Source apportionment of atmospheric aerosol in a marine dusty environment by Ionic/composition Mass Balance (IMB)

Abstract. PM10 aerosol was sampled in Santiago, the largest island of Cape Verde, for one year and analysed for elements, ions and carbonaceous material. Very high levels of dust were measured during the winter months, as a result of the direct transport of dust plumes from the African continent. Ionic and Mass Balances (IMB) were applied to the analysed compounds, permitting the determination of 6–7 different processes and source contributions to the aerosol loading: insoluble and soluble dust, sea-salt, carbonaceous material and secondary inorganic compounds resulting from the reaction of acidic precursors with ammonia, sea-salt and dust. The mass balance could be closed by the consideration and estimation of sorbed water that constituted 20–30 % of the aerosol mass. The balance methodology was compared with Positive Matrix Factorization (PMF), giving quite similar results throughout the sampling campaign. This gives confidence in the capability of both methods, which are complementary, for the source apportionment of aerosol particles.