Applying measurements of N and O isotopes to New Zealands nitrate - - PowerPoint PPT Presentation

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Applying measurements of N and O isotopes to New Zealands nitrate - - PowerPoint PPT Presentation

Jan 12, 2024 241 likes •386 views

Applying measurements of N and O isotopes to New Zealands nitrate issues: detailing soil sources Troy Baisden and Andy Phillips (GNS Science) Major contributions from: Cedric Douence & Simon Stewart Funded by FRST (2008-12), GNS GCT9,

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Applying measurements of N and O isotopes to New Zealand’s nitrate issues: detailing soil sources

Troy Baisden and Andy Phillips (GNS Science) Major contributions from: Cedric Douence & Simon Stewart

Funded by FRST (2008-12), GNS GCT9, Dartmouth (USA) internship Thanks to Jocelyn Powelson, Horizons, GNS Stable Isotope Lab, Len Wassenaar, Bernhard Mayer, Holly Winton, Liz Keller, Paul Mudge, Greater Wellington Regional Council

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GNS Science 2

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Where the N & O isotopes in NO3 come from in most of New Zealand…

Urine spots NH4 + ½ O2 + 2 H2O NO3 Drivers of lower δ18O:

  • Higher elevation nitrate production
  • Winter nitrification
  • Nitrate production on irrigated land
  • Sewage treatment + photosynthetic O

Sources of higher δ18O:

  • Nitrification in summer/evaporation
  • Nitrate-bearing fertilizer

Developed method for NZ δ15Ν and δ18O to <0.3‰ Blank ≤ 5 ppb

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GNS Science

δ18O δ15N

GNS Science

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In NZ, δ15N reflects intensity & duration of agriculture

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δ15N (‰) Mudge et al 2013 SSSAJ Winchmore Archived Soil Samples

PhD student Paul Mudge

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GNS Science

Upper Manawatu Catchment: Pasture Dominated

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GNS Science

Upper Manawatu – Pasture Streams & Rivers

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2 4 6 8 10

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2 4 6 8 10 12 14 Nov-10 Mar-11 May-11 Jul-11

δ15N – NO3 δ18O – NO3

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GNS Science

Why the Mangatarere?

  • Ideally a smaller catchment was needed with:

– Groundwater understanding – Interesting sources of nitrate to streamwater – Closer to our institute – Ability to identify hidden sources in the field using DO, EC, and temperature.

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GNS Science 8

~140 km2 Mangatarere Catchment Pastoral + Effluent Sources

Graphic: GWRC report

Headwaters Carterton Fault Masterton Fault Sewage & Landfill Piggery Effluent Town of Carterton Mangatarere Stream Larger N-limited Waiohine River

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GNS Science

0.0 1.0 2.0 5 10 15 20 NO3 (g/m3) Distance d/s of Gorge (Km)

  • 4.0
  • 2.0

0.0 2.0 Local δ18O Anom (‰) 3.0 7.0 11.0 δ15N-NO3 (‰) Masterton Fault STP Bend into GW flow Piggery Effluent

13-17 February 2012 Mangatarere Low Flow Campaign

Carterton Fault

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GNS Science

Mangatarere Stream: Seasonal Bifurcation?

!4.0% !2.0% 0.0% 2.0% 4.0% 6.0% 8.0% 0.0% 5.0% 10.0% 15.0% δ18O%NO3(‰)+ δ15N%NO3(‰)+ November% 2010% Winter%2011% January%2011% Jan%2012%Storm% Summer%2012%

δ15N – NO3 (‰) δ18O – NO3 (‰) Large summer δ18O anomaly in upper catchment samples

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GNS Science

Sewage Treatment

(Photosynthetic)

A useable tool to track sources and denitrification where impacts matter

δ15N – NO3 (‰) δ18O – NO3 (‰)

  • Negl. Atmospheric NO3;

Few Fertilizer NO3 Sources

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2 4 6 8 10

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2 4 6 8 10 12 14 From Local DAM Line: calculate δ18O anomaly

Food Web

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GNS Science

Summary?

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5 10 15 20

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5 10 15 δ18O-NO3 (‰) δ15N-NO3 (‰) Area 1 Area 2 Effluent

Soil Water Effects Nitrate Fertiliser Typical Effluent & Septic Forest & Pasture Streams

Water isotopes provide an important additional tracer.

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GNS Science

A long process… Targeted Basic Science Applied Science

Operational Monitoring

  • 1+ PhD Students
  • Initial Applications to Policy & Management
  • Investigations