Spreadsheet: 195e634d-dcd7-404c-9436-9e774c701916
Sheet: Sheet1

An Excel Workbook for Identifying Redox Processes in Ground Water | Unnamed: 1 | Unnamed: 2 | Unnamed: 3
by [NAME], [NAME], [NAME], and [NAME]
U.S. Geological Survey Open-File Report 2009-1004.
This program uses measured dissolved oxygen, nitrate, manganese, iron, sulfate, and sulfide concentrations to classify redox conditions in ground-water samples according to the framework devised by McMahon and Chapelle (2008) and extended by Chapelle and others (in press).
 | McMahon, P.B., Chapelle, F.H., 2008, Redox Processes and Water Quality of Selected Principal Aquifers, [NAME], vol. 46(2), 259-271.
 | Chapelle, F.H., Bradley, P.M., Thomas, M.A. and McMahon, P.B., 2008, Distinguishing iron-reducing from sulfate-reducing conditions in ground-water systems, [NAME], in press.
User Instructions:
1) Copy and paste the Sample ID, [NAME] (DO), NO3 as N, Mn, Fe, and SO4 concentrations into their respective columns on the worksheet "RedoxAssignment"
 | a) Be sure to include a sample ID for every redox sample because the program will stop running at the first empty cell in the Sample ID column.
 | b) Only use data that have laboratory and (or) field reporting limits (nondetect values) that are below the threshold values listed in row 3.
 | c) It is not necessary to have sample data reported in the same concentration units as those listed in columns C thru G; however the threshold concentrations will need to be converted to the same units as the data.
 |  | For example, if Mn and Fe are in mg/L, the corresponding threshold concentrations would be 0.05 and 0.1 mg/L, respectively.
 | d) The threshold concentrations can be adjusted to user specifications.
 | e) The concentration data should be in numeric format, although it will accept some text formatted data (for example, < 0.5, E7.2, > 1000).
2) Once data have been imported into the sheet, the user presses the button "Assign Redox Categories and Processes" to assign a redox state and category as defined below.
3) The button "Clear Redox" clears columns I thru L.
4) The redox program can be rerun as described in 2.
[NAME]:
1) For samples with complete water-quality results (measured O2 [DO], NO3, Mn, Fe, and SO4), the general redox category and redox process is assigned to columns J and K according to the upper-half of table 2.
 | a) For those samples having all five parameters, the "General Redox Category" is determined from the "Redox Process" in column K:
 |  | Samples that are "O2" are "Oxic"
 |  | Samples that are "Suboxic" are "Suboxic"
 |  | Samples that are "NO3, Mn(IV), Fe(III)/SO4, CH4gen" are "[NAME]"
 |  | Samples that have more than one redox state, for example, "O2-CH4gen" are "Mixed". The redox proccesses that make up the mixture also define the mixed samples as either (oxic-anoxic) or (anoxic).
 | See samples 1 thru 12 of the example dataset.
 | b) For those samples that have sulfide measurements in addition to the other five constituents, Fe(III) and SO4 reduction is differentiated in column K from the calculated Fe/Sulfide ratio in column L:
 |  | a) Samples with Fe/Sulfide ratios less than 0.3 indicate SO4-reduction is the predominant redox process and are classified as:
 |  |  | "SO4"
 |  | b) Samples with Fe/Sulfide ratios between 0.3 and 10 indicate that neither Fe(III) nor SO4-reduction predominant over the other and are classified as:
 |  |  | Mix "Fe(III)-SO4"
 |  | c) Samples with Fe/Sulfide ratios greater than 10 indicate Fe(III)-reduction is the predominant redox process and are classified as:
 |  |  | "Fe(III)"
 | See samples 13 thru 21 of the example dataset
2) For samples with incomplete water-quality results (missing one or more of the five parameters), samples are divided into two classes and assigned a redox category and redox process according the lower-half of table 2:
 | 1) Samples missing either NO3, Mn, Fe, or SO4  but have a measured [NAME] (DO) value are classified as either:
 |  | "O2 >= 0.5 mg/L"
 |  | "O2 < 0.5 mg/L"
 | See samples 22 and 23 of the example dataset.
 | c) For those samples that do not have O2 data, but have NO3, Mn, Fe, and SO4, see 4 below.
 |  | a) Each redox process is amended with an "O2?/" to include the possibility that dissolved oxygen could be present at concentrations above the threshold.
 |  | b) Each redox category in column J is also amended to indicate that Oxic processes cannot be ruled out.  In each case, the most likely redox process is listed first and the less likely process is listed second.
 | See table 2 of the report and samples 24 thru 34 of the example dataset for more detailed definitions
3) For those samples that do not have data for either NO3, Mn, Fe, or SO4, samples are classified as:
 | "Indeterminate"
 | See sample 35 of the example dataset.