Category Archives: Dryland hydrogeology

The Nitrogen Cycle and the Anthropocene

N cycle

Next week (Wednesday 29th October) the British Geological Survey at Keyworth are hosting a workshop on The Nitrogen cycle and the Anthropocene.

From the advertisement flier for the event:

“The rationale for this is that there are several types of temporal record (ice cores, sediments, tree rings) which show a reduction in 15N/14N ratios during the ‘Anthropocene’, a period in which there has been a substantial increase in the amount of reactive nitrogen in the earth’s nitrogen cycle. These changes are thought to be mainly due to the industrial synthesis and application of fertilizers, other changes in farming, and the combustion of fossil fuels. However, there does not seem to be any general agreement on the mechanism/s which cause this change in 15N/14N ratios, or indeed whether the changes in different records are related.

The workshop will therefore aim to promote discussion around: 15N depletion in organic matter in recent lake sediments; the lag between 15N in recent ice cores and lake sediments; recent 15N changes in modern plants/trees and soils; changing sources of N in glaciers and ice cores; and on how changes in source inputs to the atmosphere, and/or changes in its chemistry processes during the past few hundred years might have resulted in a decrease in 15N/14N of deposited N?”

There will be both keynote talks during the day and posters on display. The keynote talks feeature a stellar line-up of Earth Scientists.

  • Jan Zalasiewicz (University of Leicester): Stratigraphy of the Anthropocene: an overview.
  • Jan Kaiser (University of East Anglia): Isotopic evidence of sources and chemical processing of nitrogen in the atmosphere.
  • Eric Wolff (University of Cambridge): Ice core signals of a changing nitrogen cycle.
  • Tim Heaton (British Geological Survey): Sediment, soil and plant records of changes in 15N/14N ratios during the Anthropocene.

stone_edmunds joae paperI will be presenting a poster Naturally-high nitrate in unsaturated zone sand dunes above the Stampriet Basin, Namibia which is the output of a paper in the Journal of Arid Environments with Mike Edmunds, that shows: (i) high natural nitrate production in the unsaturated zone sediments above the Stampriet Basin. most likely from vegetation; (ii) that this high nitrate is variable across space; (iii) that nitrate is being introduced as pulses and moving toward groundwater and (iv) this finding is in line with observed nitrate concentrations in other drylands. Elevated nitrate is a difficult water quality issue to manage in dryland environments.