Acid rain not just a local issue

Walking in the rain in Taiwan might not be as romantic as it is in the movies, especially in winter, when a northeasterly wind starts to blow.

Last December, officials at the Central Weather Bureau found that several areas in northern Taiwan had been significantly affected by pollution, recording average acid precipitation index (pH values) readings mostly lower than five, the minimum safe value according to scientists. (The lower the number, the higher the level of acidity.)

Bureau officials pointed to an extreme case of acidity recorded at 3.6 pH in value in Keelung.

Bureau officials remind people to wear hats or use umbrellas to avoid going bald as a result of the acid rain, adding that the acidity of rain in Keelung was only slightly less acidic than vinegar.

Contradictory information

One month after the bureau issued the warning about acid rain, the Environmental Protection Adminis-tration (環1珓O護署, EPA) released a report that suggested that levels of acid rain were not as serious as had been widely assumed, especially compared to other countries.

A recent EPA report said that the average acid precipitation index (pH value) nationwide during the first 11 months of last year was 5.1, above the minimum safe value 5, while Hong Kong was reported at 4.2, Japan at 4.8, the US at 4.2, and Europe at 4.1, exceeding the minimum safe value.

Scientists said that detailed analysis of different pH values in local areas should also have been addressed.

In addition, northern Taiwan is more severely affected by overseas pollutants than the rest of the country because of northeasterly winds," said Yuan Chung-hsin (袁??新), a professor of environmental engineering at National Sun Yat-sen University (???s?j學) in Kaohsiung.

The EPA report added that the problem of acid rain in urban areas, including the three largest cities -- Taipei, Kaohsiung and Taichung -- had improved noticeably after the EPA started to monitor and control the sulfuric and nitric acid content of rain in 1991.

However, scientists conducting acid rain research with the EPA's financial assistance told the Taipei Times that the administration had concealed several problems related to acid rain.

"We cannot consider acid rain problems simply by focusing on the average acid precipitation index (pH value). Different levels of acid precipitation in different areas should been stressed," said Lin Neng-huei (林能暉), leader of the acid rain research team at theational Central University (??央?j學, NCU) in Taoyuan County.

Lin said that the administration compared the average pH value of acid rain in Taiwan to worst cases in other countries to ease people's minds.

"In fact, the average deposition of sulfides in Taiwan is about six times higher than that in the US," Lin said.

An international issue

Sulfur oxides and nitrogen oxides, thought to be carried long distances by air currents, can be converted in the atmosphere into sulfuric acid (H2SO4) and nitric acid (HNO3), generally called "acid rain."

The term acid rain was coined by British scientist Robert Angus Smith in a book titled Air and Rain: The Beginnings of Chemical Climatology.

His purpose in writing the book was to highlight local air pollution problems caused by industrial development in Manchester.

In 1980, a program called the Long Range Transport of Airborne Pollutants (LRTAP) was established in Canada to study the long-range transmission of air pollutants and their possible environmental effects because eastern Canada had become affected by emissions for the northeastern US.