Gas exchange, air-water

The Henry s Law Constant Effect of Temperature on Air-Water Partitioning Effect of Solution Composition on Air-Water Partitioning Illustrative Example 6.2 Evaluating the Direction of Air-Water Gas Exchange at Different Temperatures Illustrative Example 6.3 Assessing the Effect of Solution Composition on Air-Aqueous Phase Partitioning Availability of Experimental Data Estimation of Air-Water Partition Constants... 

Illustrative Example 6.2 Evaluating the Direction of Air-Water Gas Exchange at Different Temperatures Problem What is the direction (into water or out of water ) of the air-water exchange of benzene for a well-mixed shallow pond located in the center of a big city in each of the following seasons (a) a typical summer situation (T = 25°C), and (b) a typical winter situation (T= 5°C) In both cases, the concentrations detected in air and water are C,a = 0.05 mg-m"3 and C,w = 0.4 mg m 3. Assume that the temperature of the water and of the air is the same. 

Evaluating the Direction of Air-Water Gas Exchange at Different Temperatures... 

The three main processes by which atmospheric deposition of pesticides to the lakes occurs are wet deposition (rain and snow), dry deposition (particulates), and air-water gas exchange. For many of the banned pesticides, gas exchange across the air-water interface, in particular, is often the dominant deposition process, when compared with precipitation and dry particle exchange [42-44], The physicochemical considerations, as well as descriptions of calculation models for atmospheric deposition to lakes, rivers, and the oceans, have been reviewed extensively [45-47]. 

Bidleman, T.F. and L.L. McConnell. 1995. A review of field experiments to determine air-water gas exchange of persistent organic pollutants. Sci. Total Environ. 159 101-117. 

McConnell, L.L., Kucklick, J.R., Bidleman, T.F., Ivanov, G.P., Chernyak, S.M., 1996. Air-water gas exchange of organochlorine compounds in Lake Baikal. Russia Environ. Sci. Technol. 30, 2975-2983. 

Kremer, J.N., Nixon, S.W., Buckley, B., and Roques, P (2003b) Technical note conditions for using the floating chamber method to estimate air-water gas exchange. Estuaries 26, 985-990. 

Kremer, J.N., Reischauer, A., and D Avanzo, C. (2003a) Estuary-specific variation in the air-water gas exchange coefficient for oxygen. Estuaries 26, 829-836. 

Figure 4.10 Enantiomer fractions (EFs) of a-HCH in water and air of the southern Atlantic Ocean as a function of latitude. (Reproduced with permission from Deep-Sea Research Part II Topical Studies In Oceanography, Air-water gas exchange of a-hexachlorohexane enantiomers in the South Atlantic Ocean and Antarctica, by Liisa M. jantunen, Henrik Kylin and Terry F. Bidleman, 51(22-24), 2661-2672. Copyright (2004) Elsevier)...

Figure 4.18 Enantiomer fractions (EFs) of a-HCEi In air above Resolute Bay, Nunavut, Canada, showing a correlation (r = 0.68) when >90% open water is present (squares) but no correlation when 0-50 % open water is present (diamonds). (Reproduced with permission from Environmental Science and Technology, Hexachlorohexanes (HCHs) in the Canadian Archipelago. 2. Air-Water Gas Exchange of a- and y-HCH, by Liisa M. Jantunen, Paul A. Helm, Henrik Kylin and Terry F. Bidleman, 42(2), 465-470. Copyright (2008) American Chemical Society)...

Jantunen, L.M. Kylin, H. Bidleman, T.F, Air-water gas exchange of a-hexachlorocyclohexane enantiomers in the South Atlantic Ocean and Antarctica Deep-Sea Res. //2004,51,2661-2672. 

Jantunen, L.M. Bidleman, T.R, Reversal of the air-water gas exchange direction of hexa-chlorocyclohexanes in the Bering and Chukchi Seas 1993 versus 1998 Environ. Sci Technoi 1995, 29, 1081-1089. 

Jantunen, L.M. Helm, P.A. Ridal, J.J. Bidleman, T.R, Air-water gas exchange of chiral and achiral organochlorine pesticides in the Great Lakes Atmos. Environ. 2008, 42, 8533-8542. 

The two-film model of gas exchange Chemical enhancement The Schmidt number Surface renewal model Micrometeorological models Bubble-mediated gas transfer Laboratory Studies of Air-Water Gas Exchange... 

The most accurate determination of the gas exchange coefficient requires that careful field experiments be conducted. Although techniques for estimating kw from measurable hydraulic attributes of a water body also exist, they are less accurate due to the state of incomplete understanding of the air-water gas exchange process and the fact that multiple factors may control the exchange rate for any particular chemical (Fig. 2-13). Two different models... 

In the expressions for the gas exchange coefficient employed previously, it is evident that the air-water gas exchange flux density is proportional to the difference between a chemical concentration in the water (Cw) and the corresponding equilibrium concentration (Cw H) in air. Consequently, the difference between actual and equilibrium concentration in the water tends to decay exponentially, as expected for any first-order process. In many situations, exponential decay may provide a useful model of a volatile chemical concentration in a surface water. A classic example is degassing of a dissolved gas from a stream if the gas is present at concentration C0 upstream, atmospheric concentration of the gas is negligible, and flow is steady and uniform along the stream, then the gas concentration in the stream is given by... 

Accurate estimates of particle deposition are difficult to obtain because of the complexity of natural surfaces and the diversity of atmospheric particles. The long-term deposition of particles on vegetative surfaces often is estimated using a deposition velocity model in which the flux density of particles is calculated as the product of a modeled deposition velocity and a measured concentration of particles in the air (Hicks et al., 1987). A deposition velocity is used in a manner similar to a piston velocity in air-water gas exchange (Section 2.3). In a deposition velocity model, the flux density of atmospheric particles to the surface is... 

Jahne B, Haussecker H (1998) Air-water gas exchange. Ann Rev Fluid Mech 30 443-468... 

Studies of the air-water gas exchange process by infrared imaging techniques enable local and fast measurements of the heat transfer velocity. Applying Schmidt number scaling, the obtained gas transfer velocities are consistent with mass balance methods and are in good agreement for the... 

Jahne B, Munnich KO, Bosinger R, Dutzi A, Huber W, and Libner P (1987) On the Parameters Influencing Air-Water Gas Exchange. J Geophys Res 92 1937-1949... 

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