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Green chm-ch10 Green chm-ch10 Presentation Transcript

  • CHAPTER 10 THE GEOSPHERE, SOIL, AND FOOD PRODUCTION: THE SECOND GREEN REVOLUTION From Green Chemistry and the Ten Commandments of Sustainability , Stanley E. Manahan, ChemChar Research, Inc., 2006 [email_address]
  • 10.1. The Solid Earth Geosphere : 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 Geosphere Solid inner core <liquid outer core <mantle<crust<soil Crust consists of rocks made of minerals • 49.5% O, 25.7% Si • Mostly silicon oxides or silicates , such as quartz, SiO 2 , and potassium feldspar, KAlSi 3 O 8 . Igneous rock is solidified molten rock • Undergoes weathering to produce secondary minerals . • Clays are common secondary minerals, such as kaolinite , Al 2 Si 2 O 5 (OH) 4 . View slide
  • Human Influences on the Geosphere Desertification in which normally productive soil is converted to unproductive desert. Usually in areas with marginal rainfall As 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 problem Desertification is reversible • Recharge of underground water aquifers • Maintenance of plant cover • Genetic engineering of plants that grow under adverse conditions View slide
  • 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 Geosphere Weathering 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 earth Expansive soil Permafrost Sinkholes
  • 10.3. WATER IN AND ON THE GEOSPHERE Water 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.
  • 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, FeS 2 • Filling and destruction of wetlands Direct 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 water Major effects of mining and extractive industries
  • 10.5. THE GEOSPHERE AS A WASTE REPOSITORY Municipal refuse in sanitary landfills Methane from landfills 2{CH 2 O}  CO 2 + CH 4 (10.5.1) Leachate from landfills Minimization of the quantities of materials requiring sanitary landfill • Reduce at source • Recycle wastes • Burn for fuel Secure 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
  • Soil Soil 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 spaces Soil 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 Horizons Soil 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 Soil Silicates are the most common mineral constituents of soil, including finely divided quartz (SiO 2 ), orthoclase (KAlSi 3 O 8 ), and albite (NaAlSi 3 O 8 ). 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 (Fe 3 O 4 ), epidote (4CaO • 3(AlFe) 2 O 3 • 6SiO 2 • H 2 O), calcium and magnesium carbonates (CaCO 3 , CaCO 3 MgCO 3 ), 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 Matter The 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 Humus The 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 Solution Water 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 Technology In 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 Breeding The 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 Techniques Around 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 FERTILIZERS Carbon, hydrogen, and oxygen in plant biomass from water and atmospheric carbon dioxide Calcium, magnesium, and sulfur are usually in sufficient abundance in soil. Calcium is commonly added to soil as lime (CaCO 3 ), which neutralizes soil acidity but also adds calcium to soil. Soil}(H + ) 2 + CaCO 3  Soil}Ca 2+ + CO 2 + H 2 (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 Cycle Nitrogen cycle • Atmosphere is 79% N 2 , but the N 2 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. • NH 4 + 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 NH 3 from atmospheric elemental nitrogen and elemental hydrogen produced from natural gas. • Soil microbial processes oxidize ammoniacal nitrogen (NH 4 + ) to nitrate ion, NO 3 - , the form of nitrogen most readily used by plants. • Microbial processes release gaseous N 2 and NO 2 .
  • Synthetic Nitrogen Fertilizer Production of fertilizer nitrogen starting with the catalytic Haber process at about 1000 times atmospheric pressure and 500˚C. The reaction is N 2 + 3H 2  2NH 3 (10.8.2) Anhydrous ammonia can be applied directly below the soil surface or applied as a 30% solution of NH 3 in water. • Held in soil as ammonium ion, NH 4 + • Slowly oxidized by the action of soil bacteria using atmospheric O 2 to nitrate ion, NO 3 - , which is used directly by plants. Other forms of nitrogen include solid NH 4 NO 3 and urea,
  • Phosphorus Fertilizers Phosphorus is an essential plant nutrient required for cellular DNA and other biomolecules. Phosphorus is utilized by plants as H 2 PO 4 - and HPO 4 2- ions. Phosphate minerals that serve as fertilizer phosphorus occur as fluorapatite, Ca 5 (PO 4 ) 3 F, and, Ca 5 (PO 4 ) 3 OH. Phosphate minerals are treated to make them more water soluble 2Ca 5 (PO 4 ) 3 F ( s ) + 14H 3 PO 4 + 10H 2 O  2HF( g ) + 10Ca(H 2 PO 4 ) 2 • H 2 O (10.8.4) 2Ca 5 (PO 4 ) 3 F( s ) + 7H 2 SO 4 + 3H 2 O  2HF( g ) + 3Ca(H 2 PO 4 ) 2 • H 2 O + 7CaSO 4 (10.8.5) 
  • Potassium and Micronutrients Potassium 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 PRODUCTION Most common agricultural pesticides are insecticides and herbicides Recombinant 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 H 2 SO 4 and HNO 3 • Gaseous atmospheric SO 2 , NO and NO 2 are absorbed by soil and oxidized to sulfates and nitrates. • Soil bacteria and fungi are known to convert atmospheric CO to CO 2 . • 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 Soil Many 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.
  • Desertification The 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 it Interrelated 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 Conservation The 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 Plants The 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 Erosion Among 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 Conservation Conservation 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 Characteristics Two characteristics of tolerance for herbicides that kill competing weeds and resistance to pests, especially insects, but including microbial pests (viruses) as well The 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 Crops Insect 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 Crops The most common herbicide-resistant plants are those resistant to Monsanto’s Roundup herbicide (glyphosate, structural formula below): 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 Crops Increased efficiency of photosynthesis, which is only a few tenths of a percent in most plants Development 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 tomatoes Higher levels of lycopene, which is involved with the production of Vitamin A, in tomatoes Modification 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 once Improved transgenic varieties of grass and other groundcover crops can be quite useful • 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 energy Transgenic foods that produce contain vaccines against disease • Cholera, hepatitis B, and various kinds of diarrhea • Banana as a vaccine carrier