Blank Values and Detection Limits: Exactly 0.3 mL of low-Pb seawater was used to determine the Pb concentration procedure blank. At least three replicates of each sample were measured. The average blank over 24 analytical sessions was 5.9 pmol/kg. The detection limit (3 times the std. dev. of low concentration samples) is about 1.5 pmol/Kg.

Isotope Blanks: There are two main sources of blanks in this isotope analysis. One is due to the AG1-x8 ion exchange resin and the acids used to elute the Pb. A significant but contribution comes from the ICPMS hardware from Pb retained from previous analyses. The latter blank is determined by an "On Peak Zero" measurement on high purity 0.2M HNO₃. Because the AG1-x8 blank is so low, we cannot make an accurate measurement of its Pb isotope ratios. So we measure the most intense signal (²⁰⁸Pb) and then estimate the blanks for the other isotopes assuming an isotope composition for "typical U.S. Pb" assumed as the ratio of our U.S.-purchased laboratory Pb standard (diluted from Ultra Scientific Catalog Number ICP-082, Lot Number D00198). These blanks have been subtracted from the reported isotope ratios.

All of the signals from our large-volume samples were well above Pb concentration detection limits, but the precision of the measurement degrades relative to the Faraday cup Johnson noise (and Daly ion counter statistics) as the signal becomes weaker. We think that our isotope ratio measurements for ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb are good to the second decimal place for samples with 1-2 pmol/kg Pb.

Quality Flags:
The standard Ocean Data View flags were used (reference all flags at https://www.bodc.ac.uk/data/codes_and_formats/odv_format/):
1: Good Value: Good quality data value that is not part of any identified malfunction and has been verified as consistent with real phenomena during the quality control process.
2: Probably Good Value: Data value that is probably consistent with real phenomena but this is unconfirmed or data value forming part of a malfunction that is considered too small to affect the overall quality of the data object of which it is a part. [Used when only one replicate confirmed the reported value.]
3: Probably Bad Value: Data value recognized as unusual during quality control that forms part of a feature that is probably inconsistent with real phenomena.
4: Bad Value: An obviously erroneous data value.

BCO-DMO Processing:
- modified parameter names;
- added station latitudes and longitudes from the cruise report;
- corrected years to 2009 where they were incrementally increasing by one;
- added ISO8601 date-time fields;
- removed unnecessary columns.

Pb.csv