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United States Department of Agriculture

Agricultural Research Service

Sorption Isotherm Spreadsheet
 

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Spreadsheet from the paper entitled: On the Use of Linearized Langmuir Equations by C.H. Bolster and G.M. Hornberger, Soil Science Society of America Journal, 2007, 71(6): 1796-1806.

Spreadsheet has been modified to correct the following errors:

(11/01/12)

In earlier versions the initial guess for the n parameter in the Freundlich model did not update when data were added to spreadsheet. This has now been corrected in the new vesrion (1.6)

(3/17/10)

  1. In the original spreadsheet the L-F model (Eq. [2]) did not have the K value raised to the n power. The attached spreadsheet has corrected this.
  2. There was a typo in the units with the Langmuir K parameter in the spreadsheet. The units should have read L/mg rather than L/kg when C is in mg/L. To avoid confusion, in the updated version the units have been removed since they are dependent on the units used for C and S.
  3. I have recently shown that the traditional method of weighting data by the inverse of the variance in the dependent variable can lead to poorer parameter estimates and uncertainties than with unweighted least squares regression when applied to sorption data (C.H. Bolster and J. Tellinghuisen. 2010. On the Significance of Properly Weighting Sorption Data for Least-Squares Analysis. Soil Science Society of America 74:670-679). Therefore, the weighting option has been removed from the spreadsheet (3/2010). If weighting of data is needed, please contact me at carl.bolster@ars.usda.gov for a modified version of the spreadsheet.
  4. wi in the denominator in Eq. [5] of Bolster and Hornberger (2007 SSSAJ) should be outside of the parenthesis. (This only applies to weighted data and therefore is not applicable to current spreadsheet)

 


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Last Modified: 10/30/2014
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