Terrestrial material from

Its concentrations increase with depth and attain 180-220 p,M at 1000 m and about 280-300 xM near the bottom (Fig. 4). This buildup of silicate stock results from a large inflow of terrestrial material from the mountain shores of the Black Sea [23]. 

Extraterrestrial dust particles can be proven to be nonterrestrial by a variety of methods, depending on the particle si2e. Unmelted particles have high helium. He, contents resulting from solar wind implantation. In 10-)J.m particles the concentration approaches l/(cm g) at STP and the He He ratio is close to the solar value. Unmelted particles also often contain preserved tracks of solar cosmic rays that are seen in the electron microscope as randomly oriented linear dislocations in crystals. Eor larger particles other cosmic ray irradiation products such as Mn, Al, and Be can be detected. Most IDPs can be confidently distinguished from terrestrial materials by composition. Typical particles have elemental compositions that match solar abundances for most elements. TypicaUy these have chondritic compositions, and in descending order of abundance are composed of O, Mg, Si, Ee, C, S, Al, Ca, Ni, Na, Cr, Mn, and Ti. 

It is clear from figure 6 that the terrestrial data do not cluster about a single point but instead lie along a line of slope 0.5 on the three-isotope diagram, indicating isotopic variation due to mass-dependent fractionation. Since mass fractionation effects in Mg have not been observed in terrestrial materials [30,31], this distribution of observed isotope ratios must be due to fractionation in the ion probe. The physical process which produces the... 

Parallel (multidimensional) measurements of size- or chemically selected particles permit the simultaneous resolution of biogenic material from fossil sources (14C), discrimination between certain fossil sources and between marine and terrestrial vegetation (13C), and partial separation of agricultural burning sources (K/Fe). The term iMu represents the fraction of modern C based on standard Slk 813C represents the deviation (per mil) of the 13C/12C ratio from standard Sls (2). 

The Ca isotope ratios of meteoritic samples are of interest because they can give information on early solar system processes and because meteorites represent the materials from which the Earth accreted and hence relate to the expected values for the bulk Earth. Russell et al. (1978b) made the first measurements of stable Ca isotope variations in meteorites. They formd variations of about +l%o for the Ca/ Ca ratio in samples from six different meteorites. Although some of these samples were spiked after having separated the Ca with an ion exchange column and hence may contain artifacts, it is clear from their data that bulk meteorites have some variability in 8 Ca and that the average value is quite close to the terrestrial standard. No data on bulk meteorites have been reported since the Russell et al. (1978b) measurements, and since their one measurement of an ordinary chondrite had a poor Ca column yield, there exist no reliable measurements that can be used to verify the composition of typical chondritic meteorites. 

The studies by Lee et al. (1977, 1979), Niederer and Papanastassiou (1984), as well those by Jungck et al. (1984), Ireland et al. (1991), Weber et al. (1995) and Russell et al. (1998), report small deviations of the abundances of Ca, Ca and Ca relative to those of terrestrial materials. The most commonly observed deviation from normal terrestrial isotopic abundances is enrichment in Ca, which can be quite large (Fig. 2b). These deviations are significant because they provide direct evidence for the existence of certain (in this case neutron-rich) nucleosynthetic environments in stars (cf Cameron 1979 and references in the other papers listed above). 

Extraterrestrial materials consist of samples from the Moon, Mars, and a variety of smaller bodies such as asteroids and comets. These planetary samples have been used to deduce the evolution of our solar system. A major difference between extraterrestrial and terrestrial materials is the existence of primordial isotopic heterogeneities in the early solar system. These heterogeneities are not observed on the Earth or on the Moon, because they have become obliterated during high-temperature processes over geologic time. In primitive meteorites, however, components that acquired their isotopic compositions through interaction with constituents of the solar nebula have remained unchanged since that time. 

Thales s successor, Anaximander—the exact dates of his birth and death are unknown, but he was said to have been 64 years old in 546 B.C.—agreed that there was one primal material. But he didn t think it was ever encountered on Earth in its pure state. According to Anaximander everything in the world was made of apeiron, a substance that was infinite and eternal, and which could take on numerous forms, including those of all the familiar terrestrial materials. It is neither water nor any of the so-called elements, Anaximander said, but a nature different from them and infinite, from which arise all the heavens and the worlds within them. ... 

Table 4.2 gives current estimates for the relative abundances of the isotopes in the solar system. The isotopic compositions of most elements, especially those that exist as solids, come from measurements of terrestrial materials. Because the Earth has experienced extensive melting and differentiation, it can be considered a homogeneous isotopic reservoir. However, each of the elements can experience both equilibrium and kinetically based isotopic fractionations during igneous, evaporative, and aqueous processes. The range of compositions introduced by such processes is small for most elements and so does not obscure the overall picture. 

Solar systems are subjected to a unique set of conditions that may alter their stability and, hence, their performance and life-cycle costs. These conditions include UV radiation, temperature, atmospheric gases and pollutants, the diurnal and annual thermal cycles, and, in concentrating systems, a high-intensity solar flux. In addition, condensation and evaporation of water, rain, hall, dust, wind, thermal expansion mismatches, etc., may impose additional problems for the performance of a solar system. These conditions and problems must be considered not only individually, but also for synergistic degradative effects that may result from their collective action on any part of the system. Since these degradative effects may also reduce the system or component performance, protective encapsulation of sensitive materials from the hostile terrestrial environment is required to provide component durability. 

Inland water systems are more diverse and dynamic than marine systems (see Chapter 18) therefore, it becomes apparent that more emphasis should be placed on understanding microbial community dynamics in these highly variable systems. Lakes and rivers are intimately associated with their watersheds and hence receive a large influx of material from the surrounding terrestrial environments. This linkage affects the biogeochemical cycles and processes within the system as oftentimes members of the terrestrial community end up in the aquatic environment. 

Transfer of radioactive materials from the terrestrial environment to animals and men. C.R.C. Critical Reviews of Environmental Control, 2, 337-85. 

Some margins receive their terrestrial inputs from estuarine line-sources (numerous estuaries) with very little direct effects from rivers, while others may receive large direct inputs from rivers, such as deltaic regions these differences will have serious consequences on the amount of terrestrial material recycling that has occurred before entering the coastal zone, as well as how these materials (particulate and dissolved) will be transported offshore. 

The strength of a resonance depends on the eccentricities of the planets involved (Morbidelli Henrard 1991 Moons Morbidelli 1993). Thus, the eccentricities of Jupiter (ej) and Saturn (eg) can have a significant effect on the growth of terrestrial planets. Simulations of terrestrial-planet formation often find that ej and es decrease over time, due to the ejection of material from the system (e.g. Petit et al. 2001 ... 

Chambers Cassen 2002 O Brien etal. 2006). If no other mechanisms are invoked to enhance ej and es, they must have once been 2x larger than at present. When ej and < s are large, the amount of material from the Asteroid Belt that is incorporated into the terrestrial planets is reduced because the main-belt resonances become stronger, and material is cleared from the Asteroid Belt more rapidly (e.g. Chambers Cassen 2002 Raymond et al. 2004 O Brien et al. 2006). 

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