Chemical Processes in Aquatic Systems

O Melia, Ch. R. (1990), "Kinetics of Colloid Chemical Processes in Aquatic Systems", in W. Stumm, Ed., Aquatic Chemical Kinetics, Reaction Rates of Processes in Natural Waters, Wiley-lnterscience, New York, pp. 447-474. 

KINETICS OF COLLOID CHEMICAL PROCESSES IN AQUATIC SYSTEMS... 

Kinetics of colloid chemical processes in aquatic systems... 

A clearer understanding of the redox kinetics of processes in aquatic systems depends on a better appreciation of the relationship between structural and dynamic aspects of chemical behavior. 

As illustrated by the results presented in Figure 2 and in Table 2 at high ionic strength and high Ca2 + for favorable particle-particle interactions (e.g., in the deposition of non-Brownian particles, F = F%Taviiy + Fdrag +FlVDW Fchem = 0), transport models based on physical and hydrodynamic characteristics of a system can predict the initial kinetics of aggregation and deposition processes in aquatic systems quantitatively. In the presence of repulsive chemical interactions, however, quantitative theoretical predictions of such kinetics are very inaccurate and even many qualitative predictions are not observed. The determination of Fchem in aquatic systems merits study and development,- it is necessary for the quantitative prediction of the kinetics of colloid chemical processes in these systems. 

Absorption across biological membranes is often necessary for a chemical to manifest toxicity. In many cases several membranes need to be crossed and the structure of both the chemical and the membrane need to be evaluated in the process. The major routes of absorption are ingestion, inhalation, dermal and, in the case of exposures in aquatic systems, gills. Factors that influence absorption have been reviewed recently. Methods to assess absorption include in vivo, in vitro, various cellular cultures as well as modelling approaches. Solubility and permeability are barriers to absorption and guidelines have been developed to estimate the likelihood of candidate molecules being absorbed after oral administration. ... 

Fate of Chemicals in Aquatic Systems Process Models and Computer Codes... 

Brezonik, P.L., 1994, Chemical Kinetics and Process Dynamics in Aquatic Systems. Lewis Publishers, Boca Raton, EL. 

Morel, F. M. M., and R. J. M. Hudson (1985), The Geobiological Cycle of Trace Elements in Aquatic Systems Redfield Revisited", in W. Stumm, Ed., Chemical Processes in Lakes, John Wiley and Sons, New York, 251-281. 

Several factors govern the transport and fate of hydrophobic organic chemicals in sediment/water environments microbially mediated reactions and sorption are major processes affecting the fate of these compounds in aquatic systems [166,366-368]. Aryl halides have been shown to undergo microbially-mediated dehalogenation under anaerobic conditions [38, 52, 68, 105, 116,... 

Whether such disposal is intentional or incidental, significant quantities of pesticides and pesticide wastes end up in natural and artificial aquatic systems. Thus, any consideration of the disposal of this broad category of anthropogenic chemicals must include an understanding of the reaction mechanisms and principal pathways for degradation of pesticides in aquatic systems. Of the degradative pathways relevant to such systems, hydrolysis reactions are perhaps the most important type of chemical decomposition process ( 1 7 ). 

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