The Buffering Balance: Modeling Arctic river total-, inorganic- and organic-alkalinity fluxesC.W. Hunt, J.E. Salisbury, W. Wollheim, M. Mineau, and R.J. Stewart.

University of New Hampshire

CO2

CO2 (aq) H2CO3

HCO3- + H+

CO32- + H+

CarbonicAcid

Bicarbonate

CarbonateB(OH)4

-

HPO42-

SiO(OH)3-

NH3

H3PO4

PO43-

OH-Organic-

EstuaryRiver

Total alkalinity (T-Alk):The buffering capacity of an aqueous solution.ORThe capacity of an aqueous solution to neutralize acid.

Implications:•CO2 degassing estimates•Decreased pH•Overestimated Ω•Reduced estuary buffering

How is alkalinity defined?

Acid-Neutralizing Definition:T-Alk = [HCO3

−] + 2[CO3−2] + [B(OH)4

−] + 2[PO4−3] + [HPO4

−2] + [SiO(OH)3−] …+ [Organic-]

Ion Balance Definition[HCO3

−] + 2[CO3−2] +[OH-]- [H+ ] = [Na+]+[K+]+ 2[Ca+2] + 2[Mg+2] - [Cl-] - 2[SO4

-2] - [Organic-]

Working Definitions:C-Alk = [HCO3

−] + 2[CO3−2] ≈ [HCO3

−]

NC-Alk = [B(OH)4−] + 2[PO4

−3] + [HPO4−2] + [SiO(OH)3

−] + [Organic-]

Org-Alk = [Organic-] ≈ NC-Alk

Org-Alk% = [Org-Alk] / [Total Alk]

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

How is Org-Alk measured?

It’s not! (directly, at least)-Method 1: Difference between measured and calculated T-AlkOrg-Alk = T-Alkmeas - T-AlkDIC,pH,pCO2

-Method 2: Re-titrationOrg-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)

Gulf of Maine Org-Alk

AB

DE

C

A B C D E%

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. 2008Wisser et al. 2009Stewart 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.

,HCO3

-(lithology+urban)Org-Alk (DOC)

Model Results- Gulf of Maine

Arctic Great Rivers Observatory (GRO)/PARTNERSArctic data

Image from Tank et al. 2012

(µmol/l)

YukonMackenzie

Kolyma Yenisey Ob Lena

Oliver 1983:

[Org-Alk] = (10-pH )(DOC*10) (10-pH ) + K

DOC (µmol C/l)

Arctic Great Rivers Observatory (GRO)/PARTNERSArctic data

Model Arctic Concentration Results

Model Arctic HCO3- Flux Results

Model Arctic DOC Flux Results

Conclusions• Gulf of Maine DOC/Org-Alk% relationship most likely not

appropriate for Arctic rivers• More Arctic validation data needed, especially DIC or pCO2

• Hope to incorporate DOC quality- remote sensing opportunities

• Calibrate model coefficients for Arctic setting• Including a permafrost parameter

Future Goals

Arctic - COLORS Arctic-Coastal Land Ocean Interactions

A NASA Scoping Study

Grants NASA NNX14AD75G and NNX09AU89G

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?

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 carbondioxide in the estuarine waters of the Satilla and AltamahaRivers, Georgia, Limnol. Oceanogr., 43, 657–668, 1998.

• Cai, W.-J., Wang, Y., and Hodson, R. E.: Acid-base propertiesof 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.

Loading equation:DOC (µmol/l) = Constant * ROSlope

Slope =1 - (0.0001WL2 – 0.0193*WL + 1.4237)Constant = -0.002WL2 + 0.4552*WL + 7.275RO=Runoff (mm/d), WL=Wetland%

HCO3 (µmol/l) = Lithological HCO3- 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))