© 2016 Cengage Learning. All Rights Reserved. 7 Oceanography, An Invitation to Marine Science | 9e Tom Garrison Ocean Chemistry

© 2016 Cengage Learning. All Rights Reserved. Salt in Solution

© 2016 Cengage Learning. All Rights Reserved. 1. Water is a powerful solvent –The concentration of dissolved inorganic solids in water is its salinity. 2. Though salinity may vary with location, the ratio of dissolved solids in seawater is constant 3. Gases dissolve in seawater and cold water can hold more gas in solution than warm water Key Concepts (5)

© 2016 Cengage Learning. All Rights Reserved. 4. The ocean is a vast reservoir of carbon and the dynamics of carbon exchange between ocean and atmosphere affect Earth’s climate. 5. The ocean’s acid-base (pH) balance varies with depth and dissolved components. Carbonate chemistry serves to moderate (buffer) wide swings in oceanic pH. Key Concepts (cont’d.)

© 2016 Cengage Learning. All Rights Reserved. A. Water cycles constantly in the hydrologic cycle. B. Solution – homogeneously dispersed 1. Solvent – most abundant constituent 2. Solute – less abundant constituent C. Ion – molecule with unbalanced charge 1. Move through water in solution by diffusion 2. Saturation – no more will dissolve 3. Precipitation – forming crystals from solution I. Water Is a Powerful Solvent

© 2016 Cengage Learning. All Rights Reserved. Stepped Art Condensation Precipitation 111,000 Lakes Ocean Groundwater Precipitation 392,000 Glaciers Runoff 46,000 Transpiration and Evaporation 66,000 Evaporation 437,000

© 2016 Cengage Learning. All Rights Reserved. Simplified Hydrologic Cycle

© 2016 Cengage Learning. All Rights Reserved. A. Average seawater salinity 3.5%. B. Colligative properties 1. Heat capacity decreases with increasing salinity. 2. Salinity increases; freezing point decreases 3. Salinity increases; evaporation slows 4. Salinity increases; osmotic pressure increases II. Seawater Consists of Water and Dissolved Solids

© 2016 Cengage Learning. All Rights Reserved. Ocean Salinity Is Mostly Sodium and Chlorine Ions

© 2016 Cengage Learning. All Rights Reserved. C. Sources 1. Weathering of surface rock 2. Excess volatiles – from outgassing D. Ratio of dissolved solids is constant –Forchhammer’s principle / principle of constant proportions Components of Salinity Came from, and Have Been Modified by, Earth’s Crust

© 2016 Cengage Learning. All Rights Reserved. Processes That Regulate the Major Constituents in Seawater

© 2016 Cengage Learning. All Rights Reserved. F. The ocean is in chemical equilibrium G. Conservative constituents – long residence time H. Nonconservative constituents – short residence time E. Salinity Is Calculated by Seawater’s Conductivity

© 2016 Cengage Learning. All Rights Reserved. An Average of Worldwide Ocean Surface Salinity

© 2016 Cengage Learning. All Rights Reserved. A. Nitrogen – most abundant dissolved gas in seawater B. Oxygen – critical to marine life C. Carbon dioxide – very soluble in water 1.Moves quickly from atmosphere to ocean 2.Moves slowly from ocean to atmosphere D. Gas concentrations vary with depth III. Gases Dissolve in Seawater

© 2016 Cengage Learning. All Rights Reserved. How Concentrations of Oxygen and Carbon Dioxide Vary with Depth

© 2016 Cengage Learning. All Rights Reserved. A. Acid – releases hydrogen ion in solution B. Base – hydroxide ion combines with hydrogen ion to form water C. pH scale – measures concentration of hydrogen ions in a solution –Seawater pH about 8.0 due to dissolved CO 2 IV. The Ocean’s Acid-Base Balance Varies with Dissolved Components and Depth

© 2016 Cengage Learning. All Rights Reserved. Carbon Dioxide Combines Readily with Seawater to Form Carbonic Acid

© 2016 Cengage Learning. All Rights Reserved. The pH of Seawater

© 2016 Cengage Learning. All Rights Reserved. The Variation of pH with Depth

© 2016 Cengage Learning. All Rights Reserved. The Ocean Is Becoming More Acidic

© 2016 Cengage Learning. All Rights Reserved. 1. Water can dissolve more substances than any other natural solvent. 2. The ocean is in chemical equilibrium. 3. Dissolved substances in seawater exist as ions. 4. Dissolved gases are important in the ocean. Chapter in Perspective

© 2016 Cengage Learning. All Rights Reserved. If outgassing continues today, why aren’t the oceans getting bigger? By now shouldn’t they have covered the continents? There is more than $28 million worth of gold (at 2014 prices) in each cubic kilometer of seawater. Why don’t we remove some of it and pay off the national debt? Some Questions from Students