13 Jan 2023
13 Jan 2023
Status: this preprint is open for discussion.

Technical note: An Assessment of HgII to Preserve Carbonate System Parameters in Organic-Rich Estuarine Waters

Christopher S. Moore1, Robert H. Byrne2, and Kimberly K. Yates1 Christopher S. Moore et al.
  • 1U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, 600 4th Street South, St. Petersburg, FL 33701, USA
  • 2College of Marine Science, University of South Florida, 140 7th Avenue South, St. Petersburg, FL 33701, USA

Abstract. This work assesses the effectiveness of sample preservation techniques for measurements of pHT (total scale), total dissolved inorganic carbon (DICT), and total alkalinity (AT) in organic-rich estuarine waters. Using HgCl2-treated and untreated water samples, measurements of these carbonate system parameters were examined over a period of three months. Over this duration, continued respiration of dissolved organic matter (DOM) in untreated samples created large discrepancies in DICT concentrations, while DICT was effectively constant in treated samples. Changes in AT were observed for both treated and untreated samples, with treated samples showing the greatest variation. In response to changing AT / DICT ratios, pHT changes were observed in both treated and untreated samples but were relatively small in treated samples. Improved accuracy of results in organic-rich estuarine waters that reflect the in situ carbonate system characteristics of the samples at the time of collection can be achieved when samples obtained for DICT and AT analysis are collected and stored separately. Accurate analyses of DICT can be obtained by filtration and preservation with HgCl2. Accuracy of AT analyses can be improved by filtration and storage in polypropylene bottles at 4 °C without adding HgCl2. Quality of pHT measurements can be improved by prompt analysis in the field and, if this cannot be accomplished, then samples can be preserved with HgCl2 and measured in the laboratory within one week.

Christopher S. Moore et al.

Status: open (until 24 Feb 2023)

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Christopher S. Moore et al.

Data sets

CO2 system measurements in Hillsborough River Moore, C. S., Byrne, R. H., and Yates, K. K.

Christopher S. Moore et al.


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Short summary
This paper presents time series measurements of pH, dissolved inorganic carbon, and total alkalinity for organic rich estuarine water. The efficacy of sample preservation is examined by comparing results obtained with and without additions of the HgCl2. Our results show that addition of HgCl2 affects titration alkalinity and subsequently pH. Accurate analyses can be achieved using improvements in sample preservation techniques for carbonate system measurements in organic-rich estuarine waters.