Nitrogen Isotope Measurements-in the context of 40ºS GEOTRACES Transect Raja S. Ganeshram
N isotopes proxy nutrient utilisation Denitrification N-fixation OM Regeneration Water mass tracer
Difiore et al, JGR, 2006
Knapp et al., GBC, 2008
Sigman et al., GBC, 2006
Isotope fractionation during sedimentation Settling particles tends to get heavy on transit 3‰ difference between diatom-bound and bulk sediments Such differences are variable -no effect in margin sediments Effect of sediment?
Tracing northern & southern sourced waters -foram & diatom bound N-isotope signatures N-fixation budgets in the Atlantic -Large uncertainties Role of riverine OM & DIN on N-isotopes & C isotopes signatures Role of margin sediments -sediment denitrification
Nitrate Isotopes Water requirement: 500-1000 ml most sites. 2000 ml in surface/oligotrophic sites/underway system Sampling resolution: -12 depths @ 8 to 10 stations + 10 margins stations Other: Need good nitrate/nitrite concentration. Costs: 500 samples X £20 = 10,000 consumable + Mass spec time (no salary) 2 berths Postdoc or tech. + PhD student