US EPA

37858 

Journal Article 

Formation of chemically active chlorine compounds by reactions of atmospheric NaCl particles with gaseous N2O5 and ClONO2 

Finlayson-Pitts, BJ; Ezell, MJ; Pitts, JN, Jr 

1989 

1 

Nature
ISSN: 0028-0836
EISSN: 1476-4687 

337 

6204 

241-244 

WOS:A1989R858200061 

Participate NaCl and NaBr are known1,2 to react with NO2 in air at concentrations of a few parts per 106 (p.p.m.) to form the corresponding nitrosyl halides XNO (X = Cl, Br), a process that may contribute to the photochemistry of polluted marine areas and remote regions such as the Arctic3,4. Here we report experimental evidence that gaseous chlorine nitrate (ClONO2) and dinitrogen pentoxide (N2O5) at p.p.m. concentrations also react with NaCl particles at 298 K, to form Cl2 and ClNO2 respectively. Thus, the chloride ion in a neutral salt can be transformed into gaseous, photochemically active forms of chlorine at 298 K in a manner analogous to that reported recently for the reactions of HCl in ice with ClONO2 and N2O5 at 185û200 K (refs 5û8). This work suggests that reactions of N2O5 with NaCl in tropospheric marine areas, and possibly in cold climates where chloride salts are used on roads in the winter, should be considered in assessing the atmospheric chemistry of these regions. Furthermore, if the reactions of ClONO2 and N2O5 with NaCl occur also at stratospheric temperatures and if NaCl is present in significant concentrations, these reactions may provide another mechanism for recycling ionic halide ions into gaseous species and hence should be considered in models of stratospheric ozone depletion.