tribution, transformation trends, and modeling; and (6) international support activities.

Research Highlights

Atmospheric chemistry research is carried out in a number of institutes and universities, usually addressing urban air pollution issues such as oxidants, suspended particles, and toxic species. Recently, some attention has been directed at research projects that have regional and global implications. Most of these projects are closely related to IGAC research activities. A major focus is on greenhouse gas emissions, including CH4, N2O, and CO2. Research projects on stratospheric O3 have also been carried out. Regional-scale research activities are focused on acid precipitation and oxidants. In addition, the interesting problem of long-range transport of Asian dust and its impact on the Pacific Basin has also drawn some attention. A brief description of these projects is presented here and additional details are discussed in Chapter 5.

The panel identified significant interest in studying CH4 emissions in China. Observed to be increasing at the rate of about 1 percent per year, CH4 is one of the important trace gases implicated in global warming. With present day concentrations of about 1.75 ppm, increases in CH4 can affect global climate as well as tropospheric and stratospheric chemistry. Rice paddy fields—of which 24 percent of the world's total lie in China—are an important source of atmospheric CH4, contributing to approximately 10 to 20 percent of total global emissions. At least four groups, the Chinese Academy of Sciences (CAS) Institute of Atmospheric Physics, Chinese Academy of Meteorological Sciences (CAMS), CAS Research Center for Eco-Environmental Sciences (RCEES), and CAS Nanjing Institute of Soil Science, have either made or started measurements of CH4 emissions from rice fields. Some of the measurements were conducted as bilateral collaborations between the CAS Institute of Atmospheric Physics and the Fraunhofer Institute in Germany (Wang et al. 1992) and between the CAS Institute of Atmospheric Physics and the U.S Department of Energy (DOE)1 (Khalil et al. 1990). These groups have also started measurements of N2O emissions from soils. In addition, exchange of CO2 between the biosphere and the atmosphere is being studied at the CAS South China Institute of Botany and RCEES.

Trace gas and aerosol monitoring is carried out by various organizations. CAMS, RCEES, and Peking University operate several atmosphere stations in rural and remote areas where measurements of

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