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  • In 1963, scientists studying Hubbard Brook Experimental Forest in New Hampshire

  • made a shocking discovery.

  • Their most recent rainfall samples were nearly 100 times more acidic than usual.

  • At these levels, additional downpours of acid rain

  • would destroy the region's marine and arboreal ecosystems

  • in a matter of decades.

  • Urgently sharing their findings with fellow researchers,

  • they were determined to answer two questions:

  • what was causing this deadly rainfall? And what could be done to stop it?

  • Rain is never just composed of water.

  • Chemicals and particulates in the atmosphere can be found in every drop,

  • and some compoundslike carbon dioxide

  • make even regular rainfall slightly acidic.

  • But this pales in comparison to the powerful acids produced

  • when water interacts with oxides of nitrogen or sulfur dioxide.

  • On the pH scale which measures acidity,

  • each whole number is 10 times more acidic than the one above it.

  • And where normal rain has a pH of roughly 5.4,

  • rain that's interacted with these gases can rank as low as 3.7.

  • Oxides of nitrogen and sulfur dioxide can appear naturally

  • as a short-lived byproduct of volcanic eruptions or lightning strikes.

  • But power plants, refineries, and vehicles that use fossil fuels

  • consistently pump large quantities into the air.

  • These dangerous gases travel with the wind

  • spreading hundreds of kilometers from the pollution's source.

  • Acting like roaming clouds of destruction,

  • their presence dramatically increases the acidity of local precipitation,

  • creating acid rain, acid snow, and acid fog.

  • These all acidify lakes and streams, kill crops and forests,

  • and damage soil to inhibit future growth.

  • Over time, acid rain can even corrode human structures made of stone or metal.

  • By the 1970s, scientists in North America and Europe classified acid rain

  • as a major environmental threat.

  • But despite clear evidence tying the problem to air pollution,

  • companies denied responsibility and cast doubt on the research.

  • In the United States, corporations lobbied against regulating pollution,

  • and convinced politicians that such policies

  • would raise energy costs and threaten jobs.

  • These obstacles led the government to delay changes,

  • and mandate further research into the issue.

  • But after a decade of mounting concern, Congress finally took action.

  • Since the bulk of sulfur dioxide emissions came from power plants,

  • the government set a limit on the total amount of it

  • the electric power sector could emit each year.

  • Then, they divided the permitted emissions into a fixed number ofallowances

  • distributed to each power plant.

  • A plant could then choose to emit as much sulfur dioxide as they were allowed,

  • or reduce their emissions and sell their unused allowances to other power plants.

  • This system, known ascap and trade,”

  • offered power plants the economic flexibility to keep costs low

  • while strictly limiting pollution.

  • Many critics called these allowances licenses to pollute,

  • or said the government was selling clean air.

  • But since the cap was set to lower five years into the program,

  • it forced every utility company to reduce emissions in the long term.

  • Some plants added desulfurizing scrubbers to their smokestacks,

  • or switched to low-sulfur coal and natural gas.

  • Oxides of nitrogen emissions were also reduced

  • with relatively low-cost technologies.

  • These advances allowed the power sector to grow

  • while the cap kept pollution under control.

  • By 1985, Canada and the European Union adopted their own solutions,

  • and international treaties began circulating

  • to reduce air pollution worldwide.

  • Today, this science-driven economic policy has largely eliminated acid rain

  • across the United States and Canada.

  • And while many ecosystems still need time to recover,

  • scientists have sped up the restoration of other areas

  • by reintroducing essential organisms killed off by acid rain.

  • Some countries, like Russia, India, and China

  • still rely heavily on high-sulfur coal

  • and continue to struggle with the environmental consequences.

  • However, acid rain's relatively quick journey from major threat to minor issue

  • is rightly celebrated as a victory for policies that protect the environment.

  • Cap and trade can't solve every environmental problem.

  • But by using scientific consensus to guide policy,

  • adopting efficient technology,

  • and being unafraid to impose reasonable costs for pollution,

  • countries can stop a growing storm of destruction before it's too late.

In 1963, scientists studying Hubbard Brook Experimental Forest in New Hampshire

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B1 US TED-Ed acid rain acid sulfur pollution dioxide

Whatever happened to acid rain? - Joseph Goffman

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    ynh posted on 2021/04/14
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