Carbon dioxide and methane emissions from incubated streambed sediments from the rivers Tern and Lambourn, England (2015)

Sediment was collected using a shovel before being sieved (0.8 cm for fine, and 1.6 cm for medium and coarse) and homogenised prior to storage. The sediment was stored airtight in the cold and dark. Sediment of varying organic matter content from two geological origins (chalk and sandstone) was incubated at five temperatures (5, 9, 15, 21 and 26°C). Resorufin production was measured using a GGUN-FL30 on-line fluorometer, dissolved oxygen was measured using a Pyro-science Firesting fixed needle-type probe, and carbon dioxide and methane concentrations were measured using an Agilent 7890A Gas Chromatograph - Flame Ionisation Detector. The carbon dioxide and methane concentrations were converted to production per hour by calculating the difference in concentration between zero and five hours and normalising the production by the length of the incubation period. The data was then converted to emissions per volume of dry sediment using the Bunsen coefficient and the volume of sediment in each jar, resulting in units of milligrams of carbon per square metre per hour. Greenhouse gas concentrations were corrected for any machine drift using results from a standard gas mixture ran periodically during gas analysis. The resorufin concentration was converted to production per hour by calculating the difference in concentration between zero and five hours and normalising the production by the length of the incubation period. The production was then normalised by the concentration of resazurin added to the jar, resulting in units of nanograms of resorufin per microgram of resazurin per hour. Data were entered into an Excel spreadsheet and exported as a comma separated value file (.csv) for ingestion into the EIDC.