Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Oceans elemental residence time

Carder KI, Steward RG, Betzer BR (1982) In situ holographic of the size and settling rates of oceanic particles. Journal of Geophysical Research 87 5681-5685 Cherry RD, Higgo JJW, Fowler SW (1978) Zooplankton fecal pellets and element residence times in the ocean. Nature 274 246-248... [Pg.98]

Assuming a steady-state system in the continental run-off and the deposition of minerals in the ocean, the residence time of the elements in sea water can be estimated from the yearly rate of transport in the rivers and their average concentration in ocean water. For elements such as Zn, Cu, Ni, and Ti, the mean residence time in sea water before incorporation in solid phases is of the order of 10 years. [Pg.14]

Fig. 12. The relationship between the mean oceanic residence time, T, yr, and the seawater—cmstal rock partition ratio,, of the elements adapted from Ref. 29. , Pretransition metals I, transition metals , B-metals , nonmetals. Open symbols indicate T-values estimated from sedimentation rates. The sohd line indicates the linear regression fit, and the dashed curves show the Working-Hotelling confidence band at the 0.1% significance level. The horizontal broken line indicates the time required for one stirring revolution of the ocean, T. ... Fig. 12. The relationship between the mean oceanic residence time, T, yr, and the seawater—cmstal rock partition ratio,, of the elements adapted from Ref. 29. , Pretransition metals I, transition metals , B-metals , nonmetals. Open symbols indicate T-values estimated from sedimentation rates. The sohd line indicates the linear regression fit, and the dashed curves show the Working-Hotelling confidence band at the 0.1% significance level. The horizontal broken line indicates the time required for one stirring revolution of the ocean, T. ...
Chemically reactive elements should have a short residence time in seawater and a low concentration. A positive correlation exists between the mean ocean residence time and the mean oceanic concentration however, the scatter is too great for the plot to be used for predictive purposes. Whitfield and Turner (1979) and Whitfield (1979) have shown that a more important correlation exists between residence time and a measure of the partitioning of the elements between the ocean and crustal rocks. The rationale behind this approach is that the oceanic concentrations have been roughly constant, while the elements in crustal rocks have cycled through the oceans. This partitioning of the elements may reflect the long-term chemical controls. The relationship can be summarized by an equation of the form... [Pg.258]

The product fg gives us the fraction of the elements that are permanently removed for each visit to the surface ocean. Conversely l//l/y) gives the number of times an element is recycled before it is permanently removed. For example, for a total ocean residence time of 1600 years, P goes through 105 cycles of 15 years each before being permanently removed. [Pg.272]

Residence time and reactivity are strongly correlated through equation (7.2.9). This is true for seawater composition since Whitfield and Turner (1979) showed a rather good correlation between oceanic residence times and seawater-crustal rock partition coefficients which are taken as a measure of element reactivity in the ocean. Actually, a better estimate of reactivity is given by oceanic suspensions, so Li (1982) suggested to use pelagic clay-seawater concentration ratios as a proxy to partition coefficients. [Pg.349]

Broecker and Li (1970) and Broecker (1974) found that the 14C/12C ratio in the deep ocean was 84 percent of this ratio in the pre-bomb surface ocean. Assuming that surface carbon (dissolved and falling debris) is the only source of deep ocean carbon, calculate the residence time tc of this element in the deep-ocean. The 14C decay constant is 1.2 x 10 4a 1. [Pg.354]

Li, Y.-H. (1982). A brief discussion on the mean oceanic residence time of elements. [Pg.532]

Whitfield (1979) and Whitfield and Turner (1987) have shown that the elements in the ocean can be classified according to their oceanic residence times, z ... [Pg.394]

The geochemical fate of most reactive substances (trace metals, pollutants) is controlled by the reaction of solutes with solid surfaces. Simple chemical models for the residence time of reactive elements in oceans, lakes, sediment, and soil systems are based on the partitioning of chemical species between the aqueous solution and the particle surface. The rates of processes involved in precipitation (heterogeneous nucleation, crystal growth) and dissolution of mineral phases, of importance in the weathering of rocks, in the formation of soils, and sediment diagenesis, are critically dependent on surface species and their structural identity. [Pg.436]

The residence time of a biolimiting element can be calculated ffom/x and the average mixing time of the ocean (lOOOy) as follows ... [Pg.232]

Table 11.3 Ocean. Deepwater Scavenging Residence Times of Some Trace Elements in the ... Table 11.3 Ocean. Deepwater Scavenging Residence Times of Some Trace Elements in the ...
Th, Co, and, in some locations, Fe. Surfece-water enrichments are usually caused by rapid rates of supply to the mixed layer via atmospheric deposition or river runoff. Removal usually occurs through relatively rapid precipitation into or adsorption onto sinking particles. Trace elements controlled by scavenging tend to have short (100 to lOOOy) residence times. Since these residence times are less than the mixing time of the ocean, significant geographic gradients are common. [Pg.289]

An element s tendency towards partitioning into solid phases is related to its fundamental atomic properties. These properties follow periodic trends, giving rise to the trends shown in Figure 11.5 for the oceanic residence times of the elements. In the broadest sense, these trends reflect the relative tendency of an element towards electrostatic versus covalent interactions. Chemists have devised various measures of this tendency, such as an element s electronegativity and its ionization potential. The latter is a predictor of electrostatic interactions and is defined as the ratio, z /r, where... [Pg.555]

Lithium is a conservative element in the ocean with a residence time of abont one million year. Its isotope composition is maintained by inputs of dissolved Li from rivers (average 5 Li + 23%c, Huh et al. 1998) and high-temperature hydrothermal fluids at ocean ridges at one hand and low temperature removal of Li into oceanic basalts and marine sediments at the other. Any variance in these sources and sinks thus should cause secular variations in the isotope composition of oceanic Li. And indeed in a first attempt Hoefs and Sywall (1997) interpreted Li isotope variations in well preserved carbonate shells as indicating secular variations of the oceanic Li-cycle. [Pg.44]

Element Amount in ocean (in units of 102tl g) Residence time in millions of years ... [Pg.1133]


See other pages where Oceans elemental residence time is mentioned: [Pg.45]    [Pg.54]    [Pg.1653]    [Pg.45]    [Pg.1699]    [Pg.555]    [Pg.240]    [Pg.687]    [Pg.215]    [Pg.216]    [Pg.38]    [Pg.269]    [Pg.11]    [Pg.263]    [Pg.408]    [Pg.580]    [Pg.593]    [Pg.47]    [Pg.141]    [Pg.359]    [Pg.221]    [Pg.232]    [Pg.234]    [Pg.234]    [Pg.280]    [Pg.288]    [Pg.288]    [Pg.499]    [Pg.553]    [Pg.553]    [Pg.90]    [Pg.38]    [Pg.1133]    [Pg.22]   
See also in sourсe #XX -- [ Pg.3 ]




SEARCH



Residence time oceanic

© 2024 chempedia.info