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譯文題目: 現(xiàn)代交通運輸對環(huán)境和歷史的影響
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Environmental Impact and History of Modern Transportation
The development of internal combustion (IC) engine vehicles, and especially automobiles, is one of the greatest achievements of modern technology. Automobile shave made great contributions to the growth of modern society by satisfying many of the needs for mobility in everyday life. The rapid development of the automotive industry, unlike that of any other industry, has prompted the progress of human beings from a primitive security to a highly developed industrial one. The automobile industry and the other industries that serve it constitute the backbone of the world’s economy and employ the greatest share of the working population.
However, the large number of automobiles in use around the world has caused and continues to cause serious problems for environment and human life. Air pollution, global warming, and the rapid depletion of the Earth’s petroleum resources are now problems of paramount concern.
In recent decades, the research and development activities related to transportation have emphasized the development of high-efficiency, clean, and safe transportation. Electric vehicles (EVs), hybrid electric vehicles (HEVs),and fuel cell vehicles have been typically proposed to replace conventional vehicles in the near future.
This chapter reviews the problems of air pollution, gas emissions causing global warming, and petroleum resource depletion. It also gives a brief review of the history of EVs, HEVs, and fuel cell technology.
1.1 Air Pollution
At present, all vehicles rely on the combustion of hydrocarbon (HC) fuels to derive the energy necessary for their propulsion. Combustion is a reaction between the fuel and the air that releases heat and combustion products.The heat is converted to mechanical power by an engine and the combustion products are released to the atmosphere.An HC is a chemical compound with molecules made up of carbon and hydrogen atoms. Ideally, the combustion of an HC yields only carbon dioxide and water, which do not harm the environment. Indeed, green plants “digest” carbon dioxide by photosynthesis.Carbon dioxide is a necessary ingredient in vegetal life. Animals do not suffer from breathing carbon dioxide unless its concentration in air is such that oxygen is almost absent.
Actually, the combustion of HC fuel in combustion engines is never ideal.Besides carbon dioxide and water, the combustion products contain a certain amount of nitrogen oxides (NOx), carbon monoxides (CO), and unburned HCs,all of which are toxic to human health.
1.1.1 Nitrogen Oxides
Nitrogen oxides(NOx) result from the reaction between nitrogen in the air and oxygen. Theoretically, nitrogen is an inert gas. However, the high temperatures and pressures in engines create favorable conditions for the formation of nitrogen oxides. Temperature is by far the most important parameter in nitrogen oxide formation. The most commonly found nitrogen oxide is nitric oxide(NO), although small amounts of nitric dioxide (NO2) and traces of nitrous oxide (N2O) are present. Once released into the atmosphere, NO reacts with the oxygen to form NO2. This is later decomposed by the Sun’s ultraviolet radiation back to NO and highly reactive oxygen atoms that attack the membranes of living cells. Nitrogen dioxide is partly responsible for smog; its brownish color makes smog visible. It also reacts with atmospheric water to form nitric acid (HNO3), which dilutes in rain. This phenomenon is referred to as “acid rain” and is responsible for the destruction of forests in industrialized countries.Acid rain also contributes to the degradation of historical monuments made of marble.
1.1.2 Carbon Monoxide
Carbon monoxide results from the incomplete combustion of HCs due to a lack of oxygen.1 It is a poison to human beings and animals who inhale/breathe it. Once carbon monoxide reaches the blood cells, it fixes to the hemoglobin in place of oxygen, thus diminishing the quantity of oxygen that reaches the organs and reducing the physical and mental abilities of affected living beings.1 Dizziness is the first symptom of carbon monoxide poisoning, which can rapidly lead to death. Carbon monoxide binds more strongly to hemoglobin than oxygen. The bonds are so strong that normal body functions cannot break them. People intoxicated by carbon monoxide must be treated in pressurized chambers, where the pressure makes it easier to break the carbon monoxide–hemoglobin bonds.
1.1.3 Unburned HCs
Unburned HCs are a result of the incomplete combustion of HCs.1,2 Depending on their nature, unburned HCs may be harmful to living beings.2 Some of these unburned HCs may be direct poisons or carcinogenic chemicals such as particulates, benzene, or others. Unburned HCs are also responsible for smog:the Sun’s ultraviolet radiations interact with the unburned HCs and NO in the atmosphere to form ozone and other products. Ozone is a molecule formed of three oxygen atoms. It is colorless but very dangerous, and is poisonous because as it attacks the membranes of living cells, causing them to age prematurely or die. Toddlers, older people, and asthmatics suffer greatly from exposure to high ozone concentrations. Annually, deaths from high ozone peaks in polluted cities have been reported.3
1.1.4 Other Pollutants
Impurities in fuels result in the emission of pollutants. The major impurity is sulfur: mostly found in diesel and jet fuel, but also in gasoline and natural gas.1 The combustion of sulfur (or sulfur compounds such as hydrogen sulfide) with oxygen releases sulfur oxides (SOx). Sulfur dioxide (SO2) is the major product of this combustion. On contact with air, it forms sulfur trioxide, which later reacts with water to form sulfuric acid, a major component of acid rain. It should be noted that sulfur oxide emissions originate from transportation sources but also largely from the combustion of coal in power plants and steel factories. In addition, there is debate over the exact contribution of、natural sources such as volcanoes.
Petroleum companies add chemical compounds to their fuels in order to improve the performance or lifetime of engines.1 Tetraethy lead, often referred to simply as “l(fā)ead,” was used to improve the knock resistance of gasoline and therefore allow better engine performance. However, the combustion of this chemical releases lead metal, which is responsible for a neurological disease called “saturnism.” Its use is now forbidden in most developed countries and it has been replaced by other chemicals.1
1.2 Global Warming
Global warming is a result of the “greenhouse effect” induced by the presence of carbon dioxide and other gases, such as methane, in the atmosphere. These gases trap the Sun’s infrared radiation reflected by the ground, thus retaining the energy in the atmosphere and increasing the temperature. An increased Earth temperature results in major ecological damages to its ecosystems and in many natural disasters that affect human populations.2
Considering the ecological damages induced by global warming, the disappearance of some endangered species is a concern because this destabilizes the natural resources that feed some populations. There are also concerns about the migration of some species from warm seas to previously colder northern seas, where they can potentially destroy indigenous species and the economies that live off those species. This may be happening in the Mediterranean Sea, where barracudas from the Red Sea have been observed.
Natural disasters command our attention more than ecological disasters because of the amplitude of the damages they cause. Global warming is believed to have induced meteorological phenomena such as “El Ni?o,” which disturbs the South Pacific region and regularly causes tornadoes, inundations, and dryness. The melting of the polar icecaps, another major result of global warming, raises the sea level and can cause the permanent inundation of coastal regions and sometimes of entire countries.
Carbon dioxide is the result of the combustion of HCs and coal. Transportation accounts for a large share (32% from 1980 to 1999) of carbon dioxide emissions. The distribution of carbon dioxide emissions is shown in Figure 1.1.4
Figure 1.2 shows the trend in carbon dioxide emissions. The transportation sector is clearly now the major contributor to carbon dioxide emissions. It should be noted that developing countries are rapidly increasing their transportation sector, and these countries represent a very large share of the world population. Further discussion is provided in the next subsection.
The large amounts of carbon dioxide released into the atmosphere by human activities are believed to be largely responsible for the increase in the global Earth temperature observed during the last decades (Figure 1.3).It is important to note that carbon dioxide is indeed digested by plants and sequestrated by oceans in the form of carbonates. However, these natural assimilation processes are limited and cannot assimilate all of the emitted carbon dioxide, resulting in an accumulation of carbon dioxide in the Atmosphere.
1.3 Petroleum Resources
The vast majority of fuels for transportation are liquid fuels originating from petroleum. Petroleum is a fossil fuel, resulting from the decomposition of living matters that were imprisoned millions of years ago (Ordovician,600–400 million years ago) in geologically stable layers. The process is roughly the following: living matters (mostly plants) die and are slowly covered by sediments. Over time, these accumulating sediments form thick layers and transform to rock. The living matters are trapped in a closed space, where they encounter high pressures and temperatures and slowly transform into either HCs or coal, depending on their nature. This process takes millions of years to accomplish. This is what makes the Earth’s resources in fossil fuels finite.
Proved reserves are “those quantities that geological and engineering information indicates with reasonable certainty can be recovered in the future from known reservoirs under existing economic and operating conditions.”5 Therefore, they do not constitute an indicator of the Earth’s total reserves. The proved reserves, as they are given in the British Petroleum 2001 estimate,5 are given in billion tons in Table 1.1. The R/P ratio is the number of years that the proved reserves would last if the production were to continue at its current level. This ratio is also given in Table 1.1 for each region.5
The oil extracted nowadays is the easily extract able oil that lies close to the surface, in regions where the climate does not pose major problems. It is believed that far more oil lies underneath the Earth’s crust in regions such as Siberia, or the American and Canadian Arctic. In these regions, the climate and ecological concerns are major obstacles to extracting or prospecting for oil. The estimation of the total Earth’s reserves is a difficult task for political and technical reasons. A 2000 estimation of the undiscovered oil resources by the US Geological Survey is given in Table 1.2.6 Although the R/P ratio does not include future discoveries, it is significant. Indeed, it is based on proved reserves, which are easily accessible to this day. The amount of future oil discoveries is hypothetical, and the newly discovered oil will not be easily accessible. The R/P ratio is also based on the hypothesis that the production will remain constant. It is obvious, however, that consumption (and therefore production) is increasing yearly to keep up with the growth of developed and developing economies. Consumption is likely to increase in gigantic proportions with the rapid development of some largely populated countries,particularly in the Asia-Pacific region. Figure 1.4 shows the trend in oil consumption over the last 20 years.7 Oil consumption is given in thousand barrels per day (one barrel is about 8 metric tons). Despite the drop in oil consumption for Eastern Europe and the former USSR, the world trend is clearly increasing, as shown in Figure 1.5. The fastest growing region is Asia Pacific, where most of the world’s population lives.An explosion in oil consumption is to be expected, with a proportional increasein pollutant emissions and CO2 emissions.
1.4 Induced Costs
The problems associated with the frenetic combustion of fossil fuels are many: pollution, global warming, and foreseeable exhaustion of resources, among others.Although difficult to estimate, the costs associated with these problems are huge and indirect,8 and may be financial, human, or both.
Costs induced by pollution include, but are not limited to, health expenses, the cost of replanting forests devastated by acid rain, and the cost of cleaning and fixing monuments corroded by acid rain. Health expenses probably represent the largest share of these costs, especially in developed countries with socialized medicine or health-insured populations.
Costs associated with global warming are difficult to assess. They may include the cost of the damages caused by hurricanes, lost crops due to dryness, damaged properties due to floods, and international aid to relieve the affected populations. The amount is potentially huge.
Most of the petroleum-producing countries are not the largest petroleum consuming
countries. Most of the production is located in the Middle East, while most of the consumption is located in Europe, North America, and Asia Pacific. As a result, consumers have to import their oil and depend on the producing countries. This issue is particularly sensitive in the Middle East, where political turmoil affected the oil delivery to Western countries in 1973 and 1977. The Gulf War, the Iran–Iraq war, and the constant surveillance of the area by the United States and allied forces come at a cost that is both human and financial. The dependency of Western economies on a fluctuating oil supply is potentially expensive. Indeed, a shortage in oil supply
causes a serious slowdown of the economy, resulting in damaged perishable goods, lost business opportunities, and the eventual impossibility to run businesses.
In searching for a solution to the problems associated with oil consumption, one has to take into account those induced costs. This is difficult because the cost is not necessarily asserted where it is generated. Many of the induced costs cannot be counted in asserting the benefits of an eventual solution. The solution to these problems will have to be economically sustainable and commercially viable without government subsidies in order to sustain itself in the long run. Nevertheless, it remains clear that any solution to these problems— even if it is only a partial solution—will indeed result in cost savings, which will benefit the payers.
現(xiàn)代交通運輸對環(huán)境和歷史的影響
內燃機的發(fā)展,車輛發(fā)動機的發(fā)展,特別是汽車,是現(xiàn)代科技的最偉大的成就之一。汽車為現(xiàn)代社會的發(fā)展作出了巨大貢獻。滿足了日常通行的便利性。汽車行業(yè)的快速發(fā)展不像其他行業(yè)一樣,是促使人類從原始安全高度進步的發(fā)達工業(yè)之一。汽車產(chǎn)業(yè)和其服務產(chǎn)業(yè)構成了世界經(jīng)濟的支柱,占據(jù)了勞動人口的最大份額。
然而,在世界各地由于使用大量的汽車引起的并繼續(xù)給環(huán)境和人類的生活造成嚴重的問題??諝馕廴?,全球變暖,地球上石油資源快速損耗的問題在現(xiàn)在看來至關重要。
近幾十年來,研究和運輸有關的開發(fā)活動強調發(fā)展高效、清潔和安全的運輸。在不久的將來電動車,混合動力電動汽車和燃料電池汽車被提出取代傳統(tǒng)的車輛。
本章回顧了空氣污染的問題,氣體排放造成的全球變暖,和石油資源枯竭的問題。同時也簡要回顧了電動汽車的歷史、混合動力汽車和燃料電池技術。
1.1 空氣污染
目前,所有汽車依賴碳氫化合物燃料的燃燒熱獲得所需的能源推進。燃燒是一個反應燃料和空氣之間的釋放熱量和燃燒產(chǎn)物的關系。熱量轉化為機械動力傳遞到發(fā)動機和燃燒產(chǎn)品釋放到大氣中。碳氫化合物是一種由碳和氫的原子組成的分子。理想情況下,燃燒碳氫化合物的收益率只有二氧化碳和水,不傷害環(huán)境。實際上,綠色植物通過光合作用“消化”二氧化碳。二氧化碳是植物生活的必要組成部分。動物呼吸二氧化碳不會導致生病除非在空氣中它的濃度過高而導致沒有氧氣一樣。
實際上,碳氫化合物燃料的燃燒在內燃機中從來都不是理想的。除了二氧化碳和水,燃燒包含一個特定的產(chǎn)品:大量的氮氧化物(NOx),一氧化碳(CO),未燃燒的高碳化合物,所有的這一些對人體健康都是有害的。
1.1.1氮氧化物
氮氧化物(NOx)與空氣中氮氣之間的反應結果是氧氣。從理論上講,氮氣是一種惰性氣體。然而,發(fā)動機的高溫和高壓為氮氧化物的形成創(chuàng)造有利條件。溫度是氮氧化物形成的最重要的參數(shù)。最常見的氮氧化物是一氧化氮(NO),盡管也有少量的二氧化碳(NO2)和一氧化二氮(N2O)。一旦釋放到大氣中,一氧化氮與氧氣形成NO2。后來被太陽的紫外線分解輻射回到一氧化氮和高度活性氧原子攻擊細胞膜的活細胞。二氧化氮是煙霧的形成部分,它的存在使煙霧形成可見的褐色。它還與大氣中的水反應形成硝酸(HNO3)稀釋在雨中。這種現(xiàn)象被稱為“酸雨”,就是這種物質在工業(yè)化國家破壞森林。酸雨也有助于大理石古跡的退化。
1.1.2一氧化碳
碳氫化合物由于缺少氧氣導致不完全燃燒的結果是產(chǎn)生一氧化碳。一旦呼吸/吸入它對人類和動物來說是毒藥。一旦一氧化碳到達血液細胞,它就會與血紅蛋白中的氧結合,從而減少到達器官的氧氣含量,影響生物的身體和精神能力。
1.1.3未燃碳氫化合物
未燃碳氫化合物導致碳氫化合物不完全燃燒的結果。根據(jù)其本質上來講,未燃的碳氫化合物可能有害生物。部分這些未燃的碳氫化合物有可能直接含有有毒顆粒、苯或其他致癌化學物質危害人體健康。未燃的碳氫化合物還會產(chǎn)生煙霧,太陽的紫外線輻射與未燃的碳氫化合物有還有大氣中的一氧化氮形成臭氧臭氧和其他產(chǎn)品。臭氧是一種由三個氧原子組成的分子。它是無色的,但非常危險,是有毒的。因為它攻擊活細胞的細胞膜,使它們過早老化或死亡。幼兒、老年人和哮喘患者遭受很大威脅當暴露于高濃度臭氧中。每年有很多報道關于死于高濃度臭氧。
1.1.4其他污染物
雜質的燃料導致污染物的排放。主要的雜質是硫:主要是柴油和噴氣燃料中,也存在在汽油和天然氣中。硫的燃燒(或硫化物如硫化氫)與氧氣形成硫氧化物(SOx)。二氧化硫(SO2)是這個燃燒的主要產(chǎn)品。它與空氣接觸后形成三氧化硫,后來又與水反應生成硫酸。酸雨的主要組成部分。應該注意的是,硫氧化物排放源也主要來自燃燒煤炭的發(fā)電廠和鋼鐵工廠。此外,還有爭論的是火山等自然資源。
石油公司將化學物質添加到他們的燃料中來提高他們發(fā)動機性能。四乙鉛,經(jīng)常被簡稱為“領導”,用于改善汽油的爆震阻力,用了獲得更好的發(fā)動機的性能。然而,燃燒這種化學物質釋放鉛金屬,這種金屬會產(chǎn)生神經(jīng)系統(tǒng)疾病,稱為“鉛毒?,F(xiàn)在在大多數(shù)發(fā)達國家已經(jīng)禁止使用這種金屬,它已經(jīng)被其他化學物質取代了。
1.2全球變暖
全球變暖是由”溫室效應”而引起的問題,“溫室效應”是空氣中的二氧化碳和其他氣體引起的,如甲烷。在大氣中,這些氣體阻隔了地面太陽的紅外輻射反射,從而留住大氣中的能量和增加溫度。增加地球溫度將導致其生態(tài)系統(tǒng)遭到損害,發(fā)生自然災害影響人類生產(chǎn)活動。考慮到全球變暖而引起的生態(tài)破壞,一些瀕危物種的消失也是一個值得關注的焦點因為這些些也是人類生活的組成部分。也有擔心的是一些物種的遷移是從溫暖的海洋到寒冷的北方海域,他們可能會破壞當?shù)匚锓N種類和當?shù)赝林慕?jīng)濟生活。這可能發(fā)生在地中海,因為紅海已經(jīng)有梭魚能夠看到了。
自然災害引起我們的注意力超過生態(tài)災害。因為他們造成的損害的范圍與頻率。全球變暖是被認為誘導氣象的現(xiàn)象,如“厄爾尼諾現(xiàn)象”,它擾亂了南太平洋地區(qū),經(jīng)常引起龍卷風、洪水和干旱等問題。另一個全球變暖的結果就是極地冰帽的融化,從而導致海平面的提高,這可能在沿海地區(qū)導致整個國家永久性的洪水。
二氧化碳是碳氫化合物和煤燃燒的結果。交通運輸產(chǎn)生的二氧化碳占了很大份額從1980年到1999年(32%)?,F(xiàn)在的交通行業(yè)顯然是二氧化碳排放的主要因素。應該指出的是,發(fā)展中國家的交通行業(yè)也在迅速增長,和這些國家代表世界非常大的人口份額。在接下來的小節(jié)提供進一步討論。
人類活動產(chǎn)生的大量的二氧化碳釋被排放到大氣中,這被認為是全球氣溫升高的主要因素。從過去的幾十年里觀察,值得注意的是,確實消化二氧化碳是通過植物和海洋中的海洋生物。然而,這些自然同化過程是有限的,不能吸收所有排放的二氧化碳,這導致在大氣中二氧化碳的快速積聚。
1.3石油資源
絕大多數(shù)的交通運輸液體燃料來自石油。石油是一種化石燃料,是從數(shù)百萬年前德地質穩(wěn)定層的生物得來的。這個過程大約是:生物(主要是植物)死亡,正在慢慢地覆蓋沉積物。隨著時間的推移,這些沉積物積累形成厚層并且變換成巖石。生物被困在一個封閉的空間,在那里遇到高壓力和高溫度,它們慢慢轉變成碳氫化合物或煤炭,這取決于他們的本質。這個過程需要數(shù)百萬年來完成。這就是什么形成地球上有限的化石燃料資源。
探明儲量是“從已知的現(xiàn)有經(jīng)濟和操作條件下,合理明確表明在未來可以恢復的那些地質和工程信息的數(shù)量”。因此,他們不構成地球的總儲量的一項指標。探明儲量,就像英國石油公司在2001年估計,R / P比值的表明探明儲量將持續(xù)減少如果生產(chǎn)繼續(xù)以當前的水平開采。
現(xiàn)在提煉出來的油是在表面最容易提煉出來的油。不同地區(qū)氣候的的不同對提煉石油不構成重大問題。他們相信很多地區(qū)的更多的石油位于地殼下面,比如西伯利亞,美國和加拿大北部。在這些地區(qū),氣候和生態(tài)問題是提取或勘探石油的主要障礙。地球石油資源總儲備的估計在政治上是一項艱巨的任務。
盡管R / P比值不包括未來石油的發(fā)現(xiàn),但它是重要的。事實上,它是基于探明儲量,這很與今天的情況很接近。假設,未來的石油發(fā)現(xiàn)量和新發(fā)現(xiàn)石油不會容易。R / P比值也是保持不變。然而,由于發(fā)展中國家和發(fā)展中經(jīng)濟的增長,很明顯消費(因此生產(chǎn))每年在增加。在一些主要國家人口的的快速發(fā)展,消費是有巨大的可能會增加,尤其是在亞太地區(qū)。
盡管在東歐和前蘇聯(lián)石油消費量在下降,但在世界上石油消費量趨勢明顯增加,尤其在發(fā)展最快的亞太地區(qū),世界上大部分的人口住在哪里。很快就會到達石油爆炸的消費時期。石油消費量比例在增加而污染物排放和二氧化碳排放也在增加。