Phase Diagram for Water. Hydrogen Bonding in Water.
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Transcript of Phase Diagram for Water. Hydrogen Bonding in Water.
Phase Diagram for Water
Hydrogen Bonding in Water
Transfer Processes and Storage (Reservoirs)
Residence Time Time to replace a substance in a reservoir, or
average length of time a substance exists in a reservoir
Total Amount
Rate of Addition or Removal
Water in atm. = 11 days
Water on land = 1 year
Water in oceans = 3500 years
Importance of Water Cycle to the Earth System
Transfers heatSea level changeGreenhouse gasGlobal warming will affect itRenewable resource; energy sourceWeathering and erosion agent Interacts with the Carbon Cycle
Energy Absorbed and Released During Phase Changes of Water
Difference in Heating of Land and Ocean
Summer Winter
A True Color Picture of Earth
amount
size
Sea level also changes due to temperature.
Top Climate-Water Issues
Sea-level rise
Snow-pack loss
Redistribution of water resources
Water vapor feedback
Ice Sheet Melting & Sea Level Rise
Rate of Sea Level Rise
(Data from IPCC WGI Summary for Policymakers)
Sea-Level Rise and Water Supplies
Saltwater contamination of coastal ground-water wells
Salinity encroachment on municipal water intakes from rivers
Loss of glacial meltwaterCoastal States
Composition of Natural Waters
Carbonate Equilibria:CO2 + H2O
•CH3COOH H+ + CH3COO-
•CH2O + O2 => CO2 + H2O
•CO2 + H2O H2CO3
•H2CO3 H+ + HCO3-
Chemical WeatheringLimestones
H2CO3 + CaCO3 <==> Ca+2 + 2HCO3-
Silicates
2H2CO3 + NaAlSi3O8 ==> Na+ + 2HCO3-
+ clay minerals
2H2CO3 + CaAl2Si2O8 ==> Ca+2 + 2HCO3-
+ clay mineralsWhat happens to CO2 during chemical weathering?
Role of water? pH of river water? Seawater?
Chemical Weathering
Chemical Composition of Seawater
Six major constituents Two anions - Cl-, SO4
=
Four cations - Na+, Mg+, Ca+2, K+
pH is buffered by CO2 - CaCO3 system
Residence Time
Time to replace a substance in a reservoir, or average length of time a substance exists in a reservoir
Total Amount Rate of Addition or Removal
Sources of Sea Salt
Weathering of continentsVolcanic eruptionsHydrothermal vents
Oxygen Concentration
Solubility depends on T and SalinityWarm, saline water holds less O2
Oxygen consumption in water columnRespiration by animals
Mixing rate of oceansSluggish mixing - low rate of O2 replenishment
Carbon Dioxide Concentration
Solubility depends on T and SCO2 is released by animalsMixing rate of oceansAffects pH of seawater (What is its pH?)Similar to concentration profiles of
nutrients (PO4-3, NO3
-)
X
pH - function of dissolved CO2
Reacts with water to produce carbonic acid, which releases H+ ions
• CO2 + H2O H2CO3 H+ + HCO3- H+ +
CO3-2
H2CO3 is carbonic acid, HCO3- is the
bicarbonate ion and CO3-2 is the
carbonate ion
CO2 in Seawater
Carbonate system - buffers against large shifts in pH
Carbonates dissolve in deep water Higher CO2 makes the water less alkaline (pH ≈
7.8)
Warm, shallow water has less dissolved CO2
More alkaline than deep water (pH ≈ 8.2) Carbonate sediments are abundant
CO2 in Seawater
Carbonate System
Precipitation of CaCO3
----
HCO3- + OH- => CO3
= + H2O
Calcite (or Calcium Carbonate) Compensation Depth (CCD)
CaCO3 dissolves in deeper water due to higher CO2 content in deep water
Deepest sediments have little or no CaCO3
CCD is deeper (less dissolution) in the Atlantic Ocean than in the Pacific
Why?
The Carbonate
System
Changes in the CCD for the
Past 100 m.y.