The production of energy is growing rapidly, both per capita and in total. About 90 percent of the energy we use today comes from fossil fuel, just a few percent from nuclear fuel and about 5 percent from hydro-resources. Despite the intensive utilization of oil, gas and coal, and the pessimistic forecasts, their reserves are increasing both overall and per capita.
Globally, fossil fuel (coal, oil, peat) combustionprovides most of the power generated for industrial and domestic use. Burning of these fuels has achieved notoriety in recent years due to the large volumes of carbon dioxide (CO2) produced, the consequent buildup of this gas in the atmosphere, and its possible contribution to the greenhouse effect on the Earth. In addition, combustion of high sulphur-containing fuels in some areas has resulted in production of sulphur dioxide and sulphur trioxide that, as in the case of smelter emissions (see the previous unit) results in acid rains.
An additional environmental consequence of the use of fossil fuels for power generation derives from the many trace elements contained in the fuels. Although fossil fuels are predominantly made up of organic matter – the combustion of the carbon in these fuels being the source of energy – they also contain variable amounts of inorganic constituents retainedin the ash left after the combustion process with some emitted in fine combustion products into the atmosphere. The ash residue, called fly ash, can contain many potentially harmful elements and therefore needs to be carefully disposedof. However, some of the inorganic components are emitted during combustion and can impact the soil, water, and biosphere in the vicinity of the power plant.
Many trace elements have been detected in fossil fuels. For example, in Europe oil and coal combustion contribute significantly to atmospheric deposition of arsenic, cadmium, chromium, copper, nickel, and vanadium. Coal combustion is thought to have made a significant contribution to atmospheric lead deposition in the United Kingdom. Enhanced concentrations of uranium in many coals have resulted in enrichments of this element around coal-fired power stations. Elevated concentrations of mercury occur in some oils. Elements enriched in oil such as vanadium have also been found to be elevated in the environment in the vicinity of oil refineries.
Nuclear power generation has been utilized since the mid-1950s and accidental leakages and permitted effluentreleases have impacted the environment. The nuclear industry is now strictly regulated, but in the early years this was not so and authorized discharges of radioactivity were considerably larger. Radionuclides released at that time still pose a problem. For example, radioactive elements such as americium and plutonium released from Sellafield nuclear power station in Cumbria (England) are still retained in nearby marshy areas.
Although much of the contamination released from nuclear power plants affects only the immediate environment, the catastrophic explosion at Chernobyl in April 1986 caused widespread contamination, which seriously affected the Ukraine with radioactivity spreading over much of Europe and many other parts of the world. For example, radioactive cesium from the Chernobyl accident rained out over upland areas of the UK and high concentrations were found in sheep in the area.
Anthropogenic radioactivity in the environment poses a serious threat to human health. Of particular concern is radioactive iodine, which has been found to move through the food chain rapidly. As a result of exposure to radioactive iodine, humans are prone to increased incidents of thyroid cancer.
Geothermal energy has often been assumed to be a “clean” form of power generation. However, many geothermal areas are associated with volcanic activity and many of the hot springs actively precipitate arsenic, antimony, mercury, and thallium, whereas some geothermal waters contain very high concentrations of boron.
Hydroelectric power generation has led to problems resulting from flooding of areas where soils have been inundated it has been found that fish contain elevated concentrations of mercury. The source of the mercury has been found to be the waterlogged soil where this element becomes converted to a methylated form which is bioavailable.
Дата добавления: 2015-09-10; просмотров: 6 | Нарушение авторских правMatch the terms with definitions. | You are going to hear a report about the hydrologic cycle. Before you listen, discuss the following questions. | Terms and vocabulary | Read the text, do the exercises. | Read the text below, use the word given in capitals at the end of each line to form a word that fits in the space in the same line. | THE IMPACT OF MINING AND OIL EXTRACTION ON THE ENVIRONMENT | Read the text, do the exercises. | Answer the questions. | B. Read the text again carefully. While you read it, look for the answers to these questions. | Environmental effect of Extracting Delivering, and Using Petroleum Products |