Encyclopedia of Global Resources part 63 ppsx

Kabat, Geoffrey C. Hyping Health Risks: Environmental Hazards in Daily Life and the Science of Epidemiology. New York: Columbia University Press, 2008. Lippmann, Morton, ed. Environmental Toxicants: Hu- man Exposures and Their Health Effects. 3d ed. Ho- boken, N.J.: John Wiley & Sons, 2009. Rodricks, Joseph V. Calculated Risks: The Toxicity and Human Health Risks of Chemicals in Our Environment. 2d ed.New York:Cambridge UniversityPress, 2007. Sala, Osvaldo E., LauraA. Meyerson, and Camille Par- mesan, eds. Biodiversity Change and Human Health: From Ecosystem Services to Spread of Disease. Washing- ton, D.C.: Island Press, 2009. Skjei, Eric, and M.DonaldWhorton. Of Mice and Mole- cules: Technology and Human Survival. New York: Dial Press, 1983. Web Site World Health Organization Environmental Health http://www.who.int/topics/environmental_ health/en See also: Air pollution and air pollution control; As- bestos; Environmental degradation, resource exploi- tation and; Greenhouse gases and global climate change; Mining safety and health issues; Nuclear waste and its disposal; Pesticides and pest control; Popula- tion growth; United Nations Convention on Long- Range Transboundary Air Pollution; Water pollution and water pollution control. Helium Category: Mineral and other nonliving resources Where Found Helium isconcentratedin some naturalgas wells, particularly in Texas, Oklahoma, and Kansas. Helium is also found in the Earth’s atmosphere. Primary Uses The most important use of helium is as a cryogenic coolant, since it permits cooling to temperatures lower than any other substance. Helium is also used as a lifting gas for airships, as a replacement for nitrogen in the breathing gas for deep-sea divers, and as an inert atmosphere for welding. Technical Definition Helium (abbreviated He), atomic number 2, belongs to the last column of the periodic table of the elements. It has two naturally occurring isotopes and an average molecular weight of 4.003. Helium is a gas, having a density of 0.1637 gram/liter at 25° Celsius and 1 atmosphere of pressure. Helium boils at −268.9° Celsius. It is the most chemically inert element in the periodic table. Description, Distribution, and Forms Helium does not form any chemical compounds. It is the lightestof the noble gases,solight that itquickly escapes into space from the Earth’s atmosphere. Thus, much of the helium now found on the Earth was produced by radioactive decay. In excess of 130 million cubic meters of helium is produced annually in the United States. A majority of this helium is used by government agencies, including the Department of Energy and the National Aeronautics and Space Ad- ministration (NASA). Small quantities of helium, pure helium 4, are produced bythe radioactivedecay ofuranium orthorium in the Earth. In locations where uranium or thorium concentrations are high, helium collects in the same cavities as natural gas. The largest concentrations of helium are found in some natural gas wells in New Mexico, Texas, Oklahoma, Utah, and Kansas in the United States; in Saskatchewan and Alberta, Canada; in South Africa; and in Russia. Helium is also present in the Earth’s atmosphere. Some of this helium was produced by radioactive decay inthe Earthandsubsequently escapedinto theair. However, high-energy cosmic rays hitting the Earth’s atmosphere also produce helium by spallation, a pro- cess in which a heavier nucleus breaks into two or more lighternucleiwhen it ishitby a high-energy par- ticle. Radioactivedecay produces onlyhelium 4, while spallation produces both helium 3 and helium 4. Thus, atmospherichelium has amuch highercontent of helium 3 than the helium obtained from natural gas wells. History Helium wasdiscovered in 1868.A Frenchastronomer, Pierre Janssen, observed the emission spectrum of the Sun’s chromosphere during the August 18 solar eclipse. He saw a yellow-orange emission line that did not correspond to that of any known element. Later that year, both Janssen and an English astronomer, 568 • Helium Global Resources Sir Norman Joseph Lockyer, observed this emission again. Lockyer named this new element helium, for the Sun (helios in Greek). In 1889, William Hildebrand, an American mineral chemist, extracted a gas from a uranium-bearing mineral, uranite. Sir William Ramsay, an English chemist, performed a similar extraction on cleveite, another uranium-bearing mineral. Ramsey sent the gas to Lockyer, who showed in 1895 that it had the same emission lines he previously observed in the Sun, providing the first identification of helium on Earth. Obtaining Helium The U.S.Bureau ofMines,which establishedthree ex- perimental plants to extract helium from the Petrolia natural gas field in Clay County, Texas, had produced about 6,000 cubic meters of helium by 1920. Helium- bearing well gas, typically about 80 percent methane, is compressed and then treated to remove carbon di- oxide, hydrogen sulfide, and water vapor. The re- maining gasiscooled to atemperature of about−150° Celsius, which liquefies almost all the hydrocarbons, leaving nitrogen andheliumin thegas phase. Thisgas is compressed again, then cooled to −196° Cel- sius, at whichpoint the nitrogenliquefies,leaving almost pure helium in the gas phase. Uses of Helium Helium has a much lower density than air; thus a helium-filled balloon will rise. The first practical application of helium was as a lifting gas for lighter-than-air craft. Although hydrogen has an even lower density, making it a more efficient lifting gas than helium, the extreme flammability of hydrogen makesits use dangerous. The U.S.Navy experimented with rigid airships, called dirigi- bles, duringthe1920’s and1930’s. In themodern era, the Goodyear Aircraft Corporation built a se- ries of nonrigid airships, called blimps, which have been used as platforms for aerial photogra- phy. Helium-filled balloons are also used for scientific research in the upper atmosphere. In 1908, Heike Kamerlingh Onnes, a physicist at the University of Leiden, in Holland, liquefied helium by compressing it to a high pressure, cooling it,then allowingthe heliumto expandthrough a small opening. Expansion causes a gas to cool, and some of the helium liquefied. Since the boiling point of helium under 1 at - mosphere of pressure is −268.9° Celsius, material brought into contact with liquid helium cools rapidly. In 1911, Kamerlingh Onnes demonstrated that the electrical resistance of mercury vanishes at liquid helium temperature. He had discovered superconduc- tivity. Helium is used to dilute oxygen in the breathing gas used by deep-sea divers. Divers must breath an atmosphere at the same pressure as the surrounding water. At ocean depths the pressure is high, and both oxygen and nitrogen dissolve in body fluids. The oxygen is consumed, but the nitrogen remains in the fluids. If divers return suddenly to the surface, they can suffer the “bends,” which results when the nitrogen expands rapidly. The substitution of helium, the least soluble gas known, for nitrogen allows divers to oper- ate at depth and then return to the surface more quickly. George J. Flynn Further Reading Cook, Gerhard A. Argon, Helium, and the Rare Gases: The Elements of the Helium Group. 2 vols. New York: Interscience, 1961. Global Resources Helium • 569 Source: Mineral Commodity Summaries, 2009 Data from the U.S. Geological Survey, . U.S. Government Printing Office, 2009. Cryogenic applications 28% Pressurizing & purging 26% Welding cover gas 20% Controlled atmospheres 13% Leak detection 4% Breathing mixtures 2% Other 7% U.S. End Uses of Helium Greenwood, N. N., and A. Earnshaw. “The Noble Gases: Helium, Neon, Argon, Krypton, Xenon, and Radon.” In Chemistry of the Elements. 2d ed. Bos- ton: Butterworth-Heinemann, 1997. Henderson, William. “TheGroup 18(NobleGas) Ele- ments: Helium, Neon, Argon, Krypton, Xenon, and Radon.” In Main Group Chemistry. Cambridge, England: Royal Society of Chemistry, 2000. Krebs, Robert E. The History and Use of Our Earth’s Chemical Elements: A Reference Guide. Illustrations by Rae Déjur. 2d ed. Westport, Conn.: Greenwood Press, 2006. Ojima, Minoru, and Frank A. Podosek. Noble Gas Geo- chemistry. 2d ed. New York: Cambridge University Press, 2002. Simpson, Charles H. Chemicals from the Atmosphere. Garden City, N.Y.: Doubleday, 1969. Web Site U.S. Geological Survey Helium: Statistics and Information http://minerals.usgs.gov/minerals/pubs/ commodity/helium See also: Atmosphere; Gases, inert or noble; Hydro- gen; Oil and natural gas drilling and wells; Oil and natural gas reservoirs. Hemp Category: Plant and animal resources Where Found Hemp, Cannabis sativa, is indigenous to temperate regions in Asia. All major industrialized countries but the United States cultivate hemp for its fibers and oil- rich seeds. The former Soviet Union was the world’s leading producer untilthe 1980’s. Ukraineand Russia are the two major producers, followed by China, Can- ada, Austria, Australia, Great Britain, North Korea, Hungary,Romania,Poland,France,Italy,and Spain. Primary Uses Cannabis was initially spread around the world because of its fiber, not its intoxicant chemicals oritsnu- tritious oil seeds. It is one of the oldest sources of tex - tile fiber, whose use for cloth can be traced to 8000 b.c.e. in China and the Middle East. Hemp fiber is also used for the manufacture of cordage, sail cloth, and fish nets. Oil extracted from seeds is used in paints, medicines, and foods. Technical Definition Cannabis sativa is a multipurpose plant that has long been cultivatedfor its(bast) fiberin thestem, versatile oil in the seeds, and a resin secreted by its leaves that contains a compound, tetrahydrocannabinol (THC), known to have psychotropic effects. The somewhat confusing common names hemp and marijuana have been applied loosely to all three forms of Cannabis sativa. However, this essay focuses primarily on its fiber and seed uses. The plants are dioecious annual herbs that produce fibers of the best quality when cultivated under temperate andwarm conditions. Hemp produces the longest bast fiber among plants. Seeds are rich in oil, which is extracted and used in a variety of products. Description, Distribution, and Forms Cannabis is the genericnamefor hemp, a highly adap- tive and successful species cultivated throughout temperate and tropical regions across the globe. The clas- sification of Cannabis has been a source of much controversy for a long time. It was first thought a rela- tive of the nettle and later considered a member of the Moraceae family. Finally, Cannabis was classified into its own family, Cannabaceae, in which the genus Cannabis and Humulus lupulus (hops) are included. It was firstnamed in 1753by Carolus Linnaeusas Canna- bis sativa, which means “useful hemp” in Latin. More confusion concerning the taxonomy of Can- nabis resulted from the naming of two other closely related “species,” Cannabis indica, by Jean-Baptiste Lamarck, for hemp plants in India, and Cannabis ruderalis, by a Russian botanist, for wild Cannabis plants he observed in western Siberia and central Asia. Even today, some still doubt that Cannabis sativa and Cannabis indica are two different species. Nevertheless, Cannabis sativa is the most wide- spread among the three. It is a tall, thin annual that grows from 1.5 to 4.5 meters,withmost leaves concen- trated at the top. The leaves are dark green in color, and eachconsists offiveto nineserrated taperingleaf- lets with sharp ends and measures at 5 to 13 centimeters long and 0.76 to 2 centimeters wide. The stem is angular, hollow, branchedon top,andcovered byfine hairs. Plants can grow in both loamy soil and poor sandy soil. They can grow in altitudes as high as 2,500 570 • Hemp Global Resources meters. Cannabisrequires plentyof light andis lesstol - erant to low temperatures. Male plants are generally taller than female ones. Male flowers also bloom two to four weeks earlier than female flowers and are small, with colors ranging from pale green, yellow, and brown to purple-red. Female flowers are bundled tightly together into clusters. The cultivation of Cannabis sativa is easy. Seeds are planted 15 to 20 centimeters apart. Plants grow quickly, up to 15 centimeters a day, with an average daily growth of 2 to 5 centimeters in height. Fruits (achenes) mature 10 to 35 days after fertilization, each containing one seed. The entire life cycle can be completed within 70-110 days. Cannabis sativa can grow in almost any soil, requiring little fertilizer, and is resistant to pests and tolerant to weeds. Hemp cultivation and processing was one of the world’s most significant industries until the mid-1800’s. The labor- intensive work of harvesting and extracting fibers from thestalk, combinedwiththe emergenceof more easily extracted fiber sources such as cotton and jute, doomed hemp’s status as the top fiber crop. History Cannabis is generallybelieved to have originatedfrom the temperate regions of central Asia, near the Irtysh River, along the edge of the Gobi Desert, or the Taklimakan Desert in China’s Xinjiang Uygur Prov- ince, north of Tibet. Hemp cultivation and use date back to prehistoric times in the Middle East and China, where the fiber was used for textiles, the seeds for food, and the oil for various products. Hemp fiber imprints foundin pottery shardsin Taiwan weremore than 10,000 years old. The ancient Asian societies used hemp fibers to make clothes, shoes, ropes, and a primitive form of paper. Evidence for such uses was uncovered in the Great Wall of China and dates back to as early as 10,200 years ago. Hemp was introduced to western Asia and Egypt and, subsequently, to Europe between 1000 and 2000 b.c.e. Extensive hemp cultivation in Europe began around 500 b.c.e. From 1500 to 1700 c.e., hemp (along with flax) was the major fiber crop in Russia and Europe. In 1545, the Spanish brought hemp to South America (Chile). The earliest cultivation of hemp inNorth America took place in 1606, by French botanist Louis Hébert in Port Royal, Acadia (now in Nova Scotia). Hemp was first grown in New England by Puritans in 1645. By 1850, hemp was the third larg - est crop in the United States. Obtaining Hemp Hemp is raised and harvested in temperate regions. Upon harvest, seeds are separated from the stalks, whose leaves had been stripped off. The stalks are then processed to extract fibers through retting, pounding, and scutching. Retting begins with sub- merging the flax stems inwater andends with bacteria rotting away cellular tissues and gummy substances, leaving the outer fibers intact. Following retting, the stalk is pounded and broken up into short bits, leaving the fiber unharmed. The scutching acts to comb nonfiber residues out of the fiber. Following these steps, the well-processed hemp fiber appears creamy white and soft and has a silky sheen. Hemp fiber so extracted was used by Levi Strauss to make the original set of jeans. However, most hemp fiber is extracted as quickly and inexpen- sively as possible. As a result, hemp is mostly used for cordage, rope, canvas, andsailcloth. Fibers forhuman cloth, including jeans, are obtained primarily from cotton. Uses of Hemp All parts of Cannabis plants are useful. For centuries, Cannabis has been the source of a versatile natural fiber and oil-rich seeds. Major uses of industrial hemp include, but are not limited to, body care products, construction, essential oils, food, livestock bedding and feed, medicines, molded plastics, nutritional supplements, paper products, and textiles. Hemp oil contains omega-3, -6, and -9 fatty acids, which nourish skin and thus can be included in many cosmetic products, such as baby moisturizer, facial cream, shaving cream, shampoo, and conditioner. The mineral oil typically used in these products has been derived from fossil fuel, the use of which is not sustainable or environmentally friendly. For construction, hemp plants can be used to make caulking, ce- ment, fiberboard, flooring, insulation, paneling, plas- ter, plywood, and roofing. Hemp oil can be used to produce nontoxic paint, varnish, and detergent. The essential oil is used as emulsion in medicines and is a key ingredient in nutritional supplements. More important, hemp seeds contain high levels of proteins and essential fatty acids, which make hemp a premier food source. The plant residues that remain after harvest and processing are an excellent source of animal bedding. Meal after oil extraction from seeds contains 30 per - cent proteins, carbohydrates, and mineral nutrients Global Resources Hemp • 571 and is often used as feed for livestock. Because of its high biomass in a wide range of habitats, hemp has an unmatched potential to be a source of biofuel, either ethanol or biodiesel. Above all, however, is the versatility of hemp fiber. Hemp fiber has been valued for three characteristics: length, strength, and durability. The primary bast fibers in the bark can reach up to 40 millimeters long, making it a great raw material for papers, clothing, and textiles. The use of hemp fibers in cloth was more common than that of linen until the fourteenth cen- tury. Hemp paper is bleached with hydrogen perox- ide, a much more environmentally friendly chemical than chlorine bleach, which is required by tree-based paper mills and pollutes water sources heavily. By the 1820’s, hemp fibers were used to make 90 percent of the canvas sails, caulk, fish nets, and rigging for ships because of their strength and resistance to decay and salt water. Hemp was considered to provide the very best of canvas for painting. Estimates indicatethat five thousand textile products and as many as twenty-five thousand other products could be produced using hemp. Because hemp is adaptable to a wide range of habitats, has an extremely high biomass, and can be used in a variety of products, legalizing its cultivation may be inevitable in the near future. Ming Y. Zheng Further Reading Bócsa, Iván, and Michael Koras. The Cultivation of Hemp: Botany, Varieties, Cultivation, and Harvesting. Translated by Chris Filben. Sebastopol, Calif.: Hemptech, 1998. Brown, L. R., et al. State of the World, 1998: Worldwatch Institute Report on Progress Toward a Sustainable Soci- ety. New York: W. W. Norton, 1998. Conrad, C. Hemp: Lifeline to the Future—The Unexpected Answer for Our Environmental and Economic Recovery. Los Angeles: Creative Expressions, 1994. Leizer, C., et al. “The Composition of Hemp Seed Oil and Its Potential as an Important Source of Nutri- tion.” Journal of Nutraceuticals Functional and Medi- cal Foods 2, no. 4 (2000): 35-54. Roulac, John W. Hemp Horizon: The Comeback of the World’s Most Promising Plant. White River Junction, Vt.: Chelsea Green, 2006. Small, E., and D. Marcus. “Hemp: A New Crop with New Uses for North America.” In Trends in New Crops and New Uses, edited by Jules Janick and Anna Whipkey. Alexandria, Va.: ASHS Press, 2002. Web Sites Hemp Industries Association http://thehia.org/ North American Industrial Hemp Council, Inc. Hemp Facts http://www.naihc.org/hemp_information/ hemp_facts.html See also: Agricultural products; AmericanForest and Paper Association; Biodiversity; Biofuels; Cotton; Flax; Hydroponics; Paper; Paper, alternative sources of; Plant fibers; Plants as a medical resource; Renewable and nonrenewable resources; Textiles and fabrics. 572 • Hemp Global Resources Numerous products are derived from hemp, including this shoe from the company Simple, featuring a design by a California teenager. (Mike Blake/Reuters/Landov) Herbicides Categories: Environment, conservation, and resource management; pollution and waste disposal Herbicides are a class of pesticide used to kill or other- wise control unwanted vegetation. They are frequently employed in agriculture and forestry. Background Herbicides are used for the control of grasses, weeds, and other plant pests. These chemical compounds kill plants or inhibit their normal growth. In general, herbicides work byinterfering withphotosynthesis, so that a plant dies from lack of energy, or by a combination of defoliation (leaf removal) and systemic herbicidal action. Herbicides are used to clear rights-of-way beneath power lines and along railways and roads. In agriculture and forest management, they are used to control weeds or to remove the leaves from some crop plants to facilitate harvesting. While herbicides may be employed in lieu of tillage, their use is more often in con- junction with tillage and other agronomic practices. During wartime, defoliants and other herbicides have been used to destroy plants that an enemy uses for cover during battle or for food. Types of Herbicides Herbicides may be selective or nonselective. Selective herbicides, such as amitrole, atrazine, monuron, pyr- idine, 2,4-dichlorophenoxyacetic acid (2,4-D), and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), target a particular plant pest and will kill or stunt weeds among crop plants without injuring the crop. For example, 2,4-D targets soft-stemmed plants, while 2,4,5-T is effective against woody plants. Cereals are crops particularly suited for treatment with 2,4-D, since the compound does not harm narrow-leafed plants but kills broad-leaved weeds. Selective toxicity minimizes the environmental impact of an herbicide. Nonselective herbicides (also called broad-spectrum or general- usage herbicides) are toxic to all plants. Examples include dinoseb, diquat, paraquat, and arsenic trioxide. Nonselective compounds are best suited for areas where all plant growth is to be suppressed, such as along railroad rights-of-way. Some compounds, known as contact herbicides, kill only those plant parts to which they are directly applied. Others, called systemic herbicides, are ab- sorbed through the plant’s foliage or roots and car- ried to other parts of the plant. When mixed with the soil, some herbicides kill germinating seeds and small seedlings. Popular inorganic herbicides include ammonium sulfate, sodium chlorate, sulfuric acid solutions, and borate formulations. Among the organic herbicides are the organic arsenicals, substituted amides and ureas, nitrogen heterocyclic acids, and phenol derivatives. Phenoxyaliphatic acids and their derivatives, a major group of organic herbicides, are selective poi- sons that readily travel from one part of a plant to another. History Agricultural societies have used simple chemical herbicides such as ashes and common salts for centuries. In 1896, a fungicidal compound known as Bordeaux mixture (a combination of copper sulfate, lime, and water) was found also to be effective against some weeds. Subsequently, copper sulfate was employed as a selective weed killer in cereal crops. By the early 1900’s, sodium arsenate solutions and other selective inorganic herbicidal mixtures had been developed. In 1932, dinitrophenol compoundswere introduced. In the early 1940’s, a new generation of herbicidal compound emerged. In an attempt to mimic natural plant hormones, the defoliant 2,4-D was created. At low concentrations 2,4-D promotes retention of fruit and leaves; at higher concentrations, it overstimulates plant metabolism, causing the leaves to drop off. A related chemical, 2,4,5-T, came intogeneral usein 1948. The years after World War II saw the first large-scale application of herbicides in agriculture and other areas. The new defoliants rapidly gained acceptance because of their effectiveness against broad-leaved weeds in corn, sorghum, small grains, and grass pas- tures. A few years after their development, these defoliants were employed as chemical weapons. During its conflict with Communist guerrillas in Malaya during the late 1940’s and early 1950’s, Britain sprayed 2,4,5- T on crops and jungle foliage to deprive the guerrillas of foodand cover. The United States conducted a similar antifood and antifoliage campaign in South Viet- nam during the 1960’s. In this campaign, dubbed “Operation Ranch Hand,” massive quantities of her - bicidal mixtures were sprayed from aircraft onto Viet - Global Resources Herbicides • 573 cong food plantations, infiltration routes, staging areas, and bases. The quantity and frequency of the spraying greatly exceeded recommended levels; in addition, mechanical problems or military need often forced aircraft to dump their herbicide loads all at once, drenching the jungle below. Soldiers, civilians, and the environment were subjected to unusually high concentrations of defoliants. One of the herbicides used in this campaign was Agent Orange, a mixture that included 2,4-D and 2,4,5-T. Commercial preparations of 2,4,5-T contain varying amount of di- oxin, a highly toxic contaminant. Agent Orange has been implicated in the increased incidence of still births and birth defects among the Vietnamese living in the areas sprayed, in the cancers and other illnesses suffered by American and Australian soldiers who were involved in the operation, and in birth defects among the children of these veterans. In 1970, the United States placed severe restrictions on domestic and agricultural use of 2,4,5-T, at about the same time the defoliation campaign was halted. U.S. Regulation of Herbicides In 1947, the Federal Insecticide, Fungicide, and Ro - denticide Act (FIFRA) authorized the United States Department of Agriculture (USDA) to oversee regis - tration of herbicides and other pesticides and to determine their safety and effectiveness. InDecember,1970, the newlyformed United States Environmental Protec- tion Agency (EPA) assumed statutory authority from the USDA over pesticide regulations. Under the Fed- eral Environmental Pesticide Control Act of 1972, an amendment to FIFRA, manufacturers must register all marketed pesticides with the EPA before the product is released. Before registration, the chemicals must undergo exhaustive trials to assess their potential impact on the environment and human health. The EPA’s decision to grant registration is based onthe de- termination that unreasonable adverse effects on human health or the environment are not anticipated within the constraints of approved usage. Beginning in October, 1977, the EPA classified all pesticides to which it has granted registration as either a restricted- usage (to be applied only by certified pest control op- erators) or unclassified (general-usage) pesticide. Karen N. Kähler Further Reading Clark, J. Marshall, and Hideo Ohkawa, eds. Environ- mental Fate and Safety Management of Agrochemicals. Washington, D.C.: American Chemical Society, 2005. 574 • Herbicides Global Resources A plane is used to spray herbicide on a rice field in Arkansas. (Robert Cohen/The Commercial Appeal/Landov) _______. New Discoveries in Agrochemicals. Washington, D.C.: American Chemical Society, 2005. Crone, Hugh D. Chemicals and Society: A Guide to the New Chemical Age. New York: Cambridge University Press, 1986. Monaco, Thomas J., Stephen C. Weller, and Floyd M. Ashton. Weed Science: Principles and Practices. 4th ed. New York: Wiley, 2002. Vencill, William K., et al., eds. Herbicide Handbook. 8th ed. Lawrence, Kans.: Weed Science Society of America, 2002. Ware, George W. Complete Guide to Pest Control: With and Without Chemicals. 4th ed. Willoughby, Ohio: MeisterPro Information Resources, 2005. _______. Fundamentals of Pesticides: A Self-Instruction Guide. 2d ed. Fresno, Calif.: Thomson, 1986. Zimdahl, Robert L. Fundamentals of Weed Science. Bos- ton: Elsevier/Academic Press, 2007. Web Sites Agriculture and Agri-Food Canada Manure, Fertilizer, and Pesticide Management in Canada http://www4.agr.gc.ca/AAFC-AAC/display- afficher.do?id=1178825328101&lang=eng Health Canada Pesticides and Pest Management http://www.hc-sc.gc.ca/cps-spc/pest/index- eng.php U.S. Environmental Protection Agency Pesticides http://www.epa.gov/pesticides/index.htm See also: Agriculture industry; Environmental Pro- tection Agency; Food chain; Monoculture agriculture; Pesticides and pest control. Hill, James Jerome Category: People Born: September 16, 1838; Rockwood, Upper Canada (now in Ontario, Canada) Died: May 29, 1916; St. Paul, Minnesota James Jerome Hill was a railroad entrepreneur who contributed greatly to American economic growth. He was also a conservationist and proponent of natural science. He wrote books, gave lectures, and financially endorsed advanced scientific farming methods for opti- mum agricultural land management. Biographical Background James Jerome Hill had nine years of formal schooling, leaving upon the death of his father in 1852. He stud- ied math and land surveying, then learned bookkeep- ing and later worked for wholesalers, dealing with freight and fuel shipping and supply. Within a de- cade, Hill had begun his own freight transportation business, soon owning both steamboat and coal busi- nesses. Hill also entered banking and began buying up bankrupt companies, remaking and selling them for a great profit. When the St. Paul and Pacific Rail- road went bankrupt during the Panic of 1873, Hill went into financial collaboration with four others and bought the line. As general manager, Hill bargained for trackage rights, upgraded the Great Northern, and built rails through the upper Midwest, the Great Plains, and the Pacific Northwest, from Minnesota to Montana. As Hill came upon areas where industry was weak, he bought and placed companies along the railroad Global Resources Hill, James Jerome • 575 James Jerome Hill was a railroad executive cumconservationist who was a proponent of agricultural land management. (Hulton Ar - chive/Getty Images) lines. He also promoted European immigration, pay - ing travel and settlement expenses for incoming im- migrants. Knowing the railroad business and the changes occurring in it, Hill bargained for better rates. Knowing grain and other markets, Hill stayed keen to the fluctuations in agricultural management. Acknowledging that his rail business shipped mostly agricultural products, Hill came to be concerned about water and land use, misuse, and what would be- come known as sustainable resource management. Impact on Resource Use A savvy entrepreneur and a staunch conservationist, Hill took interest in both high-yield agriculture and sustainable resources. With concern for how farming practices degraded the soil, he began to experiment with crop rotation, hybridizing Russian wheat in the Dakotas and developing superior livestock—using the manure to yield superior crops and to conserve soil quality.He touredthe country-faircircuit, speakingto farmers on the subject of sustainable farming and conservation, the topic of several books he wrote to further the cause. He created his own lab and hired agronomists to analyze soil and train farmers, whom he paid to practice the contemporary techniques. He also purchased livestock for farmers, extracting from them only the promise to make the prize hogs, rams, and bulls available for breeding. Hill’s work was so impressive that President Theo- dore Roosevelt was prompted to hold a White House conference on conservation in 1908—despite Hill’s contention that natural resource control should stay at state and local levels. Hill not only was keen on agricultural management but also was a financial expert. Together these traits made the economic concerns of conservative land management Hill’s number-one focus. Roxanne McDonald Web Sites HistoryLink.org Spokane Neighborhoods: Hillyard Http://www.historylink.org/ index.cfm?DisplayPage=output.cfm&File_ Id=7294 Rail Serve James J. Hill http://www.railserve.com See also: Agriculture industry; Agronomy; Animal breeding; Conservation; Conservation biology; Soil management. Horticulture Categories: Scientific disciplines; environment, conservation, and resource management Horticulture is the branch of agriculture that is con- nected with the production of plants that are directly used by humans for food, medicine, and aesthetic purposes. Background The ability to produce crops, particularly those crops associated with food and fiber, is a major economic and natural resource. Horticulture, a multibillion- dollar-per-year industry, is a multidisciplinary science that encompasses all aspects of production, for fun or profit, of intensively cultivated plants to be utilized by humans for food, medicinal purposes, or aesthetic satisfaction. Crop production islargely determined by a variety of environmental conditions, including soil, water, light, temperature, and atmosphere. There- fore, horticulture science is primarily concerned with the study of how to manipulate the plants or these environmental factors to achieve maximum yield. Since there is tremendous diversity in horticultural plants, the field is subdivided into pomology, the growth and production of fruit crops; olericulture, the growth and production of vegetable crops; landscape horticulture, the growth and production of trees and shrubs; and floriculture, the growth and production of flower and foliage plants. Each of these subdivi- sions is based on a fundamental knowledge of plant- soil interactions, soil science, plant physiology, and plant morphology. Propagation Horticulture science is concerned with all aspects of crop production, from the collection and germina- tion of seed to the final marketing of the products. Plant propagation, protection, and harvesting are three areas of particular interest to horticulturists. Generally, propagation from seed is the most com - mon and least expensive way of propagatingplants. In order to prevent cross-pollination from undesirable 576 • Horticulture Global Resources varieties, plants to be used for seed production are grown in genetic isolation from other, similar plants. At maturity, the seed is collected and is usually stored at low temperatures and under 50 to 65 percent rela- tive humidity to maintain full viability. The seed is often tested for viability prior to planting to determine the percentage of seed that should germinate. At the appropriate time, the seed is usually treated with a fungicide to ensure an adequate crop stand and planted under proper temperature, water, and light conditions. For most crops, the seed is germinated in small containers, and the seedlings are then trans- planted to the field or greenhouse. For many horticultural crops it is not feasible to produce plants from seed. For some, the growth from seed may require too much time to be economically practical. In other cases, the parent plants may produce too little or no viable seed, and in still others, there may be a desire to avoid hybridization in order to maintain a pure strain. For some plants, almost any part of the root, stem, or leaf can be vegetatively prop - agated, but chemical treatment of the detached por- tion to ensure regeneration of the missing tissue is often required. For other plants, a variety of specific vegetative plant tissues, including the roots, bulbs, corms, rhi- zomes, tubers, and runners, must be used for propagation. Individual runners are used for propagation purposes, but anumber ofcuttings canbe propagated from one rhizome. Tubers are propagated by slicing the organ into several pieces, each of which must contain an “eye” or bud. Corms and bulbs are propagated by planting the entire structure. A relatively new pro- cess of generating plants from cell cultures grown in the laboratory, called tissue culture, is a method often used to propagate pure lines of crops with a high economic value. Grafting,a specializedform of vegetative propagation, is particularly useful in tree farming. The shoot from one plant with a particularly desirable fruit quality can be grafted onto the root stock of an - other, more vigorous plant with a less desirable fruit quality. Global Resources Horticulture • 577 The Chinese floral industry has vigorously expanded since the year 2000. (Xinhua/Landov) . nutrients Global Resources Hemp • 571 and is often used as feed for livestock. Because of its high biomass in a wide range of habitats, hemp has an unmatched potential to be a source of biofuel,. from cotton. Uses of Hemp All parts of Cannabis plants are useful. For centuries, Cannabis has been the source of a versatile natural fiber and oil-rich seeds. Major uses of industrial hemp include,. the last column of the periodic table of the elements. It has two naturally occurring isotopes and an average molecular weight of 4.003. Helium is a gas, having a density of 0. 1637 gram/liter