The bittersweet story of how we stopped acid rain
环保成功案例 科学家消灭酸雨的故事

A group of kids canoeing in Canada’s Killarney Provincial Park are paddling across a serene and unnaturally turquoise lake. It’s a hot sunny day, and a thirsty boy dips an aluminium cooking pot into the water to refill his fellow canoeist’s canteens. In a momentary lapse of concentration, the pot slips from his grasp. As it sinks underwater beyond reach, what’s incredible is that it’s visible all the way down to the lake floor some 50ft (15.2m) below.

在加拿大的基拉尼省公园（Killarney Provincial Park），一群孩子在宁静但颜色绿的很不自然的湖面上划独木舟。这天阳光明媚，天气炎热，一个口渴的男孩用铝锅舀水，准备加满他同伴的水壶。稍不留神，锅从手中滑落，沉入深不可及的水下。令人难以置信的是，它在深达50英尺（15.2米）的湖底仍然可见。

It’s the mid-1980s. One of the kid canoeists is me, and there’s an unfortunate explanation for this water clarity. This lake, near the nickel and copper smelters of the town of Sudbury, Ontario, has been radically altered by acid rain. Almost every living thing in the water – like the tiny algae that would normally block light from reaching the depths – has gone, leaving the water here and in lakes across the region a beautiful but eerily lifeless aquamarine.

那是1980年代中期，我也在这群孩子当中。水之所以清澈，原因很不幸。这个湖靠近安大略省萨德伯里镇（Sudbury）冶炼镍和铜的工厂，湖水已被酸雨彻底改变。水里几乎所有的生物都消失了，包括那些通常会阻碍光线到达深处的微小藻类。这个湖乃至整个地区的湖，都变成了美丽却死气沉沉的“绿宝石”。

Fast forward to 2019 and another set of lakes in a remote corner of north-west Ontario. Biologist Cyndy Desjardins is sipping coffee at breakfast following a nocturnal boat trip at the International Institute for Sustainable Development’s Experimental Lakes Area (IISD-ELA). Smiling but sleepy, she spent much of the night working in nearly pitch-dark conditions, surveying for tiny monster-like creatures: freshwater opossum shrimp called Mysis relicta. Desjardins is part of a team attempting to close the loop on an acid rain experiment that began in the 1970s.

将近2019年时，在安大略西北部偏远地区的一些湖泊，国际可持续发展研究所（International Institute for Sustainable Development's Experimental Lakes Area）的生物学家德斯贾丁斯（Cyndy Desjardins）在夜间乘船进行过实验后，喝着早餐咖啡。她面带微笑，满脸倦容。昨晚大部分时间她都在漆黑的环境下工作，寻找一些小怪兽般的生物，比如淡水负鼠虾（Mysis relicta）。德斯贾丁斯和她的团队，正努力结束始于20世纪70年代的酸雨实验。

Bitter controversy

激烈的争议

At its worst, acid rain stripped forests bare in Europe, wiped lakes clear of life in parts of Canada and the US, and harmed human health and crops in China where the problem persists. Looking back today, there is little argument that the cause was sulphur dioxide and nitrogen oxides emitted by fossil fuel combustion by cars and industrial facilities like smelters and coal-burning utilities. When combined with water and oxygen in the atmosphere, these air pollutants chemically transform into sulphuric and nitric acid. Acidic droplets in clouds then fall as rain, snow or hail.

最糟糕的是，酸雨使欧洲的森林变得光秃秃的；造成加拿大和美国部分湖泊中的生物灭绝；在问题依然严重的中国，酸雨损害了人民健康，造成农作物损失。回顾过去，几乎所有人都认为酸雨成因是汽车尾气、冶炼厂和燃煤设施等化石燃料燃烧所排放的二氧化硫和氮氧化物。当与大气中的水和氧结合时，这些空气污染物会化学转化为硫酸和硝酸。云中的酸性水滴会以雨、雪或冰雹的形式落下。

We know this now. But for a long time, acid rain was a puzzle. In 1963, as part of a long-term ecosystem study that is still ongoing today, Gene Likens collected a sample of rain at the Hubbard Brook Experimental Forest in New Hampshire’s White Mountains. That sample was “about a hundred times more acidic than we thought it should be”, says Likens, now emeritus professor in ecology at the Cary Institute of Ecosystem Sciences in Millbrook, New York. His discovery back in 1963, on the heels of work dating back to 1872 and even earlier, set the collective wheels in motion to raise awareness and isolate the cause of acid rain. Not just in North America, but across the industrialised world.

我们现在知道原因了。但之前很久，酸雨成因一直是个谜。1963年，作为长期生态系统研究的一部分，利肯斯（Gene Likens）在新罕布什尔州怀特山（White Mountains）的哈伯德溪实验森林（Hubbard Brook Experimental Forest）中收集了雨水样本，这项研究至今仍在进行。利肯斯现在是位于纽约州米尔布鲁克（Millbrook）的卡里生态系统科学研究所（Cary Institute of Ecosystem Sciences）的荣休生态学教授。利肯斯的研究资料可追溯至1872年甚至更早，1963年他的成果唤起公众关注，提高人们对酸雨成因的认识，并采取消减措施。行动不仅在北美，而且在所有工业化国家展开。

Other crucial evidence that led to action on acid rain – on both sides of the Canada-US border – came from experiments at north-west Ontario’s Experimental Lakes Area (ELA). Its soft-water lakes were far enough from sources of pollution that they had escaped the effects of acid rain, acting as a control.

加拿大和美国边境两侧为缓解酸雨采取行动，关键原因也包括安大略省西北部实验湖区（Ontario's Experimental Lakes Area）所获得实验结果。它的软水湖（水中钙镁离子含量低）距离污染源足够远，可避免酸雨的影响，起到控制作用。

Unlike many lakes, composition of the healthy ecosystem in the ELA was well documented. That enabled scientists like David Schindler, then an ELA senior scientist and now emeritus professor at the University of Alberta, Canada, to add acid experimentally to one lake and see how the ecosystem responded. ELA scientists would protectively suit up like Darth Vader, make a sulphuric acid solution and use the boat propeller to mix the cocktail across one of the lakes.

与许多湖泊不同，实验湖区中健康生态系统的成份被很好的记录下来。这使得辛德勒（David Schindler）等科学家能够在湖泊中添加酸性物质，并观察生态系统的反应。辛德勒当时是实验湖区的资深科学家，现在是加拿大阿尔伯塔大学（University of Alberta）的荣休教授。实验湖区的科学家们会像电影星球大战中的达斯·维达（Darth Vader）一样穿上防护服，制造硫酸溶液，然后用船的螺旋桨推进器在湖中混合“鸡尾酒”。

Over seven years beginning in 1976, they lowered the pH of one lake, number 223, from 6.8 (close to neutral) to 5.0 (slightly acidic). Lab studies had suggested a pH of 5.0 would not harm fish. But in the lake 223 experiment, long before it reached 5.0, it did. By the time the pH reached 5.6, most of the lake trout’s preferred food – tiny organisms that require calcium to form exoskeletons – had died as acidified waters dissolved their protective coats.

1976年后的7年间，科学家们将一个编号为223的湖泊的pH值从6.8（接近中性）降低到5.0（微酸性）。实验室内的研究表明，pH值5.0不会对鱼类造成伤害。但在对223号湖的实验中，在酸性达到5.0之前，鱼类就受到了影响。当pH值降到5.6时，大多数淡水鳟鱼喜欢的食物已经死亡，因为这些微小生物需要钙来形成外骨骼，而酸化的湖水溶解了它们的保护层。

“Lake trout stopped reproducing not because they were toxified by the acid, but because they were starving to death,” says Schindler.

辛德勒说：“鳟鱼停止繁殖，不是因为被酸毒死了，而是因为快饿死了。”

Freshwater microbiologist Carol Kelly arrived at ELA in 1978 just as acid rain experiments got underway. She became curious about a particular puzzle the lake acidification experiments had stumbled on. Her colleagues had carefully calculated the quantity of acid needed to drop lake 223’s pH to 5.0 – a simple calculation a high-school student could do. But out in the lake it became clear that their calculations were way out of whack.

淡水微生物学家凯利（Carol Kelly）于1978年到达实验湖区，当时酸雨实验刚刚开始。在湖泊酸化实验中，她偶然发现的一个特别的难题，感到很好奇。她的同事们仔细计算了将223号湖的pH值降至5.0所需要的酸的量，高中生就可以做这个简单计算。但凯利团队的计算结果显然是不正常的。

“I had given the crew orders to take the lake down to a given pH and then add enough acid to hold it there,” says Schindler. Part way through the season, the crew reported that they were running out of acid. Acidifying the lake took way more than they thought, says Kelly. “The question became, where is it going?” she says.

辛德勒说：“我已经给工作人员下了命令，要把湖水的pH值降到一定的水平，然后再加入足够的酸，使湖水保持在一定的pH值。”而实验进行到一半时，工作人员报告说酸快用完了。“湖泊酸化的过程比想象的要复杂得多。问题是，加进湖水的酸去了哪里，为什么比计算值要消耗的更多？”凯利说。

Kelly and colleagues set to work to find out, and discovered that alkali-producing microbes were capable of buffering some of the acidity, helping the lake chemistry to recover. That acid could be neutralised by bacteria living in every lake was a controversial finding at the time.

凯利和同事们开始研究这个问题，他们发现微生物产生的碱能够中和一些酸性物质，帮助湖泊恢复化学平衡。这些酸可以被湖中的细菌中和，这个发现在当时颇有争议。

“People didn’t believe it,” Kelly says. But she continued to find out just how much acid microbes could neutralise, travelling elsewhere in Canada, the US and Norway to lakes that had been acidified atmospherically, to test this natural recovery ability. The discovery that acid-neutralising bugs exist in the sediment in lots of lakes, not just at the ELA, suggested that lakes could recover if the pollution causing the acid rain were eliminated.

“人们不相信，”凯利说。但她继续研究到底有多少酸可以被中和，于是她前往加拿大、美国的其它地方，以及挪威，到大气已经酸化地区的湖泊，去测试这种自然恢复能力。不仅在实验湖区，许多湖泊的沉积物中都存在可以中和酸性物质的细菌，这一发现表明，如果停止酸雨污染，湖泊即可恢复。

Doubt and denial

怀疑和否定

Compelling photographs of starving fish from lake 223, combined with efforts by environmental groups like the Canadian Coalition on Acid Rain, helped persuade policymakers – eventually – to legislate more rigorous air quality standards.

223号湖中饥饿鱼类的照片令人震惊，加之加拿大酸雨联盟（Canadian Coalition on Acid Rain）等环保组织的努力，说服了决策者，最终制定出更严格的空气质量标准。

But acid rain research at ELA almost didn’t happen at all. Founded to address the issue of excess nutrients contaminating lakes, work that had already drawn far-reaching conclusions by the early 1970s, Canada’s federal government was poised to pull the plug on the research station. At a presentation to federal fisheries officials, Schindler says that despite considerable evidence from the US, one official accused him of inventing the idea of acid rain just to save the ELA.

但是对实验湖区的酸雨研究几乎没有展开。加拿大联邦政府成立实验湖区研究站的初衷是为了解决过量营养物质污染湖泊的问题，这项工作在20世纪70年代早期就已有定论，所以政府准备终止这个研究站。辛德勒告诉联邦渔业官员酸雨研究计划，而且有来自美国的大量证据，但官员指责他制造出酸雨研究计划只是为了拯救实验湖区研究站。

Scientists began pinpointing culprits and journalists covered the problem through the 1970s and 1980s, but some people working in industry were doing their best to obfuscate, sow doubt and delay action.

20世纪70年代和80年代，科学家们开始寻找制造酸雨的罪魁祸首，记者们也对这个问题进行了报道，但一些企业界人士却竭力混淆视听，散播怀疑言论，拖延行动。

“There were lots of deniers of acid rain,” says Likens. At the time, Likens remembers giving public lectures on the topic. On occasion someone would stand up, rudely interrupt him, and say they didn’t believe in acid rain. “I would often respond by saying, ‘Well, have you ever collected a sample of rain and analysed it?’ They would say ‘No’ and I would say, ‘Well try it some time.’”

利肯斯说：“很多人否认酸雨”。利肯斯记得曾就这个话题做过演讲。有时会有人站起来，粗鲁地打断他，说不相信有酸雨。“我经常会这样回答，‘嗯，你没有收集和分析过雨水样本吧？’他们说‘没有’，而我则说，‘我们什么时候试试吧。’”

Like with climate change, says Likens, there were many big, powerful, wealthy people involved with vested interests. From its discovery in 1963 to passage of the Clean Air Act in 1990, legislative action on acid rain took 27 years.

利肯斯说，就像气候变化一样，防治酸雨会遭到许多有钱有权的大人物或既得利益集团的反对。从1963年发现酸雨，到1990年通过《清洁空气法案》（Clean Air Act），防治酸雨的立法历时27年。

Over that time, many a cross-border argument erupted. “The first international altercation over acid rain was the US accusing Canada of acidifying lakes in the boundary waters,” says Schindler. The squabble was over a small coal-burning power plant in Atikokan, Ontario, that US representatives claimed was sending acid rain south of the border. Schindler attended a meeting in Minneapolis, Minnesota, along with other Canadian scientists and their US counterparts.

在此期间，爆发了许多跨境争论。辛德勒说：“关于酸雨的第一场国际争端，是美国指责加拿大造成了边境湖泊酸化。”争端焦点是安大略阿提科克（Atikokan）的一座小型燃煤电厂，美方称该电厂造成边境以南的酸雨。辛德勒等加拿大科学家和美国同行一起参加了在明尼苏达州明尼阿波利斯市（Minneapolis）举行的会议。

“When all the data were on the table, it was clear that the little bit of sulphur from Atikokan was inconsequential to boundary waters,” Schindler says. At the same meeting, scientists examined net international flows of emissions. It became obvious, says Schindler, that the US, particularly the Ohio Valley and industrial areas of Pennsylvania and New England, were producing more than half the acid rain that collected in Canadian lakes.

辛德勒表示：“当所有数据都摆在桌面上时，很明显，来自阿提科克的少量硫化物对边界水域没有影响。”在那次会议上，科学家们研究了国际排放净额。辛德勒说，很明显，美国，尤其是俄亥俄河谷、宾夕法尼亚和新英格兰的工业区，产生了落入加拿大湖泊中一半以上的酸雨。

The blame game continued, and acid rain “was at one time the number one Canada-US bilateral issue”, said Adèle Hurley in a speech reflecting on decades of work with the Canadian Coalition on Acid Rain, which she co-founded in 1981. The coalition was eventually disbanded following amendments to the US Clean Air Act in November 1990, establishment of the Acid Rain Program, and parallel action on the Canadian side.

这场相互指责仍在继续，赫尔利（Adele Hurley）在一次演讲中表示：“酸雨一度是加拿大与美国双边关系中的头号问题。”1981年赫尔利创建了加拿大酸雨联盟，她在演讲中回顾了自己在 数十年间通过这家机构为防治酸雨所做的努力。1990年11月，加拿大酸雨联盟成功阻止了一些修改美国《清洁空气法案》的企图，并启动了酸雨防治计划（Acid Rain Program），加拿大方面也有类似行动。

Lessons from the lakes

关于湖泊的教训

A half-century after those early experiments, lake 223 in the ELA is no longer acidic, the acid-eating microbes having done their job. Lake chemistry has returned to its pre-experimental state. Biological recovery, however, has lagged behind. Freshwater opossum shrimp are found in healthy numbers in untouched control lakes. But in 223, they are still missing. So, Desjardins and others are investigating whether reintroductions of the opossum shrimp – 10,000 painstakingly counted at a time – might jumpstart biological recovery of the ecosystem.

早期实验之后又过了半个世纪，实验湖区中的223号湖不再是酸性的了，嗜酸微生物完成了工作。湖泊的化学平衡已恢复到实验前的状态。然而，生物复苏却滞后了。淡水负鼠虾在未受污染的湖泊中数量可观。但在223号湖，仍然不见他们踪影。因此，德斯贾丁斯等人正在研究，重新引入负鼠虾是否可能启动生态系统的恢复。

Early signs look positive. Remote operated underwater vehicles searching for evidence of these mini-monsters of the deep have spotted just two Mysis shrimp swimming freely in lakes thus far, but it suggests that all that midnight catching and counting in the dark is not in vain – these tiny missing links in the ecosystem eroded by acid rain may be coming back.

早期迹象看上去是积极的。遥控潜水器在这些小生物存在的水深处搜索，已经发现两只虾在游弋。这表明，半夜在黑暗湖中的搜索和计数并非徒劳无功。在被酸雨侵蚀过的生态系统中，这些小生物又回来了。

Broader recovery, in lakes across North America, happened because acid rain was tackled at its source.

由于从源头上解决了酸雨问题，北美的湖泊得到了更广泛的恢复。

Compared with 1990 levels, sulphate ions in the atmosphere have dropped considerably, reduced to almost negligible levels at former hotspots. But the problem has not disappeared altogether. Nitrates from sources like agriculturally emitted ammonia released from fertilisers and livestock feed remain a contributor to nitric acid precipitation. And there is concern that acid rain – from both sulphur and nitrogen – is an increasing problem in Asia.

与1990年的水平相比，大气中的硫酸盐离子已大幅下降，在曾经的重污染地区已降至几乎可以忽略不计的水平。但这个问题并没有完全消失。农业排放的硝酸盐（化肥和牲畜饲料释放的氨）仍然是造成硝酸沉淀的原因之一。人们还担心，在亚洲，由硫和氮形成的酸雨正成为一个日益严重的问题。

There are no simple solutions to complex environmental problems. But are there parallels between efforts to curb acid rain and strategies for action on climate change? Schindler does see similarities in the procrastination tactics employed by industry. “Seed enough doubt, and pay for enough political campaigns, and you can delay action,” he says. “That sounds pretty crass but if you look closely, that’s how most environmental problems are addressed, and climate is no exception.”

解决复杂的环境问题没有简单的办法。但是，控制酸雨的努力与应对气候变化的策略是否有相似之处？辛德勒的确看到了业界拖延战术的相似之处。他说：“传播足够多的怀疑，为足够多的政治宣传买单，你就可以推迟行动。这听起来很粗俗，但如果你仔细观察，大多数环境问题都有这样的困境，气候问题也不例外。”

Despite this, emissions reductions have been a huge success story in tackling acid rain, says Likens. But further reductions, especially on nitrogen oxides, are needed. The current US president is proposing to cut back regulations on emissions. If this happens, says Likens, recovering lakes in places like the Adirondack Mountains in north eastern New York would be particularly vulnerable, their acid-neutralising capacity already weakened.

尽管如此，利肯斯说，在应对酸雨方面，减排已经取得了巨大的成功。但还需要进一步减排，尤其是氮氧化物。美国现任总统提议削弱减排法规。利肯斯说，如果发生这种情况，像纽约东北部阿迪朗达克山脉（Adirondack Mountains）等处的湖泊恢复将特别困难，它们中和酸的能力已经减弱。

Tackling acid rain in North America required actions in two neighbouring countries. But for climate change, the challenge is broader and solutions must be global. Nevertheless, the two issues do share similarities. Both, says Hurley, require cutting-edge science, media coverage and finding common ground, building coalitions between opposing parties.

应对北美酸雨需要两个邻国采取行动。但对于气候变化，挑战更为广泛，解决方案必须是全球性的。然而，这两个问题确实有相似之处。赫尔利说，两者都需要尖端科技支持、媒体报道，以及找到共同利益，能建立跨越对立党派的联盟。

In the fight Hurley helped to lead against acid rain, this meant talking to coal workers at sportsmen’s shows, engaging them in conversations about clean water for fishing salmon, and going for walks in war cemeteries where acidity was ruining the limestone of gravestones.

在这场对抗酸雨的战斗中，赫尔利起到了带头作用，这意味着她要在体育表演中找机会向煤炭工人演讲，让他们参与到有干净水域才能钓到鲑鱼这样的对话中，还要走访战争烈士墓地，去查看被酸雨破坏了的石灰石墓碑。

Though aspects of its legacy remain, solutions to the acid rain problem moved forward, in North America at least, because it became a non-partisan issue. Hurley reflects that “a broad spectrum of people came to believe that it was important to protect natural resources – our forests, our northern lakes and the fish they contain – resources that belong to everyone”.

尽管仍遗留一些问题，但至少在北美，酸雨的解决方案向前推进了，因为它成为了一个跨越党派问题。赫尔利认为：“人们开始广泛相信，保护我们的森林、北方的湖泊以及湖中的鱼类——这些人们共有的资源，是重要的。”

If anything can be learned from the acid rain story, it’s that the same breadth of support and dismantling of partisanship is necessary for protecting the Earth’s climate.