Temperature effects on the carbon content of marsh sediment measured through time using a CHN elemental analyzer and loss on ignition

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  • February 26, 2019
Creator
  • Atencio, Anna Nicole
    • Affiliation: College of Arts and Sciences, Department of Geological Sciences
Abstract
  • Within the last decade, interest in conserving and restoring saltmarsh for their ability to rapidly sequester, and bury carbon has increased; however, the methodology for carbon analysis in marsh cores has not been standardized. Unless marsh sediment is dried or frozen after sampling, the carbon fraction is subject to microbial degradation through time. In this paper, we examine how saltmarsh-core storage temperature affects the carbon content of subsamples through time. We also compare CHN elemental analysis to loss on ignition (LOI) for measuring marsh carbon and organic matter, respectively. We used a marsh core from French Creek, NC, U.S.A, and extracted two 10-cm long sections from the upper and lower part of the core. These sections were mechanically homogenized and placed in 3 different temperature locations including: 1) a freezer at -20°C, 2) a refrigerator at 1.5°C, and 3) an indoor lab at 24°C. We subsampled each core section 9 times over 128 days for analysis of percent carbon (elemental analyzer) and percent organic matter (LOI). The upper part of the core had an initial value of 28.5 ± 2.2 % organic carbon and 57.1 ± 0.2 % organic matter, and the lower part had an initial value of 39.2 ± 5.9 % organic carbon and 77.6 ± 0.2 % organic matter. These results are in line with average carbon and organic matter content for saltmarshes in the area. We found that the carbon content of saltmarsh cores stored at temperatures below 24°C does not steadily decrease at a level below the resolution of our method (average standard deviation of 1.9%). Similarly, no decrease in organic matter below 0.45% (average standard deviation of the LOI analyses) was observed. CHN analysis introduces more uncertainty in measurements than LOI, which is likely due to incomplete sample homogenization, which is difficult to overcome. The LOI method uses an order of magnitude larger subsample than an elemental analyzer and when percent organic matter is converted to percent carbon using the conversion equation from Craft et al. (1991) it allows for a more accurate and precise measurement when complete sample homogenization cannot be confirmed.
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  • In Copyright
Note
  • Funding: Chancellor's Science Scholars, DCERP2
Advisor
  • Rodriguez, Antonio
Degree
  • Bachelor of Science
Academic concentration
  • Geological Sciences
Honors level
  • Honors
Degree granting institution
  • University of North Carolina at Chapel Hill
Graduation year
  • 2017
Language
  • English

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