CHAPTER 10THE GEOSPHERE, SOIL, AND FOOD PRODUCTION: THE

SECOND GREEN REVOLUTION

From Green Chemistry and the Ten Commandments of Sustainability, Stanley E. Manahan, ChemChar Research,

Inc., 2006manahans@missouri.edu

10.1. The Solid EarthGeosphere: All the rocks, minerals, soil and sediments that compose the solid earth.Geosphere connection to green chemistry• Plants that provide most food for humans and animals grow on the

geosphere.• Plants growing on the geosphere already provide, and have the

potential to provide much more, biomass for use as renewable materials, such as wood, fiber, raw materials, and fuel.

• The geosphere is the source of nonrenewable minerals, ores, fossil fuels, and other materials used by modern industrialized societies.

• Modifications and alterations of the geosphere have profound effects upon the environment.

• Sources of fresh water are stored in lakes and rivers on the surface of the geosphere, move by means of streams, rivers, and canals on the geosphere, and occur in aquifers underground.

• The geosphere is the ultimate sink for disposal of a variety of wastes

Physical Nature of the GeosphereSolid inner core<liquid outer core<mantle<crust<soilCrust consists of rocks made of minerals• 49.5% O, 25.7% Si

• Mostly silicon oxides or silicates, such as quartz, SiO2, and potassium feldspar, KAlSi3O8.

Igneous rock is solidified molten rock• Undergoes weathering to produce secondary minerals.• Clays are common secondary minerals, such as kaolinite,

Al2Si2O5(OH)4.

Human Influences on the GeosphereDesertification in which normally productive soil is converted to unproductive desert.Usually in areas with marginal rainfallAs plant cover is destroyed, surface soil erodes away, surface water is lost, groundwater in underground aquifers diminishes, fresh water sources and soil accumulate salt, and eventually the land becomes unable to support agriculture, grazing, or even significant human populations.Old problemDesertification is reversible• Recharge of underground water aquifers• Maintenance of plant cover• Genetic engineering of plants that grow under adverse conditions

10.2. ENVIRONMENTAL HAZARDS OF THE GEOSPHERE

Earthquakes consisting of violent horizontal and vertical movement of Earth’s surface resulting from tectonic plates moving relative to each other.• Liquefaction of poorly consolidated ground during earthquakes• Tsunamis from earthquakes• The anthrosphere can be constructed to minimize the effects of

earthquakes. Volcanoes due to the presence of liquid rock magma near the surface• Can cause great loss of life• Can affect weather and climate, such as occurred with the

astoundingly massive eruption of Indonesia’s Tambora volcano in Indonesia in 1815.

Surface Effects on the GeosphereWeathering is the physical and chemical breakdown of rock to fine, unconsolidated particles.Erosion occurs when weathered materials are moved by the action of wind, liquid water, and ice.Landslides occur when unconsolidated earthen material slides down a slope.Creep characterized by a slow, gradual movement of earthExpansive soilPermafrostSinkholes

10.3. WATER IN AND ON THE GEOSPHEREWater commonly moves on the geosphere in streams or rivers consisting of channels through which water flows.Rivers collect water from drainage basins or watersheds.Floodplains are subjected to periodic floods.Efforts to control floods may be helpful, but also may be counterproductive.

Groundwater aquifer

Snow, iceRiverLake, impoundmentWater in soil

10.4. ANTHROSPHERIC INFLUENCES ON THE GEOSPHERE

Human alteration of Earth surface is often harmful, but can be beneficial.Harmful effects include• Aggravated flooding• Landslides, such as from piles of mine tailings

• Acid pollutants from bacterial action on exposed pyrite, FeS2

• Filling and destruction of wetlandsDirect effects of humans on the geosphere• Construction of dams and reservoirs• Flattening whole mountain tops to get to underground coal seams• Plowing natural prairies to grow crops

Anthrospheric Influences on the Geosphere (Cont.)Indirect effects• Pumping so much water from underground aquifers that the ground

subsides• Exposing minerals by strip mining that weather to produce polluted

acidic waterMajor effects of mining and extractive industries

10.5. THE GEOSPHERE AS A WASTE REPOSITORYMunicipal refuse in sanitary landfillsMethane from landfills

2{CH2O} CO2 + CH4 (10.5.1)Leachate from landfillsMinimization of the quantities of materials requiring sanitary landfill• Reduce at source • Recycle wastes • Burn for fuelSecure landfills for hazardous wastes

10.6. HAVE YOU THANKED A CLOD TODAY?Good, productive soil combined with a suitable climate and adequate water is the most valuable asset that a nation can have.Areas that once had adequate soil have seen it abused and degraded to the extent that it is no longer productive.One of the central challenges faced by the practice of green chemistry and industrial ecology is to retain and enhance the productive qualities of soil.Soil receives pollutants• Direct, such as herbicides used to control weed growth• Indirect, such as acid from acid rain

Soil Structure and Horizons

SoilSoil is a term that actually describes a wide range of finely divided mineral matter containing various levels of organic matter and water that can sustain and nourish the root systems of plants growing on it.Soil is the product of the weathering of rock by physical, chemical, and biochemical processes that produces a medium amenable to support of plant growth.Healthy soil• Contains water available to plants• Has a somewhat loose structure with air spacesSoil supports an active population of soil-dwelling organisms, including fungi and bacteria that degrade dead plant biomass and animals, such as earthworms.Generally composed of about 95% inorganic matter, but some soils contain up to 95% organic matter, and some sandy soils may have only about 1% organic matter.

Soil HorizonsSoil horizons are formed by weathering of parent rock, chemical processes, biological processes, and the action of water including leaching of colloidal matter to lower horizons.• Most important is topsoil.

• Plant roots take water and plant nutrients from topsoil• Topsoil is the layer of maximum biological activity• Rhizosphere where plant roots are especially active• Relationships between plant roots and microorganisms in the

rhizosphere

Inorganic Solids in SoilSilicates are the most common mineral constituents of soil, including finely divided quartz (SiO2), orthoclase (KAlSi3O8), and albite (NaAlSi3O8).Other elements that are relatively abundant in Earth’s crust are aluminum, iron, calcium, sodium, potassium, and magnesium contained in minerals such as geothite (FeO(OH)), magnetite (Fe3O4), epidote (4CaO•3(AlFe)2O3•6SiO2•H2O), calcium and magnesium carbonates (CaCO3, CaCO3MgCO3), and oxides of manganese and titanium in soil.Soil parent rocks undergo weathering processes to produce finely divided colloidal particles, particularly clays.• These secondary minerals hold moisture and mineral nutrients,

such as K+ required for plant growth• Can absorb toxic substances in soil, thus reducing the toxicity of

substances that would harm plants

Soil Organic MatterThe few percent of soil mass consisting of organic matter has a strong influence upon the physical, chemical, and biological characteristics of soil• Holds soil moisture• Holds and exchanges with plant roots some of the ions that are

required as plant nutrients• Temperature, moisture, and climatic conditions significantly affect

the kinds and levels of soil organic matter• Accumulates under cold, wet conditions in which soil stays

saturated with moisture• Soil from tropical rain forests loses organic matter readily when

vegetation is removed.

Soil HumusThe plant biomass residues biodegraded by soil bacteria and fungi losing cellulose and leaving modified residues of the lignin material that binds the cellulose to the plant matter.• Humification, residue is partly soluble soil humus• Humin does not dissolve and stays in the solid soil.Soil humus• Strongly influences soil characteristics• Strong affinity for water• Exchanges H+ ion and acts to buffer the pH of water in soil (the

soil solution)• Binds metal ions and other ionic plant nutrients• Binds and immobilizes organic materials, such as herbicides

applied to soil

Water in Soil and the Soil SolutionWater is taken up by plant root hairs, transferred through the plant, and evaporated from the leaves, a process called transpiration• Most of the water in normal soils is absorbed to various degrees

upon the soil solids• Waterlogging (saturation with water) is bad for soil.• Soil solution transfers nutrients between roots and the soil solid.

10.7. PRODUCTION OF FOOD AND FIBER ON SOIL—AGRICULTURE

Agriculture is the production of food and fiber by growing crops and livestock.Agriculture is very closely tied with the practice of green chemistry in many ways.• Fertilizers, herbicides, and insecticides are produced and applied to

crops and land in enormous quantities.• Annual production of millions of kilograms of these chemicals

demands the proper practice of green chemistry and engineering.• Conservation tillage, is in keeping with the best practice of green

chemistry and industrial ecology.• Biomass produced by plants can be used as a renewable source of

organic matter as a raw material and fuel.• Some plants are now being genetically engineered to produce

specific chemicals.

Agriculture and Green TechnologyIn many respects, past agricultural practices have not been very “green.”

However domestic crops temporarily remove carbon dioxide from the atmosphere and provide organic raw materials and biomass fuel without any net addition of carbon dioxide to the atmosphere.

• Greatest incursion of the anthrosphere into the other environmental spheres

• Cultivation of soil by humans has displaced native plants, destroyed wildlife habitat, contaminated soil with pesticides, filled rivers and bodies of water with sediments, and otherwise perturbed and damaged the environment.

Plant BreedingThe basis of agriculture is the development of domestic plants from their wild ancestors.Humans selected plants with desired characteristics for the production of food and fiber and developed new species that often require the careful efforts of expert botanists to relate them to their wild ancestors.Modern plant breeding techniques

Modern Plant Breeding TechniquesAround 1900 the scientific principles of heredity started to be applied to plant breeding.• First “green revolution” in the 1950s and 1960s resulted in

varieties of rice and wheat, especially, that had vastly increased yields

• Techniques used included selective breeding, hybridization, cross-pollination, and back-crossing

• Combined with chemical fertilizers and pesticides lead to much higher crop yields

• India, for example, increased its grain output by 50%.• Plants resistant to cold, drought, and insects further increased crop

yields.• Increased nutritional values such as high-lysine corn

Modern Plant Breeding Techniques (Cont.)Development of hybrids produced by crossing true-breeding strains of plants• Corn is especially amenable to hybridization.Other factors in increased productivity include development of crop varieties that resist heat, cold, and drought; irrigation; herbicides; better tillage practices.

10.8. PLANT NUTRIENTS AND FERTILIZERSCarbon, hydrogen, and oxygen in plant biomass from water and atmospheric carbon dioxideCalcium, magnesium, and sulfur are usually in sufficient abundance in soil.

Calcium is commonly added to soil as lime (CaCO3), which neutralizes soil acidity but also adds calcium to soil.

Soil}(H+)2 + CaCO3 Soil}Ca2+ + CO2 + H2 (10.8.1)This process also adds calcium to soil.Nitrogen, phosphorus, and potassium, are commonly added to soil as fertilizers.

Aspects of the Nitrogen CycleNitrogen cycle

• Atmosphere is 79% N2, but the N2 molecule is extremely stable and not directly available to plants.

• Rhizobium bacteria growing on the roots of leguminous plants, such as clover and soybeans, convert atmospheric nitrogen to nitrogen chemically bound in biomolecules.

• NH4+ is produced when plant residues and animal feces, urine, and

carcasses undergo microbial decay.• Lightning and combustion processes convert atmospheric nitrogen

to nitrogen oxides

• Ammonia manufacturing plants produce NH3 from atmospheric elemental nitrogen and elemental hydrogen produced from natural gas.

• Soil microbial processes oxidize ammoniacal nitrogen (NH4+) to

nitrate ion, NO3-, the form of nitrogen most readily used by plants.

• Microbial processes release gaseous N2 and NO2.

Synthetic Nitrogen FertilizerProduction of fertilizer nitrogen starting with the catalytic Haber process at about 1000 times atmospheric pressure and 500˚C. The reaction is

N2 + 3H2 2NH3 (10.8.2)

Anhydrous ammonia can be applied directly below the soil surface or applied as a 30% solution of NH3 in water.• Held in soil as ammonium ion, NH4

+

• Slowly oxidized by the action of soil bacteria using atmospheric O2 to nitrate ion, NO3

-, which is used directly by plants.Other forms of nitrogen include solid NH4NO3 and urea,

UreaN C NH

H

H

H

O

Phosphorus FertilizersPhosphorus is an essential plant nutrient required for cellular DNA and other biomolecules.

Phosphorus is utilized by plants as H2PO4- and HPO4

2- ions.Phosphate minerals that serve as fertilizer phosphorus occur as fluorapatite, Ca5(PO4)3F, and, Ca5(PO4)3OH.Phosphate minerals are treated to make them more water soluble

2Ca5(PO4)3F (s) + 14H3PO4 + 10H2O 2HF(g) + 10Ca(H2PO4)2•H2O (10.8.4)

2Ca5(PO4)3F(s) + 7H2SO4 + 3H2O 2HF(g) + 3Ca(H2PO4)2•H2O + 7CaSO4 (10.8.5)

Potassium and MicronutrientsPotassium required by plants• Potassium as the potassium ion, K+, is required by plants to

regulate water balance, activate some enzymes, and enable some transformations of carbohydrates.

• Potassium for fertilizer is simply mined from the ground as salts, particularly, KCl, or pumped from beneath the ground as potassium-rich brines.

Plants require several micronutrients including boron, chlorine, copper, iron, manganese, molybdenum (for N-fixation), and zinc.• Soil normally provides sufficient micronutrients.

10.9. PESTICIDES AND AGRICULTURAL PRODUCTIONMost common agricultural pesticides are insecticides and herbicidesRecombinant DNA technology is having some significant effects upon pesticide use.• For example, splicing of genetic material into cotton, corn, and

other crops that cause them to produce an insecticide that is generated by some kinds of bacteria.

• Breeding of genetically modified plants that are not affected by herbicides, for example Roundup-ready soybeans

10.10. SOIL AND PLANTS RELATED TO WASTES AND POLLUTANTS

Soil is a repository of large quantities of wastes and pollutants, and plants act as filters to remove significant quantities of pollutants from the atmosphere.• Sulfates and nitrates from the atmosphere, including acid-rain-

causing H2SO4 and HNO3

• Gaseous atmospheric SO2, NO and NO2 are absorbed by soil and oxidized to sulfates and nitrates.

• Soil bacteria and fungi are known to convert atmospheric CO to CO2.

• Lead from leaded gasoline• Organic materials, such as those involved in photochemical smog

formation, are removed by contact with plants and are especially attracted by the waxy organic-like surfaces of the needles of pine trees.

Potential Pollutants Added Deliberately to Soil• Insecticides and herbicides added to soil for pest and weed control• Chemicals from hazardous waste disposal sites can get onto soil or

below the soil surface by leaching from landfill or drainage from waste lagoons

• Petroleum hydrocarbons, are disposed on soil where adsorption and microbial processes immobilize and degrade the wastes. Soil can be used to treat sewage.

• Leakage from underground storage tanks of organic liquids, such as gasoline and diesel fuel

• PCBs contaminating soil in New York State from the manufacture of industrial capacitors

• Analyses of PCBs in United Kingdom soils archived for several decades have shown levels of these pollutants that parallel their production.

• PCBs and similar pollutants in Arctic and sub-Arctic regions believed to be due to the condensation of these compounds from the atmosphere onto soil in very cold regions (next slide).

Distillation Process of Organohalides and Other Organic Pollutants that Concentrate in Cold Regions

Degradation and Fates of Pesticides Applied to SoilMany factors are involved in determining pesticide fate.• Adsorption of pesticides to soil, strongly influenced by the nature

and organic content of the soil surface as well as the solubility, volatility, charge, polarity, and molecular structure and size of the pesticides.

• Strongly adsorbed molecules are less likely to be released and thus harm organisms, but they are less biodegradable in the adsorbed form.

• Leaching of adsorbed pesticides into water is important in determining their water pollution potential.

• Effects and potential toxicities of pesticides to soil bacteria, fungi, and other organisms

10.11. SOIL LOSS—DESERTIFICATION AND DEFORESTATION

Soil erosion refers to the loss and relocation of topsoil by water and wind action.About a third of U.S. topsoil has been lost to erosion since cultivation began on the continent and at present about a third of U.S. cropland is eroding at a rate sufficient to lower productivity.Erosion was recognized as a problem in the central United States within a few years after forests and prairie grasslands were first plowed to raise crops, particularly in the latter 1800s leading to soil conservation measures.Water erosion is responsible for greater loss of soil than is wind erosion.See erosion patterns in the continental U.S. on the next slide.

Soil Erosion Patterns in the Continental U.S.

DesertificationThe ultimate result of soil erosion and other unsustainable agricultural practices in relatively dry areas is a condition known as desertification.Desertification occurs when soil• Loses permanent plant cover• Loses its capacity to retain moisture• Dries out• Loses fertility so that plants no longer grow on itInterrelated factors involved in desertification• Wind erosion• Water erosion (which occurs during sporadic cloudbursts even in

arid areas)• Development of adverse climate conditions• Lack of water for irrigation• Loss of soil organic matter• Deterioration of soil physical and chemical properties

Desertification (Cont.)Desertification is actually a very old problem: Middle East, North Africa, southwestern U.S.Desertification is one of the most troublesome results of global warming caused by greenhouse warming.

Deforestation• Has occurred extensively in the United States, but is now being

reversed in New England• Particularly severe problem in tropical regions• Once destroyed, tropical forests are almost impossible to restore

because tropical forest soil has been leached of nutrients by the high annual rainfalls in tropical regions.

• When forest cover is removed, the soil erodes rapidly, loses the plant roots and other biomass that tends to hold it together, loses nutrients, and becomes unable to sustain either useful crops or the kinds of forests formerly supported.

Soil ConservationThe key to preventing soil loss from erosion as well as preventing desertification from taking place lies in a group of practices that agriculturists term soil conservation.

• Construction of terraces and planting crops on the contour of the land (next slide)

• Crop rotation and occasional planting of fields to cover crops, such as clover, are also old practices

• Relatively new practice of conservation tillage which involves minimum cultivation and planting crops through the residue of crops from the previous year using minimal quantities of herbicides to deter weed growth until shading by crops prevents weed growth

Soil Conservation with Contour Planting and Terraces

Perennial PlantsThe ultimate in no-till agriculture is the use of perennial plants that do not have to be planted each year.• Trees in orchards and grape vines in vinyards• A successful grain-producing plant is one that dedicates its

metabolic processes to the production of large quantities of seed that can be used for grain.

• Perennial plants put their energy into the development of large, bulbous root structures that store food for the next growing season rather than producing grain.

• Genetic engineering may eventually develop successful grain producing perennial plants

Trees and ErosionAmong the most successful plants at stopping erosion are trees, some of which grow back from their roots after harvesting.• Wood and wood products are probably the most widely used

renewable resources.• Hybrid tree varieties have been developed that are outstanding

producers of biomass.• Wood is a renewable resource used for construction in place of

steel, aluminum, and cement, all produced by very energy-intensive processes.

• Wood is about 50% cellulose, a carbohydrate polymer that is used directly to make paper.

• Cellulose can be broken down chemically or biochemically to glucose sugar which can be used by yeasts to generate ethanol and protein.

Water and Soil ConservationConservation of soil and conservation of water go together very closely.The condition of the soil largely determines the fate of the water and how much is retained in a usable condition.Soil in a condition that retains water allows rainwater to infiltrate into groundwater.Measures taken to conserve soil usually conserve water as well.

10.12. AGRICULTURAL APPLICATIONS OF GENETICALLY MODIFIED ORGANISMS

Recombinant DNA technology involves taking genetic material from two different organisms and combining them so that traits of both are displayed.During the 1970s, the ability to manipulate DNA through genetic engineering became a reality, and during the 1980s, it became the basis of a major industry.Direct manipulation of DNA can greatly accelerate the process of plant breeding to give plants that are much more productive, resistant to disease, and tolerant to adverse conditions.In the future, entirely new kinds of plants may even be engineered.Plants produced by this method are called transgenic plants.Example: corn and cotton have been genetically engineered to produce their own insecticide.Could lead to a “second green revolution”

The Major Transgenic Crops and their CharacteristicsTwo characteristics of tolerance for herbicides that kill competing weeds and resistance to pests, especially insects, but including microbial pests (viruses) as wellThe most common transgenic crop grown in the U. S. is the soybean, of which about 89% of the crop was transgenic in 2006.The percentage of U.S. corn that was transgenic in 2005 has been estimated at 52%.In 2006, it was estimated that 83% of the cotton grown in the U. S. was transgenic.Small fractions of the potato, squash, and papaya crops were transgenic.

Insect-Resistant Transgenic CropsInsect resistance has been imparted by addition of a gene from Bacillus thuringiensis (Bt) that causes the plant to produce a natural insecticide in the form of a protein that damages the digestive systems of insects, killing them.• Bt cotton has saved as much as a half million kilogram of synthetic

insecticides in the in the U. S. each year.

Herbicide-Resistant Transgenic CropsThe most common herbicide-resistant plants are those resistant to Monsanto’s Roundup herbicide (glyphosate, structural formula below):

OH

OH

OP

H

HC

HN

H

HC

OCHO

Glyphosate, Roundup herbicide

Virus resistance in transgenic crops has concentrated on papaya, a tropical fruit that is an excellent source of Vitamins A and C and is an important nutritional plant in tropical regions.• Genetically engineered papaya resistant to ringspot virus

Future Transgenic CropsIncreased efficiency of photosynthesis, which is only a few tenths of a percent in most plantsDevelopment of the ability to support nitrogen-fixing bacteria on plant roots in plants that cannot do so now“Golden rice” which incorporates -carotene in the grain• Two of the genes used to breed golden rice were taken from

daffodil and one from a bacterium!Tomatoes that ripen slowly and can be left on the vine longer than conventional tomatoesHigher levels of lycopene, which is involved with the production of Vitamin A, in tomatoesModification of the distribution of oils in canola to improve the nutritional value of the oil• Increased Vitamin E content in transgenic canola oil

Future Transgenic Crops (Cont.)Decaffeinated coffee and tea

Coffee trees in which all the beans ripen at onceImproved transgenic varieties of grass and other groundcover crops can be quite useful

N

CN

C

CC N

C

N

O

O

CH3

H3C

H

CH3

The caffeinemolecule

• Tolerances for adverse conditions of water and temperature, especially resistance to heat and drought

• Disease and insect resistance are desirable• Reduced growth rates for less mowing, saving energyTransgenic foods that produce contain vaccines against disease• Cholera, hepatitis B, and various kinds of diarrhea• Banana as a vaccine carrier