An ultra-clean technique for accurately analysing Pb isotopes and heavy metals at high spatial resolution in ice cores with sub-pg g(-1) Pb concentrations.
Measurements of Pb isotope ratios in ice containing sub-pg g(-1) concentrations are easily compromised by contamination, particularly where limited sample is available. Improved techniques are essential if Antarctic ice cores are to be analysed with sufficient spatial resolution to reveal seasonal variations due to climate. This was achieved here by using stainless steel chisels and saws and strict protocols in an ultra-clean cold room to decontaminate and section ice cores. Artificial ice cores, prepared from high purity water were used to develop and refine the procedures and quantify blanks. Ba and In, two other important elements present at pg g(-1) and fg g(-1) concentrations in Polar ice, were also measured. The final blank amounted to 0.2+/-0.2 pg of Pb with (206)Pb/(207)Pb and (208)Pb/(207)Pb ratios of 1.16+/-0.12 and 2.35+/-0.16, respectively, 1.5+/-0.4 pg of Ba and 0.6+/-2.0 fg of In, most of which probably originates from abrasion of the steel saws by the ice. The procedure was demonstrated on a Holocene Antarctic ice core section and was shown to contribute blanks of only approximately 5%, approximately 14% and approximately 0.8% to monthly resolved samples with respective Pb, Ba and In concentrations of 0.12 pg g(-1), 0.3 pg g(-1) and 2.3 fg g(-1). Uncertainties in the Pb isotopic ratio measurements were degraded by only approximately 0.2%.
Burn
Laurie J
LJ
Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U1987, Perth 6845, Western Australia, Australia.
Rosman
Kevin J R
KJ
Candelone
Jean-Pierre
JP
Vallelonga
Paul
P
Burton
Graeme R
GR
Smith
Andrew M
AM
Morgan
Vin I
VI
Barbante
Carlo
C
Hong
Sungmin
S
Boutron
Claude F
CF
D001464:Barium / Q000032:analysis*; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods*; D007053:Ice / Q000032:analysis*; D007204:Indium / Q000032:analysis*; D007554:Isotopes / Q000032:analysis; D007854:Lead / Q000032:analysis*; D015203:Reproducibility of Results
D007053:Ice; D007554:Isotopes; D007204:Indium; D001464:Barium; D007854:Lead