Natural and anthropogenic sources

It is clear that both atmospheric and surface dusts are complex materials and not all that easy to describe. A summary is given in Fig. 2 of the sources of atmospheric and surface dusts and their inter-connection. Both natural and anthropogenic sources contribute to both dusts. The inter-connection between the two dusts is wet and dry deposition from the atmosphere to the ground, and the re-entrainment of surface dust through wind and human activity into the atmosphere. Dust is an important global component of our earth, and impinges on the wellbeing of people. 

Figure 13-6a (Ivanov, 1983) is a depiction of the natural global sulfur budget. Figure 13-6b depicts the budget with natural and anthropogenic sources. Table 13-2 serves to explain Fig. 13-6 and includes the wide range of estimates of various fluxes, and demonstrates the degree of uncertainty inherent in such approaches.

Despite the difficulties, there have been many efforts in recent years to evaluate trace metal concentrations in natural systems and to compare trace metal release and transport rates from natural and anthropogenic sources. There is no single parameter that can summarize such comparisons. Frequently, a comparison is made between the composition of atmospheric particles and that of average crustal material to indicate whether certain elements are enriched in the atmospheric particulates. If so, some explanation is sought for the enrichment. Usually, the contribution of seaspray to the enrichment is estimated, and any enrichment unaccounted for is attributed to other natural inputs (volcanoes, low-temperature volatilization processes, etc.) or anthropogenic sources. 

Table 15-1 Natural and anthropogenic sources of atmospheric emissions"...

Atmospheric aerosols have a direct impact on earth s radiation balance, fog formation and cloud physics, and visibility degradation as well as human health effect[l]. Both natural and anthropogenic sources contribute to the formation of ambient aerosol, which are composed mostly of sulfates, nitrates and ammoniums in either pure or mixed forms[2]. These inorganic salt aerosols are hygroscopic by nature and exhibit the properties of deliquescence and efflorescence in humid air. That is, relative humidity(RH) history and chemical composition determine whether atmospheric aerosols are liquid or solid. Aerosol physical state affects climate and environmental phenomena such as radiative transfer, visibility, and heterogeneous chemistry. Here we present a mathematical model that considers the relative humidity history and chemical composition dependence of deliquescence and efflorescence for describing the dynamic and transport behavior of ambient aerosols[3]. 

Schuster PF, Krabbenhoft DP, Naftz DL, Cecil FD, Olson ML, Dewild IF, Susong DD, Green JR, Abbott ML. 2002. Atmospheric mercury deposition during the last 270 years a glacial ice core record of natural and anthropogenic sources. Env Sci Technol 36 2303-2310. 

Sulfur dioxide is produced by both natural and anthropogenic sources. The most important of the natural sources are volcanic eruptions, which account for about 40 percent of all natural emissions of the gas. Since volcanic eruptions are episodic events, the amount of sulfur dioxide attributable to this source in any one year varies widely. Other natural sources of the gas are forest fires and other natural burns, biological decay, and certain metabolic processes carried out by living organisms, especially marine plankton and bacteria. Natural sources release about 27.5 million short tons (25 million metric tons) of sulfur dioxide per year. 

Particulate matter is the term used to describe solid particles and liquid droplets found in the atmosphere. Particulates are produced by a host of natural and anthropogenic sources. Mist and fog are both forms of natural particulates, as are windblown soil, dust, smoke from forest fires, and biological objects, such as bacteria, fungal spores, and pollen. The incomplete combustion of fossil fuels is one of the most important anthropogenic (human-made) sources of particulates. Such processes release unhurned carbon particles, oxides of sulfur and nitrogen, and a host of organic compounds into the air. 

Most analytical methods for nickel in environmental samples do not distinguish between compounds of nickel or the nature of its binding to soil and particulate matter. It is generally impossible to say with certainty what forms of nickel are released from natural and anthropogenic sources, what forms are deposited or occur in environmental samples, and to what forms of nickel people are exposed. The form... 

In short, while the focus has been primarily on sulfuric and nitric acids as a source of acid deposition, it is clear that organic acids can also contribute significantly. The gas-phase concentrations of the simplest carboxylic acids, formic acid and acetic acid, are relatively high even in remote regions, of the order of a ppb. Both natural and anthropogenic sources have been... 

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. 

Nanoparticles originate from both natural and anthropogenic activities. This section provides a brief overview of the anthropogenically produced nanoparticles from gasoline and diesel-fuelled road vehicles, with a special focus on the emerging class of nanoparticles (i.e. ENPs). A brief overview of natural and anthropogenic sources is also presented for the completeness of the chapter. Wherever felt necessary, readers are directed to the relevant literature for detailed information. 

Airborne nanoparticles empirically fit well to log normal distributions and exhibit bimodal distributions in atmospheric urban environments. These arise from both natural and anthropogenic sources. Road vehicles remain a dominant source, contributing up to 90% of total PNCs, in polluted urban environments. 

There are many more PAHs than the EPA s 16 priority compounds shown in Fig. 1. These include other parent compounds as well as alkylated species. The large number of possible PAHs provides power to elucidate sources of PAHs to the Great Lakes. Because different sources produce different relative amounts of each PAH, the relative concentrations of PAHs in environmental media can be used to identify significant sources back out their contributions to environmental levels. Some compounds that are particularly helpful in the elucidation of sources, or may have both natural and anthropogenic sources are shown in Fig. 2. 

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. 

The most evident and common effects exerted by HS are the responses on plant growth. Many studies in recent years have confirmed the observations made in this direction by Vaughan and Malcom (1985), who reported data considering various parameters and different treatments with HS extracted from many natural and anthropogenic sources tested against a number of higher plant species. 

The western Siberian region of Russia is characterized by numerous intensive natural and anthropogenic sources of methane formation. These are marshes, tundra, permafrost, oil and gas deposits. In this region, flux FlCH4 varies widely both during the year and shorter time periods. From measurements carried out by Jagovkina et al. (2000) on the Yamal coastline in June 1996, the CH4 concentration in the atmosphere... 

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