por_nut_chem_PF2

 PI:              Will Berelson and Doug Hammond
 of:              University of Southern California
 dataset:         Porosity and pore water nutrient chemistries, sediment cores
 project/cruise:  PACFLUX II/Cruise 2, 12/11/91 to 1/31/92 
 ship:            R/V Vickers 
 
 Methodology:
 
 McManus, J.,  D.E. Hammond, W.M. Berelson, T.E. Kilgore.  D.J. DeMaster, O.
 G. Ragueneau, and R.W. Collier.  1995. Early diagenesis of biogenic opal:
 Dissolution rates, kinetics, and paleoceanographic implications.  Deep Sea
 Research. 42, 871-903.

 Hammond, D.E., J. McManus, W.M. Berelson, T.E. Kilgore, and R. Pope, 1996,
 Early diagenesis of organic material in Equatorial Pacific Sediments:
 Stoichiometry and Kinetics. Deep Sea Research II, 43, 1365-1412.

 PI Notes:
 1..Ammonia and Nitrate+Nitrite appear to be significantly influenced by artifacts
    related to core retrieval and centrifugation.
 2..Measured silicic acid has been temperature corrected for warming during 
    centrifugation.
 3..Bottom water (BW) values are from (whole-core squeezing (WCS) cores, hydro data
    or landers).
 4..PacFlux II data are from Soutar box cores with variable quality of interfaces.  
 5..Porosity is defined as the fraction of sediment volume occupied by pore
    water, so it is dimensionless.  The prodecure used to measure it was to
    weigh sediment wet, dry the sediment at 60° C until it reached a constant
    weight, and re-weigh.  A density of solid phases D=2.6 g/cc, and a salinity
    S=35 psu were assumed.  The porosity was calculated from the expression
    below, where Ww is wet weight and Wd is dry weight (both corrected for the
    tare weight of the empty container):

    Porosity = Vpw/(Vpw+Vsed)										
    where Vpw = Ww/(0.99)
    and Vsed = (Wd - (Ww-Wd)(S/990))/D
    The factor 0.99 is grams H2O per cc sea water, and the factor 990 is grams
    H2O per kg sea water.

 DMO Notes:
 1..There is no corresponding event log for these data.
 2..Although this data was not collected on R/V Thomas Thompson cruise 13
    it was a US JGOFS funded pilot project.  This data set compliments 
    the TT13 data and is therefore included here.


 Parameter      Description                               Units

 sta_name       station name 
 sample         sample identification, BW stands 
                  Bottom Water
 depth_begin    depth at which measurement/sample         centimeters
                  began
 depth_end      depth at which measurement/sample         centimeters
                  ended
 depth_core     depth in core, mid-point of interval      centimeters
                  sampled
 lat            latitude, minus = South                   decimal degrees
 lon            longitude, minus = West                   decimal degrees
 porosity       sediment porosity                      
 NH3_pw         ammonia conc. in sediment pore water      micromoles/liter
 NO3_NO2_pw       nitrate plus nitrite conc. in sediment  micromoles/liter
                  pore water
 Si_acid_pw_t   silicic acid conc. in sedment pore        micromoles/liter  
                  water, temperature corrected for 
                  warming during centrifugation