Abstract
<strong class="journal-contentHeaderColor">Abstract.</strong> This work assesses the effectiveness of sample preservation techniques for measurements of pH<sub>T</sub> (total scale), total dissolved inorganic carbon (DIC<sub>T</sub>), and total alkalinity (A<sub>T</sub>) in organic-rich estuarine waters. Using HgCl<sub>2</sub>-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 DIC<sub>T</sub> concentrations, while DIC<sub>T</sub> was effectively constant in treated samples. Changes in A<sub>T</sub> were observed for both treated and untreated samples, with treated samples showing the greatest variation. In response to changing A<sub>T</sub> / DIC<sub>T</sub> ratios, pH<sub>T</sub> 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 DIC<sub>T</sub> and A<sub>T</sub> analysis are collected and stored separately. Accurate analyses of DIC<sub>T</sub> can be obtained by filtration and preservation with HgCl<sub>2</sub>. Accuracy of A<sub>T</sub> analyses can be improved by filtration and storage in polypropylene bottles at 4 °C without adding HgCl<sub>2</sub>. Quality of pH<sub>T</sub> measurements can be improved by prompt analysis in the field and, if this cannot be accomplished, then samples can be preserved with HgCl<sub>2</sub> and measured in the laboratory within one week.
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