natwat3 - Chemical composition of natural waters 3: redox...

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1 Chemical composition of natural waters 3: redox chemistry Paradigm: The reduction-oxidation potential of a natural water body is a measure of where it sits on the continuum between oxidizing and reducing conditions; it is controlled by the dissolution of O 2 and biologically catalyzed redox reactions. A. Oxygen solubility O 2(g) O 2(aq) K H = 1.21 x 10 -3 M atm -1 (25°C) [O 2(aq) ] = (0.21 atm)(1.21 x 10 -3 M atm -1 ) = 254 μM x 32 μ g/ μ mol ÷ 1000 μ g/mg = 8.1 mg L -1 Describing aquatic environments with varying levels of dissolved oxygen: oxic conditions: measurable oxygen present (<0.06 mg L -1 to 16 mg L -1 ; <2 μ M to >500 μ M), obligate anaerobes cannot survive low O 2 conditions: <4 mg L -1 hypoxic conditions: <2 mg L -1 stressful for all aerobic organisms anoxic conditions: 0 mg L -1 only anaerobic * bacteria or archaea can survive *Note that environments may be oxic or anoxic , but not aerobic or anaerobic which are used to describe microorganisms that consume oxygen (
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natwat3 - Chemical composition of natural waters 3: redox...

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