soil chemistry lecture 1

Lithosphere (Geo-Chemistry)

Fitri Khoerunnisa, Ph.D.Mobile.081220781409

fitri@upi.edu; fkhoerunnisa(line, whatsapp)

The geosphere and geochemistry

Lithosphere:a. Geosphere and geochemistryb. Soil chemistry

The geosphere and geochemistry

A series issues :a.The extraction of earth minerals and coal. b.The low pH that drastically changes the solubilities and oxidation-reduction rates of minerals.c.Erosion caused by intensive cultivation of land wash out the topsoil from fertile farmlands.d.In some areas of industrialized countries, the geosphere has been the dumping ground for toxic chemicals, wastes, etc.

The nature of solid in geosphere

Rocks:a.composed of minerals,b.naturally occurring inorganic solid with a definite internalc.crystal structure and chemical composition. d.an aggregate of two or more minerals.

The nature of solid in geosphere

Structure and properties of minerals• The crystal structure of a mineral refers to the way in which

the atoms are arranged relative to each other (X-ray determination).

• Different minerals may have the same chemical composition, or they may have the same crystal structure, but cannot have both the identical for truly different minerals.

The characteristic of a pure crystalline mineral :a.Crystal formb.Color (luster)c. Hardness (Mohs scale : Talc (1) to diamond (10)d.Cleavage (fracture)e.Specific gravity

Kinds of Minerals

Elemental composition of the crust:a.Oxygen (49.5% ) b.Silicon (quartz, SiO2, orthoclase/KAlSi3O8) (25.7%)

c.aluminum (7.4%)d.iron (4.7%)e.calcium (3.6%)f.sodium (2.8%)g.potassium (2.6%),h.magnesium (2.1%)i.other (1.6%)

Major mineral group in the crust

Kinds of Minerals

• Clays are silicate minerals, usually containing alumunium, which constitute one of the most secondary mineral.

• Evaporites are soluble salts that precipitate from solution under special arid conditions, commonly as the result of the evaporation of seawater.

The type of evaporites:a.Halite (NaCl)b.Sylvite (KCl)c. Thenardite (Na2SO4)

d. Anhydrite (CaSO4)

e.Bischofite (MgCl2•6H2O)

f. kieserite (MgSO4•H2O)

g.gypsum (CaSO4•2H2O)

h. epsomite (MgSO4•7H2O)i. carnallite (KMgCl3•6H2O)j. polyhalite

(K2MgCa2(SO4)4•2H2O)k. kainite (KMgClSO4•11/4H2O)l. glaserite(K3Na(SO4)2)m. loeweite

(Na12Mg7(SO4)13•15H2O)

Kinds of Minerals

• Sublimates : a number of mineral substances are gaseous at the magmatic temperatures of volcanoes and are mobilized with volcanic gases. Exp: elemental sulfur, rion oxide, chlor and sulphate salts

• igneous rock:are formed under water deficient, chemically reducing conditions of high temperature and high pressure granite, basalt, quartz (SiO2), pyroxene ((Mg,Fe)SiO3), feldspar ((Ca,Na,K)AlSi3O8), olivine((Mg,Fe)2SiO4), and magnetite (Fe3O4). Igneous rocks.

• Sedimentary rocks : a result of sediment conversion (porous, soft, and chemically reactive)

• Metamorphic rock : resulted from heat and pressure conversion of sedimentary rock

The rock cycle

The rock cycle

Geochemistry

a. deals with chemical species, reactions, and processes in the lithosphere and their interactions with the atmosphere and hydrosphere.

b. explores the complex interactions among the rock/water/air/life systems that determine the chemical characteristics of the surface environment.

Weathering

Physical aspects• Other mechanical aspects are swelling and

shrinking of minerals with hydration and dehydration, as well as growth of roots through cracks in rocks.

Chemical aspects

Involves chemical mechanisms of dissolution/precipitation, acid-base reactions, complexation, hydrolysis, and oxidation-reduction.

Weathering occurs extremely slowly in dry air but is many orders of magnitude faster in the presence of water.

Weathering agent transported to chemically active sites on rock minerals and contact the mineral surfaces at the molecular and ionic level.

Weathering

Chemical Weathering

Hydration/dehydration

Dissolution

Oxidation

Dissolution with hydrolysis occurs

Acid hydrolysis

Complexation,

Soil Chemistry

• The study of the chemical characteristics of soil. • Soil chemistry is affected by mineral

composition, organic matter and environmental factors.

• Soil consists of :

(i) The unconsolidated mineral or organic material on the immediate surface of the Earth that serves as a natural medium for the growth of land plants.

Soil Chemistry

(ii) The unconsolidated mineral or organic matter on the surface of the Earth that has been subjected to and shows effects of genetic and environmental factors

Environmental factor includes: • climate (including water and temperature

effects), • macro- and micro organisms,• conditioned by relief, • acting on parent material over a period of time.

Soil Chemistry

• A product-soil differs from the material from which it is derived in many physical, chemical, biological, and morphological properties and characteristics

• An average soil sample is 45 percent minerals, 25 percent water, 25 percent air, and five percent organic matter. Different-sized mineral particles, such as sand, silt, and clay, give soil its texture.

• Topsoil is the most productive soil layer.

Composition of soil

Soil Chemistry

Soil:formed by the weathering of parent rocks as the result of interactive geological, hydrological, and biological processes. porous and are vertically stratified into horizons as the result of downward-percolating water and biological processes, including the production and decay of biomassopen systems that undergo continual exchange of matter and energy with the atmosphere, hydrosphere, and biosphereconsisting of a finely divided layer of weathered minerals and organic matter upon which plants grow, a key component of environmental chemical cycles and the most fundamental requirement for agriculture.

Nature of Soil

Soil is a variable mixture of minerals, organic matter, and water capable of supporting plant life on the earth’s surface.

It is the final product of the weathering action of physical, chemical, and biological processes on rocks, which largely produces clay minerals.

The organic portion of soil consists of plant biomass in various stages of decay.

High populations of bacteria, fungi, and animals such as earthworms can be found in soil.

Soil has a loose texture

Soil HorizonHorizons form as the result of complex interactions among processes that occur during weathering.top soil layer (A Horizon)has several inches in thicknessthe maximum layer of biological activity in the soil contains most of the soil organic matter. Metal ions and clay particles in the A horizon are subject to considerable leaching. .

Soil Horizon

Sub soil layer (B horizon)It receives material such as organic matter, salts, and clay particles leached from the topsoil.

The C horizoncomposed of weathered parent rocks from which the soil originated

Soil Particle sizes

Category of soil particle sizes:1.Gravels ( 2 -60 mm)2.Sands ( 0.06-2 mm)3.Silts (0.06-0.006 mm)4.Clays (< 0.002 mm)

Soil Constituents

Soil mineral constituent:a. quartz (SiO2)

b. Orthoclase (KAlSi3O8)

c. Albite (NaAlSi3O8)

d. Epidote (4CaO. 3(AlFe)2O3. 6SiO2.H2O)

e. Geothite (FeO(OH))f. Magnetite (Fe3O4)

g. Carbonate (CaCO3, MgCO3)

Organic Matter Soil

a. Largely determined soil productivity

b. Serves as a source of food for microorganism

c. Undergoes chemical reactions

d. Contribute to the weathering of mineral matter

Organic Matter Soil

Soil (ion Exchange)

• Organic colloids and inorganic micelles (clays) are sites of ion exchange

• Ions adsorbed to soil surfaces can be exchanged with ions in soil solution.

• Where do ions in soil come from?• Release from organic matter• Rain• Weathering of parent material

Cations Exchange

Source of charges

Strength of adsorption

Mechanism of charge balance

Cations exchange capacity

CEC factors

CEC Factors (pH)

Anions Exchange Capacity (AEC)

Relationship of CEC/AEC and pH

Measuring CEC/AEC

How to determine CEC?

Finding CEC contribution of colloid

Finding CEC of each soil type

Sodic soils

Calcareoussoils

Humid regionarable soils

Forestsoils

6

5

4

7

8

9

10

Pure waterMilk

Natural rain

BeerCoffee

Bicarbonateof soda

Milk ofmagnesia

Range found in common products

pH of Common Products & SoilspH of Common Products & Soils

pH scaleRange foundin various soils

Ion Exchanges in Soil

• Exchangeable cationsExchangeable cations (on soil surfaces) cannot be removedcannot be removed by leaching.

• Soluble cationsSoluble cations (in solution)

can be removed by leachingleaching

Ion exchange in soils

• Soil has cation exchange capacity• Organic materials exchange cations due to the

presence of carboxylate and basis functional groups

• Ion exchange causes the leaching metal ions from soil

Soil Acidity

• Plants grrow best in soil with pH near neutrality• Adicity increase limiting the productivity

Nutrients

The role of Macronutrients

Waste Disposal

Metode of disposal:a. Landfillb. Incerinationc. Recyclingd. Sustainability (biological reprocessing; energy recovery)e. Resouce recoveryf. Avoidance and reduction method

Type of wastes:a.Tracable

wastes which can be treated or rendered safeb. Intracable wastes which cannot be treated or rendered safe

Waste management

Waste disposal: Landfill

Open dumping method:any solid trashes that have been gathered only need to be piled up into two or four meters dumped in the available area before it is recycled or destroyed

Disadvantageous:1.  spreading foul odors.2.  provides the area for germs, viruses, and vermin to breed; so, it becomes the source of many diseases.3.  can contaminates the ground water.4.  prone to cause slide down.5.  occupies an unnecessarily large area

Waste disposal : Landfill

Sanitary landfills : Consisting of refuse piled on top of the ground or into a

depression such as a valley, compacted, and covered at frequent intervals by soil.

Waste disposal: Landfill

Secure landfill:Related to disposal of hazardous chemicals

Waste disposal: incerination

Incineration is a disposal method in which solid organic wastes are subjected to combustion so as to convert them into residue and gaseous products (gas, ash, heat, steam)

Waste disposal: Recycles

Recycling is a resource recovery practice that refers to the collection and reuse of waste materials such as empty beverage containers. The materials from which the items are made can be reprocessed into new products.

Recyclable material :Beverage can (alumunium), wire (Copper), aerosol can (steel), PE/PET/PP bottles, glass bottle, paperboard cartons, newspaper etc.

Waste disposal: sustainability

a. Composting : decomposition of organic matter and recycled as fertilizer

b. Anaerobic digestion : collection of processes by which microorganism breakdown biodegradable material in the absence of oxygen

c. Microbial fuel cell

Anaerobic digestion

Resources recovery

Resource recovery is the selective extraction of disposed materials for a specific next use, such as recycling, composting or energy generation. The aim of the resource recovery is to extract the maximum practical benefits from products, delay the consumption of virgin natural resources, and to generate the minimum amount of waste.

Waste reduction/ Methods of avoidance include:a.reuse of second-hand products, b.repairing broken items instead of buying new, designing products to be refillable or reusable (such as cotton instead of plastic shopping bags), encouraging consumers to avoid using disposable products c.removing any food/liquid remains from cans, d.packaging and designing products that use less material to achieve the same purpose (for example, lightweighting of beverage cans).