If you can get enough water to analyze just by centrifuging without added water or extractants, that would be the best way to estimate the chemistry of the pore water. Sequential extractions can also be useful to estimate the quantity of elements sorbed on the solid material. Column experiments by Ken Stollenwerk have proven very useful in quantifying sorption properties of the solid material. David David Parkhurst (dlpark@xxxxxxxx) U.S. Geological Survey Box 25046, MS 413 Denver Federal Center Denver, CO 80225 Project web page: http://wwwbrr.cr.usgs.gov/projects/GWC_coupled Uma Seeboonruang <usee@xxxxxxxxxxx To: David L Parkhurst <dlpark@xxxxxxxx> > cc: Subject: Re: inverse model for unsat 07/04/03 05:14 PM Dear Dr. Parkhurst, Thank you so much for your reply. This really comes down to geochemistry which I am no expert on. Your input is very invaluable. I have one more question which is not exactly relating to PHREEQC. As I mentioned that the locations of the samplings will be in the unsaturated zone and the aqueous chemistry should be from the porewater. The soil solution, or the water in the pore space, should be extracted from the soil samples in order to evaluate the chemistry and to test whether the solution is in equilibrium with the minerals, e.g. jarosite, albite, montmorillonite and so on. However, I am not certain if the method should be using just pure water and centrifuging the water to get all the aqueous ions or using other chemicals. i am thinking of just using the water. I am reading many papers, e.g. Astrom M and coworkers. They use HClO4-HNO3-HCl-HF at 200C and dilute the soil sample with diluted aqua regia to determine the chemistry. Sometimes, researchers use a series of weak acid to extract metals from the soil solution. However, the ions from this method are those that were in aqueous phase plus those that were in solid phase attached to the solid matrix. I really appreciate your input. Uma Seeboonruang Department of Civil Engineering, King Mongkut's Institute of Technology - Ladkrabang, Bangkok, Thailand On Mon, 30 Jun 2003, David L Parkhurst wrote: > > > Currently, I am working on modeling geochemistry for the acid sulfate > soil > in Thailand and I am intersted in using the PHREEQC inverse modeling to > come up with amount of mass transfer between an upper (upgradient) and > a lower (downgradient) locations. they both are in the same flowpath as > teh water infiltrates downward. However, both locations are in the unsat > zone. I am wondering if PHREEQC will be applicable in this case. > > You should be able to use inverse modeling if the downgradient water > evolves from the upgradient water. It is also possible to consider the > evolution of rain to each of the waters, if this is the basic situation you > are considering. > > David > > > > David Parkhurst (dlpark@xxxxxxxx) > U.S. Geological Survey > Box 25046, MS 413 > Denver Federal Center > Denver, CO 80225 > > Project web page: http://wwwbrr.cr.usgs.gov/projects/GWC_coupled > > >
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