INTERACTION BETWEEN NITROGEN AND SULFUR CYCLES IN THE POLLUTED MARINEBOUNDARY-LAYER

Simultaneous measurements are reported of the nitrate radical (NO3), n itrogen dioxide (NO2), ozone (O-3), and dimethylsulfide (DMS) in the n ighttime marine boundary layer over Biscayne Bay in South Florida. The se field observations are analyzed and used to initialize a boundary l ayer box model which examines tire relative importance of the various sinks for NOx in the marine boundary layer. The results show that the observed lifetime of NO3 (less than or equal to 6 min.) is probably co ntrolled both by the loss of nitrogen pentoxide (N2O5) to reaction wit h water vapor and aerosols and by the reaction between NO3 and DMS. Th e model is then extended to investigate the loss of nitrogen oxides fr om an air parcel that remains in the boundary layer with a constant se a-to-air DMS flux for several days. The principal conclusions are (1) that DMS is a much more important sink for NO3 at lower NO2 levels and (2) that the reaction between NO3 and DMS is an important sink for DM S in the marine boundary layer and could exceed that of the daytime re moval by OH.