An Optical Dye Method for Continuous Determination of Acidity in Ice Cores

Helle Astrid Kjær; Paul Travis Vallelonga; Anders Svensson; Magnus Elleskov Kristensen; Catalin Tibuleac; Mai Winstrup; Seep Kipfstuhl

doi:10.1021/acs.est.6b00026

An Optical Dye Method for Continuous Determination of Acidity in Ice Cores

Helle Astrid Kjær, Paul Travis Vallelonga, Anders Svensson, Magnus Elleskov Kristensen, Catalin Tibuleac, Mai Winstrup, Seep Kipfstuhl

Physics of Ice, Climate and Earth

8 Citations (Scopus)

Abstract

The pH of polar ice is important for the stability and mobility of impurities in ice cores and can be strongly influenced by volcanic eruptions or anthropogenic emissions. We present a simple optical method for continuous determination of acidity in ice cores based on spectroscopically determined color changes of two common pH-indicator dyes, bromophenol blue, and chlorophenol red. The sealed-system method described here is not equilibrated with CO₂, making it simpler than existing methods for pH determination in ice cores and offering a 10-90% peak response time of 45 s and a combined uncertainty of 9%. The method is applied to Holocene ice core sections from Greenland and Antarctica and compared to standard techniques such as electrical conductivity measurement (ECM) conducted on the solid ice, and electrolytic meltwater conductivity, EMWC. Acidity measured in the Greenland NGRIP ice core shows good agreement with acidity calculated from ion chromatography. Conductivity and dye-based acidity Hdye⁺ are found to be highly correlated in the Greenland NEGIS firn core (75.38° N, 35.56° W), with all signals greater than 3σ variability coinciding with either volcanic eruptions or possible wild fire activity. In contrast, the Antarctic Roosevelt Island ice core (79.36° S, 161.71° W) features an anticorrelation between conductivity and Hdye⁺, likely due to strong influence of marine salts.

Original language	English
Journal	Environmental Science & Technology
Volume	50
Issue number	19
Pages (from-to)	10485-10493
ISSN	0013-936X
DOIs	https://doi.org/10.1021/acs.est.6b00026
Publication status	Published - 4 Oct 2016

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title = "An Optical Dye Method for Continuous Determination of Acidity in Ice Cores",

abstract = "The pH of polar ice is important for the stability and mobility of impurities in ice cores and can be strongly influenced by volcanic eruptions or anthropogenic emissions. We present a simple optical method for continuous determination of acidity in ice cores based on spectroscopically determined color changes of two common pH-indicator dyes, bromophenol blue, and chlorophenol red. The sealed-system method described here is not equilibrated with CO2, making it simpler than existing methods for pH determination in ice cores and offering a 10-90% peak response time of 45 s and a combined uncertainty of 9%. The method is applied to Holocene ice core sections from Greenland and Antarctica and compared to standard techniques such as electrical conductivity measurement (ECM) conducted on the solid ice, and electrolytic meltwater conductivity, EMWC. Acidity measured in the Greenland NGRIP ice core shows good agreement with acidity calculated from ion chromatography. Conductivity and dye-based acidity Hdye+ are found to be highly correlated in the Greenland NEGIS firn core (75.38° N, 35.56° W), with all signals greater than 3σ variability coinciding with either volcanic eruptions or possible wild fire activity. In contrast, the Antarctic Roosevelt Island ice core (79.36° S, 161.71° W) features an anticorrelation between conductivity and Hdye+, likely due to strong influence of marine salts.",

author = "Kj{\ae}r, {Helle Astrid} and Vallelonga, {Paul Travis} and Anders Svensson and Kristensen, {Magnus Elleskov} and Catalin Tibuleac and Mai Winstrup and Seep Kipfstuhl",

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T1 - An Optical Dye Method for Continuous Determination of Acidity in Ice Cores

AU - Kjær, Helle Astrid

AU - Vallelonga, Paul Travis

AU - Svensson, Anders

AU - Kristensen, Magnus Elleskov

AU - Tibuleac, Catalin

AU - Winstrup, Mai

AU - Kipfstuhl, Seep

PY - 2016/10/4

Y1 - 2016/10/4

N2 - The pH of polar ice is important for the stability and mobility of impurities in ice cores and can be strongly influenced by volcanic eruptions or anthropogenic emissions. We present a simple optical method for continuous determination of acidity in ice cores based on spectroscopically determined color changes of two common pH-indicator dyes, bromophenol blue, and chlorophenol red. The sealed-system method described here is not equilibrated with CO2, making it simpler than existing methods for pH determination in ice cores and offering a 10-90% peak response time of 45 s and a combined uncertainty of 9%. The method is applied to Holocene ice core sections from Greenland and Antarctica and compared to standard techniques such as electrical conductivity measurement (ECM) conducted on the solid ice, and electrolytic meltwater conductivity, EMWC. Acidity measured in the Greenland NGRIP ice core shows good agreement with acidity calculated from ion chromatography. Conductivity and dye-based acidity Hdye+ are found to be highly correlated in the Greenland NEGIS firn core (75.38° N, 35.56° W), with all signals greater than 3σ variability coinciding with either volcanic eruptions or possible wild fire activity. In contrast, the Antarctic Roosevelt Island ice core (79.36° S, 161.71° W) features an anticorrelation between conductivity and Hdye+, likely due to strong influence of marine salts.

AB - The pH of polar ice is important for the stability and mobility of impurities in ice cores and can be strongly influenced by volcanic eruptions or anthropogenic emissions. We present a simple optical method for continuous determination of acidity in ice cores based on spectroscopically determined color changes of two common pH-indicator dyes, bromophenol blue, and chlorophenol red. The sealed-system method described here is not equilibrated with CO2, making it simpler than existing methods for pH determination in ice cores and offering a 10-90% peak response time of 45 s and a combined uncertainty of 9%. The method is applied to Holocene ice core sections from Greenland and Antarctica and compared to standard techniques such as electrical conductivity measurement (ECM) conducted on the solid ice, and electrolytic meltwater conductivity, EMWC. Acidity measured in the Greenland NGRIP ice core shows good agreement with acidity calculated from ion chromatography. Conductivity and dye-based acidity Hdye+ are found to be highly correlated in the Greenland NEGIS firn core (75.38° N, 35.56° W), with all signals greater than 3σ variability coinciding with either volcanic eruptions or possible wild fire activity. In contrast, the Antarctic Roosevelt Island ice core (79.36° S, 161.71° W) features an anticorrelation between conductivity and Hdye+, likely due to strong influence of marine salts.

U2 - 10.1021/acs.est.6b00026

DO - 10.1021/acs.est.6b00026

M3 - Journal article

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EP - 10493

JO - Environmental Science & Technology

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An Optical Dye Method for Continuous Determination of Acidity in Ice Cores

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