River carbon transport

These models are too simple to reflect realistic dynamic properties of the carbon budget. Even so, they depend on data that are poorly measured or lacking. Many potentially important compartments are missing or assumed to be unimportant. For example, no model considers carbon transported from terrestrial systems to the oceans through rivers and streams. While the amount is very small, it is continuous and cumulative (25)... 

To overcome some of these difficulties we started a program to monitor the inorganic and organic constituents in major world rivers. The study "Carbon Transport in Major World Rivers" is sponsored by the Scientific Committee for Problems of the Environment (SCOPE) and the United Nations Environment Program (UNEP). Within its framework over 50 % of the total water discharged to the sea is being monitored at least once a month. 

Chowdhury, M.I., Safiullah, S., Iqbal Ali, S.M., Mofizuddin, M. and Enamul, S., 1982. Carbon transport in the Ganges and the Brahmaputra preliminary results. In E.T. Degens (ed.), Transport of Carbon and Minerals in Major World Rivers. Pt. 1, Mitt. Geol.-Palaont. Inst. Univ. Hamburg, SCOPE/UNEP Sonderbd., pp. 457-468. 

Calcium at 4.8% is the fifth most common elemental constituent of the earth s crust after oxygen, silicon, aluminum, and iron. It is so popular in practical applications because it is found in rocks and minerals which have veiy high concentration of calcium carbonate. Calcium carbonate is the most common deposit formed in sedimentaiy rocks. The process of formation of calcium deposits begins with weathering of land surface due to the changes in heat, frost, rain, and the effect of sun. Calcium carbonate is not readily soluble in water but calcium bicarbonate is. The concentration of carbon dioxide in water is thus important for calcium carbonate transportation from the land to the sea since rain water is the carrier. It is estimated that 500,000,000 tons of minerals are carried by rivers to the seas eveiy year out of which about 10-15% of sedimentaiy rocks containing calcium carbonate are formed. 

Owing to the stability of the uranyl carbonate complex, uranium is universally present in seawater at an average concentration of ca. 3.2/rgL with a daughter/parent activity ratio U) of 1.14. " In particulate matter and bottom sediments that are roughly 1 x 10 " years old, the ratio should approach unity (secular equilibrium). The principal source of dissolved uranium to the ocean is from physicochemical weathering on the continents and subsequent transport by rivers. Potentially significant oceanic U sinks include anoxic basins, organic rich sediments, phosphorites and oceanic basalts, metalliferous sediments, carbonate sediments, and saltwater marshes. " ... 

The freshwater cycle is an important link in the carbon cycle as an agent of erosion and as a necessary condition for terrestrial life. Although the amount of carbon stored in freshwater systems is insignificant as a carbon reservoir (De Vooys, 1979 Kempe, 1979a), about 90% of the material transported from land to oceans is carried by streams and rivers. 

River transport of organic carbon, estimated earlier as 0.1 Pg C/yr, brings the sum of non-respiratory outputs to 7 Pg C/yr. Total respiration should therefore be around 50 Pg C/yr. This figure is in agreement with estimates of soil respiration rates determined from compilations of ecosystem types and their measured soil respiration rates (Ajtay et ai, 1979). 

Meybeck M (1982) Carbon, nitrogen, and phosphoms transport by World Rivers. Am J Sci 282 401 50... 

Rivers transport clay minerals primarily as part of their suspended load (silts and clays). The silt-size fraction is composed of quartz, feldspars, carbonates, and polycrystalline rocks. The clay-sized fraction is dominated by the clay minerals illite, kaolinite, chlorite, and montmorillonite. In addition to suspended particles, rivers carry as a bed load larger size fractions. The bed load constitutes only 10% of the total river load of particles and is predominantly quartz and feldspar sands. 

The products of chemical weathering, Ca, H4Si04, and 2HCOj, are transported by river runoff into the ocean, where they are then available to be returned to biogenic form by marine plankton. (Marine plankton have an enzyme, carbonic anhydrase, that converts bicarbonate to CO2.)... 

One demonstrated solution to this problem is to raise the pH of acidified lakes and rivers by adding calcium carbonate—a process known as liming. The cost of transporting the calcium carbonate coupled with the need to monitor treated water systems closely limits liming to only a small fraction of the vast number of water systems already affected. Furthermore, as acid rain continues to pour into these regions, the need to lime also continues. 

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