Organic anthropogenic Subject

On the other hand, biotic factors include natural interactions (e.g., predation and parasitism) and anthropogenic stress (e.g., the effect of human activity on other organisms). Because of the abiotic and biotic factors, the environment to which an organism is subjected can affect the life functions, growth, and reproductive success of the organism and can determine the local and geographic distribution patterns of the organism. 

Symmetrical triazines, like other anthropogenic or natural organic chemicals introduced into the environment, are subjected to microbial transformation processes. Environmental sites of most interest are agricultural fields, lakes, rivers, sediments, potable water, and groundwater. These sites also play a key role in the degradation of s-triazines and the eventual complete mineralization (e.g., C02 and NH3) of these compounds. 

Aquatic particulate matter is an important sink for numerous lipophilic anthropogenic contaminants as the result of adsorption and accumulation processes. In the adsorbed state organic contaminants can be subject to transformation as well as to transportation processes within the river system. The anthropogenic contribution to the organic load of river systems can be attributed mainly to sewage effluents derived from industrial and domestic point sources, to agricultural emissions or to shipping activities. Numerous specific compounds reflect the different sources of pollution and, therefore, are frequently detected in river systems. 

A large literature describes the transport of anthropogenically produced or distributed organic compounds such as petroleum hydrocarbons and halo-genated hydrocarbons, including the PCBs, the DDT family and the freons. Discussing this subject is beyond the scope of this chapter which deals with naturally produced oi anic compounds, and the reader is referred to the National Academy of Sciences Report (1978) on this subject. 

The soil-water interface separates solid materials (mineral and organic matter of soils and sediments) and pore waters from the overlying water column. Biogeochemical processes in wetland soils can produce large gradients of various dissolved substances across the soil-water interface. Such gradients can also develop as a result of anthropogenic inputs of nutrients and contaminants to the water column. These solutes are then subject to transport across the soil-water interface into the water column. 

The foodstuffs we consume contain large numbers of compounds at trace levels, some natural and some anthropogenic. All chemical compounds are toxic , depending on the dose relative to the size of the organism subjected to the compound and the period over which the dose(s) is/are administered (acute vs chronic toxicity). A great deal of effort has been devoted to determining toxicological dose-effect relationships for man-made chemicals... 

As for the primary trace chemical species in the remote natural atmosphere where there is no influence of anthropogenic activities, methane (CH4) emitted from lakes and marshes, biogenic volatile organic compounds (BVOCs), nitric oxide (NO) from natural soils and lightning, dimethyl sulfide (DMS) from marine organisms, O3 descended from the stratosphere can be conceived. Among them, the most important chemical species that is subjected to photolysis by the actinic flux (see Sect. 3.5) in the troposphere is O3 and NO2 (see Sects. 4.2.1 and 4.2.2). 

Dry particle deposition and wet particle deposition are important processes for pollutants that are strongly associated with aerosols in the atmosphere. For example, heavy metals released from natural and anthropogenic sources are completely associated with aerosol particles in the atmosphere. Organic chemicals with low vapor pressure are also strongly associated with aerosol particles in the atmosphere, and are thus subject to dry and wet particle deposition. Because of the importance of partitioning between aerosols and the gas phase to the process of wet and dry particle deposition, we briefly review estimation methods below. 

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