1. Department of Earth Sciences; University of Toronto; 22 Russell Street Toronto ON M5S 3B1 Canada
2. Department of Civil Engineering; University of Toronto; 35 Russell Street Toronto ON M5S 1A4 Canada
3. Department of Chemical Engineering and Applied Chemistry; University of Toronto; 200 College Street Toronto ON M5S 3E5 Canada
4. Dept. of Chemistry; Umeå University; Linnaeus väg 6 SE-901 87 Umeå Sweden
5. Air Quality Processes Research Section; Environment Canada; 6248 Eighth Line Egbert ON L0L1N0 Canada