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Contaminant Hydrogeology IV

Contaminant Hydrogeology IV. 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.

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Contaminant Hydrogeology IV

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  1. Contaminant Hydrogeology IV 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. Transport and Fate of Contaminants in Surface Waters

  3. Nature of surface waters • Free surface in equilibrium with the atmosphere • Open system; exchange with the atmosphere, biosphere and the lithosphere • Stratification • Flow velocity from 0 to x

  4. Sources of contaminants • Point sources • Non-point sources

  5. Transport in streams and rivers • Manning’s velocity The Manning formula is also known as the Gauckler–Manning formula, or Gauckler–Manning–Strickler formula in Europe. In the United States, in practice, it is very frequently called simply Manning's Equation. The Manning formula is an empirical formula estimating the average velocity of a liquid flowing in a conduit that does not completely enclose the liquid, i.e., open channel flow. All flow in so-called open channels is driven by gravity. It was first presented by the French engineer Philippe Gauckler in 1867, and later re-developed by the Irish engineer Robert Manning in 1890.

  6. Transport in streams and rivers • Manning’s velocity • 𝑣 is the cross-sectional average velocity (L/T; ft/s, m/s); k is a conversion factor of (L1/3/T), 1 m1/3/s for SI, or 1.4859 ft1/3/s U.S. customary units, if required. n is the Gauckler–Manning coefficient, it is unitless; Rh is the hydraulic radius (L; ft, m); S = the slope of the water surface or the linear hydraulic head loss (L/L) (S = hf/L).

  7. Transport in streams and rivers • Manning’s velocity – hydraulic radius Rhis the hydraulic radius (L); A is the cross sectional area of flow (L2); P is the wetted perimeter (L). The hydraulic radius is a measure of a channel flow efficiency. Flow speed along the channel depends on its cross-sectional shape (among other factors), and the hydraulic radius is a characterization of the channel that intends to capture such efficiency.

  8. Transport in streams and rivers • Manning’s velocity n - the Gauckler–Manning coefficient where d50 = median sediment diameter, m.

  9. The Gauckler-Manning roughness coefficient 0.012 < n < 0.050 smooth rough concrete mountain bed streambed

  10. Transport in streams and rivers • Chezy’s velocity C – Chezy friction coefficient - hydraulic gradient v - velocity

  11. Transport in streams and rivers Chezy friction coefficient

  12. Travel time l - length Q = v∙AJi = Q∙Ci Rate of flow (l3/t) flux of a chemical (M/t) v - velocity

  13. Miscible conservative tracer D – dispersion coefficient

  14. Miscible conservative tracer • Gaussian (normal) curve – longitudinal D where σ is the standard deviation and C(x) is concentration of the transported chemical

  15. Miscible conservative tracer • Gaussian (normal) curve – longitudinal D

  16. Miscible conservative tracer • Gaussian normal curve – longitudinal D M – mass of the tracer

  17. Miscible non-conservative tracer • Gaussian normal curve – longitudinal D M – mass of the tracer

  18. Miscible non-conservative tracer Transversal dispersion l l - the length of the transverse mixing zone

  19. Miscible non-conservative tracer • Gaussian normal curve – transversal D t = l/v w – width of the river l - the length of the transverse mixing zone

  20. Longitudinal and transversal mixing • Longitudinal mixing is dominated by the process of dispersion • Transversal mixing is caused only by flow turbulence • Turbulence is predominantly by shear velocity: u* = [gd(dx/dl)]½ where d is the depth of the river

  21. Longitudinal and transversal mixing • for straight channels: Dt = 0.15 d u* • for natural channels: Dt = 0.6 d u*

  22. Longitudinal and transversal mixing Dl = (0.011 v2 w )/(d u*) w – width of the river

  23. Lakes & estuaries • Wind driven advection • 2-d mixing • Stratification – thermocline - halocline • Tidal effects in estuaries

  24. Wind driven advection The Lake Erie surface at the east end stands ca. 1 m higher than at the west end

  25. Wind driven advection Summer lake stratification

  26. Wind driven advection Summer lake stratification

  27. Wind driven advection End of summer stratification

  28. Wind driven advection Fall mixing

  29. Wind driven advection Winter lake stratification

  30. Thermocline and halocline January 2010 temperature and salinity profiles in Arctic Ocean

  31. Thermocline and halocline

  32. Stream transport • Dissolved load • Suspended load • Bed load

  33. Solid particles in surface waters • Suspended load • Bed load

  34. Solid particles in surface waters • Mineral – metal-hydroxides - clay ρ ≈ 2.6 g/cm3 • Organic – bacteria & algae ρ ≈ 1.3 g/cm3

  35. Solid particles in surface waters and air

  36. Particle Settling Stokes’ Law • Bottom sediments record

  37. Particle Settling • Stokes’ Law

  38. Bottom sediments record

  39. Bottom sediments record

  40. How do we establish the age of layers in lake sediments record? 210Pb dating is based on a relatively constant atmospheric deposition of this radionuclide onto surface waters and subsequent sorption of 210Pb on particles in the water that eventually settle into a chronostratigraphic deposit. The 210Pb concentration (measured by its radioactivity) at any depth in the sediment is equal to its concentration in freshly deposited material (at the water/sediment interface) is multiplied by exp(-λt), where λ is the 210Pb decay constant = 0.03/year

  41. How do we establish the age of layers in lake sediments record? Therefore: Where: Ad is 210Pb activity at a depth d Aois 210Pb activity at lake sediment surface λ = 0.03/year

  42. Concentration and Partial Pressure of Gases in Air • Partial pressure = Percentage of concentration of specific gas × Total pressure of a gas • Dalton’s law • Total pressure = Sum of partial pressure of all gases in a mixture

  43. Concentration and Partial Pressure of Gases in Air

  44. Ambient Air • O2 = 20.93% = ~ 159 mm Hg PO2 • CO2 = 0.03% = ~ 0.23 mm Hg PCO2 • N2 = 79.04% = ~ 600 mm Hg PN2

  45. Air-Water Exchange Cequil = Ca/H J = -kw(Cw – Ca/H) kw is gas exchange coefficient Cw is the gas concentration in water Cais the gas concentration in air

  46. Air-Water Exchange

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