Natural water systems, chemical

Roberson, C.E. Barnes, R.B. (1978) Stability of fluoride complex with silica and its distribution in natural water systems. Chemical Geology, 21, 239-256. 

Natural water systems contain numerous minerals and often a gas phase (Fig. 1). They include a portion of the biosphere and organisms, and their abiotic environments are interrelated and interact with each other. The distribution of chemical species in waters is strongly influenced by an interaction of mixing cycles and biological cycles. 

Hazardous chemical spills may have adverse effects on natural water systems, tlie land enviromnent, and whole ecosystems, as well as tlie atmosphere. Major spills evolve from accidents (see Chapter 6) tliat somehow damage or rupture vessels, tank cars, or piping used to store, sliip, or transport liazardous materials. In such cases, the spills must be contained, cleaned up, and removed as quickly and effectively as possible. 

Garrels, R. M. and Mackenzie, F. T. (1967). Origin of the chemical compositions of some springs and lakes. In "Equilibrium Concepts in Natural Water Systems" (W. Stumm, ed.). Advances in Chemistry Series 67, pp. 222-274. American Chemical Society, Washington. 

Greenberg, J. P. and N. Mpller, 1989, The prediction of mineral solubilities in natural waters, a chemical equilibrium model for the Na-K-Ca-Cl-S04-H20 system to high concentration from 0 to 250 °C. Geochimica Cosmochimica Acta 53,2503-2518. 

Brezonik, P. L. (1994). Kinetics of biochemical reactions and microbial processes in natural waters. In Chemical Kinetics and Process Dynamics in Aquatic Systems. Lewis Publishers, Boca Raton, FL, pp. 419-552. 

Parks, G. A. (1967), "Aqueous Surface Chemistry of Oxides and Complex Oxide Minerals Isoelectric Point and Zero Point of Charge," in Equilibrium Concepts in Natural Water Systems, Advances in Chemistry Series, No. 67, American Chemical Society, Washington, DC. 

Garrels, R.M. Mackenzie, F.T. In "Equilibrium Concepts in Natural Water Systems" Stumm, W., Ed. ADVANCES IN CHEMISTRY SERIES No. 67, American Chemical Society Washington, D.C., 1967 pp. 222-42. 

A. Analysis of Wastewater and Natural Waters. The presence of certain anions in wastewater effluents can cause deterioration of natural water systems. Phosphorous and nitrogen can be present in several chemical forms in wastewaters. Phosphorous is usually present as phosphate, polyphosphate and organically-bound phosphorus. The nitrogen compounds of interest in wastewater characterization are ammonia, nitrite, nitrate and organic nitrogen. Analyses are often based on titrimetric, and colorimetric methods (3). These methods are time consuming and subject to a number of interferences. Ion Chromatography can be used to determine low ppm concentrations of these ions in less than thirty minutes with no sample preparation. 

Applications and Limitations of Chemical Thermodynamics in Natural Water Systems... 

This paper outlines the basis for applying thermodynamic principles in studying the chemistry of natural water systems of all kinds, discusses the kinds of thermodynamic models available, and indicates some important limitations of such thermodynamic approaches. The general ideas will be illustrated by considering a few examples of chemical reactions of some interest in various kinds of natural water systems. 

Thermodynamic systems are parts of the real world isolated for thermodynamic study. The parts of the real world which are to be isolated here are either natural water systems or certain regions within these systems, depending upon the physical and chemical complexity of the actual situation. The primary objects of classical thermodynamics are two particular kinds of isolated systems adiabatic systems, which cannot exchange either matter or thermal energy with their environment, and closed systems, which cannot exchange matter with their environment. (The closed system may, of course, consist of internal phases which are each open with respect to the transport of matter inside the closed system.) Of these, the closed system, under isothermal and iso-baric conditions, is the one particularly applicable for constructing equilibrium models of actual natural water systems. 

The need to abstract from the considerable complexity of real natural water systems and substitute an idealized situation is met perhaps most simply by the concept of chemical equilibrium in a closed model system. Figure 2 outlines the main features of a generalized model for the thermodynamic description of a natural water system. The model is a closed system at constant temperature and pressure, the system consisting of a gas phase, aqueous solution phase, and some specified number of solid phases of defined compositions. For a thermodynamic description, information about activities is required therefore, the model indicates, along with concentrations and pressures, activity coefficients, fiy for the various composition variables of the system. There are a number of approaches to the problem of relating activity and concentrations, but these need not be examined here (see, e.g., Ref. 11). 

Kinetics of Reactions in Natural Waters. In considering equilibria and kinetics in natural water systems, it is usually necessary to recall that widely different time scales need to be identified with chemical reactions in different systems. Relatively short times (days to weeks) are available for approach to equilibrium in rivers, smaller lakes, reservoirs, and estuaries. Times for reaction in large lakes, seas, and perhaps typical ground waters are of the order of tens to hundreds of years. In ocean waters, the reaction time may range from thousands of years to... 

In view of all of the preceding observations concerning the formal differences between closed and open systems, what general conclusions can be drawn about the applicability of equilibrium concepts in understanding and describing the chemical behavior of the elements in natural water systems Since equilibrium is the time-invariant state of a closed system, the question is under what conditions do open systems approximate closed systems. A simple example will illustrate the relationships, which are already implicit in Equation 35. If one considers the case of a simple reaction... 

Mpller N (1988) The prediction of mineral solubilities in natural waters A chemical model for the Na-Ca-Cl-SC>4-H20 system, to high temperatures and concentrations. Geochim Cosmochim Acta 52 821-837... 

Sposito, G. and J. Coves. 1988. SOIL CHEM A Computer Program for the Calculation of Chemical Equilibria in Soil Solutions and Other Natural Water Systems, The Kearney Foundation of Soil Science, University of California, Riverside, CA. 

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