An assessment of procedures to remove exogenous Sr before 87Sr/86Sr analysis of wet archaeological wool textiles

I. C.C. Von Holstein; L. Font; E. E. Peacock; M. J. Collins; G. R. Davies

doi:10.1016/j.jas.2014.10.006

An assessment of procedures to remove exogenous Sr before ⁸⁷Sr/⁸⁶Sr analysis of wet archaeological wool textiles

I. C.C. Von Holstein^*, L. Font, E. E. Peacock, M. J. Collins, G. R. Davies

^*Corresponding author for this work

11 Citations (Scopus)

Abstract

Strontium isotope analysis (⁸⁷Sr/⁸⁶Sr) has been employed as a provenancing tool for archaeological wool textiles. To date, the effect of post-depositional (soil burial environment) contamination on keratin samples, which contain ~ppm concentrations of Sr, has not been rigorously investigated. We compared published methods for removing exogenous Sr from keratinous textiles, using either: (1) compressed N₂ gas, (2) HF(aq) solution (with and without a strong oxidising agent to remove dyestuff) or (3) organic solvents. ⁸⁷Sr/⁸⁶Sr ratios and Sr contents were determined in undyed and madder-dyed/alum-mordanted moieties of the same wool textile, buried for up to three years in contrasting environments (marine sediment/fenland bog), and two archaeological textiles recovered in Iceland (one typical and one atypical of local manufacture). Undyed experimental samples had low Sr contents (0.07-0.29ppm) that were increased by both dyeing (0.14-8.92ppm) and soil burial (0.11-15.01ppm). The efficacy of Sr removal was: HF(aq)+oxidising agent>organic solvents>HF(aq)>compressed N₂. Unburied samples showed little variation in ⁸⁷Sr/⁸⁶Sr ratio between cleaning methods (0.00006-0.00035); buried samples showed greater variation (0.00257-0.00713). Archaeological samples showed Sr contents greater than experimental soil burials (1-118ppm), and ⁸⁷Sr/⁸⁶Sr values consistent with Icelandic groundwater (0.70357-0.70540). No cleaning methods retrieved original (unburied and undyed) ⁸⁷Sr/⁸⁶Sr ratios except treatment with compressed N₂ in undyed samples. Exogenous Sr from the short term soil burial environment is probably mostly present as particulates. We conclude that ⁸⁷Sr/⁸⁶Sr ratios of archaeological wool textiles recovered from wet burial environments do not accurately reflect wool provenance even after cleaning with the methods investigated.

Original language	English
Journal	Journal of Archaeological Science
Volume	53
Pages (from-to)	84-93
Number of pages	10
ISSN	0305-4403
DOIs	https://doi.org/10.1016/j.jas.2014.10.006
Publication status	Published - 1 Jan 2015

Keywords

Diagenesis
Dye
Mordant
Strontium isotope
Wool

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10.1016/j.jas.2014.10.006

Cite this

@article{4bdd03ecd804458eb93841f11520cf7d,

title = "An assessment of procedures to remove exogenous Sr before 87Sr/86Sr analysis of wet archaeological wool textiles",

abstract = "Strontium isotope analysis (87Sr/86Sr) has been employed as a provenancing tool for archaeological wool textiles. To date, the effect of post-depositional (soil burial environment) contamination on keratin samples, which contain ~ppm concentrations of Sr, has not been rigorously investigated. We compared published methods for removing exogenous Sr from keratinous textiles, using either: (1) compressed N2 gas, (2) HF(aq) solution (with and without a strong oxidising agent to remove dyestuff) or (3) organic solvents. 87Sr/86Sr ratios and Sr contents were determined in undyed and madder-dyed/alum-mordanted moieties of the same wool textile, buried for up to three years in contrasting environments (marine sediment/fenland bog), and two archaeological textiles recovered in Iceland (one typical and one atypical of local manufacture). Undyed experimental samples had low Sr contents (0.07-0.29ppm) that were increased by both dyeing (0.14-8.92ppm) and soil burial (0.11-15.01ppm). The efficacy of Sr removal was: HF(aq)+oxidising agent>organic solvents>HF(aq)>compressed N2. Unburied samples showed little variation in 87Sr/86Sr ratio between cleaning methods (0.00006-0.00035); buried samples showed greater variation (0.00257-0.00713). Archaeological samples showed Sr contents greater than experimental soil burials (1-118ppm), and 87Sr/86Sr values consistent with Icelandic groundwater (0.70357-0.70540). No cleaning methods retrieved original (unburied and undyed) 87Sr/86Sr ratios except treatment with compressed N2 in undyed samples. Exogenous Sr from the short term soil burial environment is probably mostly present as particulates. We conclude that 87Sr/86Sr ratios of archaeological wool textiles recovered from wet burial environments do not accurately reflect wool provenance even after cleaning with the methods investigated.",

keywords = "Diagenesis, Dye, Mordant, Strontium isotope, Wool",

author = "{Von Holstein}, {I. C.C.} and L. Font and Peacock, {E. E.} and Collins, {M. J.} and Davies, {G. R.}",

year = "2015",

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doi = "10.1016/j.jas.2014.10.006",

language = "English",

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pages = "84--93",

journal = "Journal of Archaeological Science",

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TY - JOUR

T1 - An assessment of procedures to remove exogenous Sr before 87Sr/86Sr analysis of wet archaeological wool textiles

AU - Von Holstein, I. C.C.

AU - Font, L.

AU - Peacock, E. E.

AU - Collins, M. J.

AU - Davies, G. R.

PY - 2015/1/1

Y1 - 2015/1/1

N2 - Strontium isotope analysis (87Sr/86Sr) has been employed as a provenancing tool for archaeological wool textiles. To date, the effect of post-depositional (soil burial environment) contamination on keratin samples, which contain ~ppm concentrations of Sr, has not been rigorously investigated. We compared published methods for removing exogenous Sr from keratinous textiles, using either: (1) compressed N2 gas, (2) HF(aq) solution (with and without a strong oxidising agent to remove dyestuff) or (3) organic solvents. 87Sr/86Sr ratios and Sr contents were determined in undyed and madder-dyed/alum-mordanted moieties of the same wool textile, buried for up to three years in contrasting environments (marine sediment/fenland bog), and two archaeological textiles recovered in Iceland (one typical and one atypical of local manufacture). Undyed experimental samples had low Sr contents (0.07-0.29ppm) that were increased by both dyeing (0.14-8.92ppm) and soil burial (0.11-15.01ppm). The efficacy of Sr removal was: HF(aq)+oxidising agent>organic solvents>HF(aq)>compressed N2. Unburied samples showed little variation in 87Sr/86Sr ratio between cleaning methods (0.00006-0.00035); buried samples showed greater variation (0.00257-0.00713). Archaeological samples showed Sr contents greater than experimental soil burials (1-118ppm), and 87Sr/86Sr values consistent with Icelandic groundwater (0.70357-0.70540). No cleaning methods retrieved original (unburied and undyed) 87Sr/86Sr ratios except treatment with compressed N2 in undyed samples. Exogenous Sr from the short term soil burial environment is probably mostly present as particulates. We conclude that 87Sr/86Sr ratios of archaeological wool textiles recovered from wet burial environments do not accurately reflect wool provenance even after cleaning with the methods investigated.

AB - Strontium isotope analysis (87Sr/86Sr) has been employed as a provenancing tool for archaeological wool textiles. To date, the effect of post-depositional (soil burial environment) contamination on keratin samples, which contain ~ppm concentrations of Sr, has not been rigorously investigated. We compared published methods for removing exogenous Sr from keratinous textiles, using either: (1) compressed N2 gas, (2) HF(aq) solution (with and without a strong oxidising agent to remove dyestuff) or (3) organic solvents. 87Sr/86Sr ratios and Sr contents were determined in undyed and madder-dyed/alum-mordanted moieties of the same wool textile, buried for up to three years in contrasting environments (marine sediment/fenland bog), and two archaeological textiles recovered in Iceland (one typical and one atypical of local manufacture). Undyed experimental samples had low Sr contents (0.07-0.29ppm) that were increased by both dyeing (0.14-8.92ppm) and soil burial (0.11-15.01ppm). The efficacy of Sr removal was: HF(aq)+oxidising agent>organic solvents>HF(aq)>compressed N2. Unburied samples showed little variation in 87Sr/86Sr ratio between cleaning methods (0.00006-0.00035); buried samples showed greater variation (0.00257-0.00713). Archaeological samples showed Sr contents greater than experimental soil burials (1-118ppm), and 87Sr/86Sr values consistent with Icelandic groundwater (0.70357-0.70540). No cleaning methods retrieved original (unburied and undyed) 87Sr/86Sr ratios except treatment with compressed N2 in undyed samples. Exogenous Sr from the short term soil burial environment is probably mostly present as particulates. We conclude that 87Sr/86Sr ratios of archaeological wool textiles recovered from wet burial environments do not accurately reflect wool provenance even after cleaning with the methods investigated.

KW - Diagenesis

KW - Dye

KW - Mordant

KW - Strontium isotope

KW - Wool

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DO - 10.1016/j.jas.2014.10.006

M3 - Journal article

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JO - Journal of Archaeological Science

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