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CH3041
ON-LINE LECTURE 5
pH THE MASTER VARIABLE
Natural Water Systems
pH 5.5 - 9
• Exogenic cycle : “large” acid-base titration
mountains dissolve ®
ocean sediments
• water is made acid by CO2, this dissolves
basic rocks and it is this balance that determines the pH of most water bodies.
• pH (& pE) control 2o clay
mineral formation, dissolution and direction of any alteration.
• pH controls biological
activity which in
turn influences [CO2]aq and DO.
turn influences [CO2]aq and DO.
• Acid rain/snow in Canada
(Ohio SO2)
Ž 100s lakes with pH < 5 (high [Al3+])
Ž reproduction and hatchling success = 0
Ž 100s lakes with pH < 5 (high [Al3+])
Ž reproduction and hatchling success = 0
