IN-SITU SINGLE-PARTICLE CHARACTERIZATION AT CAPE GRIM

This paper describes operation of the particle analysis by laser mass spectrometry (PALMS) instrument at Cape Grim. Several changes to the i nstrument improved the uniformity of ionization, simplified data analy sis, and reduced the minimum analyzable particle size to 0.16 I-lm Alm ost all of the particles analyzed by PALMS at Cape Grim during clean m arine conditions contained some sea salt. Almost all of the sulfate fo und during clean marine conditions was mixed with sea salt rather than in separate ammonium sulfate or sulfuric acid aerosols. Metals such a s Cr, Fe, and Sn were detected in a few particles even in clean marine air masses. An NO+ peak in the mass spectra was associated with Mg, C a, and Sr. This association could be caused either by the water retent ion of various salts or by different reactivities. It provides a remin der that other components of sea salt besides NaCl need to be consider ed for heterogeneous chemistry.