Rainfall is naturally acidic. Carbon dioxide reacts with water vapour in the atmosphere to produce weak carbonic acid. This is enough to give rainfall a typical low acidity of between 5-6 pH (where 7 is neutral). By itself this can account for chemical weathering of carbonate-based rocks (chalk and limestone) over time.
降雨是天然的酸性。二氧化碳与大气中的水蒸气反应，产生弱碳酸。这足以使降雨具有典型的低酸度，pH值在5-6之间（其中7为中性）。这本身可以说明碳酸盐类岩石（白垩和石灰石）随着时间的推移而发生的化学风化。
Human activity has resulted in greater acidity of rainfall and more widespread impacts over shorter time periods. The release of large quantities of sulphur dioxide and nitrogen oxide into the atmosphere, largely as a result of burning fossil fuels, has resulted in reactions with water vapour to produce much stronger acidity in rainfall (pH of 3 and 4) and precipitation (rain and/or snow) being the chemical equivalent of sulphuric acid and nitric acid.
人类活动导致了降雨的酸度增加，并在较短的时间内产生更广泛的影响。大量的二氧化硫和氧化氮释放到大气中，主要是由于燃烧化石燃料，与水蒸气发生反应，在降雨中产生更强的酸度（pH值为3和4），降水（雨和/或雪）是硫酸和硝酸的化学等效。
The most significant contributors of sulphur dioxide and nitrogen oxide in the past 80 years have been 在过去的80年中，二氧化硫和氮氧化物的最主要贡献者是 :
- Coal-fired power-stations 燃煤发电站
- Rapid industrialisation in newly emerging economies burning coal and oil. 新兴经济体的快速工业化，燃烧煤炭和石油
- The rise in car production, ownership and use. 汽车生产、拥有和使用的增加
- Increasing air traffic. 不断增加的空中交通
Whilst the contributing gases to acid rain are generated in urban, industrial centres, the effects of acid rain are often experienced hundreds, if not thousands, of miles away from the pollution source. The action of prevailing winds distributes the atmospheric pollutants downwind so that when the resultant acid rain/snow falls, it is affecting different territory in, often, different countries.
虽然造成酸雨的气体是在城市和工业中心产生的，但酸雨的影响往往是在离污染源几百甚至几千英里以外的地方出现。盛行风的作用使大气中的污染物顺风分布，因此，当产生的酸雨/雪落下时，往往影响到不同国家的不同地区。
The international scale of this problem makes it difficult to attribute blame to any one particular source area or get source countries to accept responsibility for their emissions. Norway, for example, receives over 90% of its sulphur deposition from other countries, but that may be from Britain, northern France, Germany or Poland depending on the wind direction.
这个问题的国际规模使得我们很难将责任归咎于任何一个特定的污染源地区，也很难让污染源国家对其排放承担责任。例如，挪威90%以上的硫沉降来自其他国家，但根据风向，可能是来自英国、法国北部、德国或波兰。
If rain or snow falling onto ground, buildings or into lakes is highly acidic, the chemical impacts can have rapid and widespread consequences 如果落在地面、建筑物或湖泊中的雨雪是高酸度的，其化学影响会产生迅速而广泛的后果 :
- Building stone weathers faster – particularly older monuments constructed of limestone and chalk. Cathedrals and minsters, such as York Minster, require more regular, expensive, renovation of weathered stone, and the Taj Mahal in India is experiencing similar problems as a result of India’s rapid emergence as an industrial power.
建筑石料的风化速度加快--尤其是用石灰石和白垩建造的古老纪念碑。大教堂和教堂，如约克大教堂，需要更经常、更昂贵地翻新风化的石头，而印度的泰姬陵也正经历着类似的问题，因为印度迅速成为一个工业大国。
- Forests can be decimated as roots are highly sensitive to acidity of water. The fine nutrient-absorbing rootlets are damaged, weakening growth and opening the tree up to infection and disease. Over 50% of forests in the Netherlands are reported to have been damaged by acid rain. In countries where the production of timber is a significant export, such as Canada, any damage affects the economy as well as the environment.
由于根部对水的酸度高度敏感，森林可能会被砍伐。吸收营养的细小根系被破坏，削弱了生长，使树木受到感染和疾病的影响。据报道，荷兰超过50%的森林被酸雨破坏。在木材生产为重要出口的国家，如加拿大，任何损害都会影响经济和环境。
- A secondary consequence, as forests decline, is that habitat and the forest ecosystem suffer. Plants and animals that depend on the forest cover reduce in number.
随着森林的减少，一个次要的后果是，生境和森林生态系统受到影响。依赖森林覆盖的植物和动物的数量减少。
- Rivers and lakes may receive a constant influx of acidic water from the catchment area, or it may be a sudden influx in spring as acid ‘snow’ melts with warmer temperatures, releasing a flush of acidity that has accumulated over the winter. This can be particularly damaging to young immature fish or ‘fry’. Many salmon rivers and lakes of Scotland and Canada have seen significant falls in salmon stock that is attributed to the effects of raised acidity of the water.
河流和湖泊可能会从集水区不断涌入酸性水，也可能在春天突然涌入，因为酸性 "雪 "随着气温升高而融化，释放出积累了一个冬天的酸性物质。这对年轻的未成年鱼或 "鱼苗 "的伤害尤其大。苏格兰和加拿大的许多鲑鱼河流和湖泊都出现了鲑鱼数量大幅下降的情况，这都是由于水的酸度升高造成的。
- Human health may be affected if acidity in the water increases corrosion of water pipes. Swedish health consultants traced the cause of intestinal discomfort and ‘green hair’ amongst children in rural parts of Sweden in the 1980s to rapid corrosion of Copper pipes supplying water to older properties.
如果水中的酸度增加了对水管的腐蚀，人类的健康也会受到影响。瑞典的健康顾问将20世纪80年代瑞典农村地区儿童的肠道不适和 "绿头发 "的原因归结为向老房子供水的铜管的快速腐蚀。
In affected regions 在受影响的地区 :
- Lime (crushed limestone) has been spread over the surface of lakes to neutralise the acid in Scotland and Canada. Lime is alkali.
在苏格兰和加拿大，石灰（碎石灰石）被撒在湖泊表面以中和酸。石灰是碱性的。
- Copper pipes have been replaced by plastic piping delivering water to homes in Scandinavia.
在斯堪的纳维亚半岛，铜管已经被塑料管取代，向家庭输送水。
In source regions 在源头地区 :
- International agreements since the 1970s have resulted in cuts in emissions of contaminants and polluting emissions, particularly in Europe and North America. The European Union has been a major driver in seeking agreement amongst member countries to reduce sulphur dioxide and nitrogen oxide emissions since 1979. In 1988 an EU directive required power stations to reduce emissions – in the UKs case, by 60% in sulphur dioxide and 30% in nitrogen oxide. This is achieved in part by lining chimney flues with limestone to neutralise the acidic gas emitted (flue-gas desulphurisation), partly by subsidising power-stations to change to low-sulphur coal, and by encouraging the growth of gas-fired power-generation, subsidising sustainable, renewable energy production(particularly wind power) and reducing coal-burning facilities.
自20世纪70年代以来，国际协议导致了污染物和污染排放的削减，特别是在欧洲和北美。自1979年以来，欧盟一直是寻求成员国之间达成协议以减少二氧化硫和氮氧化物排放的主要动力。1988年，欧盟的一项指令要求发电站减少排放--就英国而言，二氧化硫减少60%，氮氧化物减少30%。这部分是通过在烟囱烟道内衬石灰石以中和排放的酸性气体（烟气脱硫）来实现的，部分是通过补贴发电站改用低硫煤，以及鼓励燃气发电的增长，补贴可持续的可再生能源生产（特别是风力发电）和减少燃煤设施。
International Assessment of Acid Rain 酸雨的国际评估The areas suffering the worst effects of acid rain emerged in the 1970s and ‘80s in NE North America and Central, Eastern and Northern Europe.
受酸雨影响最严重的地区出现在20世纪70年代和80年代的北美东北部和中欧、东欧和北欧。
International transboundary emission agreements since then have been largely effective in significantly reducing sulphur and nitrogen emissions and reducing the scale and impact of acid rain degradation. The problem has not been solved, but by contributing countries agreeing to strict emission reductions the issue is less severe than in the latter decades of the twentieth century.
从那时起，国际跨界排放协议在很大程度上有效地减少了硫和氮的排放，降低了酸雨退化的规模和影响。这个问题并没有得到解决，但是通过贡献国同意严格的减排，这个问题已经没有二十世纪后几十年那么严重。
The current focus for acid rain action is in Asia where the rapid industrialisation of India, China and neighbouring nations has seen the rapid expansion of coal-fired power stations and direct burning of high-sulphur-content coal by industry. Compounded by the continuing growth of Asian megacities and the rapid rise in car ownership, the challenge for dealing with the consequences of acid rain has shifted firmly to the Newly Industrialising Countries (NICs) of Asia.
目前酸雨行动的重点在亚洲，印度、中国和邻国的快速工业化使燃煤发电站迅速扩张，工业界直接燃烧高硫含量的煤炭。再加上亚洲大城市的持续增长和汽车保有量的迅速增加，应对酸雨后果的挑战已经牢牢转移到亚洲的新兴工业化国家（NICs）。
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