Sorption of Iron on Surfaces: Modelling, Data Evaluation, and Measurement Uncertainty

Abstract

Assessment of the likely outcome of engineered invention strategies in acid mine drainage often involves complex geochemical modelling activities. Geochemical modelling is based on chemical thermodynamic data. In addition sorption models, kinetical reaction rates and transport tools are included into the modelling codes because the interactions between solution components and surfaces, reaction time and transport are considered important features characterising the site‐specific situation. In the determination of both thermodynamic data and sorption coefficients, speciation calculations play an important role. By applying the probabilistic speciation code Ljungskile to some simplified acid mine drainage scenarios, the strong impact of chemical speciation on the complete measurement uncertainty budget of geochemical modelling predictions is shown. The complete measurement uncertainty budget in combination with other metrological concepts like traceability is an essential element of quality assurance for experimental data. The elements of quality assurance are provided by international agreements and normative documents on national and international levels. The following discussion will focus on some metrological issues of sorption data.

9th International Mine Water Congress 2005

“…The boomerang-shaped field represents the pH-E H region of natural waters as determined by Baas-Becking et al (1960). The data follow the lower boundary set for oxidized mine water and correlate closely with the E H -pH calculated for the Fe(III)/Fe(II) couple (Meinrath et al, 2004). The redox regime is strongly influenced by the shallow layer of tailings, affected by AMD.…”

“…The question, whether a Fe(II) sulfate phase should be solubility limiting will not be further discussed. The authors are well aware of the limitations of thermodynamic modelling (Meinrath et al, 2000, Meinrath 2001, Meinrath & May, 2002, Meinrath et al, 2004, Ödegaard-Jensen et al, 2004. In Figure 3 the concentrations of Fe and S in the WA sample from the l996 sampling campaign are correlated with concentrations which remain after 10 days in solution, after filtration through 0.45 µm filter paper (FAS).…”

Water Management at Abandoned Flooded Underground Mines

“…Nitzsche et al (2000) or Meinrath et al (2004) varied different constants in the database within their error range and were able to show the uncertainties of such numerical codes -and their results might be surprising for those who tend to discuss the 2 nd or 3 rd decimal place in the results of the programmes (Fig. Yet, the chemical thermodynamic database is based on experimental results, which have an inherent experimental error range.…”

Minerals and Mine Drainage

“…Water Environment Research, Volume 77, Number 6 1882 found to have the highest bioavailability and highest probability of being remobilized under changing water quality conditions. In an effort to better understand the reliability of complex geochemical modeling exercises, Meinrath et al (2004) used a probabilistic speciation code (Ljungskile) to identify the complete measurement uncertainty budget.…”