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Environmental Geochemistry I.

Aleš Bajer

Tento projekt je spolufinancován Evropským sociálním fondem a Státním rozpočtem ČR InoBio – CZ.1.07/2.2.00/28.0018

Environmental Geochemistry

Selected topics:

The Earth and Lithosphere

The structure of the Earth

Principles of Geology

Internal (endogenic) processes: Plate tectonics, Earthquakes,

Volcanoes

Surface processes: Weathering, Mass Wasting

Principles of Soil Science

Environmental Geochemistry

Selected topics:

Water and hydrosphere

The hydrologic cycle

Oceanic circulation

Composition of sea water

Fresh water

Ground water

Glaciers and Ice Ages

Desert and desertification

Human impact on water

Environmental Geochemistry

Selected topics:

Atmosphere

Structure of the atmosphere

Composition of the atmosphere

Origin and evolution of atmosphere

Human impact on the atmosphere

Environmental Geochemistry

Selected topics:

Biosphere

Biogeochemical evolution, Gaia hypothesis

Waste and Waste management

Mineral and energy resources

Alternative energy resources

Seminar work:

themes:

Ecological problems of your hometown or country

Geochemistry – current important problems for example : Expansion of solar energy in CZ

Fresh water pollution (Brno dam)

Motor - vehicle traffic in cities

etc…….

- 5 pages max.

- PowerPoint presentation (15 - 20min.)

Environmental geochemistry

Exam:

Possible after presenting your seminar work and

handing over it in writing form.

written test

Environmental geochemistry

Structure of the Earth

Theory of Earth layers

- Core: Fe, Ni

Inner Core

Outer Core

- Mantle: denser than Crust,

Fe, Mg, Silicates

- Crust: thin surface layer

(8 elements, O, Si, Al, Fe,

Ca, Mg,K, Na)

Continental crust

Oceanic Crust

Structure of the Earth

Theory of Earth layers

- Hot layer „Asthenosphere“

between Mantel and Crust

- Rigid crust floats on

plastic Asthenosphere

Plate tectonics theory

- above surface layers:

Hydrosphere

Atmosphere

Biosphere

Structure of the Earth

Geochemical classification of the elements

-lithophiles: elements concentrated in the crust

Si, Al, Mg, Ca etc.

- chalcophiles: element (metal) concentrated in crust combination

with sulfur - Cu, Zn, Pb, Sn etc. important ore minerals

-siderophiles: element concentrated in core – Ni, Fe, Co, Pt, Au…

-atmosphiles: volantile elements, concentrated in the atmosphere

H, N, He, innert gasses

Structure of the Earth

The Earth´s Crust

-The thinnest and outermost layer (cool, rigid, brittle)

- Two types:

Oceanic crust : 5-10 km thick, composed mostly of basalt

Continental crust: 22 – 50 km thick, composed mostly of granitic

rocks

Structure of the Earth

Plate Tectonics

- The rigid lithosphere floats on the asthenosphere

- the litosphere is broken into seven large and several small plates

- plates moved in different directions

- three types of plate boundaries

Structure of the Earth

Structure of the Earth

Structure of the Earth

Structure of the Earth

Structure of the Earth

Structure of the Earth

Earthquakes

- is a vibration generated by sudden slippage of rocks along

the fault

- occur along tectonic plate boundaries

- produce seismic waves (primary waves P, shared waves S)

- measurement by seismograf

Structure of the Earth

Earthquakes damage

- landslides

- tsunamis

Structure of the Earth

Earthquakes damage

Structure of the Earth

Volcanoes

- Magma forms in three geologic environments:

subduction zones

spreading centers (ridges) especially mid-oceanic ridges, basaltic magma

mantle plumes (hot spots), Hawaiian Islands

- many types of volcano exist

Structure of the Earth

Volcanoes

Structure of the Earth

Volcanoes

Structure of the Earth

Volcanoes – forming of Caldera

Structure of the Earth

Mass Wasting

-main factors: steepness of the slope

rock type and layer orientation

water and vegetation

earthquakes and volcanoes

Structure of the Earth

Types of Mass Wasting

Principles of Geology

Minerals

- fundamental building component of rocks

- natural, anorganic, with crystaline structure and

characteristic chemical composition

- made up of elements (gold, quartz, pyroxene)

Main rock forming minerals

- only 20 of 3000, 10 = 90% rocks

(Feldspar, Pyroxene, Amphibole, Mica, Clay Minerals,

Olivine – Quartz, Calcite, Dolomite)

Important mineral groups

- oxides, sulfides, sulfates, halides, carbonates, phosphates,

native elements, silicates

Minerals

Feldspar - more than 50% of the Earth´s crust

- major component of common rocks

- 2 groups: orthoclase (K)

plagioclase (Ca, Na)

- resourse of mineral nutrients

Pyroxene - dark colour

- Mg, Fe

- occur in mafic rocks

Amphibole - similar to pyroxene

- more stabile than pyroxene

Minerals

Mica - plate shaped

- muscovite (K)

- biotite (Fe, Mg)

- occur in continental crust (igneous and metamorphic rocks)

Clay minerals - formation from Feldspar by weathering

- small crystals

- occur in surface rocks (sedimentary)

- important component of soil

Olivine - green

- mainly in oceanic rocks

- togehter with pyroxene in mantle rock

Minerals

Carbonates - calcite, dolomite

- near surface

- made up of organism bodies (corals)

- occur in sedimentary rocks (limestone)

Other important minerals

Ore minerals

- pyrite, chalcopyrite, galena, sfalerite – metal ore

- gold, silver, copper

- halite, gypsum, barite – building material

Accesory minerals

- rock forming (small amount)

- chlorite, serpentinite, garnet, limonite, epidote

Rocks

3 main types:

igneous, sedimentary, metamorphic

rock cycle

igneous rock – weathering – sediments – litification – sedimentary

rock – metamorphism – metamorphic rock – melting – magma –

solidification – igneous rock

There could be more variants of cycle.

Igneous rocks - forms from magma

- 2 group: intrusive (volcanic) rocks, plutonic rocks

- granite – rhyolite, diorite – andesite, gabro - basalt

Rocks Sedimentary rocks - made up of all kinds of rocks during the weathering (decompose)

- devided into three types: clastic, organic and chemical

clastic can be:

disintegrated (unconsolidated) – small fragments rocks: clay, silt,

sand, gravel

consolidated (cemented) – fragments are lithified by solution

under the pressure: conglomerate, sandstone, shale, limestone

- most widespread rocks on the surface

- formed by process called erosion

- important term is a transport by wind, gravity, stream …..and

deposit

- main soil forming rocks

- limestone can be formed by clastic, organic and chemical

processes

Rocks

Relative abundance of sedimentary rocks

Rocks Metamorphic rocks - formed by sedimentary and igneous rocks during increased

temperature and pressure

- at metamorphism the composition and the texture are changing

- special metamorphic minerals: garnet, actinolite, chlorite,

sillimanite…

- the texture is changing to coarser grain, layer texture (foliation)

- limestone – marble

- sandstone – quartzite

- shale – low slate, middle schist, high gneiss

- other metamorphic rocks: amphibolite, eclogite, granulite

Rocks

Rock cycle: rocks are continously changed over geological time

Soils - thin layer formed by interaction among lithosphere, atmosphere,

hydrosphere and biosphere, so called pedosphere

- contain 4 substances: mineral matter, organic matter, air, water

- a thin, fragile and vanishing resource

- soil is the basic natural resource (Aldo Leopold)

- important process is weathering (decomposition and desintegra-

tion)

- two types of weathering: mechanical and chemical

Soils - mechanical weathering is desintegration of rock into small pieces

and 6 main processes are involved here:

- unloading – causes the small cracks and thin layers

- freezing and thawing – expansion force of water, occur in daily

cycle

- heating and cooling – contraction and expandion is different for

different colour of minerals and rocks, this changes lead to

exfoliation

- wetting and drying – important at clay minerals

- organism – generally reduces size of rocks and minerals

- chemical weathering is decomposition of minerals and rocks

as chemical reactions transform them into new chemical

combinations, there are involved 6 main processes

Soils - chemical weathering is decomposition of minerals and rocks

as chemical reactions transform them into new chemical

combinations, there are involved 6 main processes

- dissolution – is dissolving of solid in liquid, for example NaCl

and CaCO3

- hydrolyses – is procces of reaction with water to form

hydroxydes, very important for soil forming

- acidification – natural water is weak acid that dissolves

minerals and rocks, some manmade air pollutants make up

strong acid that accelerates natural chemical weathering

- hydration – is combination of a solid mineral with water, this

reaction causes increasing of chemical structure

- oxidation – very important on surface, mineral reaction with

oxygen, most evident in iron-rich minerals

- reduction – important process in stagnant water condition –

grey-blue colour is typical

Soil profile - soil body consists of several layers called soil horizons

- on surface there is material called litter (dead plant or animal

matter)

- surface horizon – O horizon

mixture of organic component (litter and humus) and small

amount of minerals

- A horizon

mineral horizon that is dark colour due to high contents of

organic matter, it is mixture of sand, silt and clay

- E horizon

develops zone of elluviation (leaching), all matter is removed

down, typical light colour (white colour)

- B horizon

horizon of accumulation or illuviation, typical brown colour

due to iron mineral coloids

Soil profile - C horizon

zone of litter altered parrent material by soil-forming processes

Main processes:

- additions, for example organic matter

- losses (leaching)

- translocations, movement of organic

matter, clay, nutrients from one layer

to another

- transformation, clay, primare

minerals to secondary minerals

Soil forming factors

- Parent rock

strong influence that sinks during the time, provides nutrients

- Climate

influence on horizons development

- Geomorphology

orientation of slope, northern slope means more intensive and

deep development of soils

southern slope means retarded development of soils

- Time

more older = more differential soil profile

- Man

fertilization, erosion, occupation of quality land (stocks etc.)

Time

Climate impact on Soil

Brief history of life

Human precursors 8 – 5 mil. years

Primitive man 1 mil. Years

Homo sapiens sapiens 40.000 years