In situ measurement of CO2 and water vapour isotopic compositions at a forest site using mid-infrared laser absorption spectroscopy.
Isotopes Environ Health Stud
; 52(6): 603-18, 2016 Dec.
Article
in En
| MEDLINE
| ID: mdl-27142631
ABSTRACT
We conducted continuous, high time-resolution measurements of CO2 and water vapour isotopologues ((16)O(12)C(16)O, (16)O(13)C(16)O and (18)O(12)C(16)O for CO2, and H2(18)O for water vapour) in a red pine forest at the foot of Mt. Fuji for 9 days from the end of July 2010 using in situ absorption laser spectroscopy. The δ(18)O values in water vapour were estimated using the δ(2)H-δ(18)O relationship. At a scale of several days, the temporal variations in δ(18)O-CO2 and δ(18)O-H2O are similar. The orders of the daily Keeling plots are almost identical. A possible reason for the similar behaviour of δ(18)O-CO2 and δ(18)O-H2O is considered to be that the air masses with different water vapour isotopic ratios moved into the forest, and changed the atmosphere of the forest. A significant correlation was observed between δ(18)O-CO2 and δ(13)C-CO2 values at nighttime (r(2)≈0.9) due to mixing between soil (and/or leaf) respiration and tropospheric CO2. The ratios of the discrimination coefficients (Δa/Δ) for oxygen (Δa) and carbon (Δ) isotopes during photosynthesis were estimated in the range of 0.7-1.2 from the daytime correlations between δ(18)O-CO2 and δ(13)C-CO2 values.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Spectrum Analysis
/
Steam
/
Carbon Dioxide
/
Forests
/
Isotopes
Language:
En
Journal:
Isotopes Environ Health Stud
Journal subject:
SAUDE AMBIENTAL
Year:
2016
Type:
Article
Affiliation country:
Japan