Atmosphere beryllium‐7 concentrations over the Pacific Ocean

Abstract

Atmospheric 7Be is used as a tracer of stratospheric and upper tropospheric air, but most measurements of 7Be in surface air have been restricted to continental regions. We report here the extensive temporal and areal distribution of atmospheric aerosol 7Be concentration in the marine boundary layer. Measurements of 7Be have been carried out for the weekly filter samples collected at the Pacific island stations where are located between 30° N and 30° S in 1981 and 1985. High annual mean concentrations among the stations are observed at latitude between 20° and 30° in both hemispheres. There is little seasonal variation of 7Be at the nine stations. The lowest concentrations are found in the equatorial region due to relatively little subsidence of the air from the upper layer in this area and high precipitation within the ITCZ (intertropical convergence zone) resulting in rapid removal of the aerosol containing the 7Be. The significant correlation between the 7Be concentrations and the nitrate concentrations at the stations in the North Pacific supports the assumption that nitrate is transported from continental sources to the marine boundary layer through the free troposphere by the westerlies.

Describing the annual cyclic behaviour of 7Be concentrations in surface air in Oceania

“…Data sources 7 Be data used in this study were obtained from our own measurements carried out at Brisbane (Australia), the Environmental Measurements Laboratory Surface Air Sampling Program database (EML, 1999), measurements performed by the National Radiation Laboratory of New Zealand (Matthews, 1996), the University of the South Pacific (Garimella et al, 2003), and measurements performed as part of the Sea-Air Exchange program (Uematsu et al, 1994). The location of each sampling station is shown in Fig.…”

“…The sampling and analytical techniques for most stations have been previously reported in the literature (see, e.g., Feely et al, 1989;Garimella et al, 2003;Matthews, 1996;Uematsu et al, 1994). We only provide a description of our own methods.…”

“…The well reported annual cycle is said to be the manifestation of several meteorological factors including stratosphere-to-troposphere exchange (Feely et al, 1989). There have been few studies of 7 Be in surface air reported for sites in Oceania (Garimella et al, 2003;Hicks and Goodman, 1977;Uematsu et al, 1994). Most measurements carried out in the region are of a monitoring nature only, and little interpretation of the data has been performed.…”

Beryllium‐10 and beryllium‐7 in precipitation in Dübendorf (440 m) and at Jungfraujoch (3580 m), Switzerland (1998–2005)

“…There is a need for deposition flux observations to improve the wet scavenging routines of the models. A number of 7 Be deposition observations exist [e.g., Baskaran et al , 1993; Bleichrodt , 1978; Brown et al , 1988; Crecelius , 1981; Dibb , 1989; Graham et al , 2003; Hasebe et al , 1981; Huh et al , 2006; Ishikawa et al , 1995; Olsen et al , 1985; Papastefanou et al , 1995; Todd et al , 1989; Turekian et al , 1983; Uematsu et al , 1994; Young and Silker , 1980], but many of them cover only a period of less than 5 years, and they are not evenly distributed over the globe. The year‐to‐year variation of deposition is large due to production changes as well as changes in the local precipitation rate.…”

Neutron Activation Analysis of Atmospheric Aerosols from a Small Pacific Island Country: A Case of Suva, Fiji Islands

“…1 Two high-volume air samplers, with flow rates of 1.0 and 2.0 m 3 /min, were used to collect aerosols on Whatman-41 filter papers (size 203 × 254 mm 2 ). These filters have a high collection efficiency of over 95% each for marine aerosols (Prospero et al, 2003) and for aerosols containing 7 Be (Uematsu et al, 1994). Further, Whatman-41 filters have very low blank levels of heavy metals and trace elements (USEPA, 1999).…”