1. The Buffering Balance: Modeling Arctic river total-, inorganic- and organic-alkalinity fluxes C.W. Hunt, J.E. Salisbury, W. Wollheim, M. Mineau, and R.J. Stewart. University of New Hampshire

2. CO 2 CO 2 (aq) H 2 CO 3 HCO 3 - + H + CO 3 2- + H + Carbonic Acid Bicarbonate Carbonate B(OH) 4 - HPO 4 2- SiO(OH) 3 - NH 3 H 3 PO 4 PO 4 3- OH - Organic - Total alkalinity (T-Alk): The buffering capacity of an aqueous solution. OR The capacity of an aqueous solution to neutralize acid. Implications: CO 2 degassing estimates Decreased pH Overestimated Ω Reduced estuary buffering

3. How is alkalinity defined? Acid-Neutralizing Definition: T-Alk = [HCO 3 − ] + 2[CO 3 −2 ] + [B(OH) 4 − ] + 2[PO 4 −3 ] + [HPO 4 −2 ] + [SiO(OH) 3 − ] …+ [Organic - ] Ion Balance Definition [HCO 3 − ] + 2[CO 3 −2 ] +[OH - ]- [H + ] = [Na + ]+[K + ]+ 2[Ca +2 ] + 2[Mg +2 ] - [Cl - ] - 2[SO 4 -2 ] - [Organic - ] Working Definitions: C-Alk = [HCO 3 − ] + 2[CO 3 −2 ] ≈ [HCO 3 − ] NC-Alk = [B(OH) 4 − ] + 2[PO 4 −3 ] + [HPO 4 −2 ] + [SiO(OH) 3 − ] + [Organic - ] Org-Alk = [Organic - ] ≈ NC-Alk Org-Alk% = [Org-Alk] / [Total Alk]

4. Where has Org-Alk been documented? Hunt et al. 2011, 2014 Cai et al. 1998, Cai and Wang 1998 Wang et al. 2012 Abril et al. 2014 De Kluijver et al. 2014

5. How is Org-Alk measured? It’s not! (directly, at least) -Method 1: Difference between measured and calculated T-Alk Org-Alk = T-Alk meas - T-Alk DIC,pH,pCO2 -Method 2: Re-titration Org-Alk = T-Alk (second titration) -Method 3: Estimation Org-Alk = f(DOC, pH) Oliver 1983 BETTER TOOLS ARE NEEDED! Requires 3 carbonate measurements Poor precision, hysteresis,time-consuming Small n, possible errors at higher Alk/pH O-Alk, Difference method (DIC+pH, µmol/l)

6. Gulf of Maine Org-Alk A B D E C AB CDE %

7. Water Balance Model (WBM) Vorosmarty et al. 1998 (Appendix B) FrAMES Water Transport Model (WTM, STN) Vorosmarty et al. 2000 Other functions* “Vertical” movement of water (precip, ET, etc.) Wollheim et al. 2008 Wisser et al. 2009 Stewart et al. 2011 “Horizontal” movement of water (river network routing using STN or Simulated Topological Network) Nitrogen, Reservoirs, Transient Storage * These are often embedded within WBM, WTM 1.2., HCO 3 - (lithology+urban) Org-Alk (DOC)

8. Model Results- Gulf of Maine

9. Arctic Great Rivers Observatory (GRO)/PARTNERS Arctic data Image from Tank et al. 2012 (µmol/l)

10. Yukon Mackenzie Kolyma Yenisey Ob Lena Oliver 1983: [Org-Alk] = (10 -pH )(DOC*10) (10 -pH ) + K DOC (µmol C/l) Arctic Great Rivers Observatory (GRO)/PARTNERS Arctic data

12. Model Arctic Concentration Results

13. Model Arctic HCO 3 - Flux Results

14. Model Arctic DOC Flux Results

15. Conclusions Gulf of Maine DOC/Org-Alk% relationship most likely not appropriate for Arctic rivers More Arctic validation data needed, especially DIC or pCO 2 Hope to incorporate DOC quality- remote sensing opportunities Calibrate model coefficients for Arctic setting Including a permafrost parameter Future Goals

16. Arctic-Coastal Land Ocean Interactions A NASA Scoping Study Grants NASA NNX14AD75G and NNX09AU89G

17. Questions? I have many, such as: What factors are missing in the model for DOC, HCO3? Is there a better way to model Arctic O-Alk? We eventually need DOC quality in order to understand DOC color signature. Can SUVA get us there? What data are needed to improve understanding of Artic O-Alk? Strategies for modeling Arctic river pH? How can we simulate the potential release of DOC from thawing permafrost?

18. References Abril, G., S. Bouillon, F. Darchambeau, C.R. Teodoru, T.R. Marwick, F. Tamooh, F. Ochieng Omengo, N. Geeraert, L. Deirmendjian, P. Polsenaere, and A.V. Borges. 2014. Technical Note: Large overestimation of pCO2 calculated from pH and alkalinity in acidic, organic-rich freshwaters. Biogeosciences bg-2014-341 Amiotte-Suchet, P., J.-L. Probst, and W. Ludwig (2003), Worldwide distribution of continental rock lithology: Implications for the atmospheric/soil CO2 uptake by continental weathering and alkalinity river transport to the oceans, Global Biogeochem. Cycles, 17(2), 1038, doi:10.1029/2002GB001891. Cai, W.-J. and Wang, Y.: The chemistry, fluxes and sources of carbon dioxide in the estuarine waters of the Satilla and Altamaha Rivers, Georgia, Limnol. Oceanogr., 43, 657–668, 1998. Cai, W.-J., Wang, Y., and Hodson, R. E.: Acid-base properties of dissolved organic matter in the estuarine waters of Georgia, USA, Geochim. Cosmochim. Ac., 62, 473–483, 1998. de Kluijver, A., Schoon, P. L., Downing, J. A., Schouten, S., and Middelburg, J. J.: Stable carbon isotope biogeochemistry of lakes along a trophic gradient, Biogeosciences, 11, 6265-6276, doi:10.5194/bg-11-6265-2014, 2014. Hartmann, Jörg; Moosdorf, Nils (2012): Global Lithological Map Database v1.0 (gridded to 0.5° spatial resolution). doi:10.1594/PANGAEA.788537, Supplement to: Hartmann, Jens; Moosdorf, Nils (2012): The new global lithological map database GLiM: A representation of rock properties at the Earth surface. Geochemistry, Geophysics, Geosystems, 13, Q12004, doi:10.1029/2012GC004370 Hunt, C.W., J.E. Salisbury and D. Vandemark. (2013) CO2 Input Dynamics and Air-Sea Exchange in a Large New England Estuary. Estuaries and Coasts 37(5): 1078-1091 C.W. Hunt, J.E. Salisbury, D. Vandemark. (2011) Contribution of non-carbonate anions to total alkalinity and overestimation of pCO2 in New England and New Brunswick rivers. Biogeosciences, doi:10.5194/bg-8-3069-2011 Kicklighter, DW, Hayes, DJ, McClelland, JW, Peterson, BJ, McGuire, AD and JM Melillo. 2013. Insights and issues with simulating terrestrial DOC loading of Arctic river networks. Ecological Applications 23(8): 1817-1836. Tank, S. E., P. A. Raymond, R. G. Striegl, J. W. McClelland, R. M. Holmes, G. J. Fiske, and B. J. Peterson (2012), A land-to-ocean perspective on the magnitude, source and implication of DIC flux from major Arctic rivers to the Arctic Ocean, Global Biogeochem. Cycles, 26, GB4018, doi:10.1029/2011GB004192. Wang, Z. A., D. J. Bienvenu, P. J. Mann, K. A. Hoering, J. R. Poulsen, R. G. M. Spencer, and R. M. Holmes (2013), Inorganic carbon speciation and fluxes in the Congo River, Geophys. Res. Lett., 40,511–516, doi:10.1002/grl.50160.10.1002/grl.50160.

19. Loading equation: DOC (µmol/l) = Constant * RO Slope Slope =1 - (0.0001WL 2 – 0.0193*WL + 1.4237) Constant = -0.002WL 2 + 0.4552*WL + 7.275 RO=Runoff (mm/d), WL=Wetland% HCO3 (µmol/l) = Lithological HCO 3 - load (Amiotte-Suchet et al. 2003) Global 1° lithology (Hartmann and Moosdorf 2012) Respiration Removal of DOC: RespVf (m/d) = KResp * RespQ10 (waterT - Resp_Tref) / 10 RespRemoval = DOC * (1 - 10 (-RespVf / HL) ) HL=Hydraulic Load (m/d) Photolysis Removal of DOC: PhotoVf (m/d) = KPhoto * PAR * (PhotoDepth * ChannelDepth) PhotoRemoval = HPOA * (1 - 10 (-PhotoVf / HL) )