Apes Chapter 3 Presentation.ppt

Chapter 3

THE NATURE OF SCIENCE

• What do scientists do?

– Collect data.

– Form hypotheses. – Develop theories,

models and laws about how nature works.

Testing Hypotheses

• Scientists test hypotheses using controlled experiments and constructing mathematical models.

– Variables or factors influence natural

processes

– Single-variable experiments involve a control and an experimental group.

– Most environmental phenomena are

multivariable and are hard to control in an

experiment.

Scientific Reasoning and Creativity

• Inductive reasoning

– Involves using specific observations and

measurements to arrive at a general conclusion or hypothesis.

– Bottom-up reasoning going from specific to general.

• Deductive reasoning

– Uses logic to arrive at a specific conclusion. – Top-down approach that goes from general to

Limitations of Environmental

Science

• Inadequate data and scientific understanding can limit and make some results controversial.

– Scientific testing is based on disproving rather than proving a hypothesis.

MODELS AND BEHAVIOR OF

SYSTEMS

• Usefulness of models

– Complex systems are predicted by developing a model of its inputs, throughputs (flows), and

outputs of matter, energy and information. – Models are simplifications of “real-life”.

Systems can be affected by

1. Feedback loops 2. Time delays

1. Feedback Loops:

• Outputs of matter, energy, or information fed back into a system can cause the system to do more or less of what it was doing.

– Positive feedback loop causes a system to

change further in the same direction (e.g. money earning interest)

2. Time delays

• Time delays in a system in which the effects are not know for some time • Allows the problem to

build up slowly and then whole system changes

Ex: population growth, toxic waste leaks, forest

destruction from air pollutant

3. Synergy

• 2 or more processes combined have a

greater effect on a system than the sum of each would have.

Law of conservation of problems

“We can never do just one thing”

• Solution for a problem usually leads to other problems

Ex: addition of MTBE to gasoline to reduce air pollution, then polluted groundwater

• Must consider when we search for solutions

Anticipating Environmental Surprises

Should be aware of:

• Abrupt shifts in stable systems • Synergistic interactions

Matter: Forms, structure, quality

• Pages 47 – 51 Chemistry/Biology review • Chlorinated hydrocarbons: C, H, Cl

DDT, PCB’s (polychlorinated biphenyls) • Chlorofluorocarbons (CFC’s) freon

• N₂O nitrous oxide NO nitric oxide

• NO₂ nitrogen dioxide CO carbon monoxide • SO₂ sulfur dioxide NH₃ ammonia

Matter quality

• A measure of how useful a form of matter is as a resource based on availability and concentration

• High quality – concentrated, found near Earth’s surface, great potential for use Coal, Salt, Al can

• Low quality – dilute, found deep

underground or in ocean, in atmosphere with little potential for use.

Fig. 2-8, p. 39

High Quality Low Quality

Salt

Solid _Gas

Coal _{Coal-fired power plant emissions}

Gasoline

Automobile emissions Solution of salt in water

Material Efficiency

• Total amount of material needed to

produce each unit of goods or services • Only 2-6% of matter resources flowing

Energy Forms & Quality

Energy -Capacity to do work and transfer heat

ENERGY

• Energy is the ability to do work and transfer heat.

– Kinetic energy – energy in motion

• heat, electromagnetic radiation

– Potential energy – stored for possible use

Electromagnetic Spectrum

• Many different forms of electromagnetic radiation exist, each having a different wavelength and energy content.

Electromagnetic Spectrum

• Ionizing radiation

Cosmic, gamma, xrays, ultraviolet

Enough energy to knock e- from atoms

Can disrupt living cells, interfere with body processes

• Nonionizing radiation Not as energetic

Heat v. temperature

• Heat – energy that transfers between objects due to temp difference

Heat Transfer

1. Convection – through movement of heated materials

(asthenosphere/tectonic plates)

2. Conduction – through collisions of atoms metals conduct heat

Energy Quality

• High quality – concentrated/useful electricity, chem energy in coal/gasoline • Low quality – dispersed/ little ability to do

Chem/Phys Changes

Law of conservation of matter

“There is no away”

Can’t get rid of anything – will show up somewhere else.

Factors determining harmful effects of pollutants:

1. Chemical nature: Hg vs. Cu

2. Concentration: PPM, PPB, PPT

Categories of Persistence

1. Degradable, nonpersistent – broken down to acceptable levels by natural processes

Biodegradable – by living organisms

2. Slowly degradable, persistent – takes decades or longer DDT (

Dichloro-Diphenyl-Trichloroethane)and most plastics

Nuclear Changes

1. Natural radioactive decay 2. Nuclear fission

1. Natural radioactive decay - isotopes emit particles and/or energy to attain a stable nuclear configuration

a. Alpha – stopped by skin, paper b. Beta – stopped by wood or Al foil

c. Gamma – partially stopped by lead or concrete

Half life

• Amount of time needed for ½ of the nuclei in a radioisotope to decay to more stable isotope.

• Generally takes 10 - ½ lives for an isotope to decay to a safe state.

Radiation exposure

• Background sources – soil, rocks, air, water, food, cosmic rays from space Granite contains Uranium-238 which

decays to Radon-222 (associated with lung cancer)

Cosmic rays exposure increases as altitude increase and in airplane travel

2. Nuclear Changes: Fission

• Nuclear fission: nuclei of certain

isotopes with large mass numbers are split apart into

lighter nuclei when struck by neutrons.

3. Nuclear Changes: Fusion

• Nuclear fusion: two isotopes of light elements are forced together at extremely high

temperatures until they fuse to form a heavier nucleus.

Radiation exposure

• Man-made sources

x-rays, luminous dial watch, TV, smoke detector (Americium), fiesta ware

Coal-fired power plants give off more

Effects of ionizing radiation

• Genetic damage from mutations in DNA – can lead to genetic defects in the next

generation

Damage varies with:

• Type of radiation, penetrating power,

source (outside or inside body) and ½ life • In general radioisotopes with intermediate

½ lives pose greatest threat

ENERGY LAWS

• The first law of thermodynamics: we cannot create or destroy energy.

– We can change energy from one form to another.

• The second law of thermodynamics: energy quality always decreases.

– When energy changes from one form to another, it is always degraded to a more dispersed form. – Usually takes the form of heat given off at lower

Energy Efficiency

• A measure of how much useful work is accomplished by a particular input of energy into a system

• Only about 16% of the energy used in the US ends up performing useful work.

• Wasted through the 2nd law or

How does 2

Law affect life?

molecules & biochemical processes, and then give off low quality heat to your

surroundings

Matter/energy change laws and

environmental problems

Sinks

• Waste and pollution concentrates in sinks • Storage places such as air, water, soil,

organisms

• As population increases and more

resources are used the capacity of the

Sustainable Low-Throughput

Economies: Learning from Nature

• Matter-Recycling-and-Reuse Economies: Working in Circles

– Mimics nature by recycling and reusing, thus reducing pollutants and waste.

Best solution is low-throughput economy

• Reuse and recycle most nonrenewable resources

• Use renewable resources sustainably • Efficient use of matter/energy resources • Reduce unnecessary consumption

• Emphasize pollution prevention and waste reduction