Annual fallout of32Si,210Pb,22Na,35S and7Be in rains in India

Abstract

The concentration of radioisotopes rBe, ~S were measured in Bombay since 1956 and ~2Na, ~a~ z~Si since 1963. In Khandala and other stations such measurements have been made at irregular periods since 1961. In addition several measurements especially that of 32Si were made in 1970. Data available todate from Indian stations is summarised and critically analysed. We conclude that appreciable amounts of ~S, 2~Na and 8JSi, over and above their production by cosmic rays, were produced during the high yield Russian tests as evidenced by their fallout between 1962-66. Based on the bomb produced excess the half period for their removal from the stratosphere is deduced to be less than 1 year. The ' excess' contribution of 3aSi due to bombs is, however, small; about 1~0 of its inventory in the oceans. The present study shows that for stations where orogeny is the principal mer nism of precipitation, the annual fallout is independent of the annual rainfall.

Beryllium-7 deposition at Fayetteville, Arkansas, and excess polonium-210 from the 1980 eruption of Mount St. Helens.

“…(Peirson, 1963) and is comparable to the re ported values of 4.3 (dpm/cm2/y) at Westwood (41°N), N. J., (Walton and Fried, 1962), 9.5 (dpm/cm2/y) at Rijswijk (52°N), Netherlands (Bleichrodt and Van Abkoude, 1963), 7.6 (dpm/ cm2/y) at Bombay (19"N), India (Lal et al, 1979), and 8.1 (dpm/cm2/y) at Quillayute (49'N), Washington (Crecelius, 1981). It is worthy of note here, however, that Turekian et al (1983) have recently reported the values of 17.1 (dpm/cm2/y) at Bermuda (33'N) and 22.7 (dpm/cm2/y) at New Haven (41°N), Connecticut.…”

The Missing Silica Sink: Revisiting the Marine Sedimentary Si Cycle Using Cosmogenic 32Si

“…Cosmogenic 32 Si, produced by cosmic ray spallation of 40 Ar in the atmosphere (Lal et al, ; Morgenstern et al, ; Fifield and Morgenstern, ), is a natural tracer with t 1/2 = 140 years that can be used to examine diagenetic alteration of biogenic silica (Polak et al, ; Tréguer et al, ; Lal, ). Once entering the ocean (Lal et al, ), 32 Si is taken up by siliceous organisms and delivered to the seafloor after these organisms die and sink (Figure ). The specific activity of 32 Si in marine biogenic silica varies within relatively well defined limits: typically ~5–40 disintegrations per minute (dpm)/kg (Somayajulu et al, , ; Craig et al, ; Fifield & Morgenstern, ).…”

Observation of fallout rates of atmospheric 7Be and 22Na produced by cosmic rays—concerning estimation of the fallout rate of atmospheric 26Al

“…In 1961 and 1962, a large amount of radioactive materials was released by the detonations of nuclear weapons and an abrupt increase in the level of radioactivity in the atmosphere occurred. Nevertheless, the concentration level of ?Be has not changed since 1963 [Silker, 1972;Kolb, 1974;Lal et aL, 1979). For the period of our observation, therefore, we can conclude that the main part of ?Be in the atmosphere is a cosmic ray origin.…”

“…and 1964, was about one order of magnitude higher than a level of cosmogenic 22Na given by Lal and Peters [1967]. Afterwards the concentration began to decrease and was becoming constant after 1966 [Roedel, 1968;Cigna et al, 1970;Kolb, 1974;Lal et al, 1979], because 22Na produced by the weapon tests had decayed sufficiently or had been removed by fallout process of the stratospheric-tropospheric exchange of air Paper number 80A0861. 0148-0227/81/080A-0861501.00 masses.…”