The background atmospheric concentrations of cyclic perfluorocarbon tracers determined by negative ion-chemical ionization mass spectrometry

T h e b a c k g r o u n d a t m o s p h e r i c m i x i n g r a t i o s f o r a r a n g e o f c y c l i c p e r f l u o r o c a r b o n s ( c y c l i c P F C s ) , w i d e l y u s e d i n a t m o s p h e r i c d i s p e r s i o n s t u d i e s , h a v e b e e n m e a s u r e d b y g a s c h r o m a t o g r a p h y m a s s s p c t r o m e t r y i n n e g a t i v e i o n c h e m i c a l i o n i z a t i o n m o d e . B a c k g r o u n d c o n c e n t r a t i o n s r a n g e f r o m < 1 fl I ’ t o > I O f l I I. w h e r e f e m t o l i t r e i s e x p e s s e d a s p a r t s i n 1 0 l i ( p p q v ) . B e c a u s e o f t h e i r v e r y l o n g a t m o s p h e r i c l i f e t i m e s ( > 3 0 0 0 y r ) t h e p r e s e n t d a y c o n c e n t r a t i o n s r e p r e s e n t t h e a c c u m u l a t e d e m i s s i o n s f r o m a l l s o u r c e s , a l t h o u g h s i g n i f i c a n t c o m m e r c i a l p r o d u c t i o n d i d n o c o m m e n c e u n t i l t h e 1 9 6 0 s . C y c l i c P F C s a r e p o t e n t g r e e n h o u s e g a s e s : h o w e v e r , t h e i r a t m o s p h e r i c c o n c e n t r a t i o n s a r e c u r r e n t l y s o l o w a s t o m a k e a n i n s i g n i f i c a n t c o n t r i b u t i o n t o g l o b a l w a r m i n g , ( ~ ’ 2 0 0 2 E l s e v i e r S c i e n c e L t d . A l l r i g h t s r e s e r v e d . Kq~~u~ords: Cyclic pertluorocarhonx Pcrflu~)ro~~~ethylcyclohex~~~cs: Tracers; Background atmospheric conccntrat~ons: NISI-MS