http://hdl.handle.net/10453/11584 2013-05-20T21:27:30Z http://hdl.handle.net/10453/19425 Sources and toxicity of pollutants Sanchez-Bayo Francisco Sanchez-Bayo F, van den Brink PJ, Mann RM Modern living standards depend largely on the production and usage of thousands of chemicals, many of which are toxic and synthetically produced. These substances are discharged into the air, soil, water bodies and the sea through a variety of ways, becoming pollutants of our environment. The investigation of their fate and impacts they have on ecosystems is called ecotoxicology, a multidisciplinary science which intends to evaluate the nature of the discharge, the transformation and distribution of toxicants in the environment, exposure, lethality and sublethal effects on organisms, population responses, and changes in community structure and ecosystem function. The sources and mode of action of some of the most common groups of toxicants are described in this chapter, leaving their fate and effects in organisms and ecosystems for the subsequent chapters. 2011-01-01T00:00:00Z http://hdl.handle.net/10453/19426 Concluding remarks Sanchez-Bayo Francisco; Van Den Brink Paul; Mann Reinier Sanchez-Bayo F, van den Brink PJ, Mann RM The new millennium started with a legacy of unprecedented contamination of the world ecosystems left in the wake of the various activities of humankind. Chemical pollutants have become so diverse (see Chapter 1) and widespread that there is hardly any region of the world that is not currently affected by their impacts. With the exception, perhaps, of the desert wilderness areas (for which information on pollution is still lacking), every other ecosystem on earth, from the polar regions to the tropics, whether on land or in the oceans, has been shown to contain residues or traces of organic and inorganic pollutants of anthropogenic origin. 2011-01-01T00:00:00Z http://hdl.handle.net/10453/19427 Thermophysical Properties of Natural Glasses at the Extremes of the Thermal History Profile Thomas Paul; Sestak J; Heide K; Fuglein Ekkehard; Simon Peter Sestak J, MAres JJ, Hubik P Natural amorphous glassy silicates are widely distributed and are found in quantities that range from micrograms to kilo tonnes and, hence, their occurrence is from microscopic glassy inclusions to ¿glassy mountains¿ [1]. These natural glasses have two generic origins which may be generalised as vitreous glasses, formed from the melt state by relatively rapid cooling at cooling rates that inhibit crystal formation, or diagenetic glasses, formed by a dissolution-precipitation mechanism where crystallisation is inhibited by the Ostwald¿s rule of stepwise petrogenesis [2]. The thermal histories of a range of natural glasses are depicted in the schematic of Fig. 19.1 and vary signi?cantly from the typical conditions used in the glass industry which are optimised between processing speed and energy conservation. In the extremes, tektites like moldavites are formed by extremely fast heating and melting at very high temperatures (> 3,000 K) followed by quenching at extreme cooling rates ( 10 K/s). By contrast the formation of amorphous glasses from mineral diagenesis or biotic processes occurs at much lower temperatures and over longer time periods; the formation of sedimentary opal, for example, occurs at ambient temperatures, it is essentially isothermal, and takes place over long periods of time of the order of months to years 2011-01-01T00:00:00Z http://hdl.handle.net/10453/17299 Eutrophication and arsenic speciation in lake waters Hasegawa Hiroshi; Rahman Mohammad; Rahman Ismail Carolann D. Webber Arsenic (As) is widely distributed in aquatic environments in various forms. In natural waters, the dominant inorganoarsenicals (iAs) are incorporated into microorganisms such as phytoplankton, and are converted to methylarsenicals and/or more high order organoarsenicals. In addition, the organoarsenicals are mineralized to iAs and methylarsenicals by bacteria. The cycling of As species would depend on the bioactivity of organisms. Microorganisms, such as phytoplankton and organisms of higher trophic levels, produce methylarsenicals in natural waters with maximum concentrations in summer. The degradation and mineralization of organoarsenic compounds are thought to depend mostly on bacterial activities, which influence the As cycling in aquatic environment. Arsenic metabolism in aquatic organisms results in the occurrence of thermodynamically unstable arsenite and methylarsenic compounds in natural waters. The inorganic forms (As(V) and As(III)) and the methylated forms (methylarsonic acid (CH3AsO(OH)2); MMAA(V) and dimethylarsinic acid ((CH3)2AsO(OH)); DMAA(V)) are the main arsenic species present in natural waters. Although the predominant form of methylarsenicals is consistently DMAA(V) followed by MMAA(V), the existence of trivalent methylarsenic species in the environment has also been reported. 2010-01-01T00:00:00Z