SUBSTITUTION OF CHLORIDE IN SEA-SALT PARTICLES BY INORGANIC AND ORGANIC-ANIONS

Depletion of chloride in sea-salt particles was studied at a site near the Arctic Ocean. The investigation was based on size-segregated part icle sampling using a Berner low-pressure impactor. According to the i mpactor measurements, average chloride losses were close to 100% for s ubmicron particles. However, this is successively less for increasing particle size in the supermicron size range. The main constituents rep lacing chloride from supermicron sea-salt particles were sulfate and n itrate followed by MSA(-) and oxalate, and with malonate and succinate giving a minor Contribution. Anions of organic dicarboxylic acids bec ame more important for air spending a longer time over the continent. Our analysis suggests that principal mechanisms accumulating sulfate i nto sea-salt particles are cloud processing and, to a lesser degree, h eterogeneous reactions taking place in deliquescent sea-salt particles . Mechanisms for the chloride replacement by nitrate are less clear. T he distributions of MSA(-) and oxalate over the sea-salt particle size range were similar to each other, whereas other organic anions analyz ed here had a peak concentration at a somewhat larger particle size. B etter understanding on the chemistry associated with sea-salt particle s requires investigating not only reactions in deliquescent sea-salt p articles, but also the interactions between these particles and clouds . (C) 1998 Elsevier Science Ltd. All rights reserved.