the Scheldt), it is not possible to make generalizations about the importance of these systems on a
global scale.
Conclusions
Many estuaries are supersaturated with a variety
of gases, making them locally, and occasionally
regionally, important sources to the atmosphere.
However, estuarine systems are also highly variable
in the amount of gases they contain. Since most estuaries studied to date are in Europe or the North
American continent, more data are needed before
global budgets can be reliably prepared.
Glossary
Air–water interface The boundary between the
gaseous phase (the atmosphere) and the liquid
phase (the water).
Catabolic Biochemical
process
resulting
in
breakdown of organic molecules into smaller
molecules yielding energy.
Denitrification Reduction of nitrate via nitrite to
gaseous endproducts (nitrous oxide and dinitrogen
gas).
Ebullition Gas transport by bubbles, usually from
sediments.
Estuary Semi-enclosed coastal body of water with
free connection to the open sea and within which
sea water is measurably diluted with fresh water
derived from land drainage.
Gas solubility The amount of gas that will dissolve
in a liquid when the liquid is in equilibrium with
the overlying gas phase.
Henry’s Law Constant Proportionality constant
relating the vapor pressure of a solute to its mole
fraction in solution.
Liquid laminar thickness The thickness of a layer at
the air/water interface where transport of a
dissolved species is controlled by molecular
(rather than turbulent) diffusion.
Molecular diffusivity (D) The molecular diffusion
coefficient.
Nitrification Oxidation of ammonium to nitrite
and nitrate.
Practical salinity scale A dimensionless scale for
salinity.
Redfield stoichiometry Redfield and colleagues
noted that organisms in the sea consistently
removed nutrient elements from the water in a
fixed ratio (C : N : P=106 : 16 : 1). Subsequent
workers have found that nutrient concentrations
in the sea typically are present in those same ratios.
Transfer coefficient The rate constant which
determines the rate of transfer of gas from liquid
to gas phase.
See also
Air–Sea Transfer: Dimethyl Sulfide, COS, CS 2 , NH 4 ,
Non-Methane Hydrocarbons, Organo-Halogens.
Air–Sea Transfer: N 2 O, NO, CH 4 , CO.
Further Reading
Bange HW, Rapsomanikis S, and Andreae MO (1996)
Nitrous oxide in coastal waters. Global Biogeochemical
Cycles 10: 197--207.
Bange HW, Dahlke S, Ramesh R, Meyer-Reil L-A,
Rapsomanikis S, and Andreae MO (1998) Seasonal
study of methane and nitrous oxide in the coastal
waters of the southern Baltic Sea. Estuarine, Coastal
and Shelf Science 47: 807--817.
Barnes J and Owens NJP (1998) Denitrification and
nitrous oxide concentrations in the Humber estuary, UK
and adjacent coastal zones. Marine Pollution Bulletin
37: 247--260.
Cai W-J and Wang Y (1998) The chemistry, fluxes and
sources of carbon dioxide in the estuarine waters of the
Satilla and Altamaha Rivers, Georgia. Limnology and
Oceanography 43: 657--668.
de Angelis MA and Lilley MD (1987) Methane in surface
waters of Oregon estuaries and rivers. Limnology and
Oceanography 32: 716--722.
de Wilde HPJ and de Bie MJM (2000) Nitrous oxide in the
Schelde estuary: production by nitrification and
emission to the atmosphere. Marine Chemistry 69:
203--216.
Elkins JW, Wofsy SC, McElroy MB, Kolb CE, and Kaplan
WA (1978) Aquatic sources and sinks for nitrous oxide.
Nature 275: 602--606.
Frankignoulle M, Abril G, Borges A, et al. (1998) Carbon
dioxide emission from European estuaries. Science 282:
434--436.
Frost T and Upstill-Goddard RC (1999) Air–sea exchange
into the millenium: progress and uncertainties.
Oceanography and Marine Biology: An Annual Review
37: 1--45.
Law CS, Rees AP, and Owens NJP (1992) Nitrous oxide:
estuarine sources and atmospheric flux. Estuarine,
Coastal and Shelf Science 35: 301--314.
Liss PS and Merlivat L (1986) Air–sea gas exchange rates:
introduction and synthesis. In: Baut-Menard P (ed.) The
Role of Air–Sea Exchange in Geochemical Cycling,
pp. 113--127. Dordrecht: Riedel.
Muller FLL, Balls PW, and Tranter M (1995) Processes
controlling chemical distributions in the Firth of Clyde
(Scotland). Oceanologica Acta 18: 493--509.
Raymond PA, Caraco NF, and Cole JJ (1997) Carbon
dioxide concentration and atmospheric flux in the
Hudson River. Estuaries 20: 381--390.
GAS EXCHANGE IN ESTUARIES 481
global scale.
Conclusions
Many estuaries are supersaturated with a variety
of gases, making them locally, and occasionally
regionally, important sources to the atmosphere.
However, estuarine systems are also highly variable
in the amount of gases they contain. Since most estuaries studied to date are in Europe or the North
American continent, more data are needed before
global budgets can be reliably prepared.
Glossary
Air–water interface The boundary between the
gaseous phase (the atmosphere) and the liquid
phase (the water).
Catabolic Biochemical
process
resulting
in
breakdown of organic molecules into smaller
molecules yielding energy.
Denitrification Reduction of nitrate via nitrite to
gaseous endproducts (nitrous oxide and dinitrogen
gas).
Ebullition Gas transport by bubbles, usually from
sediments.
Estuary Semi-enclosed coastal body of water with
free connection to the open sea and within which
sea water is measurably diluted with fresh water
derived from land drainage.
Gas solubility The amount of gas that will dissolve
in a liquid when the liquid is in equilibrium with
the overlying gas phase.
Henry’s Law Constant Proportionality constant
relating the vapor pressure of a solute to its mole
fraction in solution.
Liquid laminar thickness The thickness of a layer at
the air/water interface where transport of a
dissolved species is controlled by molecular
(rather than turbulent) diffusion.
Molecular diffusivity (D) The molecular diffusion
coefficient.
Nitrification Oxidation of ammonium to nitrite
and nitrate.
Practical salinity scale A dimensionless scale for
salinity.
Redfield stoichiometry Redfield and colleagues
noted that organisms in the sea consistently
removed nutrient elements from the water in a
fixed ratio (C : N : P=106 : 16 : 1). Subsequent
workers have found that nutrient concentrations
in the sea typically are present in those same ratios.
Transfer coefficient The rate constant which
determines the rate of transfer of gas from liquid
to gas phase.
See also
Air–Sea Transfer: Dimethyl Sulfide, COS, CS 2 , NH 4 ,
Non-Methane Hydrocarbons, Organo-Halogens.
Air–Sea Transfer: N 2 O, NO, CH 4 , CO.
Further Reading
Bange HW, Rapsomanikis S, and Andreae MO (1996)
Nitrous oxide in coastal waters. Global Biogeochemical
Cycles 10: 197--207.
Bange HW, Dahlke S, Ramesh R, Meyer-Reil L-A,
Rapsomanikis S, and Andreae MO (1998) Seasonal
study of methane and nitrous oxide in the coastal
waters of the southern Baltic Sea. Estuarine, Coastal
and Shelf Science 47: 807--817.
Barnes J and Owens NJP (1998) Denitrification and
nitrous oxide concentrations in the Humber estuary, UK
and adjacent coastal zones. Marine Pollution Bulletin
37: 247--260.
Cai W-J and Wang Y (1998) The chemistry, fluxes and
sources of carbon dioxide in the estuarine waters of the
Satilla and Altamaha Rivers, Georgia. Limnology and
Oceanography 43: 657--668.
de Angelis MA and Lilley MD (1987) Methane in surface
waters of Oregon estuaries and rivers. Limnology and
Oceanography 32: 716--722.
de Wilde HPJ and de Bie MJM (2000) Nitrous oxide in the
Schelde estuary: production by nitrification and
emission to the atmosphere. Marine Chemistry 69:
203--216.
Elkins JW, Wofsy SC, McElroy MB, Kolb CE, and Kaplan
WA (1978) Aquatic sources and sinks for nitrous oxide.
Nature 275: 602--606.
Frankignoulle M, Abril G, Borges A, et al. (1998) Carbon
dioxide emission from European estuaries. Science 282:
434--436.
Frost T and Upstill-Goddard RC (1999) Air–sea exchange
into the millenium: progress and uncertainties.
Oceanography and Marine Biology: An Annual Review
37: 1--45.
Law CS, Rees AP, and Owens NJP (1992) Nitrous oxide:
estuarine sources and atmospheric flux. Estuarine,
Coastal and Shelf Science 35: 301--314.
Liss PS and Merlivat L (1986) Air–sea gas exchange rates:
introduction and synthesis. In: Baut-Menard P (ed.) The
Role of Air–Sea Exchange in Geochemical Cycling,
pp. 113--127. Dordrecht: Riedel.
Muller FLL, Balls PW, and Tranter M (1995) Processes
controlling chemical distributions in the Firth of Clyde
(Scotland). Oceanologica Acta 18: 493--509.
Raymond PA, Caraco NF, and Cole JJ (1997) Carbon
dioxide concentration and atmospheric flux in the
Hudson River. Estuaries 20: 381--390.
GAS EXCHANGE IN ESTUARIES 481