Re: question about phreeqc

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

> I am not a geochemist, and I am aware that I would not be able to apply
phreeqc without one on the project.  At the moment, I am only interested in
whether the model is appropriate for the application I have in mind:  I
want to identify a geochemical "signature" from a mining operation on a
river, whereby I can monitor water chemistry downstream, and say whether
the releases from such-and-such a mine continue to be measureable at
increasing distances from the mine itself.  Part of the concern is that the
mines are in Mongolia, and the stream runs into Russia, but also that the
impact of the mines my be far-reaching geographically.

> The area we want to work in is a watershed with many mines located right
on
the streams.  Most of the mines are placer mines, not cyanide mines, so
there may be no major chemical transformations to look for, just the
chemistry of the mined soils as they are suspended by the stream.   If you
think quantification of downstream extent of mining impact on water quality
is an appropriate application of the model, let me know.  If its not and
there is another tool, please help steer me in the right direction.  If
there's no way to do what I want, please just set me straight.  I am trying
to develop a budget for the project, so I will also soon be interested in
what kind of data set is needed to apply the model (if it is appropriate),
and possible co-investigators who could lead this element of the work.

> From your description, I don't think PHREEQC is a tool that would help
determine fingerprints of mining downstream. PHREEQC is designed to
identify major reactions or predict water chemistry given a set of chemical
reactions. If the effects on the water chemistry are small ("no major
chemical transformations"), I think you need to look elsewhere. It sounds
like you want a chemical signature that is unique to the mines and that
could be trace element concentrations or ratios of element concentrations
in the sediments or possibly an isotopic signature in Sr or maybe other
isotopes.

David

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