Relative weathering intensity of calcite versus dolomite in carbonate-bearing temperate zone watersheds: Carbonate geochemistry and fluxes from catchments within the St. Lawrence and Danube river basins

Kathryn Szramek, Jennifer McIntosh, Erika L. Williams, Tjasa Kanduc, Nives Ogrinc, Lynn M. Walter

Research output: Contribution to journalArticle

58 Citations (Scopus)

Abstract

Calcite and dolomite solubilities in open weathering environments are proportional to pCO2 and inversely proportional to temperature, and dolomite solubility is progressively greater than calcite below 25°C. The continent-scale weathering budget reveals the significance of the Northern Hemisphere (NH) to globally integrated riverine fluxes of Ca2+, Mg2+, and HCO3-. The NH contributes 70% of the global HCO3- flux while only 54% of the riverine discharge. We present results of a comparative hydrogeochemical study of carbonate mineral equilibria and weathering fluxes in two NH carbonaterich river basins. Surface water geochemistry and discharge were determined for head water streams in Michigan and Slovenia within the St. Lawrence and Danube river basins. Michigan watersheds are established atop carbonate-bearing glacial drift deposits derived from erosion of Paleozoic strata with thick soil horizons (100-300 cm). Slovenia watersheds drain Mesozoic bedrock carbonates in alpine and dinaric karst environments with thin soil horizons (0-70 cm). Carbonate weathering intensity is a parameter that normalizes river runoff and HCO 3- concentration to catchment area (meq HCO 3- km-2 s-1), summing calcite and dolomite contributions, and is used to gauge the effects of climate, land use, and soil thickness on organic-inorganic carbon processing rates. Importantly, Michigan riverine discharge is one-tenth of Slovenian rivers, providing the opportunity to evaluate the kinetics of carbonate mineral equilibration. The study rivers are HCO3- - Ca2+ - Mg2+ waters, supersaturated for calcite at pCO2 values in excess of theatmosphere. As discharge varies, HCO3- concentrations differ by less than 20% for any location, and Mg2+/ Ca2+ remains relatively fixed for Michigan (0.5) and Slovenia streams (0.4), requiring that dolomite dissolution exceed calcite on a mole basis. The ability of calcite and dolomite dissolution to keep pace with increased discharge indicates carbonate weathering is limited only by water flux and temperaturedependent solubility in these watersheds. Carbonate weathering intensity in Michigan and Slovenia exceeds the world average by factors between 2 and 20, and dolomite weathering intensity, estimated from riverine Mg 2+ fluxes, exceeds the world average by factors between 2 and 15. Thus global fluxes of carbonate-related weathering products appear heavily skewed toward carbonate-bearing environments at higher latitudes with relatively low mean annual temperatures and high discharge.

Original languageEnglish (US)
Article numberQ04002
JournalGeochemistry, Geophysics, Geosystems
Volume8
Issue number4
DOIs
StatePublished - Apr 2007

Fingerprint

Bearings (structural)
river basins
Geochemistry
Calcium Carbonate
Carbonates
weathering
geochemistry
Weathering
calcite
Watersheds
Catchments
dolomite
carbonates
river basin
Rivers
watershed
catchment
Fluxes
carbonate
Carbonate minerals

Keywords

  • Calcite
  • Carbonate mineral weathering
  • Dolomite
  • Geochemical fluxes
  • Rivers

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Relative weathering intensity of calcite versus dolomite in carbonate-bearing temperate zone watersheds : Carbonate geochemistry and fluxes from catchments within the St. Lawrence and Danube river basins. / Szramek, Kathryn; McIntosh, Jennifer; Williams, Erika L.; Kanduc, Tjasa; Ogrinc, Nives; Walter, Lynn M.

In: Geochemistry, Geophysics, Geosystems, Vol. 8, No. 4, Q04002, 04.2007.

Research output: Contribution to journalArticle

@article{516516445cff42d4ba4de57578e1430a,
title = "Relative weathering intensity of calcite versus dolomite in carbonate-bearing temperate zone watersheds: Carbonate geochemistry and fluxes from catchments within the St. Lawrence and Danube river basins",
abstract = "Calcite and dolomite solubilities in open weathering environments are proportional to pCO2 and inversely proportional to temperature, and dolomite solubility is progressively greater than calcite below 25°C. The continent-scale weathering budget reveals the significance of the Northern Hemisphere (NH) to globally integrated riverine fluxes of Ca2+, Mg2+, and HCO3-. The NH contributes 70{\%} of the global HCO3- flux while only 54{\%} of the riverine discharge. We present results of a comparative hydrogeochemical study of carbonate mineral equilibria and weathering fluxes in two NH carbonaterich river basins. Surface water geochemistry and discharge were determined for head water streams in Michigan and Slovenia within the St. Lawrence and Danube river basins. Michigan watersheds are established atop carbonate-bearing glacial drift deposits derived from erosion of Paleozoic strata with thick soil horizons (100-300 cm). Slovenia watersheds drain Mesozoic bedrock carbonates in alpine and dinaric karst environments with thin soil horizons (0-70 cm). Carbonate weathering intensity is a parameter that normalizes river runoff and HCO 3- concentration to catchment area (meq HCO 3- km-2 s-1), summing calcite and dolomite contributions, and is used to gauge the effects of climate, land use, and soil thickness on organic-inorganic carbon processing rates. Importantly, Michigan riverine discharge is one-tenth of Slovenian rivers, providing the opportunity to evaluate the kinetics of carbonate mineral equilibration. The study rivers are HCO3- - Ca2+ - Mg2+ waters, supersaturated for calcite at pCO2 values in excess of theatmosphere. As discharge varies, HCO3- concentrations differ by less than 20{\%} for any location, and Mg2+/ Ca2+ remains relatively fixed for Michigan (0.5) and Slovenia streams (0.4), requiring that dolomite dissolution exceed calcite on a mole basis. The ability of calcite and dolomite dissolution to keep pace with increased discharge indicates carbonate weathering is limited only by water flux and temperaturedependent solubility in these watersheds. Carbonate weathering intensity in Michigan and Slovenia exceeds the world average by factors between 2 and 20, and dolomite weathering intensity, estimated from riverine Mg 2+ fluxes, exceeds the world average by factors between 2 and 15. Thus global fluxes of carbonate-related weathering products appear heavily skewed toward carbonate-bearing environments at higher latitudes with relatively low mean annual temperatures and high discharge.",
keywords = "Calcite, Carbonate mineral weathering, Dolomite, Geochemical fluxes, Rivers",
author = "Kathryn Szramek and Jennifer McIntosh and Williams, {Erika L.} and Tjasa Kanduc and Nives Ogrinc and Walter, {Lynn M.}",
year = "2007",
month = "4",
doi = "10.1029/2006GC001337",
language = "English (US)",
volume = "8",
journal = "Geochemistry, Geophysics, Geosystems",
issn = "1525-2027",
publisher = "American Geophysical Union",
number = "4",

}

TY - JOUR

T1 - Relative weathering intensity of calcite versus dolomite in carbonate-bearing temperate zone watersheds

T2 - Carbonate geochemistry and fluxes from catchments within the St. Lawrence and Danube river basins

AU - Szramek, Kathryn

AU - McIntosh, Jennifer

AU - Williams, Erika L.

AU - Kanduc, Tjasa

AU - Ogrinc, Nives

AU - Walter, Lynn M.

PY - 2007/4

Y1 - 2007/4

N2 - Calcite and dolomite solubilities in open weathering environments are proportional to pCO2 and inversely proportional to temperature, and dolomite solubility is progressively greater than calcite below 25°C. The continent-scale weathering budget reveals the significance of the Northern Hemisphere (NH) to globally integrated riverine fluxes of Ca2+, Mg2+, and HCO3-. The NH contributes 70% of the global HCO3- flux while only 54% of the riverine discharge. We present results of a comparative hydrogeochemical study of carbonate mineral equilibria and weathering fluxes in two NH carbonaterich river basins. Surface water geochemistry and discharge were determined for head water streams in Michigan and Slovenia within the St. Lawrence and Danube river basins. Michigan watersheds are established atop carbonate-bearing glacial drift deposits derived from erosion of Paleozoic strata with thick soil horizons (100-300 cm). Slovenia watersheds drain Mesozoic bedrock carbonates in alpine and dinaric karst environments with thin soil horizons (0-70 cm). Carbonate weathering intensity is a parameter that normalizes river runoff and HCO 3- concentration to catchment area (meq HCO 3- km-2 s-1), summing calcite and dolomite contributions, and is used to gauge the effects of climate, land use, and soil thickness on organic-inorganic carbon processing rates. Importantly, Michigan riverine discharge is one-tenth of Slovenian rivers, providing the opportunity to evaluate the kinetics of carbonate mineral equilibration. The study rivers are HCO3- - Ca2+ - Mg2+ waters, supersaturated for calcite at pCO2 values in excess of theatmosphere. As discharge varies, HCO3- concentrations differ by less than 20% for any location, and Mg2+/ Ca2+ remains relatively fixed for Michigan (0.5) and Slovenia streams (0.4), requiring that dolomite dissolution exceed calcite on a mole basis. The ability of calcite and dolomite dissolution to keep pace with increased discharge indicates carbonate weathering is limited only by water flux and temperaturedependent solubility in these watersheds. Carbonate weathering intensity in Michigan and Slovenia exceeds the world average by factors between 2 and 20, and dolomite weathering intensity, estimated from riverine Mg 2+ fluxes, exceeds the world average by factors between 2 and 15. Thus global fluxes of carbonate-related weathering products appear heavily skewed toward carbonate-bearing environments at higher latitudes with relatively low mean annual temperatures and high discharge.

AB - Calcite and dolomite solubilities in open weathering environments are proportional to pCO2 and inversely proportional to temperature, and dolomite solubility is progressively greater than calcite below 25°C. The continent-scale weathering budget reveals the significance of the Northern Hemisphere (NH) to globally integrated riverine fluxes of Ca2+, Mg2+, and HCO3-. The NH contributes 70% of the global HCO3- flux while only 54% of the riverine discharge. We present results of a comparative hydrogeochemical study of carbonate mineral equilibria and weathering fluxes in two NH carbonaterich river basins. Surface water geochemistry and discharge were determined for head water streams in Michigan and Slovenia within the St. Lawrence and Danube river basins. Michigan watersheds are established atop carbonate-bearing glacial drift deposits derived from erosion of Paleozoic strata with thick soil horizons (100-300 cm). Slovenia watersheds drain Mesozoic bedrock carbonates in alpine and dinaric karst environments with thin soil horizons (0-70 cm). Carbonate weathering intensity is a parameter that normalizes river runoff and HCO 3- concentration to catchment area (meq HCO 3- km-2 s-1), summing calcite and dolomite contributions, and is used to gauge the effects of climate, land use, and soil thickness on organic-inorganic carbon processing rates. Importantly, Michigan riverine discharge is one-tenth of Slovenian rivers, providing the opportunity to evaluate the kinetics of carbonate mineral equilibration. The study rivers are HCO3- - Ca2+ - Mg2+ waters, supersaturated for calcite at pCO2 values in excess of theatmosphere. As discharge varies, HCO3- concentrations differ by less than 20% for any location, and Mg2+/ Ca2+ remains relatively fixed for Michigan (0.5) and Slovenia streams (0.4), requiring that dolomite dissolution exceed calcite on a mole basis. The ability of calcite and dolomite dissolution to keep pace with increased discharge indicates carbonate weathering is limited only by water flux and temperaturedependent solubility in these watersheds. Carbonate weathering intensity in Michigan and Slovenia exceeds the world average by factors between 2 and 20, and dolomite weathering intensity, estimated from riverine Mg 2+ fluxes, exceeds the world average by factors between 2 and 15. Thus global fluxes of carbonate-related weathering products appear heavily skewed toward carbonate-bearing environments at higher latitudes with relatively low mean annual temperatures and high discharge.

KW - Calcite

KW - Carbonate mineral weathering

KW - Dolomite

KW - Geochemical fluxes

KW - Rivers

UR - http://www.scopus.com/inward/record.url?scp=35349017202&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=35349017202&partnerID=8YFLogxK

U2 - 10.1029/2006GC001337

DO - 10.1029/2006GC001337

M3 - Article

AN - SCOPUS:35349017202

VL - 8

JO - Geochemistry, Geophysics, Geosystems

JF - Geochemistry, Geophysics, Geosystems

SN - 1525-2027

IS - 4

M1 - Q04002

ER -