Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

WRT CaBA/CRF Conference 02/12/14 - Steve Granger

401 views

Published on

In December 2014 WRT held a Catchment Based Approach and Catchment Restoration Fund Conference in Exeter. The North Wyke Research Institutes's Steve Granger gave a presentation on their work developing an isotopic source apportionment method for phosphate in the Taw Catchment.

Published in: Environment
  • Be the first to comment

  • Be the first to like this

WRT CaBA/CRF Conference 02/12/14 - Steve Granger

  1. 1. Stable Isotopes: A tool for phosphate apportionment on the River Taw? Steve Granger Taw River Improvement Project Research funded by the WRT
  2. 2. Forms of Phosphorus North Wyke Sub-catchments of the Taw are failing for phosphorus Particulate P (>0.45µm) Soluble P (<0.45µm): Organic
  3. 3. Forms of Phosphorus North Wyke Sub-catchments of the Taw are failing for phosphorus Particulate P (>0.45µm) Soluble P (<0.45µm): Inorganic
  4. 4. Phosphate Concentrations at Taw Bridge Year 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06 07 08 09 10 11 12 13 Phosphateconcentration(gPl -1 ) 0 200 400 600 800 Phosphate Concentration Cycles Environment Agency data
  5. 5. Isotope: atoms of a given element that contain the same number of protons in their nuclei but differ in the number of neutrons Stable Radioactive 0.02% 99.98% Trace Tracing Phosphate with Stable Isotopes
  6. 6. Isotope: atoms of a given element that contain the same number of protons in their nuclei but differ in the number of neutrons Tracing Phosphate with Stable Isotopes Stable isotopes: 1. Different Mass 2. Same Chemical Reactivity Measurement: • Isotope Ratio Mass Spectrometer • Ratio of the HEAVY to LIGHT isotope (δ) • Compare it to an international standard • Express the value a ‰
  7. 7. Kinetic fractionation: the extra neutron results in slower reactions Fry. (2006) Tracing Phosphate with Stable Isotopes
  8. 8. Using δ18O as a tracer for phosphate There is only one stable isotope of P Most P naturally occurs associated with O, and in its inorganic reactive forms it is phosphate (PO4). Might the δ18O of the PO4 molecule might be used? When PO4 is cycled through biological reactions some O becomes detached and replaced with water O. If we know the temperature and the δ18OH2O the value of δ18OPO4 is predictable. The P-O bond in PO4 is very stable at natural temperature and pH So is the δ18OPO4 is different to the predicted value it may tell us something about the origin of the PO4
  9. 9. Sources of PO4 What are the values of δ18OPO4 in different potential PO4 sources? Are they different and consistent? (Young et al., 2009). Establishing the δ18OPO4 of different PO4 sources
  10. 10. Tamburini et al (2010) • Soil • Fertilizer • Manure Establishing the δ18OPO4 of different PO4 sources
  11. 11. Upper Taw Catchment Source values and variability Establishing the δ18OPO4 of different PO4 sources
  12. 12. Taw Marsh 1 µg P l-1 Sticklepath 4 µg P l-1 Ford Brook 11 µg P l-1 September 2013 N
  13. 13. Sticklepath 4 µg P l-1 Taw Green 68 µg P l-1 Wickington 8 µg P l-1 Newlands 66 µg P l-1 Cocktree 7 µg P l-1 deBathe 154 µg P l-1 September 2013 6450 N
  14. 14. Newlands 66 µg P l-1 Spires Lake 86 µg P l-1 North Tawton 1611 µg P l-1 Bondleigh 1659 µg P l-1 Taw Bridge 2286 µg P l-1 Ashridge 10 µg P l-1 Bondleigh Brook 70 µg P l-1 Clapper Brook 152 µg P l-1 September 2013 9832 Cheese factory: 8100 N
  15. 15. Taw Bridge 17.8‰ (16.5) 2286 µg P l-1 September 2013 16.9‰ 9832 Cheese factory: 16.5‰ 8100 Taw Green 17.7‰ (16.2) 68 µg P l-1 19.6‰ 6450
  16. 16. Spires Lake 17.7‰ (16.0) 86 µg P l-1 September 2013 Cocktree 18.8‰ (18.0) 7 µg P l-1 deBathe 17.1‰ (16.8) 154 µg P l-1 Taw Green 17.7‰ (16.2) 68 µg P l-1 Taw Bridge 17.8‰ (16.5) 2286 µg P l-1
  17. 17. Upper Taw Catchment Source values and variability Establishing the δ18OPO4 of different PO4 sources
  18. 18. Taw River Improvement Project • Within this limited study it is suggested that the main sources of PO4 in the Upper Taw are sewage treatment works, septic tanks and possibly mineral fertilisers. • the P dynamics in the river could be linked quite strongly to septic tanks and could explain the complicated story of rising concentrations in the lower half of the sub- catchment. They are a truly diffuse source and difficult to quantify • These sources are likely to change over time (e.g. during storm events) hence more work is required and more sources need to be investigated.
  19. 19. Questions? Taw River Improvement Project TRIP Research Partnership
  20. 20. Taw Marsh 3 µg P l-1 Sticklepath 4 µg P l-1 Ford Brook 5 µg P l-1 March 2013 N
  21. 21. Sticklepath 4 µg P l-1 Taw Green 8 µg P l-1 Wickington 4 µg P l-1 Newlands 8 µg P l-1 Cocktree 16 µg P l-1 deBathe 36 µg P l-1 March 2013 479 N
  22. 22. Newlands 8 µg P l-1 Spires Lake 24 µg P l-1 North Tawton 33 µg P l-1 Bondleigh 32 µg P l-1 Taw Bridge 25 µg P l-1 Ashridge 9 µg P l-1 Bondleigh Brook 24 µg P l-1 Clapper Brook 21 µg P l-1 March 2013 3938 N

×