Atmospheric fluxes and marsh‐soil inventories of ⁷Be and ²¹⁰Pb

Abstract

The atmospheric flux of 7Be over a 2‐year period at a coastal site (Norfolk, Virginia) and at an inland site (Oak Ridge, Tennessee) typically supports inventories ranging from 1.0 to 2.0 pCi/cm2 (1 pCi = 0.037 Bq), with the highest inventories generally occurring in the spring and the lowest occurring in the fall. The calculated average daily fluxes required to support these inventories range from 0.013 to 0.026 pCi cm−2 d−1. Despite the different production‐source terms for 7Be and 210Pb, there is a high degree of correlation between their measured total monthly deposition reflecting the importance of washout in removing both radionuclides from the atmosphere. Beryllium 7 inventories in soil and vegetated marsh cores compare favorably with inventories calculated from the atmospheric deposition data. Lead 210 inventories in soil and vegetated marsh cores may be enriched (by 20–30%) in relation to inventories calculated from its depositional flux to bucket samplers. Possible explanations for this enrichment are that above‐ground vegetation is more efficient at collecting dry aerosols (containing short‐lived radon daughters) than buckets or that foliage is an effective trap for particles containing sorbed 210Pb which may be eroded from unvegetated surfaces by wind or water. The vertical distribution and inventory of both 7Be and 210Pb in marsh cores are affected by the presence of vegetation and the location of the groundwater table.

Phosphorous cycling in the Gulf of Maine : a multi-tracer approach

“…7Be and 2lOpb activities also had a wide range in specific activity, 21 to 1442 dpm L-t, and 2 to 160 dpm Ll , respectively (Tables 1 and 2). These activities are similar to those found in other areas (Turekian et al, 1983;Olsen et. al., 1985;Todd et al, 1989;Baskaran et a!., 1993;Kim et al, 1998).…”

“…A lack of correlation between the absolute activity of 32p and 33 p and rainfall was also found in measurements of 32 p and 33p at Bermuda . In contrast, several investigations have found relationships between rainfall amount and the absolute activity 7Be and 2lOpb in rainfall samples integrated over longer time scales (Olsen et al, 1985;Todd et al, 1983;Turekian et al, 1983;Baskaran et al, 1993;Kim et aI., 1998). The lack ofa linear relationship found in this study suggests that radionuclide activities at our site are not controlled by dilution alone, but rather by other processes, such as source and scavenging intensity.…”

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.…”

Use of 7Be to document soil erosion associated with a short period of extreme rainfall

“…2 cm can usually be explained by the downward movement of soil particles through fissures formed during relatively dry periods (e.g. Olsen et al, 1985) and/or by bioturbation by soil fauna that can transport 7 Be to greater depths (e.g. Wallbrink and Murray, 1996; Kaste et al, 2007).…”