Efforts to control acid rain

Efforts to control acid rain
Acid rain can best be curtailed by reducing the amount of sulfur dioxide and nitrogen oxides released by power plants, motorized  vehicles, and factories. The simplest way to cut these emissions is to use less energy from fossil fuels. Individuals can help. Every time a consumer buys an energy-efficient appliance, adds insulation to a house, or takes a bus to work, he or she conserves  energy and, as a result, fights acid rain. 

Another way to cut emissions of sulfur dioxide and nitrogen oxides is by switching to cleaner-burning fuels. 

For instance, coal can be high or low in sulfur, and some coal contains sulfur in a form that can be washed out easily before burning. By using more of the low sulfur or cleanable types of coal, electric utility companies and other industries can pollute less. The gasoline and diesel oil that run most motor vehicles can also be formulated to burn more cleanly, producing less nitrogen oxide pollution. Clean burning fuels such as natural gas are being used increasingly in vehicles. Natural gas contains almost no sulfur and produces very low nitrogen oxides. Unfortunately, natural gas and the less-polluting coals tend to be more expensive, placing them out of the reach of nations that are struggling economically. 

Pollution  can  also  be  reduced  at  the  moment  the  fuel  is  burned.  Several  new  kinds  of burners  and  boilers  alter  the  burning process  to  produce  less  nitrogen  oxides  and  more free  nitrogen,  which  is  harmless.  Limestone  or  sandstone  added  to  the combustion chamber can capture some of the sulfur released by burning coal. Once sulfur dioxide and oxides of nitrogen have been formed, there is one more chance to keep them out of the atmosphere. In smokestacks, devices called scrubbers spray a mixture of water and powdered limestone into the waste gases (flue gases), recapturing the sulfur. Pollutants can also be removed by catalytic converters. In a converter, waste gases pass over small beads coated with metals. These metals promote chemical reactions that change harmful substances to less harmful ones. In the United States and Canada, these devices are required in cars, but they are not often used in smokestacks. 

Once acid rain has occurred, a few techniques can limit environmental damage. In a process known as liming, powdered limestone can be added to water or soil to neutralize the acid dropping from the sky. In Norway and Sweden, nations much afflicted with acid rain, lakes are commonly treated this way. Rural water companies may need to lime their reservoirs so that acid does not eat away water pipes. In cities, exposed surfaces vulnerable to acid rain destruction can be coated with acidresistant paints. Delicate objects like statues can be sheltered indoors in climate-controlled rooms. 

Cleaning up sulfur dioxide and nitrogen oxides will reduce not only acid rain but also smog, which will make the air look clearer. 

Based on a study of the value that visitors to national parks place on clear scenic vistas, the U.S. Environmental Protection Agency  thinks that improving the vistas in eastern national parks alone will be worth $1 billion in tourist revenue a year. 

A -National Legislation 

In the United States, legislative efforts to control sulfur dioxide and nitrogen oxides began with passage of the Clean Air Act of 1970. This act established emissions standards for pollutants from automobiles and industry. In 1990 Congress approved a set of amendments to the act that impose stricter limits on pollution emissions, particularly pollutants that cause acid rain. These amendments aim to cut the national output of sulfur dioxide from 23.5 million tons to 16 million tons by the year 2010. Although no national target is set for nitrogen oxides, the amendments require that power plants, which emit about one-third of all nitrogen oxides released to the atmosphere, reduce their emissions from 7.5 million tons to 5 million tons by 2010. These rules were applied first to selected large power plants in Eastern and Midwestern states. In the year 2000, smaller, cleaner power plants across the country came under the law. 

These 1990 amendments include a novel provision for sulfur dioxide control. Each year the government gives companies permits to release a specified number of tons of sulfur dioxide. Polluters are allowed to buy and sell their emissions permits. For instance, a company can choose to reduce its sulfur dioxide emissions more than the law requires and sell its unused pollution emission allowance to another company that is further from meeting emission goals; the buyer may then pollute above the limit for a certain time. Unused pollution rights can also be "banked" and kept for later use. It is hoped that this flexible market system will clean up emissions more quickly and cheaply than a set of rigid rules. Legislation enacted in Canada restricts the annual amount of sulfur dioxide emissions to 2.3 million tons in all of Canada‘s seven easternmost provinces, where acid rain causes the most damage. A national cap for sulfur dioxide emissions has been set at 3.2 million tons per year. Legislation is currently being developed to enforce stricter pollution emissions by 2010. 

Norwegian law sets the goal of reducing sulfur dioxide emission to 76 percent of 1980 levels and nitrogen oxides emissions to 70 percent of the 1986 levels. To encourage cleanup, Norway collects a hefty tax from industries that emit acid pollutants. In some cases these taxes make it more expensive to emit acid pollutants than to reduce emissions. 

B -International Agreements 

Acid rain typically crosses national borders, making pollution control an international issue. Canada receives much of its acid pollution from the United States—by some estimates as much as 50 percent. Norway and Sweden receive acid pollutants from Britain, Germany, Poland, and Russia. The majority of acid pollution in Japan comes from China. Debates about responsibilities and cleanup costs for acid pollutants led to international cooperation. In 1988, as part of the Long-Range Trans boundary Air Pollution Agreement sponsored by the United Nations, the United States and 24 other nations ratified a protocol promising to hold yearly nitrogen  oxide  emissions  at  or  below  1987  levels.  In  1991  the  United  States  and Canada  signed  an  Air  Quality  Agreement  setting national limits on annual sulfur dioxide emissions from power plants and factories. In 1994 in Oslo, Norway, 12 European nations agreed to reduce sulfur dioxide emissions by as much as 87 percent by 2010.  Legislative actions  to  prevent  acid  rain  have  results.  The  targets  established  in  laws  and  treaties are  being  met,  usually  ahead  of schedule.  Sulfur  emissions  in  Europe  decreased  by  40 percent  from  1980  to  1994.  In  Norway  sulfur  dioxide  emissions  fell  by  75 percent  during the  same  period.  Since  1980  annual  sulfur  dioxide  emissions  in  the  United  States  have dropped  from  26  million tons  to  18.3  million  tons.  Canada  reports  sulfur  dioxide emissions  have  been  reduced  to  2.6  million  tons,  18  percent  below  the proposed limit of 3.2 million tons. 

Monitoring stations in several nations report that precipitation is actually becoming less acidic.

In Europe, lakes and streams are now growing less acid. However, this does not seem to be the case in the United States and Canada. The reasons are not completely understood, but apparently, controls reducing nitrogen oxide emissions only began recently and their effects have yet to make a mark. In addition, soils in some areas have absorbed so much acid that they contain no more neutralizing alkaline chemicals. 

The weathering of rock will gradually replace the missing alkaline chemicals, but scientists fear that improvement will be very slow unless pollution controls are made even stricter.