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. Author manuscript; available in PMC: 2020 Oct 15.
Published in final edited form as: Environ Sci Technol. 2019 Sep 26;53(20):11684–11693. doi: 10.1021/acs.est.9b04478

Table 1.

Arsenic- and sulfide-containing test solutions prepared in this study.

As(III)-O μg/L 1 As(V)-O μg/L 1 pH ΣH2S mg/L2 [S/As]3 [HS-/OH-]4 As2S3 SI5
Arsenic oxyanion mixtures 750 150 5.5 1.0 3 310 −0.28
750 150 5.5 4.2 13 1250 0.05
750 150 7.0 1.0 3 140 −1.44
750 150 7.0 4.2 13 560 −1.58
750 150 8.5 1.0 3 9 −5.15
750 150 8.5 4.2 13 34 −4.12
As(III)-O μg/L1 As(V)-O μg/L1 pH ΣH2S mg/L2 [S/As]3 [HS-/OH-]4 As2S3 SI5
As-S chromatography tests 8000 250 7.0 10 2.8 710 −0.02
15000 1000 8.5 10 1.6 35 −1.53
8000 250 8.5 20 5.6 130 −3.34
ΣAs μg/L6 Ratio7 pH ΣH2S mg/L2 [S/As] [HS-/OH-]4 As2S3 SI5
As2S3 solubility tests 11527 11526 5.4 0.10 0.02 30 −0.88
8326 8325 5.4 0.18 0.05 60 −0.10
4339 4338 5.4 0.30 0.16 90 0.07
3478 347 5.4 0.50 0.34 160 0.15
316 2.95 5.4 2.4 18 750 0.19
365 0.14 5.4 9.5 61 2930 0.23
427 0.10 5.4 12 66 3700 0.08
575 0.05 5.4 16 65 4940 −0.01
577 0.02 5.4 16 65 4930 −0.03
1251 0.0004 5.4 24 45 7310 −0.15
1653 0.0018 5.4 40 57 12300 −0.37
As(III)-O μg/L1 As(V)-O μg/L1 pH ΣH2S mg/L2 [S/As]3 [HS-/OH-]4 As2S3 SI5
Natural matrices 500 8 500 7.02 0.99 4.6 140 −1.77
500 9 500 7.15 1.48 6.9 175 −1.58
1

Initial concentration of arsenite and arsenate prior to adding dissolved sulfide.

2

Initial total dissolved sulfide concentration.

3

Initial molar ratio of sulfide to arsenite; final [S/As] ratio is given for the As2S3 solubility experiments.

4

Initial molar ratio of bisulfide to hydroxide.

5

Calculated saturation index (SI) of disordered As2S3 [using Geochemist’s Workbench, v. 12 and the “thermo.com.V8.R6+” database updated to include solubility constants from ref [8]; SI values near 0 correspond to equilibrium with disordered As2S3, negative and positive values correspond to undersaturated and oversaturated conditions, respectively].

6

Measured total concentration of arsenic determined in As2S3 solubility experiments.

7

Measured ratio of [arsenite/thioarsenic] species in As2S3 solubility experiments.

8

Chickasaw National Recreation Area – Site 1.

9

Chickasaw National Recreation Area – Site 3.