Open AccessVariable source and age of different forms of carbon released from natural peatland pipes
Author(s) -
Billett M. F.,
Dinsmore K. J.,
Smart R. P.,
Garnett M. H.,
Holden J.,
Chapman P.,
Baird A. J.,
Grayson R.,
Stott A. W.
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 - 10.1029/2011jg001807
Subject(s) - dissolved organic carbon , peat , hydrology (agriculture) , environmental science , storm , isotopes of carbon , drainage basin , composition (language) , carbon fibers , stable isotope ratio , carbon cycle , environmental chemistry , geology , total organic carbon , chemistry , oceanography , ecology , ecosystem , geography , linguistics , philosophy , geotechnical engineering , cartography , physics , quantum mechanics , biology , materials science , composite number , composite material
We used the carbon isotope composition ( 14 C and δ 13 C) to measure the source and age of DOC, POC, dissolved CO 2 and CH 4 ( δ 13 C only) released from three natural peat pipes and the downstream catchment outlet of a small peatland in northern England. Sampling under different hydrological extremes (high flows associated with storm events and low flows before or after storms) was used to explore variability in C sources as flow paths change over short periods of time. The δ 13 C composition of organic C differed ( δ 13 C‐DOC −28.6‰ to −27.6‰; δ 13 C‐POC −28.1‰ to −26.1‰) from that of the dissolved gases ( δ 13 C‐CO 2 −20.5‰ to +1.1‰; δ 13 C‐CH 4 −67.7‰ to −42.0‰) and showed that C leaving the catchment was a mixture of shallow/deep pipe and non‐pipe sources. The isotopic composition of the dissolved gases was more variable than DOC and POC, with individual pipes either showing 13 C enrichment or depletion during a storm event. The 14 C age of DOC was consistently modern at all sites; POC varied from modern to 653 years BP and evasion CO 2 from modern to 996 years BP. Differences in the isotopic composition of evasion CO 2 at pipe outlets do not explain the variability in δ 13 C and 14 C at the catchment outlet and suggest that overland flow is likely to be an important source of CO 2 . Our results also show that the sources of CO 2 and CH 4 are significantly more variable and dynamic than DOC and POC and that natural pipes vent old, deep peat CO 2 and POC (but not DOC) to the atmosphere.