Re: PHREEQC-2.7

["David L Parkhurst" <dlpark@xxxxxxxx>]

> 1)      When I entered the seawater chemical analysis of NORDSTROM into
the PHREEQC-2.7, the obtained results ? ex. Saturation indices - were
different from those described in the pdf-Example-1 (without U).

I don't understand what is different. Looking in the manual, the saturation
indices, calcite .76 and gypsum -.63 for example, are the same as your
spreadsheet.

> 2)      When I checked the molal concentration of the mineral species, it
was found that the minor Fe, Mn & Si minerals are given in higher amounts.
I don't know, may my simple calculations are wrong.

There is no information about molal concentrations of minerals in PHREEQC
speciation calculations. The saturation index can not be converted into an
amount of mineral. The saturation index simply states the thermodynamic
state of the water relative to a mineral. It indicates whether a mineral
should dissolve (SI < 0) or precipitate (SI > 0). SI near zero may mean
that a mineral is reacting sufficiently fast to maintain equilibrium, or it
may be a coincidence. You need to consider the mineralogy of your system
and the kinetics of mineral formation and precipitation.

> 3)      I tried to correlate the obtained PHREEQC-2.7 data with the
classical simplified "Probable Salt Combination Model" but the difference
still very big. Attached herewith my calculation sheet.

I don't know the probable salt method, but it looks like it distributes the
solutes among a series of salts. There is nothing in PHREEQC that
corresponds with this calculation.

David



David Parkhurst (dlpark@xxxxxxxx)
U.S. Geological Survey
Box 25046, MS 413
Denver Federal Center
Denver, CO 80225

Project web page: https://wwwbrr.cr.usgs.gov/projects/GWC_coupled



                                                                                                           
                      "Dr. Samir                                                                           
                      El-Manharawy"            To:       "David L Parkhurst" <dlpark@xxxxxxxx>             
                      <geo230@xxxxxxxx>        cc:                                                         
                                               Subject:  PHREEQC-2.7                                       
                      03/14/03 12:45 AM                                                                    
                      Please respond to                                                                    
                      "Dr. Samir                                                                           
                      El-Manharawy"                                                                        
                                                                                                           
                                                                                                           




Dear Prof. Dr. David Parkhurst
U.S. Geological Survey, Denver, Colorado.
 <?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office"
/>
Once more I ask your kind help to understand the comprehensive PHREEQC-2.7
program. Let me tell you first that I am not well familiar with your modern
higher kinetics, but I promise to follow your instructions. I noticed the
following points:

1)      When I entered the seawater chemical analysis of NORDSTROM into the
PHREEQC-2.7, the obtained results ? ex. Saturation indices - were different
from those described in the pdf-Example-1 (without U).
2)      When I checked the molal concentration of the mineral species, it
was found that the minor Fe, Mn & Si minerals are given in higher amounts.
I don't know, may my simple calculations are wrong.
3)      I tried to correlate the obtained PHREEQC-2.7 data with the
classical simplified "Probable Salt Combination Model" but the difference
still very big. Attached herewith my calculation sheet.


I am sure that you are so busy, and not expect an early reply.

Best regards,
Samir El-Manharawy       (See attached file: SW_NORDSTROM-PHRQ1.XLS)

Attachment: SW_NORDSTROM-PHRQ1.XLS
Description: application/msexcel