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Methane Sources in the Waters of Lake Michigan and Lake Superior as Revealed by Natural Radiocarbon Measurements
Author(s) -
Joung DongJoo,
Leonte Mihai,
Kessler John D.
Publication year - 2019
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2019gl082531
Subject(s) - methane , radiocarbon dating , methanogenesis , environmental science , hydrology (agriculture) , carbon cycle , oceanography , groundwater , dissolved organic carbon , geology , environmental chemistry , ecology , ecosystem , chemistry , paleontology , geotechnical engineering , biology
The methane dynamics in the waters of Lakes Michigan and Superior, components of the North American Great Lake system, were investigated using measurements of methane concentration and natural radiocarbon ( 14 C‐CH 4 ) dissolved in these lake waters. All 14 C‐CH 4 measurements were above modern levels regardless of location and depth with a range of 117‐145% modern carbon (pMC). Methane concentrations in the deep basin of both lakes were low, ranging from 3.3 to 4.3 nM, with minimal vertical variation. However, the concentrations of CH 4 increased toward coastal areas in both lakes, possibly due to higher groundwater inputs and aerobic methanogenesis associated with primary productivity. Except for one site, 14 C‐CH 4 dissolved in the waters of Lake Michigan was greater than in Lake Superior by ~12 pMC, a difference that was likely due to inputs of excess 14 CH 4 from nuclear power plants along the coast of Lake Michigan.