Quantitative Speciation of Lead in Selected Mine Tailings from Leadville, CO

Abstract

We have characterized Pb speciation in selected tailings from the Leadville, CO, area using a variety of analytical techniques, including X-ray absorption fine structure (XAFS) spectroscopy. Samples from three locations were analyzed, including two chemically distinct tailings piles located within the city limits [Apache (pyrite-rich, low pH) and Hamms (carbonate-rich, near-neutral pH)] and tailings material deposited as overbank sediments along the Arkansas River approximately 13 km downstream from Leadville (Arkansas River tailings). Extended XAFS (EXAFS) spectra of these multicomponent samples were fit using linear combinations of model compound spectra. In accordance with pH differences among the samples, adsorbed Pb accounts for ∼50% of total Pb (Pb T ) in fine fractions of the near-neutral pH Hamms tailings, whereas Pbbearing jarosites account for the majority of Pb T in the fine fractions of the low pH Apache and Arkansas River tailings. EXAFS analyses following sequential extraction by MgCl 2 and EDTA show evidence of significant redistribution (readsorption) of Pb during the MgCl 2 extraction and for removal of adsorbed Pb and dissolution of Pb-carbonates during the EDTA extraction. Changes in Pb speciation with water extraction (dissolution of anglesite and precipitation of plumbojarosite) are observed in one sample of Arkansas River tailings. These molecular-scale results show that Pb speciation varies dramatically among environments in the Leadville area and that Pb occurs in a number of phases not amenable to definitive characterization by conventional microanalytical and/or chemical extraction techniques.

Geological and anthropogenic factors influencing mercury speciation in mine wastes: an EXAFS spectroscopy study

“…The EXAFS-based speciation procedure for Hg is similar to that previously developed for and applied to other metal(loid)s such as arsenic (1,2) , lead (3)(4)(5) , and zinc (6,7) . It involves the comparison of an EXAFS spectrum collected from a Hg-bearing sample with a spectral library of model compounds previously generated from an assortment of Hg minerals and sorbed species (Figure 3).…”

The effect of phytostabilization on Zn speciation in a dredged contaminated sediment using scanning electron microscopy, X-ray fluorescence, EXAFS spectroscopy, and principal components analysis

“…For soils and sediments, the micrometer scale of resolution is appropriate because fine particles of similar composition and structure formed by biotic and abiotic natural processes tend to aggregate Isaure et al, 2002Isaure et al, , 2005Manceau et al, 2002b;Kirpichtchikova et al, 2003;Manceau et al, 2004;Sarret et al, 2004). This second approach is preferable because it is less invasive than chemical extraction (Ostergren et al, 1999;Calmano et al, 2001). Regardless of the approach used, the set of EXAFS spectra obtained either on soil fractions after physical or chemical treatments, or on minimally perturbed soil by µ-EXAFS, are analyzed by principal component analysis (PCA) (Wasserman, 1997;Wasserman et al, 1999;Ressler et al, 2000;Manceau et al, 2002a).…”

Zn speciation in a soil contaminated by the deposition of a dredged sediment by synchrotron X-ray techniques

“…However, the existence of multiple species is a real limitation, and this drawback is generally overcome by fractionating the soil to reduce its heterogeneity in isolating or removing some metal species [2,3]. Still, this approach is not fully satisfying because it has been found that chemical and physical treatments can cause artefacts in modifying the very chemistry one is trying to probe [4]. In this work, we used the new combination of three synchrotronbased x-ray techniques, i.e., x-ray microfluorescence (µSXRF), microdiffraction (µXRD), and absorption spectroscopy (µEXAFS and bulk EXAFS), as discussed by Manceau, et.…”