) >Ca +>SO/ >CL>Na > Mg +. These ions come dissolved from the rocks and soils through which the river water runs. 

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