Application of synchrotron radiation technique to analysis of environmental samples

Zaw, Myint; Szymczak, Ron; Twining, John

doi:10.1016/s0168-583x(01)01231-9

Cited by 8 publications

(7 citation statements)

References 6 publications

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“…(Waychunas et al, 1983; Combes et al, 1989; Zhao et al, 1994; Manceau and Gates, 1997; O’Day et al, 2004). This information can be used to identify Fe species and monitor temporal and spatial redox changes in field and laboratory samples (Bajt et al, 1994; Zaw et al, 2002; Schmid et al, 2003; O’Day et al, 2004; Wilke et al, 2005; Root et al, 2007; Fittschen et al, 2008; Karlsson et al, 2008; Marcus et al, 2008; Mitsunobu et al, 2008; Root et al, 2009). …”

Section: Introductionmentioning

confidence: 99%

Surficial weathering of iron sulfide mine tailings under semi-arid climate

Hayes

Root

Perdrial

et al. 2014

Geochimica et Cosmochimica Acta

120

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Mine wastes introduce anthropogenic weathering profiles to the critical zone that often remain unvegetated for decades after mining cessation. As such, they are vulnerable to wind and water dispersion of particulate matter to adjacent ecosystems and residential communities. In sulfide-rich ore tailings, propagation to depth of the oxidative weathering front controls the depth-variation in speciation of major and trace elements. Despite the prevalence of surficial mine waste deposits in arid regions of the globe, few prior studies have been conducted to resolve the near-surface profile of sulfide ore tailings weathered under semi-arid climate. We investigated relations between gossan oxidative reaction-front propagation and the molecular speciation of iron and sulfur in tailings subjected to weathering under semi-arid climate at an EPA Superfund Site in semi-arid central Arizona (USA). Here we report a multi-method data set combining wet chemical and synchrotron-based X-ray diffraction (XRD) and X-ray absorption near-edge spectroscopy (XANES) methods to resolve the tight coupling of iron (Fe) and sulfur (S) geochemical changes in the top 2 m of tailings. Despite nearly invariant Fe and S concentration with depth (130–140 and 100–120 g kg−1, respectively), a sharp redox gradient and distinct morphological change was observed within the top 0.5 m, associated with a progressive oxidative alteration of ferrous sulfides to (oxyhydr)oxides and (hydroxy)sulfates. Transformation is nearly complete in surficial samples. Trends in molecular-scale alteration were co-located with a decrease in pH from 7.3 to 2.3, and shifts in Fe and S lability as measured via chemical extraction. Initial weathering products, ferrihydrite and gypsum, transform to schwertmannite, then jarosite-group minerals with an accompanying decrease in pH. Interestingly, thermodynamically stable phases such as goethite and hematite were not detected in any samples, but ferrihydrite was observed even in the lowest pH samples, indicating its metastable persistence in these semiarid tailings. The resulting sharp geochemical speciation gradients in close proximity to the tailings surface have important implications for plant colonization, as well as mobility and bioavailability of co-associated toxic metal(loid)s.

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Section: Introductionmentioning

confidence: 99%

Surficial weathering of iron sulfide mine tailings under semi-arid climate

Hayes

Root

Perdrial

et al. 2014

Geochimica et Cosmochimica Acta

120

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“…Other techniques, such as x-ray absorption near edge structure (XANES) spectroscopy and extended x-ray absorption fine structure (EXAFS), can be used to directly measure the oxidation state of a metal in a solid matrix and requires no wet-chemical extraction step. XANES and EXAFS have both been used to determine the oxidation states of iron in environmental samples and in the emissions from atmospheric pollution sources (Torok et al, 1994;Zaw et al, 2002), where analyte concentrations are elevated. However, work addressing the oxidation state of transition metals in atmospheric samples using these techniques has not been reported.…”

Section: Introductionmentioning

confidence: 99%

Application of synchrotron radiation for measurement of iron red-ox speciation in atmospherically processed aerosols

2007

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Abstract. In this study, ambient atmospheric particulate matter samples were collected using a size-resolved impactor sampler from three urban sites. The purpose of this study is to gain a better understanding of transformations of aerosolbound iron as it is processed in the atmosphere. Thus, the aerosol samples were artificially aged to represent long-term transport (10 to 40 days) or short-term transport (1 to 10 days) and were measured for iron at several time points. At each time point, iron was measured in each size fraction using three different techniques; 1) inductively coupled plasma-mass spectrometry (ICPMS) for total iron, 2) x-ray absorbance near edge structure (XANES) spectroscopy for the measurement of total Fe(II) and Fe(III), and 3) a wetchemical method to measure soluble Fe(II) and Fe(III). Prior to aging, the XANES spectroscopy results show that a majority (>60% for each size fraction) of the total iron in the PM is in the form of Fe(III). Fe(III) was shown to be a significant fraction of the soluble iron (sometimes >50%), but the relative significance of Fe(III) was found to vary depending on the site. Overall, the total soluble iron depended on the sampling site, but values ranged from less than 1% up to about 20% of the total iron. Over the course of the 40 day aging period, we found moderate changes in the relative Fe(II)/Fe(III) content. A slight increase was noted in the coarse (>2.5 µm) fraction and a slight decrease in the 0.25 to 0.5 µm fraction. The soluble fraction generally showed (excepting one day) a decrease of soluble Fe(II) prior to 10 days of aging, followed by a relatively constant concentration. In the short-term transport condition, we found that the sub-micron fraction of soluble Fe(II) spikes at 1 to 3 days of aging, then decreases to near the initial value at around 6 to 10 days. Very little change in soluble Fe(II) was observed in the super-micron fraction.

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“…performed by Zhu et al found that aerosols which are high in inorganic sea salt components (chloride, nitrate, and sulfate) tend to resist the photo-reduction of Fe (III) to Fe(II) during atmospheric transport (Zhu et al, 1993).…”

Section: Introductionmentioning

confidence: 99%

Application of synchrotron radiation for measurement of iron red-ox speciation in atmospherically processed aerosols

Majestic¹,

Schauer²,

Shafer³

2007

Preprint

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Abstract. In this study, ambient atmospheric particulate matter (PM) samples were collected using a size-resolved impactor sampler from three urban sites. The purpose of this study is to gain a better understanding of transformations of aerosol-bound iron as it is processed in the atmosphere. Thus, the aerosol samples were artificially aged to represent long-term transport (10 to 40 days) or short-term transport (1 to 10 days) and were measured for iron at several time points. At each time point, iron was measured in each size fraction using three different techniques; 1) inductively coupled plasma-mass spectrometry (ICPMS) for total iron, 2) x-ray absorbance near edge structure (XANES) spectroscopy for the measurement of total Fe(II) and Fe(III), and 3) a wet-chemical method to measure soluble Fe(II) and Fe(III). Prior to aging, the XANES spectroscopy results show that a majority (>60% for each size fraction) of the total iron in the PM is in the form of Fe(III). Fe(III) was shown to be a significant fraction of the soluble iron (sometimes > 50%), but the relative significance of Fe(III) was found to vary depending on the site. Overall, the total soluble iron depended on the sampling site, but values ranged from less than 1% up to about 18% of the total iron. Over the course of the 40 day aging period, we found moderate changes in the relative Fe(II)/Fe(III) content. A slight increase was noted in the coarse (>2.5 μm) fraction and a slight decrease in the 0.25 to 0.5 μm fraction. The soluble fraction generally showed (excepting one day) a decrease of soluble Fe(II) prior to 10 days of aging, followed by a relatively constant concentration. In the short-term transport condition, we found that the sub-micron fraction of soluble Fe(II) spikes at 1 to 3 days of aging, then decreases to near the initial value at around 6 to 10 days. Very little change in soluble Fe(II) was observed in the super-micron fraction. These results show that changes in the soluble iron fraction occur within the lifetime of urban aerosols (1–3 days) and, therefore, atmospheric processing can have a large effect on human exposure to soluble iron.

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Application of synchrotron radiation technique to analysis of environmental samples

Cited by 8 publications

References 6 publications

Surficial weathering of iron sulfide mine tailings under semi-arid climate

Surficial weathering of iron sulfide mine tailings under semi-arid climate

Application of synchrotron radiation for measurement of iron red-ox speciation in atmospherically processed aerosols

Application of synchrotron radiation for measurement of iron red-ox speciation in atmospherically processed aerosols

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