10 Be and 7 Be measurements on New Zealand rains (1995-1997) : progress report

Monthly rain collections have been made at Gracefield (Lower Hutt, New Zealand) since September 1995, at Kaitoke (50 km inland from Lower Hutt) since January 1997, and at Dunedin (South Island, New Zealand) since February 1997. Measurements of 10Be and 7Be have been made principally to provide local flux rate data for application to current and future cosmogenic isotope studies of soil, loess, marine sediments and groundwater. The results so far show that 10Be concentrations in rain vary considerably on a monthly time frame (1.07 to 5.04 x 104 atoms cm-3 rain or 1.21 to 4.23 x 105 atoms cm-2 from September 1995 to February 1997), but that annual fluxes are relatively constant (2.70 x 104 atoms cm-3 rain or 2.97 x 105 atoms cm-2 from September 1995 to August 1996; 2.76 x 104 atoms cm-3 rain or 2.91 x 105 atoms cm-2 from March 1996 to February 1997). 7Be data are similarly variable on a monthly basis, ranging from 0.670 to 2.976 x 104 atoms cm -3 between December 1995 and March 1997 (0.704 to 2.096 x 105 atoms cm-2). The 10Be results are similar to those derived from a rain collected at the Gracefield site in 1987 (2.50 x 104 atoms cm-3 or 2.86 x 105 atoms cm-2), and are within 20% of published results from other mid-latitude, continental sites (India and USA). (author). 21 refs., 2 tabs., 6 figs