1. Chris Gammons, John Babcock, Bev Plumb, Steve Parker Montana Tech, Butte, MT Spatial and temporal variations in nutrient concentration and speciation in Silver Bow Creek

2. Monitoring databases for nutrients in surface waters often look like this Why so messy?

3. Outline of talk Site description Synoptic variations Seasonal variations Diel variations Lateral (bank to bank) variations Implications for monitoring

4. SBC-1 Above WWTP

5. WWTP discharge

6. SBC-3 3 km below WWTP

7. Warm Springs Ponds

8. Synoptic changes in nutrient concentration SBC-3 below WWTP, August, 2006 Nitrite (NO 2 - ) forms as intermediate during oxidation of NH 4 + to NO 3 - Nitrosomonas

10. Decrease in NH 4 + due to nitrification Increase in NO 3 - due to nitrification Decrease in DIN due to assimilation Synoptic changes (different years)

11. Nitrate + Nitrite Ammonium DIN Dissolved Inorganic N Seasonal changes in nutrient concentrations SBC at Warm Springs Ponds ■ WSPOU INLET ○ WSPOU OUTLET Winter months

12. Diel changes SBC-3 below the Butte WWTP

13. Nutrient isotopes: synoptic

14. Nutrient isotopes: diel Δ = 14.1 ‰ Δ = 20 ‰ NH 4 -oxidizing bacteria preferentially metabolize 14 N Isotopic separation is less during day (faster rates) Isotopic trends inconsistent with denitrification

15. 1000 ft Silver Bow Creek WWTP discharge USGS gaging station How far below the confluence of SBC and WWTP before combined flow is mixed, bank-to-bank? Lateral variations in water chemistry

16. Bank-to-bank profiles in specific conductance (SC)

18. 1000 ft 2400 feet Silver Bow Creek WWTP discharge USGS gaging station How far below the confluence of SBC and WWTP before combined flow is mixed, bank-to-bank?

19. Implications for nitrate monitoring The sample you collect is representative only of a given spot in a given stream reach on a given day and at a certain time of day  For streams like Silver Bow Creek, consider taking 24-h integrated samples, or sample at same time of day for long-term trend analysis For highly polluted waters, be sure to sample for all nutrients (e.g., ammonium, nitrite) Stable isotope signatures of nitrate are also affected by synoptic and diel variations Be careful that you are not sampling water from a stream or river that is not completely mixed

20. USGS 104b Montana Water Center Students  Bev Plumb  John Babcock  Stacey Wilcox  Erika Sholey  Brian Kuhn Acknowledgements

21. References Plumb, B. (2009) Geochemistry of nutrients in Silver Bow Creek, MT. M.S. Thesis, MT Tech. Gammons, C.H., Babcock, J., Parker, S.R., Poulson, S.R. (2011) Diel cycling and stable isotopes of dissolved oxygen, dissolved inorganic carbon, and nitrogenous species in a stream receiving treated municipal sewage. Chemical Geology, 283, 44-55. Questions??