Over the past 10-15 years atmospheric chemistry has evolved from a young research discipline devoted primarily to local problems of urban pollution and air quality to a mature science concerned with the hemispheric to global scale cycling of a wide variety of chemical species. To a large extent this change has resulted from an increasing realization that human activities can cause chemical disturbances to the natural troposphere on scales far beyond local concerns. Well-known examples include changes in the regional-to-global concentrations of certain nitrogen compounds, lead and other heavy metals, artificial radionuclides, a number of synthetic organic substances, certain acid-forming species, carbon dioxide and methane. These chemical changes in the atmosphere can often extend to the earth's soils, oceans, and biota far from the original source region. They can result in alterations in the earth's climate, changes in vital nutrient cycles, and impact significantly on the public health and quality of life on earth. The Atmosphere/Ocean Chemistry Experiment (AEROCE) will be a coordinated multi-institutional atmospheric and marine chemistry research project centered in the North Atlantic region. The ultimate goal of the AEROCE project will be the development of a predictive capability for the continentally derived species observed in the marine troposphere over the North Atlantic. The selection of sites and the measurement protocol in AEROCE has been developed jointly by modelers and field experimentalists. This AEROCE research element will be concerned with studying trace elements in the atmosphere over the North Atlantic by measuring in atmospheric samples from the AEROCE Network sites. These data will be used to develop a chemical climatology for the atmosphere over the North Atlantic, i.e., a description of the mean concentrations of the trace elements and the temporal and areal variability of the means. Particular emphasis will be placed on assessing how physical, chemical, and biological processes in the atmosphere and oceans affect the concentrations and fluxes of trace elements. The transport of dust and the scavenging of dust by rain will be investigated to understand how the chemistry and air-sea exchange of mineral dust is coupled to the geochemical cycling of other substances. Improved estimates of the distribution and flux of atmospheric sea-salt will be made by considering combinations of variables that affect sea-salt production. Chemical tracers will be used to delineate the concentrations of certain elements and the biological productivity of the waters bordering the sampling sites.
