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Molcules and Materials- First year uni > Biogeochemical cycling > Flashcards

Biogeochemical cycling Flashcards

1
Q

what is biogeochemical cycling?

A

the distribution of a substance between different compartments of an environmental system involving chemical, physical and biological, geological processes

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2
Q

define a biogeochemical cycle?

A

a conceptual model of the processes involved in the biogeochemical cycling of given substance, this may be a model of global, regional or local scale

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3
Q

what is the significance of biogeochemical cycling?

A

geochemical cycles turned what we see now as what it is, so we want to see how this earth system has been formed

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4
Q

Describe how did co2 in the atmosphere gradually decrease by biogeochemical cycling?

A

more and more algae formed over time, so oceans became more oxygenated so oxygenated started to accumulate at the atmosphere and co2 decreases

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5
Q

define a reservoir

A

a specific aggregate entity within a system; biosphere; lithosphere; atmosphere

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6
Q

define a burden

A

the mass of a substance in a specific reservoir or system = concentration x volume

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7
Q

define a source

A

a flux of material into a reservoir

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8
Q

define a sink

A

a flux of material out of a reservoir; often assumed to be proportional to the content of the reservoir

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9
Q

define a budget

A

a balance sheet of all sources and sinks of a reservoir

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10
Q

define a cycle

A

a system consisting of 2 or more connected reservoirs, where a large part of the material is transferred through the system

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11
Q

define mixing time

A

the time taken for a given substance to achieve uniform distribution throughout the whole of a given reservoir

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12
Q

define horizontal mixing time

A

time taken for complete mixing to occur in a horizontal sense

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13
Q

define vertical mixing time

A

time taken for complete mixing to occur in a vertical sense

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14
Q

define overall mixing time

A

time taken for complete mixing to occur in both a horizontal and vertical sense which is equivalent to whichever is the longest and vertical times

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15
Q

what is the order in which mixing time increases in the atmosphere?

A

boundary layer
troposphere
stratosphere

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16
Q

what influences mixing time? (2)

A

size (mass or volume)

fluidity/viscosity

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17
Q

What type of compartment will have longer mixing times?

A

large and viscous

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18
Q

What type of compartment will have shorter mixing times?

A

small and fluid

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19
Q

what does a short mixing time mean?

A

changes in concentrations arising from changes in inputs to the compartment will occur pretty quickly |(why the atmosphere is most responsive to anthropogenic change)

20
Q

What defines lifetime/residence time?

A

the average time taken for a substance to stay in a reservoir before it is removed

21
Q

what does t = A/R mean?

A

the lifetime equals the amount of the substance in the reservoir divided by teh rate of addition or removal of the substance from that reservoir

22
Q

what does A represent in t = A/R?

A

The burden e.g mass of a substance in a reservoir

23
Q

what does S and R represent and when are they equal?

A

S = sources
R = sinks
they are equal at a steady state

24
Q

what does it mean if a substance has a long lifetime?

A

they will show little spatial and vertical variability as they lifetimes exceed both the vertical and horizontal mixing times of the troposphere

25
Q

what are environmental transfer processes?

A
  • processes via which a substance is transferred between 2 compartments
26
Q

Name some examples of environmental transfer processes

A
  • riverine transport of dissolved and suspended material from land to oceans
  • transport of dissolved and suspended material from atmosphere to land and oceans via precipitation
  • transport of gas and particles from the land/ocean to atmosphere
27
Q

define flux

A

defined as the rate at which a substance is transferred between compartments (rate at which a transfer mechanism occurs)

28
Q

what is dry deposition?

A

the direct transfer of gases and particles to the land or water surface i.e a transfer mechanisms

29
Q

what is wet deposition?

A

the removal from the atmosphere of substances dissolved in precipitation

30
Q

what is the driving force between all the earth’s sphere (lithosphere, biosphere, hydrosphere, atmosphere)?

A

solar energy

31
Q

which sphere has the shortest mixing times but also most fluid of all?

A

atmosphere

32
Q

what is the largest gas in the atmosphere?

A

nitrogen, 78.08%

33
Q

describe the differences in mixing times for the different layers of the atmosphere?

A
  • boundary layer is only s few hours
  • troposphere is only a few weeks
  • stratosphere is only a year
34
Q

describe the lithosphere?

A

envelope of the earth where soils occur, an interface between the earth, atmosphere and biosphere

35
Q

describe the mixing time of the litosphere?

A

longgg

36
Q

name some different types of weathering

A
  • physical
  • chemical
  • oxidation
  • dissolution
  • biological
37
Q

what are some consequences of weathering?

A
  • soil formation
  • ions loss to the oceans
  • soils can be suspended in water and carries away to oceans
38
Q

whats the difference between chemical and physical weathering?

A
  • chemical; break down of rocks by chemical reactions by water
  • physical; break down of rocks into smaller processes by physical means such as ice, wind
39
Q

name 4 processes associated with the hydrosphere?

A
  • evaporation/precipitation
  • sedimentation
  • groundwater and river discharge
  • ocean circulation
40
Q

describe the ocean as a reservoir

A
  • very large
  • not as fluid as atmosphere
  • mixing time is longer
  • respond more slowly to anthropogenic change and sea pollution tends to be more localised than air pollution
41
Q

describe the nitrogen cycle

A
  • biological fixation of nitrogen from the atmosphere where its taken up by plants
  • incorporated into organic molecules
  • when plants/organisms die they go through soil processes and release particles into the atmosphere by decomposition
42
Q

how can anthropogenic influences change the water cycle?

A
  • dam building
  • re distribution of precipitation
  • groundwater use
  • sea level rise and glacial meting
43
Q

how can dam building affect the water cycle?

A
  • water transport will be reduced and large areas flooded, more evaporation from local reservoir which can have an effect on the local climate
44
Q

what are the impacts of anthropogenic changes to the water cycle?

A
  • air pollution
  • acid rain
  • eutrophication
  • forest fertilization
45
Q

What is phosphorus cycling|?

A

Phosphate in rocks enters the soil, the phosphate is absorbed by plans, the phosphates pass from organisms to organism in a food chain or food web

Molcules and Materials- First year uni (13 decks)

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