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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
