the buffering balance: modeling arctic river total-, inorganic- and organic-alkalinity fluxes c.w....
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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))