INTRO TO MARINE SCIENCE - Lecture 7

Chemistry of Seawater: Salts

Compounds can _________ (break apart) in solvents.

dissociate

Cations

positive ions

Anions

negative ions

Conservative Constituents

• major dissolved ions not generally removes or modified by organisms

• relatively low rate of chemical reaction

Nonconservative Constituents

• generally present at much lower concentrations

• concentrations modified by biological and chemical processes

• dissolved gasses, nutrients, etc

What accounts for most of the positively charged ions found in the ocean?

earth’s crust

Physical/chemical weathering breaks rock apart and allows what to happen?

water to dissolve out salts

Where is it believed that the most negative ions (anions) derived from?

earth’s mantle and early atmosphere

What is the calculated age of the oceans?

3.5 Gy

rate of salt addition = 

rate of salt removal

Evaporite deposition

trapping of seawater on land

Adsorption and precipitation 

sinking clays bind positive ions and eventually deposit them as sediment

Biological activity

biological oozes

Chemical and physical ion exchange at tectonic spreading centers

entire oceanic volume centers over 10 My

Residence time

average amount of time that a substance remains in ocean water

Residence time = total amount of substance/rate of __________________.

supply or removal