IMARI, JAPAN — ON Japan's southern island of Kyushu, the people can cite many foreign intrusions over the centuries. Genghis Khan. European warships. Missionaries. And one atomic bomb over Nagasaki.
Now they see a new danger on the horizon: acid rain. It is starting to appear in the prevailing winds from China, where coal-burning power plants are spewing out harmful sulfur compounds. The most ominous threat lies in China's plans to double its coal-burning plants within a decade.
"The air currents [with Chinese pollution] have reached Japan," says Hiromasa Ueda, a Kyushu University professor. "Plants, marshes, rivers, and lakes are seeing the effects of acidification."
So far, Japan has not stated much publicly about the problem for fear of offending China. But behind the scenes, it is trying to head off a potential ecological disaster.
A year ago, it launched a "Green Aid Plan" to curb third- world pollution, with most of the effort directed at China's coal plants. Last April, Japan held its first "policy dialogue" with Beijing on the problem.
In October, Japan invited officials from China, South Korea, Mongolia, and Russia to discuss "environmental cooperation," such as joint research on acid rain.
Japan has also begun to construct a China-Japan Friendship Environmental Protection Center in Beijing. When the center opens in 1995, it will bring about 600 Chinese and Japanese together to work on pollution, transfering Japanese aid, know-how, and commercial technology to help curb acid rain, says Green Aid officer Mitsutoshi Oriyama.
Early next year, Japan plans to install "desulfurization" technology on an operating 210-megawatt, coal-burning power plant on China's Shandong peninsula in the Yellow Sea.
The equipment will be a test of whether Japanese technology can work under Chinese conditions. It also will serve as a showcase to help convince China to either buy or make similar equipment.
"China has no plans ... to remove sulfur on a large scale," says Charles Johnson, coauthor of a recent study on Asian coal and an expert at the East-West Center in Hawaii. "The Chinese argue that the investment is just too expensive. "
Average cost for desulfurization equipment is about $400 million per power plant, says Saburo Kato, director for global environment in Japan's Environment Agency. With China planning 200 new power plants in this decade, the potential bill for such equipment is $80 billion.
"China will ask us for financing. But it will be difficult," says Mr. Kato. "Of course, this is up to negotiations."
The wider range of desulfurization technology made in the United States may be better suited for China, Dr. Johnson says. "Japan's technology tends to go Cadillac class, which China can't afford."
In recent months, Mr. Oriyama says, China has begun to show concern about air pollution; but its general attitude is still that the West cannot demand that China's backward economy be slowed by antipollution measures.
Last year, China emitted 16.22 million tons of sulfur dioxide, an increase of 8.6 percent over 1990, according to Wang Dehui, deputy for planning in China's National Environmental Protection Agency.
Speaking recently in Japan, Mr. Wang said the soot and sulfur pollution has become serious in Chinese cities. The number of Chinese cities that detect acid rain increased by 7.8 percent in 1991. In some cities, Wang said, acid rain could be found 75 percent of the time.
China, the world's largest coal producer, relies on its abundant coal deposits for about three-quarters of its energy. In 1990, it burned just over 1 billion tons, and expects to increase that by about 40 percent by the end of the decade, Dr. Johnson says.
About 69 percent of the sulfur oxides emitted in Asia came from China, based on 1987 data, he adds. "The problem is growing so rapidly that a few [demonstration] plants won't solve anything," he says. Programs in place "can only slow down the rate of growth in air pollution."
South Korea, which also has begun to worry about border-crossing pollutants from China, will join with Japan next year to monitor the air and sea near their neighboring shores.
In the last two years, Japan has monitored air pollution from China, using aircraft and a ship to take measurements off western Kyushu Island in the Korea Strait.
"We were very surprised at our first results," says researcher Naoki Kaneyasu at the National Institute for Resources and Environment. "The air pollution over the sea was as high as any urban area."
So-called "plumes" of pollution had traveled more than 1,000 miles from the mainland.
Pinning all blame on China is difficult, however, because of sulfur emissions from Japanese factories, which have installed anti-pollution equipment, and from a belching volcano on Sakurajima Island in southern Kyushu.
Japan also receives the so-called "yellow dust" that blows off China's steppes. High in calcium, the dust may be helping to mitigate the effects of sulfur in the atmosphere.
"If not for yellow dust," Mr. Kaneyasu says, "Japan would have extreme acid rain now."