Chapter 4

Question 1

what are the most critical environmental challenges facing the Earth result from cycle disturbance

Answer 1

• global warming
• acid deposition
• the spread of oceanic dead zones

Question 2

matter

Answer 2

• Everything is either matter or energy
• Earth’s supply of energy is virtually infinite
• Earth’s supply of matter is limited to what now exists
• Matter, unlike energy, has mass and takes up space
  ex) Atoms- protons, neutrons, and electrons

Question 3

emissions from stacks

Answer 3

These emissions end up some where creating undesirable consequences
•Acid deposition
•Global warming

Question 4

molecules

Answer 4

Molecules are more than one atom joined together

Question 5

compound

Answer 5

When two or more different atoms come together, they are called a compound
ex) water (H2O)

Question 6

four major kind of organic compounds

Answer 6

-Carbohydrates, fats, proteins and nucleic acids

Question 7

matter exists in three different states

Answer 7

Solid, Liquid, Gas

Question 8

how can matter be transformed from one state to another

Answer 8

Matter can be transformed from one state to another by changes in heat and/or pressure

Question 9

law of conservation of matter

Answer 9

Matter can neither be created nor destroyed, only transformed from one form into another

Question 10

biogeochemical cycles

Answer 10

Matter cycles among components of the ecosphere

• These cycles are essential to life
• Nutrients are elements necessary for life

Question 11

macronutrients

Answer 11

are needed in fairly large amounts by all organisms

Question 12

mirconutrients

Answer 12

are required in smaller amounts by most species

Question 13

about 97% of organic mass is composed of six nutrients

Answer 13

• Carbon
• Oxygen
• Hydrogen
• Nitrogen
• Phosphorus
• Sulphur

Question 14

biogeochemical cycles

Answer 14

are the biological, chemical, and geological processes and components by which materials cycle through ecosystems.
Nutrients are stored in compartments:
-There is often a large, slow-moving abiotic pool Nutrients move between compartments: -Rapidly interacting biotic-abiotic exchange pool

Question 15

3 differences in ecosystems varying

Answer 15

Ecosystems vary substantially in terms of the speed of cycling and the relative proportion of nutrients in each compartment
e.g., temperate vs tropical forest soils
Speed of cycling may also change within a cycle, depending on season and type of nutrient
e.g., 300 years for an atom of carbon to pass through the entire carbon cycle
Residence time: the typical length of time something stays in one compartment
e.g., CO2 in the atmosphere (5–7 years)

Question 16

cycles can be classified according to the main source of their matter

Answer 16

1. Gaseous cycles have most of their matter in the atmosphere, e.g., the nitrogen cycle
2. Sedimentary cycles hold most of their matter in the lithosphere, e.g., phosphorus and sulphur cycles
   - Elements in sedimentary cycles tend to cycle more slowly than those in gaseous cycles; elements may be locked in geological formation for millions of years

Question 17

human induced accumulation

Answer 17

• Under natural conditions, recycling rates between components achieve a balance over time in which inputs and outputs are equal
• Human activities speed up transference between cycles components
• Many pollution problems result from human-induced accumulation in one or more components of a cycle that is too great for natural processes to dissipate

Question 18

sedimentary cycles

Answer 18

• These cycles mobilize materials from the lithosphere to the hydrosphere and back to the lithosphere
• Some involve a gaseous phase, some do not
• Such cycles rely on geological uplift over long periods to complete the cycle
• We will discuss phosphorus and sulphur, but other elements follow similar pathways
  e. g., calcium, magnesium, and potassium

Question 19

weathering of rocks

Answer 19

• Weathering of rocks in the Earth’s crust plays an important role in supplying long-term inputs to biogeochemical cycles, and is part of the rock cycle
  ex) Mechanical weathering, chemical weathering
• The rock cycle involves the transformation of rocks from one type to another
  e. g., volcanic rocks are eroded and washed into the ocean the resulting sediments are turned into sedimentary rocks over millions of years

Question 20

the decomposers

Answer 20

Detritus food chains are the main means by which nutrients in the biotic component of the ecosphere are recycled to the abiotic component for future reuse; they are Earth’s major mediator in nutrient recycling
-Decomposer organisms include fungi, earthworms, slugs, snails, beetles, ants, termites, and heterotrophic bacteria. Each plays its own role in nutrient recycling

Question 21

earths water

Answer 21

• Only Earth has water in liquid form
• Water occurs in a fixed supply that cycles between various reservoirs, driven by energy from the sun.
• The largest reservoir is the ocean, with over 97% of the water on Earth
• Most of the rest is tied up in polar ice caps (>2%)
• A small amount occurs as freshwater (< 1%)

Question 22

agricultural water use

Answer 22

-Worldwide, agriculture claims about 2/3 of total water withdrawal and 85% of consumption.
-Aral Sea, once the fourth largest inland body of water in world, has been drained. Why?
–Water was diverted for agriculture
-Lake Chad in northern Africa went from 400,000 sq. km to less than 1,000 sq. km.

Question 23

residence times

Answer 23

• Ice as glaciers: as long as >100,000 years
• Deep ocean: up to 37,000 years
• Groundwater: days (unconfined) to > 1,000,000 years (unconfined)
• Surface water: minutes to years
• Atmosphere: 9–12 days
• Surface water pollution gets ‘flushed’ by movement, groundwater pollution may not

Question 24

hydrological cycle

Answer 24

The hydrological cycle involves movement of water amongst the oceans, atmosphere, and terrestrial systems, all fuelled by energy from the sun

Question 25

evaporation

Answer 25

conversion of water from a liquid to gas

-86% of atmospheric water is evaporated from ocean surface

Question 26

transpiration

Answer 26

evaporation from the leaves of plants

Question 27

evapotranspiration

Answer 27

evaporation from soil and plants

Question 28

precipitation

Answer 28

Precipitation occurs when gaseous water in the atmosphere cools and condenses into liquid form on tiny particles called condensation nuclei, and falls as rain, snow, or hail
-Moisture content in the air increases with an increase in temperature

Question 29

relative humidity

Answer 29

The amount of moisture held in the air compared to how much could be held if fully saturated at a particular temperature
-At 100% RH, air is saturated; clouds, fog, and mist form

Question 30

ground water

Answer 30

water below the Earth’s surface in the saturated zone

-Lakes, streams, and other evidence of surface water occur where the land surface is below the water table

Question 31

where does rain fall

Answer 31

• Clouds are moved by winds and continue to grow until precipitation occurs
• 76% of precipitation falls over oceans
• 24% falls over continents and joins ice, lakes, rivers, and groundwater under the force of gravity

Question 32

what is something that occurs in all three phases on matter?

Answer 32

-solid, liquid and vapour = water

Question 33

sublimation

Answer 33

the process for direct transfer between the solid and vapour phases of matter, regardless of direction

Question 34

where is most fresh water

Answer 34

Canada is estimated to have up to one-third of the world’s fresh water, but most of it is held in a solid state as ice

Question 35

humans interfere in the hydrologic cycle by

Answer 35

• the storage and redistribution of runoff to augment water supplies for domestic, agricultural, and industrial uses
• the building of storage structures to control floods
• the drainage of wetlands
• the pumping of groundwater
• cloud seeding
• land-use changes such as deforestation, urbanization, and agriculture that affect runoff and evapotranspiration patterns
• climatic change caused by interference with biogeochemical cycles

Question 36

eutrophication

Answer 36

A natural process of nutrient enrichment of water bodies that leads to greater productivity

Question 37

oligotrophic

Answer 37

systems have relatively low nutrient levels

Question 38

eutrophic

Answer 38

systems have high nutrient levels

Question 39

mesotrophic

Answer 39

systems have intermediate levels of nutrients

Question 40

what are two limiting factors for plant growth

Answer 40

Phosphorus and nitrogen are often the two main limiting factors for plant growth in aquatic ecosystems

Question 41

how is eutrophication caused

Answer 41

• Eutrophication can happen naturally over thousands of years under certain conditions
  ex) Shallow lakes, fertile soils, rock composition
• Cultural (human-induced) eutrophication speeds up the eutrophication process mostly through the addition of phosphates and nitrates to the water body
• About eight times the natural amount of phosphates and nitrates currently enter the oceans each year

Question 42

effects of eutrophication

Answer 42

• Nutrient enrichment encourages increased growth of aquatic plants, favouring growth of phytoplankton over benthic plants rooted in the substrate
• Benthic plants get shaded out and thus produce less oxygen at depth
• Oxygen depletion is further increased by the decay of the large mass of phytoplankton produced
• Fish decline due to oxygen depletion

Question 43

effects of eutrophication: oxygen sag curve

Answer 43

when organic wastes are added to a body of water, oxygen levels fall as the number of bacteria rises to help break down the waste
The oxygen sag curve is measured by the biological oxygen demand (BOD)

Question 44

effects of eutrophication: biological oxygen demand

Answer 44

the amount of dissolved oxygen needed by aerobic decomposers to break down the organic material in a given volume of water at a certain temperature over a given period

Question 45

eutrophication: what can we do about it

Answer 45

• The main way to control eutrophication is to limit the input of nutrients into water bodies
• It can be difficult to deal with diffuse, non-point sources, such as runoff from urban areas and agricultural land
• Point sources of pollution, or single discharge points, include effluent discharges from sewage plants or industrial processes
• Oceans are now developing eutrophic ‘dead zones

Question 46

lake erie: eutrophication control

Answer 46

• Up to 90 per cent of the bottom layer of the central zone of the lake became oxygen-deficient in the summer, causing huge algae mats and beach closures
• The natural eutrophication process that might have taken thousands of years was overtaken by a cultural eutrophication within only 50 years
• Phosphorous controls have improved water quality, but significant problems still remain

Question 47

acid deposition: what is it

Answer 47

-Acidity is a measure of the concentration of hydrogen
ions in a solution and is measured using the pH scale,
which ranges from 0 to 14
-Acidic deposition is a term that includes rainfall, snow,
fog, and dry deposition from dust with a pH lower <5.6

Question 48

acids

Answer 48

are chemicals that release hydrogen ions (H+)

when dissolved in water

Question 49

base

Answer 49

is a chemical that releases hydroxyl ions (OH-)

Question 50

how is acid deposition caused

Answer 50

• Increases in acidity are due to human interference in the sulphur and nitrogen cycles
• The largest sources are the smelting of sulphur-rich metal ores and the burning of fossil fuels for energy
• These point sources of pollution are easier to monitor and control than the other main source of acids, which is nitrogen emissions from combustion
  e. g., transportation, thermoelectric generation

Question 51

what are the effects of acid deposition: aquatic

Answer 51

• Disfigurement, death and extirpation of insects and fish, food chain effects through depletion of food sources
• Acid shock: pulse of acidity in spring with snow melt
• Chemical changes, e.g., enhanced metal solubility

Question 52

what are the effects of acid deposition: terrestrial effects

Answer 52

• Tissue death in plant leaves
• Once in the soil, acids leach away nutrients required for plant growth, leading to nutrient deficiencies
• Metals dissolved in soil water inhibit plant nutrient uptake and can lead to food chain effects
• Microbial activity is inhibited
• Inhibition of crop growth

Question 53

what are the effects of acid deposition: ecosystem sensitivity

Answer 53

• Critical load: the maximum level of acid deposition that can be sustained in an area without compromising ecological integrity
• Areas with deep soils and carbonate rock have a high buffering capacity, and are not as sensitive to acid deposition, while areas with thin soils and non-carbonate rock are more susceptible

Question 54

what are the effects of acid deposition: socio-economic effects

Answer 54

• The most direct impact on human health may come from inhalation of airborne acidified particles
• Loss of natural resources leads to economic losses
• Buildings and plumbing are damaged

Question 55

what can we do about acid deposition

Answer 55

• One of the main challenges of acid deposition is that it is not localized; in Canada, over half originates in USA
• International efforts are required: Canada addressed the problem through national, bilateral, and multilateral efforts
• Policy target value (PTV): the annual target deposition of 20 kilograms per hectare as an acceptable goal, taking political and economic costs into account
• Scientific target value (STV): a further reduction of 75% in SO2 emissions is needed to address the situation adequately according to scientific research

Question 56

biogeochemical cycles and human activity

Answer 56

• PTV and STV are often in conflict:
  1. total allowable catch in fisheries
  2. annual allowable cut in forestry
  3. designation of endangered species
• Advances in science have allowed for more comprehensive definitions of critical loads that combine SOx and NOx for aquatic and terrestrial ecosystems
• Canada has met all its goals and commitments for acid deposition reductions, yet acid deposition remains a significant problem in Canada
• Sulphur has been easier to control than nitrogen

Question 57

implications

Answer 57

• Understanding the nature of matter and how nutrients cycle in the ecosphere is key to appreciating many of the more challenging environmental issues that society faces
• Acid deposition, eutrophication, and global change all have their roots in disruption of biogeochemical cycles