Mass in the ocean

From Figure 9.1, it can be seen that the major form of carbon in the atmosphere is C02(g), constituting over 99% of atmospheric carbon. Carbon dioxide makes up 0.035% by volume of atmospheric gases, or 350 ixatm = 350 ppmv. The atmosphere has a mass of CO2 that is only 2% of the mass of total inorganic carbon in the ocean, and both of these carbon masses are small compared to the mass of carbon tied up in sediments and sedimentary rocks. Therefore, small changes in carbon masses in the ocean and sediment reservoirs can substantially alter the CO2 concentration of the atmosphere. Furthermore, there is presently 3 to 4 times more carbon stored on land in living plants and humus than resides in the atmosphere. A decrease in the size of the terrestrial organic carbon reservoir of only 0.1% y-1 would be equivalent to an increase in the annual respiration and decay carbon flux to the atmosphere of nearly 4%. If this carbon were stored in the atmosphere, atmospheric CO2 would increase by 0.4%, or about 1 ppmv y-l. The... 

Figure 1 Schematic illustration of the production and fate of Th in seawater. Radioactive decay of dissolved produces Th that initially exists as a dissolved species. Dissolved Th may either undergo radioactive decay to Ra, or it may be adsorbed to particles. Radioactive decay is represented by a decay constant, A (A = ln(2)/radioactive half-life)), and uptake by particles (scavenging) is represented by a first-order rate constant, k. Th is initially sorbed by small slowly settling particles (supersript s ), which form the vast majority of partiele mass in the ocean. Th sorbed to small particles may undergo radioactive decay to Ra it may desorb (return to solution, represented by the first-order rate eonstant -i) or it may sink from the water colunm, where the loss of particulate Th is represented by the first-order rate constant 2-Similar processes influence " Th, which is produced by radioactive decay of and which...

When REE fractionation is discussed, it is common to normalize the data to the values in shale which are thought to be representative of the REEs in the upper continental crust. The shale-normalization not only helps to eliminate the well-known distinctive even-odd variation in natural abundance (the Oddo-Har-kins effect) of REEs but also visualizes, to a first approximation, fractionation relative to the continental source. It should be noted, however, that different shale values in the literature have been employed for normalization, together with the ones of the Post-Archean Australian Sedimentary rocks (PAAS) adopted here (Table 1). Thus, caution must be paid on the choice of the shale values if one ought to interpret small anomalies at the strictly trivalent lanthanides such as Gd and Tb. Alternatively, for detailed arguments concerning fractionation between different water masses in the ocean, it has been recommended that the data are normalized relative to the REE values of a distinctive reference water mass, for example, the North Pacific Deep Water (NPDW, Table 1). The NPDW-normalization eliminates the common features of seawater that appeared in the shale-normalized REE pattern and can single out fractionation relative to the REEs in the dissolved end product in the route of the global ocean circulation. 

Residence times were computed hy r = M/Q where M for a particular constituent is equal to its concentration in seawater times the mass of the oceans, and is equal to the concentration of the constituent in average river water times the annual flux of river water to the ocean. 

Bromine is substantially less abundant in crustal rocks than either fluorine or chlorine at 2.5 ppm it is forty-sixth in order of abundance being similar to Hf 2.8, Cs 2.6, U 2.3, Eu 2.1 and Sn 2.1 ppm. Like chlorine, the largest natural source of bromine is the oceans, which contain 6.5 x 10 %, i.e. 65 ppm or 65mg/l. The mass ratio Cl Br is 300 1 in the oceans, corresponding to an atomic ratio... 

As can be seen in Fig. 2-1 (abundance of elements), hydrogen and oxygen (along with carbon, magnesium, silicon, sulfur, and iron) are particularly abundant in the solar system, probably because the common isotopic forms of the latter six elements have nuclear masses that are multiples of the helium (He) nucleus. Oxygen is present in the Earth s crust in an abundance that exceeds the amount required to form oxides of silicon, sulfur, and iron in the crust the excess oxygen occurs mostly as the volatiles CO2 and H2O. The CO2 now resides primarily in carbonate rocks whereas the H2O is almost all in the oceans. 

Cochran JK, Masque P (2003) Short-lived U/Th-series radionuclides in the ocean tracers for scavenging rates, export fluxes and particle dynamics. Rev Mineral Geochem 52 461-492 Cohen AS, O Nions RK (1991) Precise determination of femtogram quantities of radium by thermal ionization mass spectrometry. Anal Chem 63 2705-2708 Cohen AS, Belshaw NS, O Nions RK (1992) High precision uranium, thorium, and radium isotope ratio measurements by high dynamic range thermal ionization mass spectrometry. Inti J Mass Spectrom Ion Processes 116 71-81... 

The initial U activity in the mantle wedge (Uw) is set to an arbitrary value of 1 and all the other nuclides are scaled relative to Uw The initial U activity in the oceanic crust is twice the activity in the mantle wedge. The Th/U ratios of the mantle wedge and the slab are both equal to 2.5. This value is relevant for modeling the higher ( Th/ Th) observed in some arc lavas. Fluid is added to a portion of mantle wedge, and the mass fraction of fluid (f) and the composition of the mixture at time step i is given by (same equation for all the nuclides) ... 

As the volatilisation flux strongly depends on the absolute contaminant mass, the volatilisation mass flux divided by the total amount of DDT in the first level of the ocean model is examined instead. This parameter is called volatilisation rate. It reflects the proportion of the mass abundant in the oceanic surface layer that was volatilised within one model time step. It depends upon how much of the DDT is dissolved in water and upon wind speed and sea surface temperature. The volatilisation on the other hand would mainly mirror the deposition and emission pattern, because those are supersposed onto the volatilisation defining patterns and dominating because of the stationary application in the scenario. 

Environmental distribution After 40 years of continuous application of DDT to vegetation (80%) and soil (20%), 73% of the total mass present in the environment in December 1990 are stored in soil, 24 % in the ocean, 2 % in vegetation, and less than one percent in the atmosphere (Table 3.2).The high storage in soil is caused by its strong absorptive capacity of organochlorine compounds, which is related to its organic matter content. The only source of DDT and DDE in the ocean is deposition... 

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