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Unformatted text preview: 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 , Ca Anions: Cl , CO , SO
+ + 2+ 3-2 4-2 2+ Salts
Salts are formed by combining cations and anions to form solids that have no charge.
Cations: K , Na , Mg , Ca Anions: Cl , CO , SO
+ + 2+ K+ + Cl- = 3-2KCl 4-2 2+ Ca+2 + 2Cl- = CaCl2
KCl, NaCl, MgCl , CaCO , CaSO
2 3 4 Conversely, if solid salts are mixed with water they dissolve and the ions go into solution solid solution
Water KCl NaCl
CaCO3 CaSO4 K + Cl Na + C-l +
+ Water CO3-2
- Ca+2 and SO4-2 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? River Salt Composition
KCl NaCl MgCl
2 KAlSi3O8 CaAl2Si2O8 NaAlSi3O8 CaCO
3 Ion Carbonate Calcium Sulfate Silicate Chloride Sodium Magnesium Potassium River Water 35.15 20.39 12.14 11.67 5.68 5.79 3.41 2.12 CDominated by Carbonate, Calcium, Sulfate, and Silicate aSO
4 Ocean Salt Composition
Ion Sea Water (%) Chloride 55.04 Sodium 30.62 Sulfate 7.68 Magnesium 3.69 Calcium 1.15 Potassium 1.10 Carbonate 0.40 Silicate .0004 Cl- Na+ Na+ and Cl(85% of total) Dominated by Chloride and Sodium Percentage of Total Dissolved Minerals River Water Ion Sea Water 35.15 Carbonate .40 20.39 Calcium 1.15 79% 11.67 Silicate .0004 12.14 Sulfate 7.68 5.68 Chloride 55.04 85% 5.79 Sodium 30.62 3.41 Magnesium 3.69 2.12 Potassium 1.10 } } Alterations • Enrich Remove Chloride and Sodium in ocean water Silica, Calcium, Carbonate from river water Enriching Sodium and Chloride
Solubility: ease of salt dissolution in water sodium, potassium, and ammonium salts are soluble chloride, bromide and iodide salts are soluble.
Once these types of ions reach the oceans they stay dissolved NaCl Solubility 350 g/L Ion Chloride Sodium Sulfate Magnesium Calcium Potassium Carbonate Silicate Sea Water (%) 55.04 30.62 7.68 3.69 1.15 1.10 0.40 .0004 Both chloride salts and sodium salts are extremely soluble in water and do not combine with other elements to form solids Alterations • Enrich Remove Chloride and Sodium in ocean water Silica, Calcium, Carbonate from river water Calcium and Carbonate Removal
Incorporation into shells of marine invertebrates Ca2+ + CO32- = CaCO3 Life and Silica
• Remove Silica, Calcium, Carbonate Diatoms Use silica as structural material Percentage of Total Dissolved Minerals Ion Carbonate Calcium Silicate Chloride Sodium Magnesium Potassium Sulfate River Water Sea Water .40 35.15 1.15 20.39 .0004 11.67 55.04 5.68 30.62 5.79 3.69 3.41 1.10 2.12 7.68 12.14 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 380 ppm Global Temperature CO2 Middle Ages Industrial Revolution Ocean Temperature Oceans can buffer changes in atmospheric temperature Present and Future Problems Gases/Heat Gas Warmer oceans ? October, 2005 Rising CO2 and Ocean Chemistry Gases Dissolve in Water Gases Gas dissolution Composition of the Atmosphere Gases Nitrogen 78.1% Oxygen 20.9% Argon 0.93% CO
2 0.038% Oxygen
Solubility: 0.043 g/L
(20oC) Carbon Dioxide - O C +
O - Solubility = 1.69 g/L 380 ppm CO2 Solubility = 1.69 g/L Between 1800 and 1994, the oceans have removed about 118 billion metric tons of CO2. Equivalent to 48 percent of all fossil fuel emissions Middle Ages Industrial Revolution Buffering Carbon Dioxide also is an Acid Dissolution of Carbon Dioxide CO2 + H2O H CO
2 3 H2CO3 H+
H+ is acid
Water + HCO
3- C O2 Acid Acids (H+) are reactive and dissolve a number of substances Common Acid Dissolution CuO + 2HCl → CuCl2 + H2O Ag O + 2 HCl → 2 AgCl + H O
2 2 CaCO3 Fe2O3 Fe2O3 + 6H+ CaCO3 + H+ 2Fe3+ + 3H2O Ca2+ + HCO3- Invertebrate shells and skeletons largely CaCO3
Corals, “lithic” plankton, clams, oysters CO2 Water H+ pH change: 8.179 to 8.104 CaCO3 + H+ Ca2+ + HCO3- 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 Coral Reef Bleaching Temperature and Acidity
http://www.npr.org/templates/story/story.php?storyId=17243164 Anthropogenic Inputs of Solutes to the Oceans Homework II Oceanic Dead Zones Due Friday, October 2nd in class Assignment is posted on the website ...
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- Fall '09