⁷Be and ²¹⁰Pb total deposition fluxes at New Haven, Connecticut and at Bermuda

Abstract

The total deposition fluxes of 21øpb and 7Be were determined at, New Haven, Connecticut, and Bermuda over approximately the same annual period in 1977-1978. The 21øpb flux has remained virtually constant at New Haven from 1973 to 1978, the flux in the 1977-1978 period being 1.2 dpm/ cm:/y. The 21øpb flux at Bermuda is 0.69 dpm/cm:/y. This lower flux than expected from model calculations is due to the establishment of a blocking high pressure cell during the summer which deflects continental air. The 7Be fluxes at New Haven and Bermuda are 22.7 and 17.1 dpm/cm:/y, values consistent with western North Atlantic oceanic standing crop measurements, but higher than some other estimates. Where the difference cannot be attributed to differences in sampling it is ascribable to regional differences compatible with the oceanic data. INTRODUCTION The natural radionuclides produced in the atmosphere provide useful tools for the study of the behavior of aerosols since the source terms are definable and the measurements generally insensitive to normal environmental contaminations. This has been recognized for some time and useful summaries of the use of cosmogenic and uranium decay series radionuclides in atmospheric studies exist [see, for example, Lal and Peters, 1967; Turekian et al., 1977]. In this paper we will discuss the behavior of two natural radionuclides, 2•øPb and 7Be. 21øpb (22-year half-life) is produced ultimately from :::Rn (3.8-day half-life) which emanates from soils. 7Be (54-day half-life) is produced by cosmic rays. Although the major production of 7Be is in the stratosphere, nevertheless, because of the short decay halflife of 7Be and the long (---1 year) residence time of stratospheric aerosols, most of the 7Be flux to the earth's surface is from tropospheric production. Only at sites and times of stratospheric air intrusion into the troposphere is the 7Be flux from the stratospheric reservoir significant. The production of 7Be decreases with descent through the troposphere because of the attenuation of the cosmic ray flux by interactions with atomic targets in the atmosphere. We have made monthly total atmospheric precipitation collections for 7Be and :løpb at two sites in the Atlantic Ocean basin as part of the SEAREX program (sponsored by the National Science Foundation). The aim of the quasisynoptic program was to determine the atmospheric deposition fluxes for the two radionuclides at the two sites over the same time period (1977-1978). Such a data set can then be used to answer the following questions: (1) How do the fluxes of the two radionuclides differ from the continental margin to an island 'downwind' along the prevailing westerlies? (2) What are the relations of the 21øpb and 7Be fluxes to the theoretical predictions for these nuclides? (3) What is the

Sedimentation rates in the central lake constance determined with210Pb and137Cs

“…cm -2. y-i is assumed (A. Mangini, pers. communication) [19]. This almost complete z'~ inventory contrasts to that determined recently in Lake Zurich by Erten et al [6].…”

Fine sediment sources in Conservation Effects Assessment Project watersheds

“…At Goodwin Creek, the atmospheric influxes of Moreover, long events or events that are preceded by multiple, other storms may experience washout of the radionuclides before the end of the event (Turekian et al 1983). The durations of the other three events in Goodwin Creek lasted longer than 8 hours.…”

Influence of model resolution on the atmospheric transport of <sup>10</sup>Be

“…We simply average over whatever period the observations cover and compare them with the modelled 5-yr mean fluxes. There are 7 Be observations from 37 stations (Baskaran et al, 1993;Bleichrodt, 1978;Brown et al, 1988;Crecelius, 1981;Hasebe et al, 1981;Heikkilä et al, 2008a;Hirose et al, 2004;Huh et al, 2006;Igarashi et al, 1998;Knies, 1994;McNeary and Baskaran, 2003;Olsen et al, 1985;Todd et al, 1989;Turekian et al, 1983;Uematsu et al, 1994;Young and Silker, 1980), 210 Pb from 71 stations (Baskaran et al, 1993;Graustein and Turekian, 1986;Huh et al, 2006;Hirose et al, 2004;McNeary and Baskaran, 2003;Nijampurkar and Clausen, 1990;Todd et al, 1989;Turekian et al, 1977Turekian et al, , 1983 and 10 Be from 21 stations (Chengde et al, 1992;Graham et al, 2003;Heikkilä et al, 2008a;Monaghan et al, 1986;Somayulu et al, 1984). The modelled 5-yr mean deposition fluxes of 7 Be, 10 Be and 210 Pb are shown in Figures 4, 5 and 6, together with the location and measured flux of the observations.…”