Estimating Sediment Denitrification Rates Using Cores and N2O Microsensors

Area of Science:

• Environmental Science
• Biogeochemistry
• Ecology

Background:

• Denitrification is crucial for removing reactive nitrogen from the biosphere.
• Accurate measurement of denitrification is vital for understanding the global nitrogen cycle and greenhouse gas emissions (N2O).
• Existing methods for measuring denitrification have limitations, including insufficient sensitivity and sample disturbance.

Purpose of the Study:

• To develop and describe a novel method for estimating sediment denitrification rates.
• To overcome the limitations of existing measurement techniques.
• To provide a reliable method for assessing nitrogen cycling in aquatic systems.

Main Methods:

• Combines sediment coring, acetylene inhibition, and microsensor measurements of accumulated nitrous oxide (N2O).
• Minimizes disturbance to sediment structure, allowing for continuous N2O accumulation records.
• Includes procedures for sample collection, sensor calibration, acetylene inhibition, N2O measurement, and rate calculation.

Main Results:

• The method enables reliable estimation of denitrification rates with minimum values as low as 0.4-1 µmol N2O m^-2 h^-1.
• Allows for the estimation of both actual and potential denitrification rates by manipulating nitrate availability and temperature.
• Can be adapted to measure N2O emissions directly by omitting the acetylene inhibition step.

Conclusions:

• The described method offers a low-disturbance, sensitive, and versatile approach for measuring denitrification rates in various aquatic systems.
• It provides valuable insights into nitrogen cycling and greenhouse gas production.
• The technique can be further modified, for example, by incorporating 15N tracers for combined nitrification-denitrification assessments.