1 / 32

Study Motivations

Modeling the export of DOC from large watersheds and its influence on the optical properties of coastal waters. C.W. Hunt 1 , W.M. Wollheim 2,3 , J.S. Salisbury 1 , R.J. Stewart 3 , K.W. Hanley 4 and G.R. Aiken 4 ASLO Session SS54, New Orleans LA February 19, 2013. Study Motivations.

rico
Download Presentation

Study Motivations

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Modeling the export of DOC from large watersheds and its influence on the optical properties of coastal waters C.W. Hunt1, W.M. Wollheim2,3, J.S. Salisbury1, R.J. Stewart3, K.W. Hanley4and G.R. Aiken4 ASLO Session SS54, New Orleans LA February 19, 2013

  2. Study Motivations • River transport of DOC is a major component of global C cycle • River-borne DOC also influences the reactivity and optical properties of inland and coastal ocean aquatic systems • Recent studies* indicate that wetland abundance within small and large catchments is correlated with DOC quantity and quality at the catchment mouth *Hanley et al. 2013in review, Buffam et al. 2007

  3. DOC Quality- SUVA254 Aromatic DOC absorbs strongly Little light passes through sample UV light at 254 nm Image by K.W. Hanley

  4. Study Approach • Couple a dynamic hydrological model (FrAMES, 6min) to a process-based DOC quantity/quality model using parameters found in literature. • Simulate DOC loading as a function of land cover and runoff conditions. Partition DOC quality into Hydrophobic Organic Acids (HPOA, aromatic) and non-HPOA stocks. The %HPOA can be used to derive SUVA254. • Test model in 17 USA watersheds with processing (Respiration and photo-oxidation) turned on and off Butman et al. 2012

  5. Chapter 1: Large Rivers

  6. How do wetlands affect DOC quantity and quality? Forest Strongly UV-absorbing, DOC-enriched Wetlands Weakly UV-absorbing, DOC-depleted Organic Layer Mineral Layer

  7. Upstream inputs HPOA Non-HPOA River DOC HPOA HPOA Non-HPOA Respiration Local Input Photo Non-HPOA GPP* Downstream exports HPOA Non-HPOA

  8. St Mary's River

  9. Conclusions and Future Work • The model shows promise for predicting bulk DOC loading and export at the catchment mouth • Adding two compartments (HPOA and nHPOA) is helpful, but… • There is information we are not capturing in DOC quality (SUVA)

  10. Amazon River Study From Salisbury et al. 2011

  11. From Salisbury et al. 2011

  12. Model Parameter Values- after Monte Carlo

  13. Monte Carlo Results

  14. Monte Carlo Results

  15. References Butman, D., Raymond, P.A., Butler, K. and G. Aiken. 2012. Relationships between Δ14C and the molecular quality of dissolved organic carbon in rivers draining to the coast from the conterminous United States. Global Biogeochemical Cycles, 26: GB4014. Hanley, K.W., Wolheim, W.M., Salisbury, J., Huntington, T., and G. Aiken. 2013. Controls on dissolved organic carbon quantity and quality in large North American rivers. Global Biogeochemical Cycles, in review. Raymond, P.A. and J.E. Saiers. 2010. Event controlled DOC export from forested watersheds. Biogeochemistrydio 10.1007/s10533-010-9416-7. Salisbury, J., Vandemark, D., Campbell, J., Hunt, C.W., Wisser, D., Reul, N., and B. Chapron. 2011. Spatial and temporal coherence between Amazon River discharge, salinity, and light absorption by colored organic carbon in western tropical Atlantic surface waters. J. Geophys. Res. 116: COOHO2.

  16. Methods • The fraction of DOC as hydrophobic organic acids (HPOA%) was determined according to Hanley et a. 2012: • HPOA% = ((1.19 * log10(wetlands%)) + 3.762) / 8.792 • Finally, the specific ultraviolet absorbance of DOC at 254 nm, an indicator of DOC aromaticity, was estimated: • SUVA-254=(HPOA% * 8.792) - 1.126

  17. *from Hanley et al. 2013in press

  18. Processing and DOC Quality Upstream DOC (HPOA) Upstream DOC (non-HPOA) Photo degradation DOC (HPOA) DOC (non-HPOA) Resp GPP*

  19. FrAMES 1. 2. Water Balance Model (WBM) Vorosmarty et al. 1998 (Appendix B) Water Transport Model (WTM, STN) Vorosmarty et al. 2000 Other functions* Wollheim et al. 2008 Wisser et al. 2009 Stewart et al. 2011 “Vertical” movement of water (precip, ET, etc.) “Horizontal” movement of water (river network routing using STN or Simulated Topological Network) Nitrogen, Reservoirs, Transient Storage Grid Cell 1. 2. * These are often embedded within WBM, WTM

  20. WBM Grid Cell Precipitation Snowmelt ET Snowpack Rooting Zone Recharge Shallow Groundwater Detention Pool

  21. Model Parameter Values

  22. Sources of DOC in Rivers Riverine DOC Soil Organic Matter Image by K.W. Hanley

  23. 1. 2. DOC added to new groundwater DOC transported out of organic horizon 4. Weakly UV-absorbing, DOC-depleted groundwater enters stream 3. Preferential sorption of humic and fulvic acids to mineral soils and extensive microbial processing Without wetlands, DOC removal and fractionation can occur in the subsurface… Organic Horizon Mineral Horizon

  24. 1. DOC added to new groundwater 3. Strongly UV-absorbing, DOC-rich groundwater enters stream With wetlands, DOC depletion and fractionation are less likely… 2. Subsurface flow through deep and often anaerobic organic horizon - little sorption or microbial processing Organic Horizon Mineral Horizon

More Related