The Chemistry of Seawater Chapter 6

The pH of Seawater H +  Hydrogen cation OH -  Hydroxide anion H + = OH - H + < OH - H + > OH - NeutralAlkalineAcidic

pH Measurement

Buffering Capacity of CO 2 Buffer  Substance that prevents sudden, or large, changes in acidity or alkalinity of a solution CO 2 + H 2 O  H 2 CO 3  H + + HCO 3 -  2H + + CO 3 2- Too basic Too acidic

Salinity Units of Concentration  Weight  Volume  Moles

Ocean Salinity Measured in grams of salt per kilogram of seawater  1kg of seawater is made up of 965 g of water and 35 g of salt  35‰

Dissolved Salts Ionic bonds

Major Constituents

Conservative ions Nonconservative ions

Sources of Salt Chemical weathering  Riverine input  Most cations  Anions from Earth’s mantle

Sources of Salt Volcanic gases Hydrogen sulfide Sulfur dioxide Chlorine

Sources of Salt Hydrothermal vents  Discovered in 1977  Geyser on the seafloor  Spews super-hot, mineral-rich water  Very biodiverse

Sources of Salt Hydrothermal vents  Black Smokers Hottest of the vents Spew iron and sulfide, which combine to form iron monosulfide  White Smokers Cooler temp Barium, Calcium and Silicon

Regulating the Salt Balance

Rivers vs. Oceans

Residence Time RT = Amount of ion Rate of sup/removal

Principle of Constant Proportions Constant composition 1819 – Alexander Marcet 1865 – Georg Forchhammer Challenger expedition  William Dittmar  Chloride ion

Determining Salinity Electrical conductivity  More ions = greater conductance  Salinometer  Salinity (‰) = X chlorinity (‰)