High diurnal variation in dissolved inorganic C, δ13C values and surface efflux of CO₂ in a seasonal tropical floodplain

Bass, A.M., O'Grady, D.O', Berkin, C., LeBlanc, M., Tweed, S., Nelson, P.N., and Bird, M.I. (2013) High diurnal variation in dissolved inorganic C, δ13C values and surface efflux of CO₂ in a seasonal tropical floodplain. Environmental Chemistry Letters, 11 (4). pp. 399-405.

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Diurnal variations in aquatic systems may be a major factor influencing carbon cycling. However, few studies have examined diurnal variation on floodplains and wetlands, especially in the tropics. Stable isotope analysis of dissolved inorganic carbon (δ¹³C(DIC)) provides insight into the driving factors behind diurnal physio-chemical variability, but to date, the manual collection of large sample numbers at high temporal frequency has been prohibitive. Here, we report one of the first, high-resolution isotopic studies of δ¹³C(DIC) on a tropical floodplain using acidification-interface cavity ring-down spectrometry. Water samples were analysed for δ¹³C(DIC) and other water quality parameters at 15-min intervals for 24 h. Our results show significant diurnal variation in both DIC concentration and δ¹³C(DIC). Maximum DIC concentration, recorded overnight, was approximately 100 % greater than during the day. Maximum DIC concentration coincided with minimum δ¹³C(DIC) as a result of shifting autotrophic/heterotrophic balance. Changes were significant over small time scales and showed CO₂ gas evasion estimates could vary by as much as 50 % based on measurements taken less than 5 h apart. These data show that to accurately evaluate the role of tropical floodplains in global carbon dynamics, a comprehensive understanding of diurnal variation will be essential.

Item ID: 27509
Item Type: Article (Research - C1)
ISSN: 1610-3661
Keywords: diurnal hydrochemistry; floodplain; tropical; dissolved carbon; carbon dioxide evasion, stable isotope
Date Deposited: 06 Jun 2013 06:29
FoR Codes: 04 EARTH SCIENCES > 0402 Geochemistry > 040203 Isotope Geochemistry @ 90%
09 ENGINEERING > 0909 Geomatic Engineering > 090905 Photogrammetry and Remote Sensing @ 10%
SEO Codes: 96 ENVIRONMENT > 9605 Ecosystem Assessment and Management > 960501 Ecosystem Assessment and Management at Regional or Larger Scales @ 100%
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