Photochemical oxidation of chlorocarbons: A significant source of hci in remote tropical rains

Measurements in remote tropical rains, show that that HCl concentrations ra nge between 1.5 and 3.2 mu eq L-1 and that the annual wet deposition is 200 0-5000 mu eq HCl m(-2). The poteneial contribution of HCl to the acid-base equilibrium is 10% to 40%. This atmospheric remotion of HCl indicates the e xistence of an emission and/or a production of the acid of 2.8-7 ppbv year( -1). The analysis of known atmospheric sources of HCl, shows that none of t hem can explain the presence of this acid in remote tropical rains. Until n ow, a non evaluated source is the production of HCl from the photochemical oxidation of atmospheric chlorocarbons. In this paper, using the tropospher ic concentrations of CH3Cl, CH2Cl2, CHCl3, CH3CCl3, CH2ClCH2Cl, C2HCl3, C2C l4 and CHF2C in the tropic, the corresponding rate constants with the OH ra dical, and the yield of HCl formation, a production of HCl for the tropical troposphere ranging from 1.7 ppbv yr(-1) to 3.4 ppbv yr(-1) is estimated. Therefore , it is concluded that the HCl found in remote tropical rains, is largely coming from the photooxidation of chlorocarbons emitted to the glo bal atmosphere by natural and anthropogenic sources.