Equipment

The workhorse of the DeLucia Stable Isotope Lab is a Thermo Delta V Advantage Isotope Ratio Mass Spectrometer (IRMS).  The lab boasts a wide array of peripheral devices that can be used with the IRMS including (left to right in photo) a Costech 4010 Elemental Analyzer for d13C and d15N analysis in solids, Gasbench II for d13C and d18O analysis in discreet gas samples, and a Thermo Temperature Conversion Elemental Analyzer (TC/EA) for d2H and d18O analysis in liquids and solids.  We also retain a device known as a Spooling Wire Microcombustion Device (SWiM IRMS, above the IRMS in photo), built by a former plant biology graduate student, which is one of only a handful of these devices in existence.  This Moving Wire can be used for d13C analysis in individual pollen grains, as well as small weight molecular compounds in solution.  We also possess a CO2 Carbon Isotope Analyzer (CCIA-36ED) Cavity RingDown Spectrometer (CRDS), which uses a laser-based system for continuous flow or discreet gas sample d13C analysis.  Also pictured is a Cryogenic Distillation vacuum line that can be used to concentrate gases such as CO2, remove water from gas samples, and extract water from soil and plant tissue.

 

Current Isotope Work

At the Energy Farm, we believe our perennial bioenergy crops are adding new carbon to the soil as a result of a larger root system and the elimination of annual tillage practices.  By measuring the baseline d13C ratio of our soil (a mix of C3 and C4 photosynthesis from soybean and maize over the last 100 years), the d13C of the organic matter input (C4 only), and the d13C of the soil over time we can use a simple mixing model to calculate the fraction of the soil organic matter that is incorporated directly from our bioenergy crop.  We have also used this technique in various areas around the state of Illinois to answer the same question, and relate C storage to paired native prairie ecosystems.  This is a relatively slow process in bulk soils, so we are also tracking other more labile C pools such as particulate organic matter (POM) and using carbon isotopes to answer many related questions.

When determining the residence time of soil C potentially stored under bioenergy perennial cropping systems, a discussion of soil priming is important.  Soil priming can be defined as the stimulation in decomposition of existing (old) soil C as a result of the addition of (new) organic matter. This would be of particular interest during land use change from one cropping system to another, such as annual row crop to perennial grass bioenergy crop. To assess priming we are conducting both lab incubation and field experiments using soil and litter of varying C isotopic ratios, and examining the ratio of the respired CO2.

It has been shown that Miscanthus x giganteus, a potential bioenergy crop grown at the Energy Farm, demonstrates efficient N cycling. The genes and microbes required for fixation to occur have been found associated with this species, but no one that we are aware of has quantified rates of N fixation for M. x giganteus in the field.  We have been working on using both a natural abundance technique, and a labeled dilution model to do this. The first method relies on a difference in the d15N between air and soil N. Since these are the two potential sources of N available to the plant, the ratio of N in the plant depends on the amount of uptake from the two pools. The second technique uses an applied label of concentrated 15N to the soil. Tracking the soil d15N and the plant d15N over time one can use a mathematical model to quantify the N from fixation and the N taken up from the soil.

Sample Submission

In order to submit solid samples for d13C and d15N analysis, please contact Mike Masters at mmasters@illinois.edu. Please provide a short description of the type of sample, the number of samples you would like to submit, analysis parameters, and your current affiliation. Samples must be dried, ground, weighed, and enclosed into tin capsules prior to analysis. Samples will be run with laboratory standards that have been calibrated against NAEA standards. Delta scale values and calculations of current machine precision and accuracy will be provided for each run. Price structure below.

University of Illinois Affiliation: $6.50 per sample
Other Academic Affiliations: $8.00 per sample
Non-Academic Institutions: $10.00 per sample