LAND POLLUTION IS the degradation of the land surface through misuse of the soil by poor agricultural practices, mineral exploitation, industrial waste dumping, and indiscriminate disposal of urban wastes. It includes visible waste and litter, as well as pollution of the soil. The contamination of land usually results from its commercial and industrial uses or from the spillage and dumping of waste, including landfill. These activities leave behind levels of trace metals, hydrocarbons and other compounds on the land, which have the potential to cause harm to people or the environment. The main human contributors to pollution are landfills. About half of the waste is disposed of in landfills. The gradual decomposition of landfill wastes over several decades also generates new environmental problems in the form of air pollutants. Trace organic gases are emitted from landfills, along with significant amounts of methane and carbon (IV) oxide, both of which are greenhouse gases. Garbage and other forms of waste arising from homes, municipalities, industries, and agricultural practices are the major sources of pollution on the land environment. The indiscriminate discharge of these wastes into the environment creates a filthy environment.
Unlike contaminated air and water, which directly affect human health, pollution of the land from the dumping or burial of solid wastes affects people less directly. The primary environmental concern is that a waste material in the soil may migrate into surface water or groundwater where it can be ingested and harm living organisms. Soil pollution is mainly due to chemicals in pesticides. Soil erosion and degradation are some of the problems facing the state of the land. The causes are losing six hectares of land every year, and losing 24 billion tons of topsoil. Globally, a minimum of 15 million acres of prime agricultural land is lost to overuse and mismanagement every year. Desertification is threatening about one-third of the world’s land surface.
TYPES OF WASTE
Litter is waste material dumped in public places such as streets, parks, picnic areas, bus stops, and near shops. The accumulation of waste threatens the health of people in residential areas. Waste decays, encourages household pests, and turns urban areas into unsightly, dirty, and unhealthy places to live in. The following measures can be used to control land pollution. Anti-litter campaigns can educate people against littering, organic waste can be dumped in places far from residential areas, and inorganic materials such as metals, glass, paper, and plastic can be reclaimed and recycled.
One of the main factors influencing fast generation of municipal sewage and garbage and agricultural, commercial, and industrial wastes is population growth. The world human population has increased tremendously, and there has been phenomenal urban growth due to the migration of rural-area dwellers to urban areas. The larger the population, the larger the wastes generated and the greater the pollution. Pollution becomes even more pronounced when the population is crowded into a smaller space.
The sources of domestic wastes are garbage, rubbish, and ashes. Municipal wastes emanate from bulky wastes, street refuse, and dead animals. Municipal solid wastes are wastes collected by private or public authorities from domestic, commercial, and industrial sources. No two wastes are the same. The wastes generated within a municipality vary widely depending on the community and its level of commercial venture. The data on waste will depend on the level of sophistication of the waste management operation. Domestic waste from a house will vary from week to week and from season to season. Waste varies from socioeconomic groups and from country to country. In most cases, the number of refuse dumps decreases with increasing distance from the city center. Other factors that influence the distribution of solid waste dumps in cities are distance from main markets, positions of residential houses, commercial and industrial centers, and topographic characteristics of the city that determine accessibility by vehicles.
Commercial wastes are traceable to markets, stores, and shops, while industrial wastes are from factories, power plants, and treatment plants. Commercial, domestic, agricultural, and industrial activities generate vast amount of wastes, which include paper, food, metals, glass, wood, plastics, and dust. Effluents from domestic and industrial sources are also potential land pollutants. Many commercial houses and industries, especially in developing countries, do not have an organized method of disposing of their wastes. They are dumped indiscriminately, thus constituting a menace, and if they are toxic or in any way harmful, they become hazardous to the health of the public. Spillage of oil on land is a source of pollution. Land can also be polluted by the introduction of pesticides. Acid deposition also changes the integrity of the land. Contamination of land gives rise to impairment of the quality of groundwater, and impoverishment of soil to the extent of not supporting plant and animal life. Land pollution leads to the uptake of pollutants by plants, thereby introducing the pollutant to the food chain.
Garbage or trash is a component of municipal solid waste, which includes all of the wastes commonly generated in residences, commercial buildings, and institutional buildings. Municipal solid wastes consist of such things as paper, packaging, plastics, food wastes, glass, wood, and discarded appliances. Similar kinds of wastes generated by industrial facilities also are part of municipal solid wastes. The additional wastes generated by manufacturing processes, construction activities, mining and drilling operations, agriculture, and electric power production are referred to as industrial wastes. The environmental threats posed by municipal and industrial wastes are varied. Though defined as nonhazardous wastes, many of these wastes are capable of harming human health and the viability of other living species. They contain discarded hazardous wastes like batteries, paints, solvents, and waste motor oil, items that add trace metals and organic compounds to the inventory of potential contaminants in soil.
Land pollution occurs in many forms. Some of the sources of land pollution are agricultural, commercial, industrial, military, and from the general public. About half of the waste is disposed of in landfills.
Environmental pollution by industrial wastes has become a threat to the continued existence of plants, animals, and humans. Industrial pollution contains traces of quantities of raw materials, intermediate products, final products, coproducts, and by-products, and of any ancillary or processing chemicals used. They include detergents, solvents, cyanide, trace metals, mineral and organic acids, nitrogenous substances, fats, salts, bleaching agents, dyes, pigments, phenolic compounds, tanning agents, sulfide, and ammonia. Many of these substances are toxic. Because of the larger volumes of waste materials, landfills are the preferred method of waste disposal. The pollutants arising from a particular industry are different from those arising from another industry. The waste generated differs from industry to industry. The level of pollution arising from the industry depends on the nature and magnitude of its wastes.
Pollution by trace metals occurs largely from industries, trade wastes, agricultural wastes, and automobile exhausts. These wastes are large in magnitude and varied in types. They include large quantities of raw materials, by-products, coproducts, and final products. Mining is a major area where metal pollution occurs. Apart from natural occurrence such as erosion, metal pollution on land is a direct result of anthropogenic activities. The dumping of old or damaged vehicles on land occurs especially in developing countries. Also, the dumping of obsolete or dangerous military wastes on sites is another source of pollution. Apart from trace metals, the wastes contain organic materials, biological and chemical warfare explosives, pesticides, solid objects, and other materials peculiar to military operations. Trace metals in soil also can enter the food chain via uptake by plants and vegetation that are subsequently consumed by animals and humans, with deleterious consequences. Land disposal sites serve as breeding grounds for disease-carrying organisms.
Pollution from agricultural practices is due to animal wastes, materials eroded from farmlands, plant nutrients, vegetation, inorganic salts, and minerals resulting from irrigation and pesticides that farmers use on their farms to increase agricultural yield and fight pests and weeds. Agricultural wastes are made up of unwanted parts of crops during harvesting season. Examples are maize sheaves and cobs, maize stalks of guinea corn, millet and rice and their chaffs, yam vines, cassava stems, and yam and cassava peelings. Studies have shown that groundwater can be contaminated through seepage by leachate arising from solid wastes dumped on the ground. Land application of wastes is the most economical, practical, and environmentally sustainable method for managing agriculture wastes, especially animal wastes. Application of agricultural wastes to the land recycles valuable nutrients and organic matter into the system from which they originated. Land application can also be an effective component of management strategies for other organic wastes like food processing wastes.
Radioactive wastes are peculiar and dangerous. Their harmful effects on living organisms are induced by radiation, rather than by chemical mechanisms. They also remain dangerous for several years. Radioactive wastes are products of usage of nuclear energy. An example is the mining of uranium ore and its processing into nuclear fuel, which is used for electric power production. Power plants may also be radioactive. The environmental impacts of nuclear waste vary with the nature and form of the waste material. The most dangerous of these include the spent fuel from nuclear reactors, as well as the radioactive liquids and solids produced from any reprocessing of spent fuel. This high-level waste is characterized by the intensity of its radioactivity and long half-life. Death from exposure to intense radiation can occur, depending on the intensity and duration of the exposure. Human exposure can occur through inhalation of radioactive substances and ingestion of food containing radioactive materials.
WAYS TO MINIMIZE WASTE
The best way to avoid the environmental problems of solid waste disposal is to desist from generating wastes in the first instance. Pollution prevention programs aimed at this objective have become widespread. Recycling and reuse of materials are ways to avoid waste generation. At the residential level, recycling programs for newspapers, glass, and metal containers have been implemented. However, some municipal programs have been criticized for increasing environmental emissions of air pollutants from the fuel combustion.
The ultimate land disposal methods used for municipal solid wastes are land filling, land farming, and deep well injection. Land filling of solid wastes involves the controlled disposal of solid wastes on or in the upper layer of the Earth’s mantle, which has been excavated to a depth of about 13 ft. (4 m.). When solid wastes are placed in sanitary landfills, biological, chemical, and physical processes occur. Biological decay of organic materials occurs by either aerobic or anaerobic processes, resulting in the evolution of gases or liquids. The chemical oxidation of waste materials occurs, dissolving and leaching of organic and inorganic materials by water and leachate moving through the fill also occur.
Land filling in moist climates produces large quantities of leachate that are toxic and of high organic strength and require treatment in waste-water plants. Land filling in dry climates produces localized air pollution problems. There is also movement of dissolved material by concentration gradients and osmosis. Initially, the organic material in the landfill undergoes aerobic decomposition due to some oxygen amount obtained in air trapped in the landfill. Within a few days, the oxygen content is exhausted and long-term decomposition occurs under aerobic conditions. The anaerobic conversion of organic compounds occurs in the transformation of high molecular weight compounds catalyzed by enzymes in soil bacteria into compounds suitable for use as a source. However, landfill sites cause soil and groundwater contamination if not properly operated. Additional environmental problems with landfill are odors, litter, scavengers, and rat infestation.
Solid wastes are those wastes from human and animal activities. In the domestic environment, the solid wastes include paper, plastics, food wastes, and ash. Improper management of solid wastes has direct adverse effects on health. Solid wastes may contain human pathogens, animal pathogens, and soil pathogens. Inadequate storage of such wastes provides a breeding ground for vermin, flies, and cockroaches, which may act as passive vectors in disease transmission. The pathogens that can cause fecal-related diseases are viruses, bacteria, protozoa, and helminths. As proper waste management involves recycling, reuse, transformation, and disposal, it is relevant to know the physical, chemical, energy, and biological properties of wastes. The physical properties that are relevant include density, moisture content, particle size distribution, field capacity, hydraulic conductivity, and shear strength. Chemical analyses required are proximate analysis, ultimate analysis, and energy content analysis. The important elements in waste energy transformation are carbon, hydrogen, oxygen, nitrogen, and sulfur.
Only 2 percent of waste is actually recycled. Solid waste recycling implies recovery of a component of waste for use in a manner different from its initial function. Recycling consists of recovering from waste the matter of which a product was made and reintroducing it into the production cycle for reproduction of the same item. Composting after decomposition by aerobic bacteria mostly readily recycles garbage, grass, and organic matter. Composting may be defined as the decomposition of moist, solid, organic matter by the use of aerobic microorganisms under controlled conditions. The end product of the decomposition is a sanitary, nuisance-free, humus-like material that can be used as soil conditioner and as partial replacement for fertilizer. In a typical operation, the municipal wastes are presorted to remove noncombustible materials and those that might have salvage value such as paper, cardboard, rags, metals, and glass. Refuse is then shredded and stacked in long piles where it degrades to humus much as it would in soil. Usually, the decomposed material contains less than 1 percent of each of the three primary fertilizer nutrients. The final step is grinding and bagging for ultimate sale as soil conditioner.
Plants die because of land pollution. Crops are affected, as they do not mature and grow well. There are three ways that people pollute the land: littering all over the land, improper garbage disposal, and dumping of chemical fluids on the land. It is not uncommon to see people throw the trash on the road while in the car. Every day, people are polluting the land. Because of pollution, people do not only affect the cleanliness of the land, but also destroy the beauty and increase avenues of contracting diseases. These negative tendencies have effects on tourism potentials of nations as tourists are turned off. Tourists won’t like to take risks in an unsafe environment because of pollution. Mosquitoes live in littered empty cans. Thus, the threat of mosquito bite is imminent in a polluted land. A greater proportion of land pollution is instigated and carried out by man. Governments of nations should be alive to their responsibilities of providing a safe and secured world environment to its people.
