Acid rain gathers among clouds or dust that can float freely through the atmosphere, reaching into every corner of the world wherever the wind happens to blow. Rain in often particularly acidic in areas downwind from heavy industrial zones.

Unfortunately many uninhabited regions, even nature conservation areas otherwise completely free of man-made pollution, are exposed to the same threat. Tragic examples are Germany's Black Forest and America's great redwoods, now both yellowed and blighted by acid rain.

Acid clouds easily travel across national borders, stirring up disputes between countries. For example, the most heavily damaged forests of France and Germany lie downwind from Britain's centers of heavy industry; emissions from heavy industry in the American Midwest get blown towards the northeastern United States and neighboring Canada.

As the seasons change, so the winds shift their direction and the roles of polluter and pollution victim are reversed. America blames Canada, Canada blames America; Britain claims "It has nothing to do with us," while France and Germany point the finger at Britain and threaten to take their case to the international court.

Not even the wisest judge can determine where the blame lies. Without thorough research, who can prove which shower of acid rain has emanated from which country? In fact, any country where coal is burnt, oil is refined and petrochemical products are processed can hardly avoid some blame for contributing to acid rain to a certain extent.

A report issued in April by Taiwan's Environmental Protection Administration confirms that the local rainfall is at its most acidic during the spring, when rainbearing clouds drift over from heavily industrialized mainland China. Acid rain expert F. Herbert Bormann of Yale University in the United States also mentioned during a visit to Taiwan last year that some of Taiwan's acid rain might be due to pollution from heavy industry in southern mainland China, which has led some to speculate that even if Wang Yung-ch'ing moves his petrochemical empire across the Taiwan Strait it won't necessarily mean that Taiwan will escape pollution from Taiwan Plastics! Of course, all of this still awaits corroboration by scientific research.

Overseas environmental protection experts have claimed that pollution is bound to turn the whole globe into a single nation with common environmental concerns. The example of acid rain seems to prove this to be a golden saying.

Acid rain is not just without boundaries, it also appears in a variety of guises. Acid rain per se is simply acidic pollution in the form of rainwater, but of course it can attach itself to water whether in its liquid, solid or gaseous state. In additions to adsorption by clouds, which then become "acid clouds," it can lurk in snow and turn it into "acid snow." Like a character at a masked ball, it can also appear in a blend of gaseous and liquid states, in the form of "acid fog."

Where there is fog, the atmosphere is still. So if an area suffers from acid fog it is usually the result of local pollutants, and no blame can be attached to neighboring countries. Professor Chang Chen-nan of the department of environmental science at Tunghai University, who is researching into acid fog, considers that if fog occurs in Taipei city or certain industrial zones it may well be highly acidic.

In addition to localized acid fog, the sulphuric and nitric acids that make rainwater acidic can also attach themselves to microscopic particulates (dust) suspended in the air, so they can be said to exist in gaseous form too.

Associate Professor Gaston J. Wu of National Taiwan University's department of chemistry points out that in addition to breathing acidified air, the human body can also take in acidic gas through the skin and hair, just as we carry a whiff of scent along with us when we emerge from a heavily perfumed environment. As to what the effects of prolonged exposure to abnormally acidic air might be, no research is going on in that precise area at present.

Observation conducted abroad of dust on walls or in crannies of buildings has found that if any such dust containing sulphurous or nitrous oxides comes into contact with moisture, the action of photosynthesis turns it into sulphuric or nitric acid. Its effect on buildings can be seen in corrosion, rusting, crumbling and deterioration of various kinds.

With acid rain, acid clouds, acid snow and acid fog we now have more and more acid floating around in the air. It is really all the same type of pollution, and in whatever guise it appears scientists call it by the general term "acid precipitation." So the problems associated with acid rain certainly don't go away just because it doesn't happen to be raining.

Areas adjoining industrial zones often suffer from acid rein. Shown here is a thermal power plant at Hsieho, eastern Taiwan.

Wind-driven power generation avoids emissions that cause acid rain. Wind power is used to generate electricity in California. （photo by Arthur Cheng）

Vehicle exhaust emissions are a major cause of urban acid rain.

Researchers have discovered that acid rain is responsible for corroding objects standing in the open.

Despite the lack of funding, Taiwan acid rain researchers are in good heart. A seminar on acid rain attracts full attendance. （photo by Huang Li-li）