The Cycling and Deposition of Sulfur, Nitrogen and Organic Acids Over the North Atlantic Ocean

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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. Wet deposition will be collected at the four islands in the North Atlantic Ocean: Bermuda, Ireland, Barbados and Tenerife. The wet deposition will be analyzed for Ca++, Mg++, Na+, K+, Cl-, H+, NH4+, NO3-, SO4=, and methanesulfonate (MSA). The resulting data and their variability will be used to establish a chemical climatology for wet deposition over the North Atlantic Ocean. The sources (natural and anthropogenic) that affect the composition of wet deposition will be investigated. The sampling sites are downwind of North America and thus are ideal stations for investigating not only the fate of the North American plume but also the interaction of the plume with the North Atlantic Ocean background atmosphere.