poros_nut_chem_pw

 PI:              Will Berelson and Doug Hammond
 of:              University of Southern California
 dataset:         Porosity and pore water nutrient chemistries, sediment cores
 project/cruise:  EqPac/Cruise TT013, Benthic survey
 ship:            R/V Thomas Thompson
 
 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..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 Note:
 1..Additional porosity/pore water data for this area are available from PACFLUX II, 
    a JGOFS pilot project.  See the PACFLUX II data file on this system.


 Parameter      Description                               Units
 
 event          event number from event log
 sta            station number from event log
 sample         sample identification
 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
 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