environmental chemistry chapter 19: sustaining the geosphere copyright © 2011 by dbs

Environmental Chemistry

Chapter 19:Sustaining the Geosphere

Copyright © 2011 by DBS

Contents

• 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

• 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

• 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

• 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

• 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

• 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 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


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


Geospheric Topography Influence on Air Pollution (Figure 19.2)

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


• Mass Movements and Landslides

• Figure 19.3. Illustration of a Landslide


Harmful Effects of Landslides

• Landslide into the reservoir behind the Vaiont Dam, Italy, killed 2,600 people in 1963

• Mt. Huascaran, Peru, killed 20,000 people in 1970

• Tendency toward landslides can be predicted

• Warning of landslides by devices such as tilt meters

• Harmful Surface Movements Other Than Landslides

– Rockfalls

– Creep (slow, gradual movement that can cause much damage)

– Frost and freeze/thaw cycles

The Vulnerable Coasts


• 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

• Hurricanes in Atlantic and Gulf of Mexico

• Typhoons in Indian Ocean and Pacific

• Cause devastating storm surges


Tsunamis

• 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


Coastal Erosion (Figure 19.4)

• • Normal erosive processes • Storm surges • Human influences

– Much of the loss results from unwise construction siting


Preserving the Coastline

• Beach nourishment (restoration of sand)

• Coastlines

The Threat of Rising Sea Levels

• Melting glaciers can raise sea levels

– Greenland

– Antarctica

Building the Geosphere

Building on the Geosphere

• Engineering Geology

• Large public works projects

– 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

• 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

• Many kinds of excavations

• Simple dirt excavation

• Blasting of rock may be required

• Water infiltration is frequently a problem

• Slumping

• Excavations Below the Surface– Tunnels

– Mines

– Subways

– Underground caverns

• Seismic testing often used

Digging the Dirt

• Figure 19.5. Underground Tunnel to Convey Water

Digging the Dirt

Green Underground Storage

• Underground excavations rank high in sustainability

– Temperature stability

– No outside structure maintenance

• Storage facilities in limestone formations most common

• 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


• Hydrogeology addresses hydrosphere/geosphere interaction

• Water both on top and within geosphere

• Water falling on the geosphere as precipitation

– Flow on surface in streams • Held in soil • Evaporate to atmosphere

– Infiltrate to groundwater aquifers

• Groundwater recharge is desirable

– Hampered by paving

– May be done artificially


• Flooding

• 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


• Figure 19.8. Reservoir to Control Flooding


China’s Three Gorges Dam Project

• Yangtze River, dam completed 2006

• Largest dam and largest single powerplant project in one location

• Reservoir as deep as 175 meters

• Greatest consumption of dirt, stone, concrete

• 1.13 million people displaced

• 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

• 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


• 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

• 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

• Properly done and restored, surface mining need not be harmful

– Reservoirs left from rock and sand mining

• Approaches to surface mining

• 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


Environmental Effects of Mining and Mineral Extraction

• Adverse effects of underground mining including subsidence, disturbance of aquifers

• One of the more damaging effects is acid from pyrite, FeS2

• One of the most damaging mining byproducts consists of tailings remaining from beneficiation of ores

• Pyrite in coal tailings produces acid

• Uranium tailings used for construction fill have caused radioactive radon emissions into buildings

Waste Disposal and the Geosphere


• Ability to receive wastes is an important aspect of geosphere’s natural capital


Municipal refuse

• 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 • Gas production

• Despite restrictions, hazardous materials get into landfills

• Sanitary landfills produce gases

{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


• Figure 19.9. Construction of a Sanitary Landfill


Landfills for Hazardous Substances

• 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


• 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


Deposits Formed by Sedimentary or Metamorpic Processes

• 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

• Deposit enriched in a desired mineral (usually metal) is an ore

• 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

Concentration factor =Concentration of material in ore

Average crustal abundance

Extraction and Mining

Extraction and Mining

• Past surface mining practices have left unsightly spoils banks

– Subject to erosion

• Modern mine reclamation practices

– 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

– 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

• 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

• Table 10.1 shows metal resources

Metals

• Figure 19.10. Decreasing percentages of metal in ore, the example of copper

Nonmetal Mineral Resources


• Many nonmetal mineral resources are mined in large quantities

• Examples: • Gravel • Rock • Sand • Clay

Clays

– Fireclay

– Kaolin

– Bentonite

– Fuller’s earth

– Ball clay

• Clays have many uses

– Filler

– Brick

– Tile

– Portland cement

– Refractories

– Pottery

– Sewer pipe

– Drilling muds

– Whiteware (Chinaware)

– Petroleum refining catalysts

– Pesticide carriers

– Sealers


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)


Micas are complex aluminum silicate minerals

• Muscovite: K2O•3Al2O3•6SiO2•2H2O

– 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


Phosphates

• Sources: • Ca5(PO4)3OH • Ca5(PO4)3F

• Greatest use for fertilizer manufacture

• Other uses

– Animal feeds

– Detergent builders (formerly)

– Pesticides

– Medicines


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


Fillers

• Used in: • Carbon black • Battery cases • Paper • Rubber

• Minerals used in fillers include

– Carbon black

– Diatomite

– Barite

– Fuller’s earth

– Kaolin

– Mica

– Limestone

– Pyrophyllite (Al2Si4O10(OH)2)

– Wollastonite (CaSiO3)


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


Sand and Gravel

• Largest amounts of all non-fuel minerals

• Monetary value very high because of huge quantities

• Used in construction

– Portland cement manufacture • Concrete structures • Dams

– Road paving

• 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


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


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

environmental chemistry chapter 19: sustaining the geosphere copyright © 2011 by dbs

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