EPSc 116: Resources of the Earth

Lecture 24 on Ch. 9: Fertilizer and Chemical Minerals

ThemesLook at earth as a source of “chemicals,” rather than just metals

3 general groups of non-metals: fuels, fertilizer and chemical minerals, building materials

Chemical minerals are mostly precipitates from waterForm in an aqueous, sedimentary environmentTheir solubility is important to their use

Three elements essential for plant growth: nitrogen, phosphorus, potassium

Huge use of mineral-derived fertilizers: good and bad results

Halite (table salt) is the most used “chemical mineral”

Many minerals used in foods, supplements, cosmetics, medicines, toothpaste

Chapter 9 deals with a wide range of everyday and "exotic" chemical ppts.

Many of the minerals come from same geologic and chemical processes.

Water-solubility is a very big issue (1) allows build-up of dissolved constituents and eventual precipitation (2) accounts for the need for fertilizer for plants(3) causes the susceptibility of such precipitates/minerals to leaching

Geologically: Basin forms, seawater becomes isolated, water evaporates, brine forms.Saturation is reached, and one or more minerals precipitate

Evaporites are sedimentary deposits consisting of layers of individual

minerals, i.e., chemical precipitates.

Chemically Precipitated Minerals

Development of Evaporite Deposits

Evaporation – faster than water influx

Possible isolation from influx

Possible desert environment

Concentration of dissolved ions increases

Saturation is reached

Nucleation of tiny crystals occurs

Sequential precipitation of minerals

CVS4, Fig. 9.17 Evaporite basin

CVS4, Fig. 9.15

Chemically: seawater becomes increasingly concentrated (brine) and finally reaches saturation.

Cations (Na+, Ca2+) and anions (Cl-, SO42-)

build up; exceed solubility (i.e., no more can dissolve).

Sequence of minerals ppt. from evaporating seawater: CaCO3 CaSO4 NaCl Mg & K sulfates Mg & K chlorides

Much limestone forms/formed this way.NaCl (halite) and CaSO4 (anhydrite) common

CVS4, Fig. 9.16

Seawater Evaporation

Seawater

1,000,000 grams

1 metric ton 100%

% % %

(tonne)

Salt harvesting in Thailand.

© Copyright 2012, Photographer = Mike Kramer, FreeLargePhotos.com.

View of Great Salt Lake from a commercial jet.

© Copyright 2012, Photographer = Roy Tennant, FreeLargePhotos.com.

Lake Bonneville at night. Photo from National Geographic.

Lake Bonneville salt flats used as a speedway for cars and other vehicles.

Fertilizer as Example of Important Chemical Mineral

Large tonnages of rock mined for fertilizer

Chemically intense processing

Strong (+, -) environmental implications of mining, processing, and use

N, P, K (nitrogen, phosphorus, potassium) are essential plant nutrients

Incorporation into essential molecules such as proteins and DNA

Act as catalysts to important biochemical reactions

http://gardening.ktsa.com/Fall-Fertilizer/8151849

Apply nutrients to (poor/depleted) soil in water-soluble form that plant roots can take up.

Bioavailability (ability to be drawn into and used by plants) is the issue – with fertilizers, bioavailability is essential.

Note: with other chemicals, such as toxins, bioavailability is the fear (undesired).

Goals of Fertilizer Application

N, K, P: Essential Elements for Plants

For centuries, we used biological products as fertilizer: manure, guano, dead fish, bones, wood ash. Now have gone back to geological sources.

N: not much nitrogen in typical rocks (air has 78%) Natural nitrate (NO3) deposits form from evaporation of water, but nitrate is so water-soluble that minerals typically dissolve away again Manufacture of nitrogen fertilizer from nitrogen (from air) plus methane

(natural gas, CH4)

K: potassium is a geochemically abundant elementMajor component in some feldspar (pink mineral in granite) Evaporite minerals, such as KCl

P: phosphorus is essential in DNA, ATP, ADP (energy cycles of cells)Often the life-limiting element Bad aspect is eutrophication

http://libertylake.org/protection-information/

Liberty Lake, WA, in the 1970s, while suffering from eutrophication. Algae completely cover the surface.

http://05lovesgeography.blogspot.com/2011/02/eutrophication.html

Eutrophication

Entry of too much nutrient material into a lake causes algae to bloom (covering the water and blocking light) and then die (consuming oxygen from the water during their decay).

http://www.madrimasd.org/blogs/universo/2010/10/04/136756

Paracas, Peru

Value of Guano: From the Past to the Present

Found mainly on the coasts and coastal islands of Peru, Chile, West Indies, and Africa.

About 6 wt% phosphorus, 9 wt% nitrogen, 2 wt% potassium, and water

Guano from bats is considered the best organic fertilizer one can buy.

Chincha Islands off of Peru.

Guano = Valuable bird droppings

http://www.fertilizer101.org/facts/

World population

CVS4, Fig. 9.3

Change in world population vs. fertilizer use Since 1950, population ~doubled, but fertilizer use increased 10-fold.

CVS4, Fig. 9.4

World’s largest nitrate deposits are in present-day northern Chile. Extremely arid. Before late 1800s, Peru and Bolivia owned these areas.

Marine Evaporite Deposits

CVS4, Fig. 9.11

US and Canadian deposits of gypsum and anhydrite (Ca sulfate), halite (NaCl), and potassium salts. The latter mined for fertilizer (K).

Major Phosphate Deposits of the United States

CVS4, Fig. 9.6

Although ~90% of present phosphate production comes from

Florida and N. Carolina, the largest amounts of recoverable phosphate are in Phosphoria Fm.

http://www.buriedtreasurefossils.com/Chile_Fossil_Shark_Teeth.htm

http://www.eoearth.org/article/Phosphate

Phosphorite Deposits

The rocks most commonly mined as phosphate ore are sedimentary “phosphorites.”

Form from the remains of ancient organisms and also chemical precipitation from nutrient-rich upwellings in shallow ocean.

Phosphate [(PO4)3-] occurrences: bones, teeth, mineral apatite Ca5(PO4)3(OH,F,Cl), igneous rocks, sedimentary deposits and rocks.

Shark’s tooth in phosphorite from Chile.

Non-fossiliferous phosphorite, Florida

Need Phosphate in More Soluble Form

Phosphorite rock requires extensive chemical processing, e.g.,

Ca3(PO4)2 + 2H2SO4 + 6H2O CaH4(PO4)2 + 2H2O + 2(CaSO4 2H2O)phosphate rock acid water monocalcium phosphate water gypsum

[Production of phosphate fertilizer accounts for huge use of sulfuric acid]

Keep processing to get higher concentrations of phosphate in more solubleform.

Hitchhiker elements (solid solution): uranium (0.01 - 0.03 wt. % U3O8),vanadium, cadmium, selenium occur in natural phosphate deposits. Unfortunately, they can become concentrated in the fertilizer (spread onfields) or in the waste products (as in Florida) from phosphate fertilizerproduction.

.

(atomic substitution)

CVS4, Table 9.1

Problems with Mining, Processing, andUse of Fertilizer

Phosphogypsum stack in Florida

Disruption of huge expanses ofcoastal/environmentally sensitive land

Waste gypsum (phosphogypsum)

Uranium release from crushed material

Heavy-metal residues in the waste products

Eutrophication due to use of phosphatefertilizer

CVS4, Fig. 9.10

Flat-lying phosphate deposits in Florida and N. Carolina are mined by mobile drag-lines. Overburden removed, phosphate mined, then land returned to approx. original state.

Ca3(PO4)2 + 2H2SO4 + 6H2O

CaH4(PO4)2 + 2H2O + 2(CaSO4 2H2O)fertilizer gypsum

Other Chemical Elements/Minerals

Sulfur: Vulcanization (toughening) of rubber; H2SO4, chemicals Volcanoes, solfatoras, sulfate sediments, FeS2 Sulfur captured from coal-fired power plants & petroleum distillation

Halite (NaCl): Great Salt Lake; other bedded evaporite deposits; salt domesWaste Isolation Pilot Plant (nuclear wastes), New MexicoSalt: once so valuable that people were paid their salaries in salt Uses: de-icer, chemical industry (Cl2 gas), food

Fluorine: Teflon, toothpaste, HF in industry, flux in steel Fluorite, CaF2 Sources in U.S. and Mexico

Sodium sulfate and sodium carbonate: detergent, paper, baking. Evaporites. At lead-recycling plant, incorporate unwanted sulfur into saleable Na2SO4.

World and US reserves of chemical elements: very large

CVS4, Table 9.2 part 1

CVS4, Table 9.2 part 2

Salt mine under Lake Erie

Salt mine under the former Michigan basin

Underground Mining for Salt

Salt can be mined as solid material or by solution mining, i.e., pumping down steam and retrieving a brine.

Layers of bedded salt, i.e., sedimentary deposition.

CVS4, Fig. 9.B Jefferson Island salt dome, LA,

beneath Lake Peigneur

Lake Peigneur connects to Gulf of Mexico via a canal.

Mine shaft was sunk into the salt dome in 1920. Much salt removed since.

Many aquifer rock layers have been bent upward by the salt; acts as great oil traps due to salt and shale.

Oil drilling began in 1980. Accidentally emptied the whole lake into the salt mine below. No casualties.

Salt Dome Saga

Effects of “Salting-Out” in Soils

Salt-affected soils are visible on rangeland in Colorado. Salts dissolved from the soil accumulate at the soil surface and are deposited on the ground and at the base of the fence post.

From Wikipedia

Waste Isolation Pilot Plant near Carlsbad, New Mexico. Former mine in bedded salt. Has accepted nuclear waste for 10 years.

Dry Environment of Mined-Out Salt Deposits: Further Use

Naturally (Geologically) Formed and Deformed Salt

Photographed by TA Chris Thom on departmental field trip to eastern Italy along the Adriatic coast

Photographed by TA Chris Thom on departmental field trip to eastern Italy along the Adriatic coast

Deformation of Ductile, Layered Salt (NaCl = Halite)

Gypsum Caves: Very Rare

Naica crystal caves, 160 km south of Chihuahua, Mexico

Cave of Swords

Garcia-Ruiz, et al. Formation of Natural Gypsum Megacrysts.

Fluid inclusions in gypsum

http://www.pyepimanla.com/octobre-novembre/articles/religion-divers/divers/cave-of-giants-naica.html

CVS4, Table 9.3

Actual Minerals Used in Foods and Other Personal Products

Final Comments on Chemical MineralsWorld and US reserves of chemical minerals are very large, but the

geologic environments that host these materials are oftenenvironmentally sensitive.

Evaporites are not just the result of, but also a great indicator of, hot dryenvironments – of geologic and climate interest. Remember Wegener.

Evaporite minerals found on Mars Occurrence suggests earlier presence of much water on Mars’ surface

Lots of interest, speculation, and new research

Environmental impacts of mining, processing, using chemical minerals:Dig up from environmentally sensitive areas (deserts, coasts)Processing: grinding (energy, powders), use of acids, use of much

water, chemical residuesSolid wastes: gypsum, contaminated by uranium and heavy metalsFertilizer: enters groundwater & runoff, causes eutrophication of water

bodies, "salting out" in soils Capture and re-use of phosphate and other “nutrients” from sewage

1884 advertisement for guano