Composition of Ocean Waters

Salts and Salinity

Ions Ions are stable forms of elements that acquire an electrical charge by gaining or losing electrons Elements that lose electrons and become positively charged are called cations. Elements that gain electrons and become negatively charged are called anions. Cations: K +, Na +, Mg 2+, Ca 2+ Anions: Cl -, CO 3 -2, SO 4 -2

Salts KCl, NaCl, MgCl 2, CaCO 3, CaSO 4 Cations: K +, Na +, Mg 2+, Ca 2+ Anions: Cl -, CO 3 -2, SO 4 -2 Salts are formed by combining cations and anions to form solids that have no charge. K + + Cl - = KCl Ca Cl - = CaCl 2

Conversely, if solid salts are mixed with water they dissolve and the ions go into solution KClK + + Cl - NaClNa + + Cl - Water solid solution CaCO 3 CaSO 4 Ca +2 and CO 3 -2 Ca +2 and SO 4 -2

Ocean Salinity originates from dissolution of salts and erosion of rocks and minerals as water moves at or below the earth surface River water contains dilute amounts of dissolved salts that are ultimately delivered to the oceans As water evaporates, the oceans concentrate the salts to levels far exceeding those found in rivers. Average Ocean Salinity = 3.5%

What kind of Salts?

KCl NaCl MgCl 2 CaCO 3 CaSO 4 KCl NaCl MgCl 2 CaCO 3 CaSO 4 River Water Ion Carbonate Calcium Sulfate Silicate Chloride Sodium Magnesium Potassium River Salt Composition Dominated by Carbonate, Calcium, Sulfate, and Silicate KAlSi 3 O 8 CaAl 2 Si 2 O 8 NaAlSi 3 O 8 KAlSi 3 O 8 CaAl 2 Si 2 O 8 NaAlSi 3 O 8

Ocean Salt Composition Ion Chloride Sodium Sulfate Magnesium Calcium Potassium Carbonate Silicate Sea Water (%) Dominated by Chloride and Sodium Na + and Cl - (85% of total) Cl - Na +

River Water Sea Water Ion Carbonate Calcium Silicate Sulfate Chloride Sodium Magnesium Potassium Percentage of Total Dissolved Minerals } 79% } 85%

Enrich Chloride and Sodium in ocean water Remove Silica, Calcium, Carbonate from river water Alterations

sodium, potassium, and ammonium salts are soluble chloride, bromide and iodide salts are soluble. NaCl Solubility 350 g/L Solubility: ease of salt dissolution in water Enriching Sodium and Chloride Once these types of ions reach the oceans they stay dissolved

Ion Chloride Sodium Sulfate Magnesium Calcium Potassium Carbonate Silicate Sea Water (%) Both chloride salts and sodium salts are extremely soluble in water and do not combine with other elements to form solids

Enrich Chloride and Sodium in ocean water Remove Silica, Calcium, Carbonate from river water Alterations

Calcium and Carbonate Removal Incorporation into shells of marine invertebrates Ca 2+ + CO 3 2- = CaCO 3

Diatoms Life and Silica Remove Silica, Calcium, Carbonate Use silica as structural material

River Water Sea Water Ion Carbonate Calcium Silicate Chloride Sodium Magnesium Potassium Sulfate Percentage of Total Dissolved Minerals

Extra Credit Questions 1. Cations become positively/negatively charged by gaining/losing electrons. 2. The dominant ion in river water is ___ 3. The dominant ion in sea water is ___ 4. Marine invertebrate shells are made from ____

Other Constituents in Ocean Water

The Oceans, Heat, and Carbon Dioxide

Middle Ages Industrial Revolution 380 ppm CO 2 Global Temperature

Ocean Temperature Oceans can buffer changes in atmospheric temperature

Gas Gases/Heat Present and Future Problems Warmer oceans ?

October, 2005

Rising CO 2 and Ocean Chemistry

Gases Dissolve in Water Gas Gases dissolution

Composition of the Atmosphere Gases Nitrogen78.1% Oxygen20.9% Argon0.93% CO %

Oxygen Solubility: g/L (20 o C)

Carbon Dioxide C O O Solubility = 1.69 g/L

Middle Ages Industrial Revolution removed about 118 billion metric tons of CO 2. Between 1800 and 1994, the oceans have Equivalent to 48 percent of all fossil fuel emissions 380 ppm Solubility = 1.69 g/L CO 2 Buffering

Carbon Dioxide also is an Acid

CO 2 Water Acid CO 2 + H 2 O H 2 CO 3 H 2 CO 3 H + + HCO 3 - H + is acid Acids (H + ) are reactive and dissolve a number of substances Dissolution of Carbon Dioxide

Common Acid Dissolution CuO + 2HCl → CuCl 2 + H 2 O Ag 2 O + 2 HCl → 2 AgCl + H 2 O View edEx's map Taken in a place with no name (See more photos or videos here)more photos or videos here CaCO 3 + H + Ca 2+ + HCO 3 - Fe 2 O 3 + 6H + 2Fe H 2 O Fe 2 O 3 CaCO 3

Invertebrate shells and skeletons largely CaCO 3 Corals, “lithic” plankton, clams, oysters

CaCO 3 + H + Ca 2+ + HCO 3 - CO 2 Water H+H+ Acidification of the oceans Inhibits the calcification and growth of invertebrates Analysis of coral cores shows a steady drop in calcification over the last 20 years pH change: to 8.104

Coral Reef Bleaching Temperature and Acidity

Anthropogenic Inputs of Solutes to the Oceans Homework II Oceanic Dead Zones Due Friday, October 2 nd in class Assignment is posted on the website