Beryllium-7 Measurements
Dr David Kakdo 
University of Miami

This dataset contains Be-7 concentrations for stations occupied during October
1997 and June-October 1998.  For each sample, approximately 700L of seawater
from the upper 50m of the water column was pumped through iron-impregnated 
acrylic fiber packed into a cylindrical cartridge using a 1.5" hose and
centrifugal pump. Water was pumped at a rate of approximately 14 L/min.  Thus
each sample required about 50 min of pumping.  In most cases, double or triple
samples were collected at any one depth and later combined.  Be-7 collection
efficiency was confirmed at 0.90 +/- 0.02.

On land, the fibers were dried, ashed, and placed in a marenelli beaker for
gamma counting. The Be-7 has a readily identifiable peak at 478 keV. The
detector was calibrated for this geometry by adding a commercially prepared
solution of known gamma activities to an ashed fiber and counting it in the
marenelli beaker. The counting efficiency was 0.04 for this geometry.  The
limit of detection used in this work, defined at the 99.7% confidence level,
is SL (3(b, where (b is the standard deviation of the blank measurements.

To estimate the atmospheric deposition of Be-7, samples of snow (m2 in area)
were also collected, and plastic buckets were deployed (1-3 weeks) to collect
fallout over known time periods.  The snow and other precipitation was then
melted, and the Be-7 removed by co-precipitation with iron-hydroxide, which 
was dried and counted by gamma spectrometry. The counting system was calibrated
for these samples by preparing NBS standards in geometries identical to the
samples.

Complete details of these measurements can be found in the following journal
article:
Kadko, D. (2000) Modeling the evolution of the Arctic mixed layer during the
fall 1997 SHEBA project using measurements of Be-7. Deep-Sea Research, in
press.