1. Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, U.K.
2. Norwegian Institute for Air Research, P.O. Box 100, NO-2027 Kjeller, Norway
3. Department of Chemistry, University of Oslo, P.O. Box 1033, NO-0315 Oslo, Norway
4. Department of Environmental and Occupational Health, USF College of Public Health, 13201 Bruce B. Downs Boulevard, MDC 56, Tampa, Florida 33612, United States
5. Kimika Analitikoa Saila, Euskal Herriko Unibertsitatea, 644 P.K., E-48080 Bilbao, Spain
6. NIVA Norwegian Institute for Water Research, Gaustadalléen, 21 NO-0349 Oslo, Norway