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| Titel |
Carbon dynamics in peatland pool systems: the role of light |
| VerfasserIn |
Amy Pickard, Kate Heal, Andy McLeod, Kerry Dinsmore |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127852
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| Publikation (Nr.) |
 EGU/EGU2016-7773.pdf |
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| Zusammenfassung |
| Open-water pools are widespread in peatlands and are considered to represent biogeochemical
hotspots within the peatland landscape. However the contribution of pool systems to wider
peatland C cycling has not been quantified fully and there is a lack of knowledge
of the role of photochemical processes in such environments. In this study, light
exposure experiments were conducted in two contrasting pools to test the reactivity
of aquatic C. The first study site was located at Cross Lochs (CL), Forsinard, in
the Flow Country of Northern Scotland, in a 412 m2 pool characterised by low
dissolved organic carbon (DOC) concentrations (∼15 mg C L−1). The second site was
located at Red Moss of Balerno (RM), a raised bog in central Scotland, in a 48 m2
pool with high DOC concentrations (∼35 mg C L−1). Experiments took place
over 9 days in situ at each pool in mid-summer 2015, with 500 mL water samples
contained in bags transparent to sunlight and in opaque control bags. After field
exposure, optical, chemical and stable C isotope analyses were conducted on the
samples. Significant differences in biogeochemical cycling of DOC were detected
between the two systems, with DOC losses as a percentage of the total C pool 15%
higher at RM than at CL after light exposure. The mean DOC concentration of
light exposed samples at RM declined steeply initially, with 83% observed DOC
degradation occurring by day 3 of the experiment. Total losses of 7.9 mg DOC
L−1were observed in light exposed samples at RM, along with decreasing E4:E6
ratios, suggesting that material remaining at the end of the experiment was humified.
Depletion of DOC was positively correlated with production of CO2 at both sites,
with concentrations of up to 4.3 mg CO2-C L−1 recorded at RM. Stable C isotope
signatures at both sites were altered under light treatment, as demonstrated by the
production of enriched δ13C-DOC (+0.46 ‰ relative to opaque bags) and depleted
δ13C-DIC (-0.97 ‰ relative to opaque bags) at RM. However, at CL, the δ13C-DOC
signature in both the light exposed and opaque bags was depleted (-0.2‰ and -0.4
‰ respectively), suggesting that microbial processing was the preferential DOC
processing pathway in this system. These results show that C in peatland pools is highly
reactive and further demonstrate the importance of photochemical processing of
C, which should be considered as a significant driver of biogeochemical cycling. |
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