Environmental Chemistry
Chapter 19:
Sustaining the Geosphere
Copyright © 2011 by DBS
Contents
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Managing the Geosphere
The Angry Earth
Earthquakes
Volcanoes
Volcanoes, Air Pollution, and the Geosphere
Destructive Land Surface Movement
The Vulnerable Coasts
Building the Geosphere
Digging the Dirt
Modifying the Geosphere to Manage Water
Water Pollution and the Geosphere
Effects of Human Activities on the Geosphere
Waste Disposal and the Geosphere
Derelict Lands and Brownfields
Earth as a Source of Essential Materials
Evaluation of Mineral Resources
Extraction and Mining
Metals
Nonmetal Mineral Resources
How Long Will Essential Minerals Last?
Green Sources of Minerals
Managing the Geosphere
Managing the Geosphere
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This chapter discusses three major related aspects of the geosphere
1. Destructive geospheric phenomena
• Volcanic eruptions
• Earthquakes
• Landslides
2. Preservation of the geosphere and modifications to it that can preserve
and enhance geospheric quality, such as restoration of contaminated
areas
3. The geosphere as a source of raw materials and the sustainability
challenges resulting therefrom
The Angry Earth
The Angry Earth
•
Solid earth consists of plates that rest on semi-molten rock below which
is very hard liquid rock (magma)
– Earthquakes from movement of solid Earth
– Molten rock ejected from volcanoes
•
Earth’s surface rock is in a constant process of achieving equilibrium
– Erosion
– Landslides
Earthquakes
Earthquakes
•
Sudden movement of tectonic plates relative to each other
•
Earthquakes are manifested by often violent shaking of ground
•
Terms pertaining to earthquakes
– Focus is location of original movement
– Epicenter is surface location above focus
– Seismic waves transmit energy from location of focus
– Body waves are seismic waves through interior of Earth
– Surface waves are seismic waves on Earth’s surface
– P-waves are compressional vibrations
– S-waves are manifested by sideways oscillations
– Seismographs detect earthquake wave motion
Earthquakes
•
Magnitude of earthquakes - Expressed on Richter scale
– Open ended, increase of 1 denotes 10-fold increase in intensity
– 4-5: Minor earthquakes
– Above 5: Damage
– Higher than 8: Great earthquakes
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Liquefaction of soil is damaging effect of earthquakes
•
Earthquake damage tends to be higher on poorly consolidated soil
•
Substantial displacement of ground can occur on surface
•
Secondary Effects of Earthquakes
•
Greatest secondary effects are due to destructive ocean wave tsunamis
(Section 19.7)
Earthquakes
Mitigating Earthquake Effects
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Earthquakes cannot be predicted or prevented
•
General locations are well known
•
Earthquakes that occur within a plate and rupture it are especially destructive
•
Adaptation measures to lessen effects
–
=Stone structures especially vulnerable
– Very strong buildings may even tip over
• The most earthquake-resistant buildings are those that are flexible and dissipate
earthquake energy
– Wood frame buildings are superior to stone structures
Volcanoes
Volcanoes
•
Volcanoes are openings in the ground from which molten rock (lava), gases,
steam, ash, and particles are ejected
– Usually a mound (often very tall), Figure 19.1
Volcanoes
•
Damaging Aspects of Volcanoes
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Molten lava up to 1400˚C
•
Pyroclastics consisting of fragments of rock and lava
•
Ash and dust may bury entire areas (ancient Pompei)
•
Nuée ardentee consisting of a “glowing cloud” of hot toxic gases and particles
flowing down a volcano side at up to 100 km/hr
•
1902 nuée ardente by the eruption of Mont Pelée in the Caribbean killed up to
40,000
•
Phreatic eruption when infiltrating water is superheated by hot magma causing a
volcano to explode
•
Adverse health effects of gases and atmospheric particles
•
Climate cooling from particles and sulfuric acid aerosols produced by sulfur
gases
Volcanoes
Damaging Aspects of Volcanoes
•
Molten lava up to 1400˚C
•
Pyroclastics consisting of fragments of rock and lava
•
Ash and dust may bury entire areas (ancient Pompei)
•
Nuée ardentee consisting of a “glowing cloud” of hot toxic gases and particles
flowing down a volcano side at up to 100 km/hr
•
1902 nuée ardente by the eruption of Mont Pelée in the Caribbean killed up to
40,000
•
Phreatic eruption when infiltrating water is superheated by hot magma causing a
volcano to explode
•
Adverse health effects of gases and atmospheric particles
•
Climate cooling from particles and sulfuric acid aerosols produced by sulfur
gases
Volcanoes
Notable Volcanic Eruptions
•
79 AD eruption of Mount Vesuvius
– Buried Roman city of of Pompei in volcanic ash
•
1815 Tambora in Indonesia
– Ejected an estimated 30 km3 of material, some reaching stratosphere
•
1883 phraetic eruption of Krakatoa in Indonesia
– Equivalent to 100 megatons of TNT
– Dust blown 80 km into the stratosphere
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1980 explosion of Mount St. Helens in Washington State
– Ejected about 1 km3 of material
– Spread ash over about half of continental U.S.
– $1 billion in damages
– Estimated 62 people killed
Volcanoes
Mitigating Effects of Volcanoes
•
Avoid them
•
Fire-resistant structures
•
Sometimes dams can be constructed to divert lava
Volcanoes, Air Pollution, and the
Geosphere
Volcanoes, Air Pollution, and the
Geosphere
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Volcanoes emit toxic and acidic gases
• CO
•
• HCl
• H2S
• SO2 • CO2
• CH4
Climate change from volcanic eruptions:
– 1815 Tambora volcano was followed by “the year without a summer” and
perceptible cooling for 10 years
– 1982 El Chicón eruption was rich in SO2 and formed a sulfuric acid aerosol
that persisted for 3 years lowering global temperature by several tenths of a
degree
Volcanoes, Air Pollution, and the
Geosphere
Geospheric Sources of Air Pollution Other Than Volcanoes
•
Heavy metals and sulfur dioxide from smelting sulfide ores from the geosphere
has contaminated air and land
•
Air pollutants from soil and its cultivation
– Greenhouse gas CH4
– N2O
•
Soil and rock can remove atmospheric pollutants
– CO metabolized by soil microorganisms
– CaCO3 can neutralize atmospheric acids
Volcanoes, Air Pollution, and the
Geosphere
Geospheric Topography Influence on Air Pollution (Figure 19.2)
Destructive Land Surface Movement
Destructive Land Surface Movement
•
Surface features formed by upward movement from Earth’s crust and action of
weathering and erosion
•
Human influences
– Sediments
– Removal of vegetation
– Improper excavations
– Beneficial effects of proper land management such as terraces, waterways,
conservation tillage
Destructive Land Surface Movement
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Mass Movements and Landslides
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Figure 19.3. Illustration of a Landslide
Destructive Land Surface Movement
Harmful Effects of Landslides
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Landslide into the reservoir behind the Vaiont Dam, Italy, killed 2,600 people in
1963
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Mt. Huascaran, Peru, killed 20,000 people in 1970
•
Tendency toward landslides can be predicted
•
Warning of landslides by devices such as tilt meters
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Harmful Surface Movements Other Than Landslides
– Rockfalls
– Creep (slow, gradual movement that can cause much damage)
– Frost and freeze/thaw cycles
The Vulnerable Coasts
The Vulnerable Coasts
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Regions of high population
•
75% of U.S. population near coastal areas
•
2005 destruction of New Orleans by hurricane Katrina
•
Extremely high insurance costs in coastal areas
Tropical cyclones
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Hurricanes in Atlantic and Gulf of Mexico
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Typhoons in Indian Ocean and Pacific
•
Cause devastating storm surges
The Vulnerable Coasts
Tsunamis
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High waves, usually caused by earthquakes
•
December 26, 2004, Indian Ocean tsunami
– Result of magnitude 9.0 quake off the west coast of Northern Sumatra
– Especially devastating to low-lying areas of Sri Lanka
– Killed approximately 200,000
The Vulnerable Coasts
Coastal Erosion (Figure 19.4)
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• Normal erosive processes
–
• Storm surges
• Human influences
Much of the loss results from unwise construction siting
The Vulnerable Coasts
Preserving the Coastline
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Beach nourishment (restoration of sand)
•
Coastlines
The Threat of Rising Sea Levels
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Melting glaciers can raise sea levels
– Greenland
– Antarctica
Building the Geosphere
Building on the Geosphere
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Engineering Geology
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Large public works projects
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Earth moving
–
Digging
–
Boring
• Dependent upon nature and properties of the geosphere on which they are located
– Load-bearing capacity
– Faults
– Fractures
Site Evaluation
– Ground stability
– Tendency toward landslides
– Water infiltration
– Depth of water table
– Faults
– Fractures
Building on the Geosphere
Kinds of Structures on the Geosphere
Highways:
• Topography
• Base rock
• Available construction materials
Railroads:
• Gradients
• Cuts through hills
• Tunnels
Bridges
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Stability of strata
• Grouting may be required
Airports:
• • Level topography
• Stability of strata
Tunnels:
• Stability of strata
• Water infiltration potential
Buildings:
• Stability of strata
• Absence of underground voids
Dams:
• Consideration of fissures leading to leakage
• Grouting may be necessary
Mines:
• Stability of strata
• Gas (methane)
• Water infiltration
Digging the Dirt
Digging the Dirt
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Many kinds of excavations
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Simple dirt excavation
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Blasting of rock may be required
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Water infiltration is frequently a problem
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Slumping
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Excavations Below the Surface
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Tunnels
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Mines
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Subways
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Underground caverns
Seismic testing often used
Digging the Dirt
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Figure 19.5. Underground Tunnel to Convey Water
Digging the Dirt
Green Underground Storage
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Underground excavations rank high in sustainability
– Temperature stability
– No outside structure maintenance
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Storage facilities in limestone formations most common
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Salt Dome Storage of Petroleum
Figure 19.6. Underground storage of
petroleum such as that in the U.S.
National Petroleum Reserve
Modifying the Geosphere to Manage
Water
Modifying the Geosphere to Manage
Water
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Hydrogeology addresses hydrosphere/geosphere interaction
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Water both on top and within geosphere
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Water falling on the geosphere as precipitation
– Flow on surface in streams
• Held in soil
– Infiltrate to groundwater aquifers
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Groundwater recharge is desirable
– Hampered by paving
– May be done artificially
• Evaporate to atmosphere
Modifying the Geosphere to Manage
Water
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Flooding
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Water leaves stream banks and spreads over flood plain
•
–
Can be worsened by human activities such as stream channeling
–
Can be controlled with levees
–
Levee failure can cause serious problems
Figure 19.7. Influence of runoff on flooding
Modifying the Geosphere to Manage
Water
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Figure 19.8. Reservoir to Control Flooding
Modifying the Geosphere to Manage
Water
China’s Three Gorges Dam Project
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Yangtze River, dam completed 2006
•
Largest dam and largest single powerplant project in one location
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Reservoir as deep as 175 meters
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Greatest consumption of dirt, stone, concrete
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1.13 million people displaced
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Has controlled flooding
•
Generating enormous amounts of sustainable electrical energy
•
Some problems
– Water pressure has affected surrounding geological strata
– Landslides
– Rural population displaced to higher ground have depleted forests
Water Pollution and the Geosphere
Water Pollution and the Geosphere
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Geosphere may be badly damaged by water pollution
– Sediments that fill and clog water bodies
– Sediments contaminated with heavy metals, PCBs, other
•
Geosphere as a source of pollutants
– Point sources from a single, identifiable source
– Nonpoint sources, such as fertilizer on agricultural land
– Heavy metals
– Acid from exposed sulfides
Effects of Human Activities on the
Geosphere
Effects of Human Activities on the
Geosphere
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Direct effects, such as strip mining or land alteration for construction
•
Indirect effects, such as subsidence due to removal of groundwater
Extraction of Geospheric Resources: Surface Mining
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Over half of U.S. coal and virtually all rock and gravel by surface mining
•
In the past, improper surface mining has scarred and devegetated large areas
leaving them subject to erosion
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Properly done and restored, surface mining need not be harmful
– Reservoirs left from rock and sand mining
•
Approaches to surface mining
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Dredging of underwater deposits
– Removal of surface spoil in open pit mining
– Strip mining in which material is removed in strips and overburden from a strip
is deposited in the preceding strip
Effects of Human Activities on the
Geosphere
Environmental Effects of Mining and Mineral Extraction
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Adverse effects of underground mining including subsidence, disturbance of
aquifers
•
One of the more damaging effects is acid from pyrite, FeS2
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One of the most damaging mining byproducts consists of tailings remaining from
beneficiation of ores
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Pyrite in coal tailings produces acid
•
Uranium tailings used for construction fill have caused radioactive radon
emissions into buildings
Waste Disposal and the Geosphere
Waste Disposal and the Geosphere
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Ability to receive wastes is an important aspect of geosphere’s natural capital
Waste Disposal and the Geosphere
Municipal refuse
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Sanitary landfill consisting of refuse piled on top of ground or in depressions and
covered with soil
•
Closed sanitary landfills can be used for recreational purposes
•
Generally not suitable for buildling construction
•
• Settling
•
Despite restrictions, hazardous materials get into landfills
•
Sanitary landfills produce gases
• Gas production
{CH2O}(biomass) + O2  CO2(g) + H2O
2{CH2O}(biomass)  CO2(g) + CH4(g)
• CH4 is a premium fuel often harvested from municipal landfills
– Gases can cause pollution problems
– Leachate from landfills may pollute water
Waste Disposal and the Geosphere
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Figure 19.9. Construction of a Sanitary Landfill
Waste Disposal and the Geosphere
Landfills for Hazardous Substances
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Secure landfills are used for hazardous substances
– Control gas emissions
– Leachate control
•
Low-level and high-level radioactive wastes in special underground storage
repositories
Derelict Lands and Brownfields
Derelict Lands and Brownfields
•
Derelict lands and brownfields are properties damaged by anthrospheric
acitivities that are unsuitable for additional use without restoration
– Often contaminated with hazardous substances
– Generally from abandoned industrial enterprises, mining
•
Many kinds of brownfields
– Rail yards
– Trucking depots
– Oil tank farms
– Textile mills
– Abandoned manufacturing plants
•
Restoration of brownfields
– Often in central locations
•
Smart growth for guidance to restoration of brownfields
Earth as a Source of Essential Materials
Earth as a Source of Essential Materials
•
Challenge to utilize available resources cost-effectively consistent with
– Resource conservation
– Environmental protection
– Material recycling
•
Metals often found in batholiths, masses of igneous rock extruded to near
surface
Deposits from Igneous Rocks and Magmatic Activity
•
Pegmatite is coarse-grained mineral material that separates from molten silica
magma and can be separated by physical means
– Example: Magnetite, Fe3O4
Deposists from Hydrothermal Activity
•
Hydrothermal mineral deposits that crystallize as hot solutions cool
– Example: Sulfides of lead, copper, and zinc
Earth as a Source of Essential Materials
Deposits Formed by Sedimentary or Metamorpic Processes
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Sedimentary deposits formed in association with sedimentary rocks
•
Evaporites formed when seawater evaporates
•
Many iron oxides were formed when the atmosphere became oxidizing by the
evolution of molecular oxygen by cyanobacteria photosynthesis
•
Placer deposits produced by flowing water
•
Metamorphic deposits when sedimentary mineral deposits are buried and
subjected to high pressures and extreme heat
•
Laterite mineral deposits formed by leaching of impurities
– Bauxite, Al2O3, formed by leaching away of silicates
Evaluation of Mineral Resources
Evaluation of Mineral Resources
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Deposit enriched in a desired mineral (usually metal) is an ore
Concentration factor =
Concentration of material in ore
Average crustal abundance
•
Low concentration factors adequate for inexpensive metals that are abundant
•
• Example: Concentration factor of 4 is adequate for abundant iron
•
High concentration factors are required for relatively inexpensive but not very
abundant minerals
•
Lower concentration factors may be adequate for rare, valuable metals
– Examples: Platinum, palladium
Extraction and Mining
Extraction and Mining
•
Past surface mining practices have left unsightly spoils banks
–
•
Subject to erosion
Modern mine reclamation practices
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Spoil banks leveled
–
Revegetation
–
Restoration
•
Mountain-top strip mining of coal
•
Mountain tops removed and dumped into valleys to get to coal
•
Underground mining required for many minerals
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Surface not disturbed much except for subsidence
–
Large piles of processed tailings may accumulate
–
Problems can arise from extractive metallurgy processes
• Mining placer deposits
– Dredging
– Hydraulic mining with high-pressure water
• Coherent deposits can be broken up with high pressure water
– Mined hydraulically
Metals
Metals
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Metals comprise most elements
•
Some metals are especially crucial because of their important uses and short
supply
– Chromium
– Platinum-group metals
– Antimony
•
In short supply for the U.S., specifically:
– Chromium
– Manganese
– Cobalt
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Table 10.1 shows metal resources
Metals
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Figure 19.10. Decreasing percentages of metal in ore, the example of copper
Nonmetal Mineral Resources
Nonmetal Mineral Resources
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Many nonmetal mineral resources are mined in large quantities
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Examples: • Gravel
• Rock
• Sand
Clays
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Fireclay
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Kaolin
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Bentonite
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Fuller’s earth
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Ball clay
Clays have many uses
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Filler
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Brick
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Tile
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Portland cement
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Refractories
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Pottery
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Sewer pipe
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Drilling muds
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Whiteware (Chinaware)
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Petroleum refining catalysts
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Pesticide carriers
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Sealers
• Clay
Nonmetal Mineral Resources
Fluorine compounds
– Fluorspar, CaF2, used as a flux in steel manufacture
– Cryolite, Na3AlF6, molten solvent for Al2O3 electrolysis
•
Fluorspar is major fluorine ore
•
Significant amounts of fluorine are recovered in processing of phosphate ore
(primarily for phosphate fertilizer production)
Nonmetal Mineral Resources
Micas are complex aluminum silicate minerals
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•
•
Muscovite: K2O•3Al2O3•6SiO2•2H2O
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Transparent
–
Tough
–
Flexible
–
Elastic
Sheet mica
–
Electronic apparatus
–
Capacitors
–
Generators
–
Transformers
–
Motors
Finely divided mica is used in many applications including
–
Roofing
–
Paint
–
Welding rods
Nonmetal Mineral Resources
Phosphates
•
Sources: • Ca5(PO4)3OH
• Ca5(PO4)3F
•
Greatest use for fertilizer manufacture
•
Other uses
– Animal feeds
– Detergent builders (formerly)
– Pesticides
– Medicines
Nonmetal Mineral Resources
Pigments
•
Naturally-occurring iron-based pigments combined with varying amounts of clay
and manganese oxides used in ocher, sienna, umber
– Brown-yellow limonite: 2Fe2O3•3H2O
– Gray-black hematite: Fe2O3
•
Manufactured pigments include
– Carbon black
– TiO2
– Zinc pigments
Nonmetal Mineral Resources
Fillers
• Used in: • Carbon black • Battery cases
• Minerals used in fillers include
– Carbon black
– Diatomite
– Barite
– Fuller’s earth
– Kaolin
– Mica
– Limestone
– Pyrophyllite (Al2Si4O10(OH)2)
– Wollastonite (CaSiO3)
• Paper • Rubber
Nonmetal Mineral Resources
Evaporites from Evaporation of Seawater and Brines
•
Sodium chloride
– Direct uses to melt road ice, in foods, other applications
– Raw material to make Cl2 and Na used to make other chemicals
•
Gypsum (CaSO4•2H2O)
– Wallboard, plaster
•
Potassium salts
– Fertilizer, various chemicals
Nonmetal Mineral Resources
Sand and Gravel
•
Largest amounts of all non-fuel minerals
•
Monetary value very high because of huge quantities
•
Used in construction
•
–
Portland cement manufacture
–
Road paving
• Concrete structures
• Dams
Old river channels and glacial deposits are important sources
Sulfur
• Greatest use for sulfuric acid
• Many other industrial and agricultural products
• Sources of sulfur
– Greatest source is H2S from sour natural gas
– From sulfide minerals, such as Pbs
– Elemental sulfur mined by hot water (Frasch) process
– Coal is a potential source of large quantities of sulfur
How Long Will Essential Minerals Last?
How Long Will Essential Minerals Last?
•
Sources of essential minerals are limited compared to the future lifetime of the human species
•
Comfortable supplies of at least 100 years
–
Bauxite (aluminum)
–
Iron ore
–
Potassium salts
•
Intermediate supplies that will support consumption at current levels for 25-100 years
•
• Chromium • Cobalt • Copper • Manganese • Nickel • Gypsum
•
• Phosphate minerals • Sulfur
•
Critical supplies with sources of 25 years or less at current rates of consumption
–
Lead
–
Tin
–
Zinc
–
Gold
–
Silver
• U.S. deficient in many essential minerals including sources of
– Aluminum
– Antimony
– Chromium
– Cobalt
– Manganese
• • Tantalum • Niobium • Platinum • Nickel • Tin
Green Sources of Minerals
Green Sources of Minerals
Finding more
•
Geophysical prospecting
•
Geochemical prospecting
•
Biogeochemical prospecting
•
Remote sensing from aircraft or satellites
Exploitation of lower grade ores
•
Enabled by improved technology
•
Requires handling much more material
•
Produces much more waste
Extraction from challenging locations
•
Ultra-deep mining with robot technology
•
Ocean bed mining
•
Manganese nodules
Green Sources of Minerals
Materials Recycling
•
Largest quantity of metal recycled is iron
•
Next is aluminum
– About 1/3 of aluminum is recycled
– Recycling aluminum consumes much less energy than from bauxite
•
Other metals widely recycled
– Copper and alloys • Cadmium • Lead • Tin • Mercury • Zinc
– Silver • Gold • Platinum
•
Nature of source material is important in recyclling
– Lead in storage batteries is readily recycled
– Aluminum from cans and other sources amenable to recycling
– Steel complicated by alloys with titanium, tungsten, other metals