Advancing Methods for Measuring Denitrification in Terrestrial and Aquatic Systems
May 27-30, 2008
At Horn Point Laboratory - University of Maryland, Cambridge, Maryland, USA
Denitrification is difficult to measure because of the analytical difficulty in detecting small increases in N2 concentrations against the large background in the environment. A number of recent advances in approaches to directly quantify denitrification in aquatic and terrestrial environments have been made, but few people are trained to use these newer approaches.
This second workshop in the Denitrification RCN series focused on recent advances in denitrification measurement techniques in terrestrial and aquatic environments. This workshop included invited talks, discussion sessions, and hands-on, training demonstrations of three advanced techniques for measuring denitrification in aquatic and terrestrial systems: membrane inlet mass spectrometry, gas-flow soil core with N2 chromatography, and isotope pairing. This workshop was co-sponsored by the RCN and Maryland Sea Grant, with additional support from Bay Instruments and Pfeiffer Vacuum.
TUESDAY, MAY 27
- Welcome and logistics. Jeffrey Cornwell & HPL Director Mike Roman
- Denitrification: The RCN and methods overview. Peter Groffman [PDF] [Reference ]
- Aquatic denitrification using MIMS N2/Ar. Jeffrey Cornwell
- Measuring denitrification in sediments using the isotope pairing technique (2) Anne Giblin [PDF]
- Denitrification in terrestrial ecosystems: A problem of scale?! Klaus Butterbach-Bahl [PDF]
- Groundwater denitrification in the Choptank Basin. Tom Fisher [PDF]
- Membrane inlet mass spectrometry – MIMS (5). Todd Kana [Methods references]
- Sediment core incubations. Jeffrey Cornwell & Mike Owens [Methods references]
- Isotope pairing technique – IPT (3). Anne Giblin & Jane Tucker [Methods references]
- Gas flow soil core (4). Klaus Butterbach-Bahl & Nicolas Brueggemann [Methods references]
- Groundwater sampling - piezometers. Tom Fisher & Anne Gustafson
WEDNESDAY, MAY 28
- Experiments, measurements, and data workup/QA-QC.
- NOx biosensors. Kevin Kroeger [Methods reference]
- River denitrification. Andy Laursen [Methods references]
THURSDAY, MAY 29
Hot and controversial topics.
- Reversal of the net N2 flux in Narragansett Bay (6). Wally Fulweiler [PDF] [Reference]
- Microbial linkages between the N and S cycles in freshwater ecosystems (7). Amy Burgin [PDF] [Reference]
- High resolution N2/Ar measurements for soil denitrification. Whendee Silver & Wendy Yang [PDF]
- MIMS technical issues. Todd Kana
- Soil and groundwater sampling issues. Tom Fisher & Klaus Butterbach-Bahl
- Sediment core issues. Mike Owens & Anne Giblin
FRIDAY, MAY 30
Scaling: From cores and incubations to whole systems discussion.
State of the art and fantasy instrumentation discussion [PDF notes] [Methods reference]
Future RCN activities & workshops. Eric Davidson
POST-WORKSHOP CONTINUING WORKING GROUPS
- N2O:N2 ratio systems meta-analysis. We may not be able to say much more then we already know. However, synthesizing the current state of knowledge will be very useful to help us ask better questions, particularly as we move into the future with better techniques. Plus to my knowledge, there are no real aquatic-terrestrial cross comparisons on the topic, so I am quite excited to look at this question on a comparative, global scale. Please contact Roxane Maranger to contribute.
- Nitrogen fixation in marine environments. If you would like to participate in a synthesis paper to gather as many negative N2 fluxes measured by MIMS together and discuss some possible explanations and mechanisms for why N fixation is occurring, please contact Wally Fulweiler.
- Denitrification across the dry to wet gradient in soils and sediments. Monica Palta