Home
Resources
Publications
An Optical Method for Carbon Dioxide Isotopes and Mole Fractions in Small Gas Samples: Tracing Microbial Respiration From Soil, Litter, and Lignin

An Optical Method for Carbon Dioxide Isotopes and Mole Fractions in Small Gas Samples: Tracing Microbial Respiration From Soil, Litter, and Lignin

Steven J Hall, Wenjuan Huang, Kenneth E Hammel

Rapid Commun Mass Spectrom. 2017 Nov 30;31(22):1938-1946.

PMID: 28851092

Abstract:

Rationale:
Carbon dioxide isotope (δ13 C value) measurements enable quantification of the sources of soil microbial respiration, thus informing ecosystem C dynamics. Tunable diode lasers (TDLs) can precisely measure CO2 isotopes at low cost and high throughput, but are seldom used for small samples (≤5 mL). We developed a TDL method for CO2 mole fraction ([CO2 ]) and δ13 C analysis of soil microcosms.
Methods:
Peaks in infrared absorbance following constant volume sample injection to a carrier were used to independently measure [12 CO2 ] and [13 CO2 ] for subsequent calculation of δ13 C values. Using parallel soil incubations receiving differing C substrates, we partitioned respiration from three sources using mixing models: native soil organic matter (SOM), added litter, and synthetic lignin containing a 13 C label at Cβ of the propyl side chain.
Results:
Once-daily TDL calibration enabled accurate quantification of δ13 C values and [CO2 ] compared with isotope ratio mass spectrometry (IRMS), with long-term external precision of 0.17 and 0.31‰ for 5 and 1 mL samples, respectively, and linear response between 400 and 5000 μmol mol-1 CO2 . Production of CO2 from native soil C, added litter, and lignin Cβ varied over four orders of magnitude. Multiple-pool first-order decay models fitted to data (R2 > 0.98) indicated substantially slower turnover for lignin Cβ (17 years) than for the dominant pool of litter (1.3 years) and primed soil C (3.9 years).
Conclusions:
Our TDL method provides a flexible, precise, and high-throughput (60 samples h-1 ) alternative to IRMS for small samples. This enables the use of C isotopes in increasingly sophisticated experiments to test biogeochemical controversies, such as the fate of lignins in soil.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AS2121236	Gasoline in Soil by WI Method			Price

As a specialist in analytical chemical Products, Alfa Chemistry offers consumers a wealth of raw materials and a full range of technologies and services.

QUICK LINKS

HEADQUARTERS

Tel:

Fax:

Email: