Sources and dynamics of greenhouse gases in agricultural streams (SAD-GAS) – a process-based approach for improved understanding of a large atmospheric source

Streams and rivers are important sources for atmospheric greenhouse gases (CO2, CH4, N2O).

This source has been found to significantly alter the strength of the terrestrial net C sink and hence the global C cycle.

However, the data basis behind these estimates relies on a number of questionable assumptions and has severe gaps especially concerning the contribution from streams draining agricultural regions.

This study aims to fill this gap by in detail investigating the magnitude, dynamics and sources of the full suite of GHGs in agricultural streams.

To do this, we propose a novel multi-process approach using high-frequency sensor measurements combined with stable isotopic characterization of the GHGs.

These methods will be applied an existing national infrastructure for monitoring of agricultural catchments which will provide the project with invaluable background data and information.

This will enable a unique source attribution and mechanistic understanding on the control of GHG emissions from agricultural streams.

The four-year PhD project contains four work packages, logically linked by studies on the main source components sustaining stream GHG emissions. The findings will be synthesized and scaled to the entire stream network of Sweden.

The results on magnitude, dynamics and sources of GHG emissions from agricultural streams are critical for a correct integration in landscape GHG balances, and for the development of emission mitigation strategies.