Evaluating Remedial Alternatives for an Acid Mine Drainage Stream: Application of a Reactive Transport Model
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- 作者：Robert L. Runkel and Briant A. Kimball
- 刊名：Environmental Science & Technology
- 出版年：2002
- 出版时间：March 1, 2002
- 年：2002
- 卷：36
- 期：5
- 页码：1093 - 1101
- 全文大小：115K
- 年卷期：v.36,no.5(March 1, 2002)
- ISSN：1520-5851
文摘
A reactive transport model based on one-dimensionaltransport and equilibrium chemistry is applied to synopticdata from an acid mine drainage stream. Model inputsinclude streamflow estimates based on tracer dilution, inflowchemistry based on synoptic sampling, and equilibriumconstants describing acid/base, complexation, precipitation/dissolution, and sorption reactions. The dominant featuresof observed spatial profiles in pH and metal concentrationare reproduced along the 3.5-km study reach by simulatingthe precipitation of Fe(III) and Al solid phases and thesorption of Cu, As, and Pb onto freshly precipitated iron(III) oxides. Given this quantitative description of existingconditions, additional simulations are conducted to estimatethe streamwater quality that could result from twohypothetical remediation plans. Both remediation plansinvolve the addition of CaCO3 to raise the pH of a small, acidicinflow from ~2.4 to ~7.0. This pH increase results in areduced metal load that is routed downstream by the reactivetransport model, thereby providing an estimate of post-remediation water quality. The first remediation plan assumesa closed system wherein inflow Fe(II) is not oxidized bythe treatment system; under the second remediation plan,an open system is assumed, and Fe(II) is oxidized withinthe treatment system. Both plans increase instream pH andsubstantially reduce total and dissolved concentrationsof Al, As, Cu, and Fe(II+III) at the terminus of the study reach.Dissolved Pb concentrations are reduced by ~18%under the first remediation plan due to sorption onto iron(III) oxides within the treatment system and streamchannel. In contrast, iron(III) oxides are limiting under thesecond remediation plan, and removal of dissolved Pboccurs primarily within the treatment system. This limitationresults in an increase in dissolved Pb concentrationsover existing conditions as additional downstream sourcesof Pb are not attenuated by sorption.