Considerations for the measurement of spectrophotometric pH for ocean acidification and other studies
Indicator‐based spectrophotometric pH is commonly used for the analysis of seawater because of its high precision and long‐term reproducibility. Users come from an increasingly diverse range of disciplines, primarily motivated by studies focused on the causes and effects of ocean acidification. Whil...
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crwiley:10.4319/lom.2014.12.830 2024-09-15T18:27:54+00:00 Considerations for the measurement of spectrophotometric pH for ocean acidification and other studies DeGrandpre, Mike D. Spaulding, Reggie S. Newton, Jenny O. Jaqueth, Emma J. Hamblock, Sarah E. Umansky, Andre A. Harris, Katherine E. 2014 http://dx.doi.org/10.4319/lom.2014.12.830 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.4319%2Flom.2014.12.830 https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lom.2014.12.830 en eng Wiley http://onlinelibrary.wiley.com/termsAndConditions#vor Limnology and Oceanography: Methods volume 12, issue 12, page 830-839 ISSN 1541-5856 1541-5856 journal-article 2014 crwiley https://doi.org/10.4319/lom.2014.12.830 2024-08-09T04:22:50Z Indicator‐based spectrophotometric pH is commonly used for the analysis of seawater because of its high precision and long‐term reproducibility. Users come from an increasingly diverse range of disciplines, primarily motivated by studies focused on the causes and effects of ocean acidification. While the analysis is readily implemented and straightforward, there are many variables that must be predetermined or measured, all of which can contribute uncertainty to the measurement. The indicator equilibrium constant and molar absorption coefficient ratios are available in the literature, but for various reasons, the conditions of analysis can be different, creating errors. Most of the parameters are temperature, salinity, and pressure dependent, posing potential additional errors. Indicator impurities and indicator perturbation of the sample pH also create uncertainties. We systematically evaluate all of the sources of error and compute how the errors propagate into CO 2 equilibrium calculations of the partial pressure of CO 2 ( p CO 2 ) and calcium carbonate saturation states (Ω). The primary sources of uncertainty originate from wavelength and absorbance errors in low quality or poorly functioning spectrophotometers (0.007 to 0.020 pH units) and indicator impurities (0.000 to >0.040 pH units). These errors generate p CO 2 and Ω uncertainties of 11‐200 µatm and 0.08‐0.38, respectively, depending upon the pH value and its uncertainty. Article in Journal/Newspaper Ocean acidification Wiley Online Library Limnology and Oceanography: Methods 12 12 830 839 |
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Open Polar |
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Wiley Online Library |
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English |
description |
Indicator‐based spectrophotometric pH is commonly used for the analysis of seawater because of its high precision and long‐term reproducibility. Users come from an increasingly diverse range of disciplines, primarily motivated by studies focused on the causes and effects of ocean acidification. While the analysis is readily implemented and straightforward, there are many variables that must be predetermined or measured, all of which can contribute uncertainty to the measurement. The indicator equilibrium constant and molar absorption coefficient ratios are available in the literature, but for various reasons, the conditions of analysis can be different, creating errors. Most of the parameters are temperature, salinity, and pressure dependent, posing potential additional errors. Indicator impurities and indicator perturbation of the sample pH also create uncertainties. We systematically evaluate all of the sources of error and compute how the errors propagate into CO 2 equilibrium calculations of the partial pressure of CO 2 ( p CO 2 ) and calcium carbonate saturation states (Ω). The primary sources of uncertainty originate from wavelength and absorbance errors in low quality or poorly functioning spectrophotometers (0.007 to 0.020 pH units) and indicator impurities (0.000 to >0.040 pH units). These errors generate p CO 2 and Ω uncertainties of 11‐200 µatm and 0.08‐0.38, respectively, depending upon the pH value and its uncertainty. |
format |
Article in Journal/Newspaper |
author |
DeGrandpre, Mike D. Spaulding, Reggie S. Newton, Jenny O. Jaqueth, Emma J. Hamblock, Sarah E. Umansky, Andre A. Harris, Katherine E. |
spellingShingle |
DeGrandpre, Mike D. Spaulding, Reggie S. Newton, Jenny O. Jaqueth, Emma J. Hamblock, Sarah E. Umansky, Andre A. Harris, Katherine E. Considerations for the measurement of spectrophotometric pH for ocean acidification and other studies |
author_facet |
DeGrandpre, Mike D. Spaulding, Reggie S. Newton, Jenny O. Jaqueth, Emma J. Hamblock, Sarah E. Umansky, Andre A. Harris, Katherine E. |
author_sort |
DeGrandpre, Mike D. |
title |
Considerations for the measurement of spectrophotometric pH for ocean acidification and other studies |
title_short |
Considerations for the measurement of spectrophotometric pH for ocean acidification and other studies |
title_full |
Considerations for the measurement of spectrophotometric pH for ocean acidification and other studies |
title_fullStr |
Considerations for the measurement of spectrophotometric pH for ocean acidification and other studies |
title_full_unstemmed |
Considerations for the measurement of spectrophotometric pH for ocean acidification and other studies |
title_sort |
considerations for the measurement of spectrophotometric ph for ocean acidification and other studies |
publisher |
Wiley |
publishDate |
2014 |
url |
http://dx.doi.org/10.4319/lom.2014.12.830 https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.4319%2Flom.2014.12.830 https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lom.2014.12.830 |
genre |
Ocean acidification |
genre_facet |
Ocean acidification |
op_source |
Limnology and Oceanography: Methods volume 12, issue 12, page 830-839 ISSN 1541-5856 1541-5856 |
op_rights |
http://onlinelibrary.wiley.com/termsAndConditions#vor |
op_doi |
https://doi.org/10.4319/lom.2014.12.830 |
container_title |
Limnology and Oceanography: Methods |
container_volume |
12 |
container_issue |
12 |
container_start_page |
830 |
op_container_end_page |
839 |
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1810469186185461760 |