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Contaminant Hydrogeology V

Contaminant Hydrogeology V. Гидрогеология Загрязнений и их Транспорт в Окружающей Среде. Yoram Eckstein, Ph.D. Fulbright Professor 2013/2014. Tomsk Polytechnic University Tomsk, Russian Federation Fall Semester 2013. Air-Water Gas Exchange of Chemicals. Thin-Film Model.

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Contaminant Hydrogeology V

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  1. Contaminant Hydrogeology V Гидрогеология Загрязнений и их Транспорт в Окружающей Среде Yoram Eckstein, Ph.D. Fulbright Professor 2013/2014 Tomsk Polytechnic University Tomsk, Russian Federation Fall Semester 2013

  2. Air-Water Gas Exchange of Chemicals

  3. Thin-Film Model Water-side control J = -Dw(Cw – Ca/H)/Zw where Zwis the thickness of the water film if Ca = 0 J = -DwCw/ Zw= -kwCw

  4. Thin-Film Model Air-side control J = -(Da/Za) (CwH - Ca) or J = – (Da - H/Za) (Cw - Ca/H) where Zais the thickness of the air film

  5. Thin-Film Model for H ≈ 0.01

  6. Estimating gas exchange coefficient

  7. Estimating gas exchange coefficient In absence of a tracer with a known gas exchange coefficient models are constructed empirically for each gas, e.g. the four models for kO2 : Neglescu & Rojanski, 1969 Owens et al., 1964 Thackston & Krenkel, 1969 Bennet & Rathbun, 1972

  8. Estimating gas exchange coefficient Similarly, gas exchange coefficients for slowly flowing waters, lakes or estuaries are approximated empirically: for slowly flowing or stagnant waters: kw[cm/sec] ≈ 4·10-4 + (4·10-5·u2w10) or ka[cm/sec] ≈ 0.3 + (0.002·uw10)

  9. Using gas exchange coefficient The air-water flux density is proportional to the difference between a chemical concentration in water [Cw] and the corresponding equilibrium concentration [CwH]. Therefore:

  10. Thin-Film of Air Model Above a Slick of NAPL while Zais the thickness of the stagnant air film above the slick, the velocity of gas transfer (vaporization) is proportional to Da of that gas

  11. Thin-Film of Air Model Above a Slick of NAPL the velocity of gas transfer (vaporization) is also dependent on the size of the slick v = 0.029·uw10·L-0.11·Sc-0.67 where: uw10 wind velocity 10m above the slick [m/hr] L is the slick diameter [m] Sc is the Schmidt number

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