Open AccessEstimation of riverine carbon and organic matter source contributions using time‐based isotope mixing models
Author(s) -
Hossler Katie,
Bauer James E.
Publication year - 2012
Publication title -
journal of geophysical research: biogeosciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2012jg001988
Subject(s) - dissolved organic carbon , biogeochemical cycle , environmental science , mixing (physics) , particulates , ecosystem , atmospheric sciences , carbon cycle , isotopes of carbon , hydrology (agriculture) , environmental chemistry , total organic carbon , ecology , chemistry , geology , biology , physics , geotechnical engineering , quantum mechanics
Rivers transport globally significant amounts of carbon (C) from terrestrial ecosystems to ocean margins. Understanding and quantifying the sources and respective contributions to riverine C has emerged as an important biogeochemical problem that can be approached through natural‐abundance isotope mass balance. Traditionally, the sources of riverine C have been identified either qualitatively or quantitatively through application of static mixing models. However, both source signatures and contributions can vary significantly with time. Here we apply two time‐based mixing models to a study of six rivers draining the northeast U.S. In the first model, a time‐averaged mixing model (TAMM), we vary only the source isotopic ( δ 13 C and Δ 14 C) signatures. In the second model, a time‐varying mixing model (TVMM), we allow both isotopic signatures and contributions to vary with time. Based on results from the TVMM, drivers of variation in riverine particulate organic C (POC), dissolved organic C (DOC), and dissolved inorganic C (DIC) include stream discharge, stream discharge and water temperature, and water temperature and vegetation phenology, respectively. Major sources include C 3 plant material, algal material and slow‐turnover soil OC (“slow SOC”), which together account for 50%–100% (95% CI) of riverine POC; C 3 plant material and slow SOC, which together typically account for 60%–100% (95% CI) of DOC; and atmospheric exchange which alone typically accounts for 40%–60% (95% CI) of DIC. Seasonal change in relative contributions from algal material, slow SOC, and photosynthesis (in response to the identified drivers) dominates the observed variation in POC, DOC and DIC, respectively. The TVMM is a novel tool to identify component contributions under more realistic non‐static conditions, and with potential application to a broad range of biogeochemical studies.