| Popis: |
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. |
