Aquatic systems, heterogeneous

Wastewaters containing chlorinated hydrocarbons (CHCs) are very toxic for aquatic system even at concentrations of ppm levels [1] thus, appropriate treatment technologies are required for processing them to non-toxic or more biologically amenable intermediates. Catalytic wet oxidation can offer an alternative approach to remove a variety of such toxic organic materials in wet streams. Numerous supported catalysts have been applied for the removal of aqueous organic wastes via heterogeneous wet catalysis [1,2]. 

Atlantis II Deep (Red Sea) and the uptake of amino acids by synthetic P-FeOOH Cln. Geochim. Cosmochim. Acta 47 1465-1470 Holm,T.R., Anderson, M.A., Iverson, D.G. Stanforth, R.S. (1979) Heterogeneous interaction of arsenic in aquatic systems. ACS Symposium Ser. Chemical modelling of aqueous systems Speciation, sorption, solubility, kinetics. 711-736... 

Ruzic, I. (1996) Trace metal complexation at heterogeneous binding sites in aquatic systems. Mar Chem., 53, 1-15. 

Abstract In this chapter, photochemical processes in natural aquatic systems involving iron in one way or another are reviewed. Homogeneous and heterogeneous processes are examined with attention given to both simple model systems in which the species distribution is generally well understood and to complex systems more typical of natural or treatment environments. Insights into mechanistic aspects are provided where possible and implications to natural and treatment systems assessed. 

It is the purpose of this paper to describe some of the major mechanisms that control arsenic in aquatic systems. Particularly, this paper addresses the problem of arsenic speciation and compartmentalization in sediments. To this end, results obtained from speciation, compartmentalization, kinetic, and adsorption studies using both field and laboratory samples will be interfaced in a descriptive model for arsenic in heterogeneous systems. The model has particular significance... 

Methods of Speciation and Fractionation. It is apparent that in order to understand the mobility of arsenic and its availability for reactions, methods of speciation and fractionation must be applied to sediment samples in field and laboratory studies. In this paper speciation refers to the separation and quantitative determination of inorganic arsenic, methanearsonic acid, and cacodylic acid. Compartmentalization involves identifying the major compartments for arsenic in a heterogeneous system (e.g. aqueous, adsorbed, occluded,...) and determining the amounts of arsenic in each compartment. Fractionation involves the extraction of arsenic from operationally defined fractions of the solid phase of an aquatic system (e.g. sediment). 

Lelieveld, J. (1994) Modeling of Heterogeneous Chemistry in the Global Environment. In Chemistry of Aquatic Systems Local and Global Perspectives, ed. G. Bidoglio and W. Stumm, Eds., Kluwer, Dordrecht (NL). 

The chemistry of phosphates as relevant to aquatic systems is discussed as an example of the importance of heterogeneous equilibria in waters. Phosphorus, present as various forms of phosphate, is of central concern to a wide variety of biological and chemical processes in natural waters, wastewater, and water treatment. Phosphate is a nutrient required for the growth of all living protoplasm that,contains approximately 2 percent phosphorus on a dry weight basis. As such, phosphorus can be the... 

Photosensltlzatlon via energy transfer In dilute solutions of sensitizer and receptor Is In general a low efficiency process. This will probably hold true for most environmental aquatic systems. Much higher efficiencies might, however, be obtained in heterogeneous reaction environments such as micelles, particles, or other Interfaces where sensitizer and reactant are concentrated. 

FCS has been applied only rarely to environmentally relevant aquatic systems, but the technique has a promising future. A major advantage is a high sensitivity that allows the study of native colloids in situ at realistic concentrations. It is also selective for specifically labeled molecules, which presents a major advantage for the analysis of chemically heterogeneous media, potentially allowing the study... 

Town, R.M., and Fillela, M. (2002). Implications of natural organic matter binding heterogeneity on understanding lead(ll) complexation in aquatic systems. Sci. Tot. Environ., 300, 143-154. 

Characterization of the ecosystem of concern is often a most difficult process. In many cases involving restoration of damaged ecosystems, there may not be a functional ecosystem, and a surrogate must be used to understand the interactions and processes of the system. Often the delineation of the ecosystem is difficult. If the protection of a marine hatchery is considered the assessment endpoint, large areas of the coastal shelf, tidewater, and marine marsh systems have to be included in the process. Even many predominately terrestrial systems have aquatic components that play a major role in nutrient and toxicant input. Ecosystems are also not stagnant systems but under succession, and they respond to the heterogeneity of climatic inputs in ways that are difficult to predict. 

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