Terrestrial surfaces

Hvunan activities have already significantly converted or modified the natural land cover of half of Earth s terrestrial surface. Virtually no region remains untouched by human impacts of some kind. The major land conversions we have accomplished over the past 10,000 years or so include (1) land clearing, mostly through deforestation and... 

An obvious correlation between polar and alpine environments is the decrease in temperature with increasing latitude or elevation. This temperature change leads to a shift in environmental phase distribution equilibria - i.e. a chemical moves from the atmosphere to terrestrial surfaces, including direct deposition to surface waters, but also to snowpack and soils from which movement into surface and groundwater is possible. This process has been termed cold condensation but should more correctly be called cold-trapping because the contaminants are not actually condensing. 

DNB will exist entirely in the vapor phase in the atmosphere (Eisenreich et al. 1981). Based on a vapor pressure of 3.2x10 mm Hg at 25°C (see Table 3-2), 1,3,5-TNB is expected to exist partly in the vapor phase and partly in the particulate phase (Eisenreich et al. 1981). The transport of vapor phase 1,3-DNB from the atmosphere to the terrestrial surface is likely to occur mainly by wet deposition, while 1,3,5-TNB is likely to be transported by both wet and dry deposition (Bidelman 1988). 

Momentum boundary layer calculations are useful to estimate the skin friction on a number of objects, such as on a ship hull, airplane fuselage and wings, a water surface, and a terrestrial surface. Once we know the boundary layer thickness, occurring where the velocity is 99% of the free-stream velocity, skin friction coefficient and the skin friction drag on the solid surface can be calculated. Estimate the laminar boundary layer thickness of a 1-m-long, thin flat plate moving through a calm atmosphere at 20 m/s. 

It is astonishing that the potassium ion plays such an important role in biochemistry, although it was present in only low concentration in terrestrial surface waters when life originated around 1017s ago. 

More land was converted to cropland since 1945 than in the 18th and 19th centuries combined, and now about one-quarter (24%) of Earth s terrestrial surface has been transformed to cultivated systems. 

Tektites are glass spheroids, which cover parts of North America (about 35-million-years old), central Europe (about 15-million-years old), western Africa (about 1.1-million-years old) and Australia-Asia (about 780000 years old). Most tektites are less than 1 mm in diameter (microtektites), although some are centimeter-sized (Koeberl et al., 1997, 1745). Researchers generally believe that tektites represent terrestrial surface materials that were melted and ejected high into the atmosphere because of large meteorite impacts (Koeberl et al., 1997, 1746). 

Though the body itself forms the primary decompositional site, the soil beneath it may be equally important. Corpses located in outdoor environments on a terrestrial surface create an interface within which soil fauna and carrion-dwelling organisms interact. The interactions in this zone are affected by soil type, vegetation, decomposition of the corpse, and a variety of environmental factors. Apart from the work by Bornemissza (1957) and Lundt (1964) the succession of insects in this interface, and within the soil itself, has been largely overlooked in the literature, and the forensic implications have yet to be considered. 

Carbon on all three planets has 8 C within the meteorite range, but with relatively depleted abundances. Carbon at the terrestrial surface... 

Variation in soil resource supply accounts for much of the spatial variation in leaf area and GPP among ecosystem types. Analysis of satellite imagery shows that 70% of the ice-free terrestrial surface has relatively open canopies (Graetz, 1991) (Figure 4). GPP correlates closely with leaf area below a total LAI of 8 (projected LAI of 4) (Schulze et al., 1994), suggesting that leaf area is a critical determinant of GPP on most of Earth s terrestrial surface. GPP saturates with increasing LAI in dense canopies, because the leaves in the middle and bottom of the canopy contribute relatively little to GPP. The availability of soil resources, especially water and nutrient supply, is... 

Figure 4 Projected foliage cover and canopy height of the major biomes. Typical values for that biome and the percentage of the terrestrial surface that it occupies are shown. The vertical line shows 100% canopy cover (reproduced by permission of Kluwer from Climatic Change, 1991, 18, 147-173).

Real terrestrial surfaces are rarely horizontally extensive, and are most often characterized by frequent changes in vegetation type and height. Particularly in naturally vegetated lands, the terrain commonly exhibits a complexity in slope and elevation that has major influences on the aerodynamics of plant canopies. Nevertheless, it is an essential first step to establish an understanding of flow through uniform canopies as a basis from which to study flows in even more complicated situations. 

Trichloroethane has a vapor pressure of 123 mm Hg at 20 °C (see Table 3-2), which means that it exists in the vapor phase in the atmosphere (Eisenreich et al. 1983). Since this compound has moderate water solubility (see Table 3-2), vapor phase 1,1,1-trichloroethane will be removed from the air via washout by rain and transported to the terrestrial surface. It has been identified in rainwater (Jung et al. 1992 Kawamura and Kaplan 1983 Pluemacher and Renner 1993 ... 

We have discussed various theories of life origin in the Earth, however, irrespective of its origin, the advent of life contribnted significant alterations to existing prebiotic geochemical cycles. Aside from the colonization of terrestrial surfaces, perhaps the most important changes happened as a result of evolution of oxygenie photosynthesis and respiration. 

Above the troposphere, in the stratosphere and mesosphere, the gas density becomes increasingly more important, and the thermal conditions become subject to complex variations, both temporal and spatial. At a height of 25-35 km, the oxygen molecules are split by the influence of solar UV radiation to form ozone in accordance with Chapman s mechanism, which is responsible for the absorption of 97% of harmful ultraviolet solar radiation. Devoid of this shield, life on the terrestrial surface would have been doomed to extinction. 

---