The silver frost on the trees of the Zao mountains in Yamagata Prefecture has become dangerously acidic, partly due to air pollution from steel plants in China’s Shanxi Province, research by environment experts showed Friday.

Acidity in the frost may kill the Aomori Todo pine and other trees, said the group, which includes Fumitaka Yanagisawa, an assistant professor specializing in environmental chemistry at Yamagata University.

The silver frosted trees near the peaks of the mountains attract tourists in January and February.

The group has measured the pH levels of ice blown onto the trees in Zao about 20 times a year since 1994 to monitor rising sulfuric acid density.

The value, ranging between 0 and 14, with 0 indicating extreme acidity, was 4.5 on average in 2005, compared with 5.3 in 1995.

Analysis of the sulfuric acid revealed that it does not originate from Japan, but may be the kind contained in coal used in Shanxi Province, the group said.

The group suspects sulfuric acid from Chinese steel mills and other factories is blown with seasonal winds to Zao, creating the acidic frost.

“Even though it has no effect (on plants) currently, they may die suddenly if the soil cannot neutralize the acidity,” Yanagisawa said, citing what happened in Germany.

“Instead of waiting for China to work on the issue, Japan needs to provide technology or take other measures to (help China) handle it,” he said.

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