Savoie, D. L., J. M. Prospero, S. J. Oltmans, W. C. Graustein, K. K. Turekian, J. T. Merrill, and H. Levy II, 1992: Sources of nitrate and ozone in the marine boundary layer of the tropical North Atlantic. Journal of Geophysical Research, 97(D11), 11,575-11,589.

Abstract: During the period April 1989 through December 1990, O₃ concentrations in the marine boundary layer at Barbados, West Indies, show a pronounced seasonal cycle. Daily averaged values in the winter and spring often fall in the range of 25-35 ppbv for periods of several days, and they seldom fall below 20 ppbv. In contrast, during the summer, values typically fall in the range of 10-20 ppbv. During the winter-spring period, there is a very strong negative correlation between O₃ and a number of aerosol species, including NO₃^-. These anticorrelations appear to be driven by changing transport patterns over the North Atlantic as opposed to chemical reactions involving O₃ and nitrogen species in the atmosphere. Analyses of isentropic trajectories clearly show that high O₃ and low NO₃^- are associated with transport from higher latitudes and high altitudes. Conversely, high NO₃^- and relatively low O₃ are associated with transport from Africa. Our study suggests that North America and the middle troposphere (and stratosphere) are not strong sources for NO₃^- over the tropical North Atlantic. The strong correlation of NO₃^- with ²¹⁰Pb and the weaker correlation with Saharan dust indicates that NO₃^- is derived principally from continental surface sources, probably in Europe and North Africa, but not from the Saharan soil material itself. During several extended periods, NO₃^- and ²¹⁰Pb were strongly correlated and their concentrations were high relative to nss SO₄ ⁼; these factors, coupled with trajectories originating in Africa, suggest that African biomass burning was a significant source at these times. In contrast, biomass burning appears to be a minor source for O₃ as measured at Barbados, perhaps accounting for an enhancement of about 5 ppbv at most during these periods.