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Characterization of glasses using infrared spectroscopy
Goldschmidt Conference Abstracts 2006
A125
Vertical REE profiles in water and DGT in the central Arctic Ocean
Characterization of glasses using infrared spectroscopy
R. DAHLQVIST1, P.S. ANDERSSON2, J. INGRI3, D. PORCELLI1
K.N. DALBY1, C.D.M. DUFRESNE1, P.L. KING1, J.M. BYRNES2, R.J. LEE3, M.S. RAMSEY3
1
University of Oxford, Department of Earth Sciences, Oxford OX1 3PR, UK ([email protected]) 2 Swedish Museum of Natural History, Laboratory for Isotope Geology, Stockholm, Sweden ([email protected]) 3 Lulea˚ University of Technology, Division of Applied Geology, Lulea˚, Sweden ([email protected]) The first vertical REE concentration profiles from the central Arctic Ocean (88°27 0 N, 0°45 0 W) to combine data for filtered water samples with data for the labile REE fraction collected with the in situ method of diffusive gradients in thin films (DGT) are presented here. During a 3-week drift station in 2001 the pack ice was used as a platform to provide ultra clean conditions for filtration, sampling of water, and deployment of DGT. The DGT-method is an in situ method which employs a hydrogel to collect labile and easily diffusible species from the natural seawater matrix. REE concentrations for the filtered water samples show no clear trend in the top 200 m of the water column. Surface water CLa is 75 pM. In contrast, results from the DGT deployments show a significant concentration increase towards the surface, with a factor of 2–3 for all REE. CLa at 10 and 200 m measured with DGT are 68 and 26 pM, respectively. This indicates that the fraction of labile metal increases towards the surface, which is contrary to the nutrient-like behavior observed for many trace elements in the oceans. We therefore conclude that a different mechanism controls the physico-chemical speciation of REE in central Arctic Ocean surface waters.
Results from the 2001 expedition are compared with published data, and with recently analyzed data from Bering Strait and the Chukchi Sea, which, through the trans polar drift, is a possible source for surface water in the central region of the Arctic Ocean. doi:10.1016/j.gca.2006.06.266
1
Department of Earth Science, UWO, London, Ont., Canada N6A 5B7 ([email protected]) 2 Astrogeology Team, USGS, Flagstaff, USA 3 IVIS Laboratory, University of Pittsburgh, USA Amorphous silicate phases, such as glasses and weathering products, are ubiquitous on Earth and planetary bodies and can be identified using infrared spectra (Wyatt and McSween, 2002; Michalski et al., 2005). We treat micro-reflectance Fourier Transform Infrared (FTIR) spectra with the Kramers–Kronig (KK) transform then deconvolve the resultant absorbance spectra using bands (from Dalby and King, 2006). This method is used to identify and quantify structural units to better characterize the silicate glasses. Synthetic and natural silicate glasses display a systematic shift in the overall FTIR KK absorbance peak maxima with increasing SiO2 content (Fig. 1). Synthetic quartzofeldspathic glass spectra were deconvolved into bands and a relationship was found between the 1010, 1050, 1100, 1150, and 1210 cm1 bands and Al/Si (Fig. 2). This method shows promise for extracting structural units from the IR spectra of multi-component silicate glasses, and for improving deconvolution of glass–mineral mixtures.
Fig. 1. FTIR peak position (KK Abs; cm1) vs. SiO2 content of glasses. Fig. 2. Percent band amplitude vs. Al/Si. Band positions (cm1) are in brackets.
References Dalby, K.N., King, P.L., 2006. Am. Mineral. (in press). Michalski, J.R., Kraft, M.D., Sharp, T.G., Williams, L.B., Christensen, P.R., 2005. Icarus 174, 161–177. Wyatt, M.B., McSween, H.Y., 2002. Nature 417, 263–266. doi:10.1016/j.gca.2006.06.267
A125
Vertical REE profiles in water and DGT in the central Arctic Ocean
Characterization of glasses using infrared spectroscopy
R. DAHLQVIST1, P.S. ANDERSSON2, J. INGRI3, D. PORCELLI1
K.N. DALBY1, C.D.M. DUFRESNE1, P.L. KING1, J.M. BYRNES2, R.J. LEE3, M.S. RAMSEY3
1
University of Oxford, Department of Earth Sciences, Oxford OX1 3PR, UK ([email protected]) 2 Swedish Museum of Natural History, Laboratory for Isotope Geology, Stockholm, Sweden ([email protected]) 3 Lulea˚ University of Technology, Division of Applied Geology, Lulea˚, Sweden ([email protected]) The first vertical REE concentration profiles from the central Arctic Ocean (88°27 0 N, 0°45 0 W) to combine data for filtered water samples with data for the labile REE fraction collected with the in situ method of diffusive gradients in thin films (DGT) are presented here. During a 3-week drift station in 2001 the pack ice was used as a platform to provide ultra clean conditions for filtration, sampling of water, and deployment of DGT. The DGT-method is an in situ method which employs a hydrogel to collect labile and easily diffusible species from the natural seawater matrix. REE concentrations for the filtered water samples show no clear trend in the top 200 m of the water column. Surface water CLa is 75 pM. In contrast, results from the DGT deployments show a significant concentration increase towards the surface, with a factor of 2–3 for all REE. CLa at 10 and 200 m measured with DGT are 68 and 26 pM, respectively. This indicates that the fraction of labile metal increases towards the surface, which is contrary to the nutrient-like behavior observed for many trace elements in the oceans. We therefore conclude that a different mechanism controls the physico-chemical speciation of REE in central Arctic Ocean surface waters.
Results from the 2001 expedition are compared with published data, and with recently analyzed data from Bering Strait and the Chukchi Sea, which, through the trans polar drift, is a possible source for surface water in the central region of the Arctic Ocean. doi:10.1016/j.gca.2006.06.266
1
Department of Earth Science, UWO, London, Ont., Canada N6A 5B7 ([email protected]) 2 Astrogeology Team, USGS, Flagstaff, USA 3 IVIS Laboratory, University of Pittsburgh, USA Amorphous silicate phases, such as glasses and weathering products, are ubiquitous on Earth and planetary bodies and can be identified using infrared spectra (Wyatt and McSween, 2002; Michalski et al., 2005). We treat micro-reflectance Fourier Transform Infrared (FTIR) spectra with the Kramers–Kronig (KK) transform then deconvolve the resultant absorbance spectra using bands (from Dalby and King, 2006). This method is used to identify and quantify structural units to better characterize the silicate glasses. Synthetic and natural silicate glasses display a systematic shift in the overall FTIR KK absorbance peak maxima with increasing SiO2 content (Fig. 1). Synthetic quartzofeldspathic glass spectra were deconvolved into bands and a relationship was found between the 1010, 1050, 1100, 1150, and 1210 cm1 bands and Al/Si (Fig. 2). This method shows promise for extracting structural units from the IR spectra of multi-component silicate glasses, and for improving deconvolution of glass–mineral mixtures.
Fig. 1. FTIR peak position (KK Abs; cm1) vs. SiO2 content of glasses. Fig. 2. Percent band amplitude vs. Al/Si. Band positions (cm1) are in brackets.
References Dalby, K.N., King, P.L., 2006. Am. Mineral. (in press). Michalski, J.R., Kraft, M.D., Sharp, T.G., Williams, L.B., Christensen, P.R., 2005. Icarus 174, 161–177. Wyatt, M.B., McSween, H.Y., 2002. Nature 417, 263–266. doi:10.1016/j.gca.2006.06.267