J. Aerosol Sci., Vol. 23, Suppl. I, pp. $711-$714, 1992 0021-8502/92 $5.00+0.00 Printed in Great Britain. Pergamon Prcss LUl CHEMICAL COMPOSITION OF SIZE DIFFERENTIATED AEROSOL SAMPLES IN INDUSTRIAL AND COASTAL ATMOSPHERES C.A. Pio; T.V. Nunes and I.M. Santos Departamento de Ambiente e Ordenamento. Universidade de Aveiro, 3800 Aveiro, Portugal ABSTRACT Thirteen ambient aerosol samples were collected with a cascade impactor and analysed for mass, water soluble ions and trace elements. The experimental data was inverted and continuous size distribution curves obtained. The majority of aerosol constituents have a bi-modal size distribution with geometric mean diameters in the ranges 0.15-0.35 ~tmand 2.5-4.5 lam. The specific analysis of each sample permits to obtain insight into the origins and production or transformation mechanisms for the aerosol components in the industrial and coastal atmospheres. KEYWORDS Atmospheric aerosol; size distribution; inorganic compounds; trace elements; particulate carbon. INTRODUCTION This paper complements the characterisation of ambient aerosols in the western region of Portugal, at a coastal sub urban location (University Campus, Aveiro) and an industrial site (Estarreja). Information related with site characteristics, analytical methods and non-size segregated results are published elsewhere (Pio et al, 1989; Pio et al, 1991; Pio and Viana, 1991 ). The aerosol was sampled with a "Sierra", model 235, cascade impactor, at 40 cuR/minute. Aerosol particles were separated into 6 fractions and collected over pre cleaned and treated Whatman EPM- 2000 glass fibre filters. A histogram of concentration as a function of size was built for each measured compound. A continuous distribution model, consisting ofa bi-modal lognormal equation was fitted to the histogram using the "Sigma-Plot" graphics sol, ware, to minimisethe differences between both curves for each stage. RESULTS AND DISCUSSION During the period going from December 1989 to March 1990 eight and five samples were collected at Aveiro Estarreja, respectively. At Estarreja directional sampling was performed when the wind was blowing directly from the industrial complex only (Pio and Viana, 1991). At Aveiro most of the samples were taken during rainy periods, from air masses transported directly from the Ocean. $711