1. Scripps Institution of Oceanography, University of California San Diego, La Jolla, CA 92037, USA.
2. Department of Chemistry, National Sun Yat-sen University, Kaohsiung, Taiwan 804, Republic of China.
3. Aerosol Science Research Center, National Sun Yat-Sen University, Kaohsiung, Taiwan 804, Republic of China.
4. Department of Medicine, Division of Infectious Diseases and Global Public Health, School of Medicine, University of California San Diego, La Jolla, CA 92093, USA.