SOES_1005_Practical_4

# SOES_1005_Practical_4 - SOES1005 Practice Practical 4...

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SOES1005 - Practice Practical 4 Dissolved Gases in the Ocean By the end of this session you will be able to: 1 Convert between the commonly used units for gas concentration 2 Understand the major controls on gas solubility in seawater 3 Understand the concept of apparent oxygen utilisation (AOU) 4 Calculate AOU values in the oceans 5 Calculate nitrate and phosphate concentrations using AOU 6 Calculate the amount of organic carbon respiration using AOU THEORY NOTE THE MATERIAL BELOW IS ALSO GIVEN IN THE LECTURE POWER POINT PRESENTATIONS Gas Solubility: Gas molecules are continually passing into and out of the sea surface. When the rates of exchange are equal, the gas is said to be at equilibrium. At gaseous equilibrium, the atmospheric and aqueous concentrations remain constant over time. If present in excess in seawater, a gas will undergo net transport from the ocean to the atmosphere until equilibrium is reached, likewise a gas will undergo net transport into the ocean if its aqueous concentration is less than the equilibrium level. Gaseous equilibrium can be represented by the following expression: Where A(g) and A(aq) represent gas A in the gaseous state and aqueous solution. Standard Temperature and Pressure (STP): Because gases are compressible and volume is inversely proportional to pressure, we need to have a consistent way of expressing data. Standard temperature is 0 o C or 273K, standard pressure is 1 atmosphere (atm). 1 mole of gas occupies 22.4 L at STP.

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