ATMOSPHERE BERYLLIUM-7 CONCENTRATIONS OVER THE PACIFIC-OCEAN

Atmospheric Be-7 is used as a tracer of stratospheric and upper tropos pheric air, but most measurements of Be-7 in surface air have been res tricted to continental regions. We report here the extensive temporal and areal distribution of atmospheric aerosol Be-7 concentration in th e marine boundary layer. Measurements of Be-7 have been carried out fo r the weekly filter samples collected at the Pacific island stations w here are located between 30-degrees-N and 30-degrees-S in 1981 and 198 5. High annual mean concentrations among the stations are observed at latitude between 20-degrees and 30-degrees in both hemispheres. There is little seasonal variation of Be-7 at the nine stations. The lowest concentrations are found in the equatorial region due to relatively li ttle subsidence of the air from the upper layer in this area and high precipitation within the ITCZ (intertropical convergence zone) resulti ng in rapid removal of the aerosol containing the Be-7. The significan t correlation between the Be-7 concentrations and the nitrate concentr ations at the stations in the North Pacific supports the assumption th at nitrate is transported from continental sources to the marine bound ary layer through the free troposphere by the westerlies.