Anthropogenic processes

Acidification the decrease of acid neutralizing capacity in water or base saturation in soil caused by natural or anthropogenic processes. 

We have studied the interaction of geologic, geochemical, geomorphic, hydrologic, and anthropogenic processes in the Sacramento Valley of north-central California, U.S.A. 

Fate-and-transport studies using computer modeling and mathematical calculations can effectively evaluate the potential for contaminant migration and degradation through the natural and anthropogenic processes active at the site. Often a brief fate-and-transport study early in the project can lead to optimal placement of monitor and recovery wells, and selection of sample analytical procedures. 

Environmental Fate. The environmental fate of hydrogen cyanide gas in air is well studied (Cicerone and Zellner 1983 Fritz et al. 1982) however, it would be useful if the role of particulate cyanides (e.g., sodium cyanide, potassium cyanide) in determining the fate of total cyanides in the air was known. Given that hydrogen cyanide occurs in the atmosphere from both natural and anthropogenic processes (Cicerone... 

Figure 3. Lithium isotope data for a range of commercially-available synthetic concentration standards (Qi et al. 1997a). The inset expands the c. 60%o range of reported natural samples. Although most anthropogenically-processed Li retains a broadly terrestrial value, nearly 20% of the samples examined show enormous isotopic enrichment in the heavy isotope.

In Part II, we discuss the potential sources, chemical properties, and toxicity of several major groups of contaminants found in the subsurface environment. Usually, the release of contaminants to the environment originates from anthropogenic processes. Even when the contaminants are naturally occurring species, we often find that human intervention or changes in natural conditions are involved in the development of pollution. Furthermore, many contaminants are relatively persistent and therefore may be found in the subsurface environment long after their acmal release. 

Inventories are compiled in various formats. For example, they can be assembled for various individual anthropogenic processes such as refining, or natural processes such as volcanic eruptions, in which emissions of all of the relevant species associated with that event are estimated. Alternatively, and more commonly, emissions inventories are compiled by species, showing the various sources that contribute to the total emissions of each. 

Nitrous oxide (N20, laughing gas ) is also produced by biological processes and, to a lesser extent, by anthropogenic processes (see Chapter 14.B.2c). While... 

Nitrous oxide is important not only as a greenhouse gas but, as discussed in Chapter 12, as the major natural source of NC/ in the stratosphere, where it is transported due to its long tropospheric lifetime (Crutzen, 1970). The major sources of N20 are nitrification and denitrification in soils and aquatic systems, with smaller amounts directly from anthropogenic processes such as sewage treatment and fossil fuel combustion (e.g., see Delwiche, 1981 Khalil and Rasmussen, 1992 Williams et al., 1992 Nevison et al., 1995, 1996 Prasad, 1994, 1997 Bouwman and Taylor, 1996 and Prasad et al., 1997). The use of fertilizers increases N20 emissions. For pastures at least, soil water content at the time of fertilization appears to be an important factor in determining emissions of N20 (and NO) (Veldkamp et al., 1998). 

Phenol is produced through both natural and anthropogenic processes. It is naturally occurring in some foods, human and animal wastes, and decomposing organic material, and is produced endogenously in the gut from the metabolism of aromatic amino acids. Phenol has been isolated from coal tar, but it is now synthetically manufactured (EPA, 2002). Currently, the largest use of phenol is as an intermediate in the production of phenolic resins, which are used in the plywood, adhesive, construction, automotive, and appliance industries. Phenol is also used in the production of synthetic fibers such as nylon and for epoxy resin precursors such as bisphenol-A. 

An objective estimate of the dynamics of the natural medium N = (N, N2) is possible with some assumptions using models of the biosphere N and climate A. The accumulated experience of numerous scientists in deriving such models has resulted in construction of point, regional, box, combined, and spatial models. This experience enables synthesizing a new type of global model, covering the key bonds between the hierarchical levels of natural and anthropogenic processes. 

Anthropogenic impacts on the oxygen and ozone cycles 4.5.3.1 Oxygen cycle and anthropogenic processes... 

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