Supplemental Text for manuscript to be submitted to Geochemical Transactions
Church, C.D., et al., “Microbial sulfate reduction and metal attenuation in pH 4 acid
QUALITY ASSURANCE AND QUALITY CONTROL FOR WATER ANALYSES
Several techniques were used to assure the quality of the analytical data for water
samples. These techniques included calculation of speciated charge imbalance, analysis
of a field blank, replicate analyses of environmental samples, and analysis of standard
reference water samples (SRWS) prepared by the U.S. Geological Survey (USGS).
The speciated charge imbalance (C.I.) was calculated using the geochemical code
WATEQ4F . The C.I. was calculated as follows: (sum cations?sum anions)C.I.(percent)??100 (1) (sum cations?sum anions)/2
where “sum cations” and “sum anions” are in units of milliequivalents per liter. The
charge imbalance calculated by WATEQ4F is twice the value that is typically reported
for cation-anion balance because the term in the denominator is the average
milliequivalents, rather than the sum of the milliequivalents. The C.I. is calculated on the
speciated results rather than the raw analytical data because C.I. is dependent on
speciation, especially for acidic solutions. The C.I. for the eight Penn Mine samples
ranged from -12% to 11%, and the mean C.I. was -3%. The charge imbalance is primarily
affected by the major ion chemistry and the errors are likely the result of analytics or
unanalyzed constituents. Nordstrom et al.  considered samples analyses with charge
imbalance of ?11 to be of sufficiently high quality for speciation calculations.
A field blank collected in Nov. 2001 was analyzed with the environmental
samples to detect potential field or laboratory contamination. The field blank data are , all constituents in the field 4
reported in table S1. With the exception of Fe, Cl, and SOblank were below their method detection limits (table S1). Concentrations of Fe and SO 4
were less than 0.5% of the lowest measured sample concentration, therefore
contamination of these constituents is considered. The concentration of 1.0 mg/L of Cl in
the field blank was only about twice the detection limit; however it is possible that
concentrations of Cl in the environmental samples have a slight positive bias.
For each of the four environmental water samples collected during 2002, a
replicate sample was collected for analysis of major cations and trace metals. Results of
the replicate analyses are given in Table S2. Values of relative percent difference for
environmental samples (RPD
) were computed using equation 2, where R1 and R2 E
represent the concentrations in the two replicate analyses.
(R1?R2)RPD??100 (2) E(R1?R2)
2For analytes below the method detection limits, RPD were not calculated. E
RPD values (Table S2) were less than 15 % for all constituents in all four replicate E
samples. The mean of the absolute RPD values for each constituent was less than 10% Efor all constituents except Cr (11%). For stable isotopes, replicate results (Table S1) were
interpreted in terms of absolute difference (AD, Table S2). Values of AD among
replicates were within 0.1 per mill for all O and S isotope measurements and within 1 per
mill for H isotopes (Table S2).
Several SRWS prepared by the USGS Water Resources Discipline Branch of
Quality Services were analyzed as “unknowns” along with the environmental samples to
check for accuracy. Standard reference water samples M6, AMW4, T159, and T163 were
used to check the analytical methods for major cations and trace metals [3,4]. The
compiled results for the SRWS include the number of analyses (n), concentrations,
standard deviation or range of analyses, reported most probable value (MPV), F-
pseudosigma (deviation), and the relative percent difference (Table S3). The relative ) S
percent difference between mean measured concentration and MPV for the SRWS (RPDwas calculated using equation 3:
(measured mean concentration?MPV) RPD ??100 (3) SMPVAnalytical accuracy improves with increasing concentration; reduced accuracy near the
method detection limit is the result of decreasing signal to noise ratio. Manganese (Mn)
and boron (B) had high RPD for one or more SRWS. However, the environmental S
samples for this study had Mn concentrations ranging from 2.4 to 8.2 mg/L, more than
100 times higher than either SRWS. Therefore, the relatively high RPD for Mn on one S
SRWS is not a large concern in terms of study results. With regard to B, the RPD ranged S
from -12.9 to -34.4 for three SRWSs with MPVs from 0.011 to 0.032 mg/L.
Concentrations of B in environmental samples from Penn Mine ranged from 0.11 to 2.8
mg/L, approximately 10 to 100 times greater than the range of B in the SRWSs. As with
Mn, the results for B from the SRWSs are not a large concern with regard to the
conclusions of this study. Additional information about the USGS SRWS program can be
obtained at URL http://bqs.usgs.gov/srs.
1. Ball, JW, Nordstrom, DK: User's manual for WATEQ4F, with revised
thermodynamic data base and test cases for calculating speciation of major,
trace, and redox elements in natural waters. U.S. Geological Survey Open-File
Report 91-183, 1991, 189 p. http://pubs.er.usgs.gov/usgspubs/ofr/ofr91183.
2. Nordstrom, DK, McCleskey, RB, Hunt, AG, Naus, CA: Questa baseline and
pre-mining ground-water quality investigation. 14. Interpretation of ground-
water geochemistry in catchments other than the Straight Creek Catchment,
Red River Valley, Taos County, New Mexico, 2002-2003. U.S. Geological
Survey Scientific Investigations Report 2005-5050, 2005, 84 p.
3. Farrar, JW: Results of the U.S. Geological Survey’s analytical evaluation
program for standard reference samples distributed in October 1999. U.S.
Geological Survey Open-File Report 00-227, 2000, 143 p.
4. Connor, BF, Currier, JP, Woodworth, MT: Results of the U.S. Geological
Survey’s analytical evaluation program for standard reference samples
distributed in October 2000. U.S. Geological Survey Open-File Report 01-137,
2001, 116 p. http://bqs.usgs.gov/srs/Report_Fall00.pdf.
Figure S1. Image collected using a down-hole camera during the sampling of sediments from the Penn Mine workings
Sediments were recovered from flooded mine workings of the Penn Mine, a Cu-Zn
mine abandoned since the early 1960s. Water chemistry, solid-phase characterization, and
microbial characterization results all indicate conditions that support anaerobic processes
such as sulfate reduction in the deep mine workings. At this site, sulfate-reducing bacteria
play a role in attenuating metals at moderately low pH.