Natural and industrial sources

Demonstrations (see below) of the acidic properties of the oxides of nitrogen and sulfur show students some of the inorganic reactions that will be background for class discussions and homework assignments. The students are also expected to know the natural and industrial sources of each gas. They must also be reminded of chemistry topics they have already studied, such as gas behavior and equilibrium, that will provide relevant background for understanding acid deposition. 

Besides the Sleipner project, the In Salah project and the Weyburn project, there are many sites, especially in the United States, where C02 from natural and industrial sources is used commercially for enhanced oil recovery. Even if those projects allow a lot of technical experience to be gained, the appropriateness of their regulative element as an example for C02 storage in general is not given. 

Halogenated hydrocarbons originate from both natural and industrial sources. Whereas direct anthropogenic emissions to the atmosphere and biosphere are often easy to assess, particularly when they are tied to major industrial activities. 

Some halocarbons are produced by both natural and industrial sources. Unfortunately, the few data concerning the magnitude of the natural sources are conflicting. For example, based on measured concentrations of methyl bromide in the sea and troposphere, Singh et al. (6) estimated that the net annual global flux from ocean to air is about 0.3 teragrams (1 Tg is 1 X 1012 g). This net emission is much larger than that derived from human activities (0.05-0.08 Tg per year) (7, 8). On the other hand, Penkett and co-workers (7) concluded that human activities were the main source of methyl bromide. 

Waste Products and Recycling No chemotoxic or radiotoxic effects on microorganisms or plants are known from exposure to environmental radioactivity from natural and industrial sources of uranium, thorium and their decay products. 

The use of high-sensitivity, portable, rapid-response gas-analyzing equipment has led to the detection of several previously unknown elemental mercury plumes associated with both natural and industrial sources. In Northern California these anomalies were detected in a brief reconnaissance program and hence represent only a sampling of the mercury vapor plumes likely to exist in the area. An inventory of elemental mercury plumes can be obtained in any area by using a high-sensitivity, portable, rapid-response mercury detector mounted in a mobile laboratory for measurement while in motion. 

As highlighted in previous reviews of nitrile hydratase, nitriles from both natural and industrial sources are a prevalent chemical functionality in our environment (i-5). In industry, nitriles find use in the production of fine chemicals, as pesticides, and as feedstock for the production of polyacrylamide and other polymers. Historically, waste products from these processes were dumped into open waterways or pumped into deep pressure wells, leading to deleterious environmental effects. Naturally occuring nitriles include... 

Radioactivity in environmental waters can originate from both natural and artificial sources. The natural or background radioactivity usuaUy amounts to <100 mBq/L. The development of the nuclear power industry as weU as other industrial and medical uses of radioisotopes (qv) necessitates the deterrnination of gross alpha and beta activity of some water samples. These measurements are relatively inexpensive and are useful for screening samples. The gross alpha or beta activity of an acidified sample is deterrnined after an appropriate volume is evaporated to near dryness, transferred to a flat sample-mounting dish, and evaporated to dryness in an oven at 103—105°C. The amount of original sample taken depends on the amount of residue needed to provide measurable alpha or beta activity. 

Mercury is widespread in the environment, originating both from natural (natural gassing of the Eailh s cmst, leaching from rocks) and industrial sources (e.g. production of caustic soda and chlorine, electrical industry, biocides, etc.). 

Particles are emitted Into the atmosphere from numerous natural and manmade sources and are also formed upon condensation of gases and vapors. Direct emissions of Suspended Particulate Natter (SPN) arise from a variety of human activities Including combustion. Industrial and agricultural practices the remainder Is formed from gas-particle conversions (chiefly from SOj oxidation to sulfuric acid as sulfate salts). Particles larger than about lOpm In diameter deposit In the vicinity of the sources, but smaller... 

Families can become exposed to excess hydrogen sulfide if they live near natural or industrial sources of hydrogen sulfide such as hot springs, manure holding tanks, or pulp and paper mills. Families may wish to keep visits to such places to a minimum. 

Carbon dioxide and water are the major waste products from most natural and industrial processes and hence are found in large quantities in the environment. If an efficient and cheap means could be found, the reduction of C02 could provide a potentially rich source of carbon for utilisation in the production of, for example, synthetic hydrocarbon fuels to replace petroleum, formic and oxalic acids for the chemical industries and foodstuffs such as glucose. 

The two ultimate sources of chemicals - nature and industrial and laboratory synthesis - are then briefly described. This review sets the stage for a discussion of how human beings become exposed to chemicals. The conditions of human exposure are a critical determinant of whether and how a chemical will produce injury or disease, so the discussion of chemical sources and exposures naturally leads to the major subject of the book - the science of toxicology. 

The nitrogen species enter the atmosphere from a variety of natural and anthropogenic sources (7). The largest sources are concentrated in urban and industrialized areas. The levels of the species in the atmosphere vary from hundreds of parts per billion by volume (ppbv, that is, 10 9 mole fraction) in these source regions to below one part per trillion by volume (pptrv, 10"12 mole fraction) in remote areas. Even at the pptrv level, these species can play significant roles in atmospheric chemistry, and measurements of species at the sub-pptrv level can yield useful information concerning atmospheric photochemistry. 

The many natural and anthropogenic sources of PAHs in combination with global transport phenomena result in the worldwide distribution of these compounds. The concentration of PAHs in any given area can vary widely, depending on the level of industrial development and transport processes. In a study of different soils collected from rural and urban areas (not from grossly contaminated locations such as near gas works or refineries) at 49 locations in Wales, UK, Jones et al.21 found a range of PAH contamination from between 0.1 to 55 fig/g soil. 

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