Soil Science

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Soil Science

Soil Science

Advance soil studies with in situ high-precision measurements of greenhouse gases and light stable isotopes.

The fractionation of light stable isotopes of soil components and their ensuing signatures are commonly used to infer past ecologic and climatic shifts in the soil record. They can also support the investigation of a variety of environmental questions.

Rugged Picarro CRDS analyzers allow you to make high-precision, lab-quality isotope and concentration measurements in the field. With those real-time results, you can redirect research on the fly to address the most interesting questions.

Research Applications

Soil respiration

Using a Picarro greenhouse gas analyzer, researchers at the Inner Mongolia Agricultural University have gained a deeper understanding of how soils absorb and emit CO2 and CH4. They quantified the flux of those gases in inner Mongolian desert grassland, while also quantifying the greenhouse contribution of livestock discharge. In a separate study, the same group explored the effect of stocking rate on soil-atmosphere methane flux during the freeze-thaw cycles.

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Using a Picarro isotopic CO2 analyzer, researchers in Australia and Italy have shown the relative CO2 contribution from roots, soil microbes and the decomposition of soil organic matter.

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Nitrogen isotopes of N2O gas can reveal the relative rates of microbial nitrification and denitrification processes in soil. Picarro’s portfolio of instruments now includes two powerful new tools for nitrogen cycle studies; isotopic N2O analyses and [N2O] + [CH4] analyses.

Researchers at Dalhousie University, in collaboration with Picarro, have used the iN2O CRDS system to determine the isotopic distribution of nitrous oxide generated from selected inorganic reactions. The data illuminated the connections between molecular dynamics underlying the formation mechanism and related isotopic signatures of N2O, as required for interpretation of observed signatures in field measurements.

Get more from the paper: Performance and application of a mid-infrared WS-cavity ringdown spectrometer for analytical N2O isotopomer analysis.

Soil metabolism

Researchers are also using Picarro analyzers to study soil incubation and metabolism. By monitoring isotopic carbon, they were able to identify variations in CO2 production under varying moisture, temperature and substrate conditions. Paul Dijkstraa and colleagues at Northern Arizona University used position-specific tracer labeling techniques and modeling to analyze the response of soil metabolism to various stressors.

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Eddy covariance

The flux of CO2 and CH4 from large areas can be quantified with eddy covariance techniques which require fast measurement of those species. Our 10 Hz, fast measuring GHG analyzer enables this, as when Prof. Wade McGillis of Columbia University used Picarro flux instrumentation on the largest green rooftop in Manhattan, NY.

Get more from the paper: Picarro’s New Flux Instrument Captures CO2, CH4 & H2O Fluxes by Measuring Concentrations at 10 Hz with the Best Precision and Lowest Drift.

Soil organic matter

After Dumas combustion, researchers at the University of Copenhagen quantitatively converted carbon content of bulk soil samples into CO2 for isotopic carbon analysis with a Picarro CRDS analyzer. They used the CM-CRDS to measure 13C in rock samples.

Get more from the paper: Precise and accurate δ13C analysis of rock samples using Flash Combustion – Cavity Ring Down Laser Spectroscopy.

Soil gas

The composition of gas within soil can be studied using a variety of Picarro analyzers. Natural soils contain CO2, CH4, and N2O. Soil gas near landfills and sequestration sites can help determine the level of greenhouse gas emissions from landfills, including fugitive losses during pipeline transport from these facilities.

Pore water

The flow of groundwater through the soil can be studied with stable isotopes. Many researchers are using Picarro water isotope analyzers to study pore water source links and process information using the natural variation in 18O and D. In fact, Wassenaar, et al., have measured pore water from equilibrated headspace water vapor of environmental and geologic cores using a Picarro isotopic H2O analyzer.

Get more from the paper: Correcting for Methane Interferences on δ2H and δ18O Measurements in Pore Water Using H2O(liquid)–H2O(vapor) Equilibration Laser Spectroscopy.

McDonnell, et al., have conducted studies using bromide tracers and isotopic water measurements to track water flow for particular sites.

Get more from the paper: Macropore flow of old water revisited: where does the mixing occur at the hillslope scale?

Soil moisture can also be evaporated from a soil sample for immediate isotopic analysis using Picarro’s Induction Module-CRDS system. The IM uses inductive heating to drive off soil moisture into a dry gas stream that feeds into a Picarro water isotope analyzer for 18O and D analysis.

Related Products

G2508 – Measure N2O, CH4, CO2, NH3, and H2O simultaneously for soil flux studies.

L2130-i – δD and δ18O of matrix-bound water extracted from organic solids

G2201-i – Continuous recirculation and discrete measurement of δ13CO2 and δ13CH4 fluxes

Carbon Isotope Analysis Systems