ciclos da natureza

7/27/2019 Ciclos Da Natureza

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EM 973

Desenvolvimento eMeio Ambiente

Arnaldo Walter

UNICAMP

[email protected]


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Ciclos na natureza e o meio

ambiente


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Objetivos e contexto

Ciclos da natureza so fundamentais para a manuteno da vida na

Terra. O ciclo da gua um exemplo claro, e no preciso

consideraes adicionais.

Ciclos de nutrientes (como Nitrognio e Fsforo) so essenciais

para as plantas e os animais.

Alteraes nos ciclos da natureza no esto associadas ao

deplecionamento dos reservatrios, mas sim alterao de

fluxos entres os reservatrios (e consequente variao das

condies fsico, qumicas e biolgicas), e poluio (alteraodas propriedades) dos sistemas da natureza (atmosfera, hidrosfera,

biosfera e litosfera).


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Princpios de Sustentabilidade (1)Miller and Spoolman. Living in the Environment : concepts, connections

and solutions.


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Princpios de Sustentabilidade (2)Miller and Spoolman. Living in the Environment : concepts, connections

and solutions.


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Natural cycles (1)http://www.learner.org/courses/envsci/unit/text.php?unit=8&secNum=2

Natural cycles are the processes by which all essential materials

flow through the living and the non-living parts of ecosystems.

Ecosystems receive materials as inputs and release them as

outputs. The cyclic path of material flow reuses the basic elements

over and over. Natural cycles supply ecosystems with nutrients, energy and

water.

Examples are the water, the carbon and the nitrogen cycles.

The smooth and steady functioning of cycles directly impactsecosystem stability. Conversely, disturbed cycles contribute

directly to ecosystem vulnerability.
http://www.learner.org/courses/envsci/unit/text.php?unit=8&secNum=2http://www.learner.org/courses/envsci/unit/text.php?unit=8&secNum=2http://www.learner.org/courses/envsci/unit/text.php?unit=8&secNum=2


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Natural cycles (2)CSU -http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html

Biogeochemical cycles are part of the larger cycles that describe

the functioning of the whole Earth. Biogeochemical cycles

correspond to the movement (or cycling) of matter through a

system.

The most important biogeochemical cycles affecting ecosystem

health are the water, carbon, nitrogen, and phosphorus cycles.

Biogeochemical cycles are cycles of materials or molecules

through the atmosphere, the hydrosphere, the lithosphere and the

biosphere.
http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html


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Biogeochemical

cycles (CSU)

Biologia + Geoqumica

= Biogeoqumica

Cincia que estuda o

ciclo do carbono (por

exemplo) e suasinterconexes com ciclos

de outros elementos

envolvidos no processo

da vida (principalmente

nitrognio, oxignio,

fsforo e enxofre).


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Nutrient cycles

CSUColorado State University.

http://www.colorado.edu/GeolSci/courses/

GEOL1070/chap04/chapter4.html

Movements through the

atmosphere are generally rapid,

while movements through the soils

are generally slow.

Increased transport by stream flow

severely disrupts the cycles of

elements without a gaseous phase.

Movements from terrestrial

biosphere to the ocean (via stream

flow, usually) must be replaced by

movements either through the

atmosphere (such as with nitrogen

and carbon) or by weathering (such

as with phosphorous or calcium).
http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html


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Water cycle (1)CSU -http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html

The most familiar of all

cycles is the water

cycle. The movement of

water is critical in all

cycles.

The water cycle helps to

demonstrate

connections between

local and globalecosystems.


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Water cycle (2)


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Water cycle (3)flows in km3/yearhttp://www.learner.org/courses/envsci/unit/text.php?unit=8&secNum=2

Water vapor

redistributes energy

from the sun around

the globe through

atmosphericcirculation.

Solar radiation drives

evaporation. This

process consumesnearly one-third of the

incoming solar energy

that reaches Earth's

surface.
http://www.learner.org/courses/envsci/unit/text.php?unit=8&secNum=2http://www.learner.org/courses/envsci/unit/text.php?unit=8&secNum=2http://www.learner.org/courses/envsci/unit/text.php?unit=8&secNum=2


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Water cycle (4)CSU

P: precipitation

Total 496,000 km3/yr (land 111,000

+ ocean 385,000)

E: evaporation

Total 496,000 km3

/yr (land 71,000+ ocean 425,000)

T: transpiration included in plant

evaporation

R: surface runoff26,000 km3/yr

SR: sub surface runoff(liquid12,000 + ice 2,000)

I: infiltration 14,000 km3/yr

S: springs 2,000 km3/yr

1 km3/yr = one trillion liters/year


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Water cycle (5)http://www.learner.org/courses/envsci/unit/text.php?unit=8&secNum=2

Estimate of the world water balance. Source: MIT OpenCourseWare.

Surface area

(million km2)

Volume

(million km3)Volume (%)

Equivalent depth

(m)Residence time

Oceans and seas 361 1,370 94 2,500 ~4,000 years

Lakes andreservoirs

1.55 0.13


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Carbon cycle (1)


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Carbon cycle (2)

CSUColorado State University.http://www.colorado.edu/GeolSci/courses/GE

OL1070/chap04/chapter4.html

One of the most

important to humans:

one of the primaryelements forming

human tissues;

and because it is

important to theclimate system;

carbon dioxide (CO2)

and methane (CH4) are

GHG.
http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html


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Carbon cycle (3)CSU

Fluxes to & from land: (GtC/year)

P: photosynthesis -120

PR: plant respiration - 60

SR: soil respiration - 60

SF: plants to soils - 60

FFF: fossil fuel formation - 0.0001FFB: fossil fuel burning - 6

DEF: deforestation - 2

Fluxes to & from ocean: (GtC/year)

D: dissolving - 107

E: exolving - 103CP: carbonate formation - 4

W: weathering - 0.6

Fluxes from volcanoes: (GtC/year)

V: 0.1


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Carbon cycle (4)IPCC (2003)


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Carbon cycles (5): carbon residence timeCSU

Some in fluxes are not balanced by out fluxes (e.g., the

atmosphere and fossil fuels). So residence time are slightly

different (and reservoirs are growing... or shrinking).

The RT of carbon in the air (mostly CO, but some CH4) is long

enough that the air is well mixed (mixes in about 1 year).

The RT of soils: some parts cycle very slowly (1,000's of years),

some parts very rapidly (a few weeks to monthse.g., leaves)

The RT of fossil fuels reflects all fuels suspected to exist: coal:

~ 350 years; oil: ~ 40 years; natural gas: ~ 60 years.

The RT of ocean: the surface water (short RT, few months to

years) and deep water (long RT, 200 to 400 years). Ocean RT

reflects the circulation of the ocean (deep water formation).
http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html


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Carbon cycles (6): silicatesCSU

Long term cycle of the carbon cycle, tied with the rock (silicate) cycle. The time

scale for this cycle is millions to hundreds of millions of years.

On this time scale, carbon cycling by plants, oceans and the atmosphere is

thought to be in balance (steady state orequilibrium) ... so carbon dioxide levels

in the atmosphere are thought to be controlled by weathering rates and rates of

volcanic eruptions.

Weathering rates are thought to be controlled by rate of tectonic uplift: more

uplift, more weathering and less atmospheric carbon dioxide. This may explain

the slow decline in atmospheric carbon dioxide from levels of several thousand

ppm about 100 million years ago, to 280 ppm in the pre-industrial time: during

this time, the Tibetan Plateau and Rocky Mountain Plateau were raised by

tectonic activity.
http://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.htmlhttp://www.colorado.edu/GeolSci/courses/GEOL1070/chap04/chapter4.html


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Nitrogen cycle (2)


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Nitrogen cycle (3): chemical cycles and

reservoirs (CSU)

F = fixation;

D = denitrification ;

O = oxidation .

Atmosphere: 4,000,000 Gt

Land Plants: 3.5

Soils: 9.5 Gt

Oceans: 23,000 Gt

Sediments and rocks:

200,000,000 Gt


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Nitrogen cycle (4):

fluxes (CSU)

Fluxes: (in Mtyear )

LF: Land Fixation 140

LD: Land denitrification 130

OF: Oceanic Fixation 50

OD: Oceanic denitrification 110

I: Industrial dixation 100FFB: Fossil fuel burning 20

BB: biomass burning 10

L: Lightning 20

D: Decay 1200

G: Growth 1200L-O: Land-to-Ocean 48 (rivers

36; dust 6; NOx 6)

O-L: Ocean-to-Land 15 (sea

spray)

Burial: 10


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Nitrogen cycles (5)CSU

Industrial fixation is used to make fertilizers to provide usable

nitrogen for crops. This flux is comparable to natural fixation.

Specialized bacteria and lightning are the only natural ways that

nitrogen is fixed.

How did agriculture survive before fertilizers? Early civilizations

had to rely on natural regeneration of fixed nitrogen:

Annual floods bring fresh sediments (e.g., Nile Valley);

Slash/burn agriculture: once the soil nutrients are depleted,

move on to a new place;Crop rotation: certain crops (e.g. soybeans) are good at fixing

nitrogen, others (e.g. corn) use it up; plant on alternate years.


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Nitrogen cycles (6): residence timesCSU

Nitrogen in the atmosphere: 14 million years; land plants: ~ 3 years; oceans: ~

20,000 years; soils: ~ 9 years

As pollutants: NOx ~ 4 days and as N2O ~ 120 years.

In reservoirs where N2 is the dominant form (of nitrogen) (e.g., atmosphere,

ocean), the residence times is long.

In reservoirs where fixed nitrogen is dominant (e.g., soils, plants), the residence

times is short.

N2 is very stable, but fixed nitrogen compounds are very reactive (that's why

plants can utilize them).

Eutrophication corresponds to increasing the nutrients in a body of water.Runoff carrying excess nitrate fertilizers enriches these bodies of water;

algae respond to this first and excess algae implies depletion of O2 in the water.


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Phosphorus cycle (1)

Importance: phosphorus is a necessary, limiting nutient and

Phosphate runoff causes eutrophication.


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Phosphorus cycle (2)


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Phophorus cycle (3): reservoirsCSU

Earth's Crust: 20,000,000,000 Mt

( recoverable : ~20,000) (most of

the phosphorus is in rocks).

Ocean: 100,000 Mt; Freshwater:

~100 Mt; Land Plants: ~3,000 Mt;

Soils: ~100,000 Mt.

Main fluxes (Mt/year)

M: Mining - 50 (humans)

F: Fertilization - 50 (humans)

W: Weathering -10

R: Runoff - 20

B: Burial - 13

D: Decay - 200

G: Growth - 200


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Phosphorus cycles (5): fluxesCSU

Ocean deposits: 5,000 years (with respect to input). Availability to

marine organisms is limited by the fact that most P is in the deep

ocean.

Land deposits: for phosphate rocks, 44 years.

Longer if less concentrated deposits are mined (~ 175 years).


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Ciclos na natureza (2)(Klee e Graedel, 2004))

A mobilizao antropognica deCarbono, Nitrognio e Fsforo.

O problema est em que tais

mobilizaes alteram ciclos vitais

no planeta.


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MobilizaoAntropognica [Gg/ano]

MobilizaoNatural [Gg/ano]

Minerao ________ Decaimentono oceano

4.860 Mobilizao

total

[Gg/ano]

118.450.281

Fsseis 7.013.630 Oceano p/atmosfera

9.991 Antropognica/Natural

10,37%

Biomassa 4.110.800 Produode plantas

107.311.000 Antropognica/Total

9,39%

Total 11.124.430 Total 107.325.851

Ciclo de CarbonoKlee e Graedel (2004)

Gg = 1.000 t

ciclos da natureza

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