Suggested citation for R phreeqc package:

Parkhurst DL, Appelo CAJ (2013). Description of input and examples for PHREEQC version 3–A computer program for speciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations, volume book 6 series Techniques and Methods. https://pubs.usgs.gov/tm/06/a43.

Charlton SR, Parkhurst DL (2011). “Modules based on the geochemical model PHREEQC for use in scripting and programming languages.” Computers & Geosciences, 37, 1653-1663. http://dx.doi.org/10.1016/j.cageo.2011.02.005.

Corresponding BibTeX entries:

  @Manual{,
    title = {Description of input and examples for PHREEQC version 3--A
      computer program for speciation, batch-reaction, one-dimensional
      transport, and inverse geochemical calculations},
    author = {D. L. Parkhurst and C. A. J. Appelo},
    publisher = {U.S. Geological Survey},
    year = {2013},
    series = {Techniques and Methods},
    volume = {book 6},
    chapter = {A43},
    pages = {497},
    url = {https://pubs.usgs.gov/tm/06/a43},
  }

  @Article{,
    title = {Modules based on the geochemical model PHREEQC for use in
      scripting and programming languages},
    author = {S. R. Charlton and D. L. Parkhurst},
    year = {2011},
    journal = {Computers & Geosciences},
    volume = {37},
    pages = {1653-1663},
    url = {http://dx.doi.org/10.1016/j.cageo.2011.02.005},
  }