About one-third of the seasonal fine dust that covers South Korea's sky comes from China, a joint study by Korea and U.S. agencies showed Wednesday, fresh scientific data that may serve as proof to buttress arguments for Seoul's worsening air quality.

Mainland China was found to have a contribution rate of 34 percent in terms of the fine dust that was observed in Korea in the May-June period, according to a tentative air quality field study by the National Institute of Environmental Research (NIER) and the National Aeronautics and Space Administration (NASA).

The findings provide grounds for an argument that the neighboring country is one of the major external factors for the occurrence of the air pollution in Korea, the Ministry of Environment said.

South Korea is grappling with worsening air quality that mainly stems from fine dust that clouds the sky during the spring season. While growing concerns have called for countermeasures, there have been few proper scientific research done to provide a basis for tackling the increasingly serious issue.

In the KORUS-AQ report, it said the fine particulate matter (PM), with a diameter of 2.5 micrometers or less, detected in the atmosphere of Seoul-based Olympic Park was caused by domestic factors, such as burning fuel, accounting for 52 percent of the contribution rate.

The remaining 48 percent of the factors came from outside, the bulk of which was found to have traveled from the eastern regions of China, including Shandong, Shanghai and Beijing, the report said.

"The contribution rate is the most important information we've gathered from this research. It is meaningful given that there have been mounting calls for a detailed analysis on the fine dust particles in relation to China's influence," an environment ministry official said.

The findings are more credible than previous reports since the field study was conducted on both land and air, the ministry said. An observation aircraft DC-8 from NASA flew over the Korean Peninsula and the Olympic Park 20 times and 52 times, respectively.

Experts agreed that the latest study will be the first step toward determining the origin and exact cause of the fine dust, noting that it is necessary to continue the research on a regular basis to accumulate data in the long term.

"This study itself cannot be conclusive proof for China's contribution," said Chang Young-ki, a professor of environmental energy engineering at Suwon University. "Having a collection of such data from repeated observations will help figure out the reasons for the fine dust and analyze the pollutants."

Source: Yonhapnews