Transcript Chapter 26 - Planet Earth

Chapter 27
Minerals and the
Environment
Importance of Minerals to Society
• Standard of living increases with availability
– Success in locating, extracting, importing and
using; measurement of wealth
– generally located in small, hidden areas (most
areas exploited)
– U.S. uses 10 tons of non-fuel minerals per year
– sand, steel and gravel
How Mineral Deposits Are
Deposited
• Ore Deposits – formed when metals are
concentrated in anomalously high amounts
by geological processes
– biosphere related and geologic cycle
– large; deeply buried; concentrated; accessible
• Mineral resources are usually extracted
from ore deposits
How Mineral Deposits Are
Formed
• Distribution of mineral resources
– Earth's formation
– Crust and Ocean
• silicates vs. manganese oxide nodules
• Plate boundaries
– Convergent and Divergent
• metallic ores vs. sulfide deposits
• Igneous processes
– gravity and density (crystallization) and hot
water (source of most ore deposits)
How Mineral Deposits are
Formed, con't.
• Sedimentary processes
– water (placer deposits – related to flow and
stream turbulence) and wind
– evaporates (calcium, sodium, potassium)
• Biological processes
– iron ore deposits
– Ca and Na (precipitated)
• Weathering processes
– parent rock (bauxite)
– secondary enrichment
Resources and Reserves
• Minerals are classified as:
– 1. Mineral Resources
• Elements, chemical compounds, minerals or rocks
that can be extracted to obtain a usable commodity
– 2. Mineral Reserves
• The portion of the resource that is identified and
from which usable materials can be legally and
economically extracted at the time of evaluation
Classification of Mineral
Resources
• Based on use:
– elements for metal production (ores) and
technology
– building materials (sand and steel)
– chemical industry
– agriculture
• Metallic minerals can be classified according
to their abundance
Availability of Mineral Resources
• When the availability of a mineral becomes
limited, there are 4 possible solutions:
1. Find more sources
2. Recycle and reuse what has already
been obtained
3. Reduce consumption
4. Find a substitute
**Choice depends on social, economic and
environmental factors
U.S. Supply of Mineral Resources
• Domestic supply:
– insufficient for current use
– imports
– political, economical and military instability
• alliances
Impacts of Mineral Development
• Environmental Impacts
– Depends on many factors – ore quality, mining
procedures, hydrologic factors, climate, rock
type, size of operation, topography, etc.
– Exploration vs. Mining and Processing
• land, groundwater and surface water, air and
vegetation are all impacted
• Copper
– topography; air (dust); surface and groundwater
(drainage); biological (nutrients, biomass, diversity)
Impact of Mineral Development
• Social Impacts
– Increased demand for housing and services in
mining areas
– land-use shifts
– closing of mines
– environmental regulation in reclamation
(consider current trend of surface mining cheaper)
Minimizing Environmental
Impact of Mineral Development
• Federal, state and
local environmental
regulation (air,
sediment and water
pollution)
– reclaiming;
stabilizing soils;
controlling air
emissions;
treatment of
contaminated water
Minimizing Environmental
Impact of Mineral Development
• On-site and off-site
treatment of waste
– engineering and
conservation
• controlling sediment
and water
– biotechnological
processes
• acid tolerant plants
• bacteria
Minerals and Sustainability
• R-to-C Ratio
– A measure of the time available for finding the
solutions to depletion of nonrenewable
resources
– R = known reserves
– C = rate of consumption
– provides a view on how scarce a particular
mineral resource may be
– small ratios: short supply; find substitutes
through technological innovations
Future of Mineral Mining
• Factors that make
more difficult and
expensive
– depletion of highgrade ores
– increasing energy
costs
– less tolerance for
environmental
damage
Mining with Microbes
• Biohydrometallurgy
– extracting minerals from rock by using
microscopic organisms
– Advantages:
• may produce minerals without large-scale excavations
• techniques may be used to decontaminate wastes
– Disadvantages:
• technology is not yet available for all mining
situations
• genetically-engineered organisms may pose a threat