Peat porewaters have contrasting geochemical fingerprints for groundwater recharge and discharge due to matrix diffusion in a large, northern bog-fen complex

Zeno F. Levy, Donald I. Siegel, Paul H. Glaser, Scott D. Samson, Soumitri S. Dasgupta

Research output: Contribution to journalArticlepeer-review

7 Scopus citations

Abstract

Although northern peatlands represent a globally significant reservoir for carbon, considerable uncertainty exists concerning solute transport systems within large (>1000 km2) peat deposits. We therefore delineated geochemical gradients linked to groundwater recharge and discharge along a 6 km transect within the 1200 km2 Red Lake Peatland of northwestern Minnesota. We used ratios of Ca/Mg and 87Sr/86Sr to distinguish discharge of calcareous groundwater (∼1.4 and 0.7155, respectively) to the peatland from the mineral substratum along a topographic gradient from a bog crest downslope to an internal fen water track and bog islands. In contrast, the stable isotopes of the porewaters (δ18O from −12.8 ‰ to −7.8 ‰) show that the active pore-spaces in these peat profiles have been flushed by recharge from the near-surface peat. We hypothesize that back-diffusion of groundwater-derived solutes from the peat matrix to active pore-spaces has allowed the geochemical signal from paleo-hydrogeologic discharge to persist into the current regime of dilute recharge. This effect has not been observed previously on the landform-scale and has important implications for carbon cycling in peatlands.

Original languageEnglish (US)
Pages (from-to)941-951
Number of pages11
JournalJournal of Hydrology
Volume541
DOIs
StatePublished - Oct 1 2016

Keywords

  • Bogs
  • Fens
  • Geochemistry
  • Hydrogeology
  • Isotopes
  • Matrix diffusion
  • Peatlands

ASJC Scopus subject areas

  • Water Science and Technology

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