Environmental spheres

Figure 5.2 Transfers of toxic substances among the major environmental spheres are very important in determining their ecotoxicological effects. 

Suggest how each of the following potential toxicants might transfer among environmental spheres based upon Figure 5.2 ... 

Some of the most important sources of the main OTCs of environmental interest (TBT and TPhT) have been identified above. Their biological effects will be determined by how the compounds are distributed between different environmental spheres, the timescales in which they are transported within the environment, and the particular organometallic species that exist under the prevailing environmental conditions. The environmental distribution of these compounds will therefore be determined by the physical, chemical, and biological properties they exhibit, and the myriad of localized conditions they are subject to. A reasonable biogeochemical cycle for OTCs can be postulated (see Figure 3) however, there is little quantitative information about fluxes between the different compartments, despite the concentrations of the various compounds having been studied. 

The environment is often seen as being composed of environmental spheres, speciflcally the atmosphere, the hydrosphere, the terrestrial environment, and the biosphere (Fig. 2). Environmental chemicals can occur in all these spheres. If a chemical occiu exclusively or predominantly in one of these spheres, its environmental fate can be reduced to the fate in that particular phase. For example, some very volatile chemicals occur exclusively in the atmosphere, whereas some very water-soluble chemicals are restricted to the aqueous phase. They are sometimes referred to as air pollutants or water contaminants and a distinct sphere-specific approach to such chemicals fate and transport may be appropriate. Most chemicals, however, do occirr in more than one of the environmental spheres in notable amounts, and a single-compartment perspective is insufficient to capture their environmental behavior. 

Despite the obvious differences between the spheres, many of the processes and mechanisms that control chemical fate are common to all of them. In all spheres, transport can occur by advection and diffusion, and marty of the chemical reactions are similar in the various spheres. One reason for the similarities is that the environmental spheres are composites of the same principal phases. The most important of these environmental phases are... 

The environmental spheres vary primarily in terms of the relative size of these phases (Fig. 3) and often also their chemical composition. Obviously, the gas phase is the dominant component of the atmosphere, but the aqueous phase is present in the form of hydrometeors (cloud and rain droplets, ice crystals), as are organic and mineral phases in the form of suspended particulate matter, called aerosols. And even though the volume taken up by these hydrometeors and aerosols may be miniscule compared to that of the gas phase, atmospheric chemical fate is often... 

FIGURE 3 The relative phase composition of the major environmental spheres. 

Based on the deflnition of environmental chemistry at the beginning of this chapter, suggest five environmental spheres. Which of these is the anthrosphere, and of what does it consist ... 

Mobile analysis is a special form of on-site analysis in the environmental sphere. For this purpose the devices (sampling, sample preparation, measurement devices) are transported in a vehicle. The equipment can be integrated permanently into the car or operated hand-held. 

To understand environmental chemistry, it is important to understand the five environmental spheres within and among which environmental chemical processes occur (Figure 1.2). These are outlined here and each is discussed in more detail throughout the remainder of this book as well as in a book on green chemistry. ... 

One of the most important ways of relating the environmental chemistry of the five environmental spheres is through biogeochemical cycles. These are commonly expressed in terms of key elements, including essential nutrient elements. Often, as is the case with the nitrogen cycle, they contain an atmospheric component, though in some cases, such as the phosphorous cycle, the atmospheric component is not significant. Before the appearance of humans on Earth, the anthrospheric... 

Other important cycles of matter are linked to the carbon cycle. The oxygen cycle describes movement of oxygen in various chemical forms through the five environmental spheres. At 21% elemental oxygen by volume, the atmosphere is a vast reservoir of this element. This oxygen becomes chemically bound as carbon dioxide by respiration processes of organisms and by combustion. 

An important aspect of ecotoxicology involves the pathways of toxicants into ecosystems and is very much tied with environmental chemistry. Toxic substances are transferred among the five environmental spheres as shown in Figure 2.22. The greatest concern is with the transfer of toxic substances into the biosphere, which can occur from water, air, the geosphere, and the anthrosphere. An important phenomenon is bioaccumulation in which toxic substances accumulate in tissue. The... 

Water s uniqne properties make it essential to life and determine its behavior in the hydrosphere and in interactions with all other environmental spheres, including its many uses in the anthro-sphere. As noted earlier in this section, these properties are due primarily to water s molecular structure, including its polar character and ability to form hydrogen bonds. The more important characteristics of water pertinent to its environmental behavior, uses, and interactions with all the environmental spheres are summarized in Table 3.1. 

Measures taken to preserve and enhance the quality of the other environmental spheres may be effective in maintaining the quality of the biosphere. This is certainly true of the atmosphere. A polluted atmosphere is generally harmful to the biosphere. Particulate matter that blocks out sunlight reduces the ability of the atmosphere to carry out photosynthesis. Particles in air that humans and other animals breathe can harm the lungs and have adverse health effects. Nitrogen oxides and sulfur oxides are phytotoxic. 

Shown as one of the five environmental spheres in Chapter 1, Figure 1.2, the anthrosphere is the part of the environment made and operated by humans. The anthrosphere is where pollutants are made and from which they are released with profound effects on aU the other environmental spheres. It is also strongly affected by pollutants, for example, acid rain that canses deterioration of stone structures and corrosion of metal components. 

What is your part of the anthrosphere How is it tied to each of the other four environmental spheres ... 

It is also useful to consider the five environmental spheres as defined and discussed in other chapters of this book ... 

The first chapter defines environmental chemistry and each of the five environmental spheres. The second chapter presents the basics of toxicological chemistry and its relationship to environmental chemistry. Subsequent chapters are grouped by sphere, beginning with the hydrosphere and its environmental chemistry, water pollution, sustainability, and water as nature s most renewable resource. Chapters then describe the atmosphere, its structure and importance for protecting life on Earth, air pollutants, and the sustainability of atmospheric quality. The author explains the nature of the geosphere and discusses soil for growing food as well as geosphere sustainability. He also describes the biosphere and its sustainability. 

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