Global distribution occurrence

A second group of important POP s is represented by chlorinated pesticides. Major attention was attributed to the environmental occurrence and fate of DDT and its numerous metabolites. As a result a comprehensive knowledge about the major properties with respect to environmental considerations (environmental stability, toxicological effects, transport processes including its global distribution etc.) exists. For instance the information on the degradation pathway under aerobic as well as under anaerobic conditions is nearly complete as illustrated in Fig. 3. 

Although the globally distributed DDT is a very well investigated xenobiotic regarding the environmental occurrence and behaviour, detailed information about the fate of DDT in the bound residues fraction is very limited. Already in 1977 Lichtenstein et al. (1977) reported the formation of bound 14C-labelled DDT on agricultural soil accompanied by a drastically reduced insecticidal activity of the associated proportion. Also recent studies confirmed the decrease of DDT toxicity with time after application to soils as a result of less bioavailibility due the incorporation into the non-extractable particulate matter (Robertson and Alexander 1998). For a better understanding of the processes leading to these observations more information is required about the incorporation of DDT residues into the non-extractable particulate matter not only of soils but also of particulate matter within the aquatic environment. 

FIGURE 26.2 Global distribution of spirolides in populations of the toxigenic dinoflagellate ostenfeldii and where the occurrence of these toxins in shellfish is proven or circumstantially associated with this dinoflagellate. 

Seismology has played a key role in the development of the plate tectonic theory, which describes and explains the motions of lithosphere plates. The global distribution of earthquakes outlines the plate boundaries, the occurrence of deep earthquakes indicates regions where plates are recycled back into Earth s mantle, and earthquake fault plane solutions provide information about the relative sense of motion at plate boundaries. 

Dickens, G.R., Modeling the Global Carbon Cycle with a Gas Hydrate Capacitor Significance for the Latest Paleocene Thermal Maximum. Natural Gas Hydrates Occurrence, Distribution, and Detection (Pauli, C.K., Dillon, W.P., eds.), AGU, Washington, DC, Geophys. Monogr. Ser. 124, pp. 19-38 (2001). 

The concentration of metals in atmospheric aerosols and rainwater (Table 7.1) is therefore a function of their sources. This includes both the occurrence of the metals in combustion processes and their volatility, as well as their occurrence in crustal dust and seawater. As a result of this, the size distribution of different metals is very different and depends on the balance of these sources. For a particular metal this distinction is similar in most global locations (Table 7.2), although some variability does occur as wind speed and distance from source exert an influence on the particle size distribution spectrum (Slinn, 1983). Once in the atmosphere particles can change size and composition to some extent by condensation of water vapour, by coagulation with other particles, by chemical reaction, or by activation (when supersaturated) to become cloud or fog droplets (Andreae et al., 1986 Arimoto et al., 1997 Seinfeld and Pandis, 1998). 

Kvenvolden K. K. and Lorenson T. D. (2001) The global occurrence of natural gas hydrate. In Natural Gas Hydra-tes.Occurrence, Distribution and Detection, Geophysical Monograph 124 (eds. C. K. Pauli and W. D. Dillon). American Geophysical Union, Washington, DC. 

INTRODUCTION 1.1 The Global Mercury Cycle FUNDAMENTAL GEOCHEMISTRY. 2.1 Solid Earth Abundance and Distribution. 2.2 Isotopic Distributions. 2.3 Minable Deposits. 2.4 Occurrence of Mercury in Fossil Fuels SOURCES OF MERCURY TO THE ENVIRONMENT. 3.1 Volcanic Mercury Emissions... 

In this chapter, sources, occurrence, distribution and processes of pollutants are described. In particular, data on emissions of carbon dioxide, sulfur dioxide, nitric oxide, nitrogen dioxide, etc. are presented, and global and regional impact as well as impact on plants and materials is summarized. 

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