Considerations on the use of carbon and nitrogen isotopic ratios for sediment fingerprinting

Brenden Riddle, Jimmy Fox, David Tyler Mahoney, William Ford, Yi Tin Wang, Erik Pollock, Jason Backus

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

Carbon and nitrogen stable isotopic ratios are increasingly used in sediment fingerprinting studies. However, questions remain regarding tracer conservativeness during sediment transport and other error considerations. We investigate conservativeness processes, including carbon oxidation and nitrogen mineralization, using experiments. We also test how other considerations impact the isotopic ratios including algae accrual into temporary sediment deposits in the river, the physical loss of organic matter via disaggregation, concentration dependent mixing, and time-varying isotopic ratios of sediment sources. Results show all processes and considerations can change isotope abundance, however, significance varied. Carbon oxidation, nitrogen mineralization and upland seasonality of sediment sources did not significantly change isotopic ratios. Algae accrual, concentration dependency mixing, physical loss of organic matter during transport, and seasonality of the in-stream sediment source significantly changed the isotopic ratios for the conditions tested. Fertilization significantly impacted the stable carbon isotopic ratio in one case considered. Results from sediment fingerprinting simulations and testing how well the virtual mixture fits the mass balance equation agreed with significance results for tracer changes, and some uncertainty considerations changed fractional contribution of sources by as much as 50%. A noteworthy recommendation is the mean isotopic ratios of sediment sources should be separated by at least 1‰ to lessen tracer conservativeness concerns in fingerprinting simulation. We recommend concentration dependent mixing becomes the accepted practice when using isotopic ratios, however, we warn against using particle size corrections. We recommend the loss of organic matter during disaggregation be accounted for in fingerprinting estimates. We recommend algae accrual in in-stream sediment deposits should either be accounted for or in-stream sediment should be treated as a time-varying source in sediment fingerprinting simulations. Finally, we recommend both the carbon and nitrogen isotopic ratio should be tested as potential tracers because the two tracers performed similarly when testing how well the virtual mixture fits the mass balance equations.

Original languageEnglish
Article number152640
JournalScience of the Total Environment
Volume817
DOIs
StatePublished - Apr 15 2022

Bibliographical note

Funding Information:
We gratefully acknowledge the financial support of this research from the Kentucky Senate Bill 271B Water Quality program and National Science Foundation Awards # 1632888 and # 1933779 . We thank three anonymous reviewers for their input on an early version of this paper, and addressing these ideas greatly improved the quality of the paper.

Publisher Copyright:
© 2022

Keywords

  • Fingerprinting
  • Isotopes
  • Sediment transport
  • Tracers
  • erosion

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Waste Management and Disposal
  • Pollution

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