Dataset: bottle_merged
Deployment: TT012

EQPAC Survey Cruises TT007 and TT011 Nutrient Data QA/QC report.
C. Garside and J.C.Garside
Bigelow Laboratory for Ocean Sciences - June 1993

    The methods and data analysis employed were those described in Garside,
1993 (submitted before the first EQPAC cruises). The following describes
specific details of the QA/QC procedure.

    During each cruise all profiles for each station were overlaid and compared
for consistency. On TT011 profiles were also overlaid on TT007 data for
comparison.  Some early standards during TT007 were identified as being low
and their concentrations were resolved by reconstruction of standard
provenance post cruise.

    Post cruise reprocessing of the data was done in conjunction with
comparisons of the results with concurrent CTD data from the shipboard CTD
mark files and historical nutrient data sets (CATO Expedition, Craig et al.,
1981 (GEOSECS); G. Heimerdinger (NODC), pers. comm.; Marumo (Hakuho Maru
Cruise KH-69-4, IBP)).

    ASW offsets were determined for each chemistry on every run. These values
were used to assign a single ASW offset for each chemistry for each batch of
ASW.

    Carryover between samples was determined in each analytical run for each
chemistry using the transition from the first to second standard and from the
fourth standard to baseline. These corrections were built into the data
reduction software.

    Post cruise checking of the CFA system revealed non-linearity in the
nitrate and (later) the silicate chemistries during TT007, which were not
detected during TT007 because of low standard concentrations. The non-
linearity was quantified and a correction applied.

    Once nutrient data had been corrected and similar profiles were obtained
for each station, nutrient versus sigmat plots were prepared; we expected these
relationships to be tight even if individual cast profiles at the same station
differed because of internal wave and spatial variability. Generally these
relationships were good, with some surprising outliers not evident in the
profiles. The outliers seem to be attributable to problems in the CTD records
and to mis-trips. Nutrient data have been nulled out only if they are
inconsistent with the general depth profile for the station and inconsistent
in the nutrient density plots for the station and analytical problems could
be identified from the CFA records.  Final QA/QC of these data will require
further effort in developing relaible bottle CTD data at workshops during the
latter half of 1993. For this reason nutrient data have been archived 
referenced to station, CTD number and bottle number.

References

CATO Expedition Data Report, 1990. Physical, Chemical and Biological Data -
     CATO Expedition. SIO Reference 90-4, University of California, Scripps
     Institution of Oceanography, La Jolla, CA 92093. 
Craig. H, W. S. Broecker and D. Spencer. 1981. GEOSECS Pacific Expedition,
     Volume 4 Sections and Profiles.  IDOE/NSF, US Government Printing Office,
     Washington D.C. 20402.
Garside. C. 1993. Nutrient Protocols. in U.S. JGOFS Equatorial Pacific Process
     Study Sampling and Analytical Protocols. eds. S. Kadar, M. Leinen and J.W.
     Murray. USJGOFS Planning and Coordination Office, WHOI, Woods Hole, MA
     02543.
G. Heimerdinger pers. comm,  NODC Archive 5oN - 5oS, 130oW - 150oW nutrient
     data set. 
Marumo. R, et al., 1970. Preliminary Report of the Hakuho Maru Cruise KH-69-4
     (IBP Cruise). ed. Marumo.  R. Ocean Research Institute, University of
     Tokyo.