Strontium isotopes as tracers of ecosystem processes: theory and methods

doi:10.1016/S0016-7061(97)00102-X

Geoderma

Volume 82, Issues 1–3, February 1998, Pages 197-225

https://doi.org/10.1016/S0016-7061(97)00102-X Get rights and content

Abstract

The strontium (Sr) isotope method can be a powerful tool in studies of chemical weathering and soil genesis, cation provenance and mobility, and the chronostratigraphic correlation of marine sediments. It is a sensitive geochemical tracer, applicable to large-scale ecosystem studies as well as to centimeter-scaled examination of cation mobility within a soil profile. The ⁸⁷Sr/⁸⁶Sr ratios of natural materials reflect the sources of strontium available during their formation. Isotopically distinct inputs from precipitation, dryfall, soil parent material, and surface or groundwater allow determination of the relative proportions of those materials entering or leaving an ecosystem. The isotopic compositions of labile (soil exchange complex and soil solution) strontium and Sr in vegetation reflect the sources of cations available to plants. Strontium isotopes can be used to track the biogeochemical cycling of nutrient cations such as calcium. The extent of cation contributions from in situ weathering and external additions to soil from dust and rain can also be resolved with this method. In this paper, we review the geochemistry and isotopic systematics of strontium, and discuss the use of this method as a tracer of earth surface processes.

Introduction

Soils lie at the interface of the atmosphere, biosphere, hydrosphere and lithosphere, and are a key component of global biogeochemical cycles. Thus quantification of the processes involved in weathering and pedogenesis is a crucial aspect of element cycling models. On a watershed scale, information about cation fluxes and the identity and the magnitude of their sources and sinks is used to assess the effects of environmental change on terrestrial ecosystems.

The variation of isotope abundances in the Earth provides a means of tracing physical and chemical processes that have operated over geologic time. Isotopic tracer studies provide an extra dimension for tracking the fate of specific elements or families of elements; thus isotopic analysis is an increasingly important technique in environmental studies. Radioactive isotopes have long been used as a direct dating tool; for pedologic studies, radiocarbon and U-series methods have been successfully used to date Quaternary sediments and soils (see Faure, 1986). Cosmogenic isotopes (e.g., ¹⁰Be, ¹⁴C, ²⁶Al, ³²Si, ³⁶Cl) can yield information pertaining to sedimentation rate, the age of biogenic carbon, and the timing of subaerial exposure. Variations in the stable isotopic composition of light elements such as carbon, oxygen, hydrogen, nitrogen and sulfur are useful indicators of environmental temperature variations and biologic processes (see Hoefs, 1987).

Radiogenic isotopes, which are the isotope products of radioactive decay, can be used as geochemical tracers. In recent years, natural variations in isotope ratios of strontium (Sr) have been increasingly applied to studies of earth surface processes. These studies have shown that Sr isotopes can be a powerful tool in studies of chemical weathering and soil genesis, cation provenance and mobility, and the chronostratigraphic correlation of marine sediments. In this paper, we review the geochemistry and isotopic systematics of strontium in earth surface materials, and discuss analytical considerations in the measurement of Sr isotopes and its use as an ecosystem tracer. A companion paper (Stewart et al., 1998) details the application of Sr isotopes to models of soil–vegetation–atmosphere cation cycling.

Section snippets

Rubidium–strontium mineral chemistry

Strontium (atomic number 38) is a divalent alkaline earth element. Its ionic radius (1.18 Å) is similar to that of calcium (1.00 Å), and Sr substitutes for Ca in minerals including plagioclase feldspar, apatite, sulfates such as gypsum and anhydrite, and carbonates (calcite, dolomite and especially aragonite). In some minerals Sr²⁺ can also substitute for K⁺ when Si⁴⁺ is replaced by Al³⁺ (e.g., vermiculite, smectite). Strontium has four naturally occurring isotopes, with approximate abundances

The strontium cycle

Strontium in rocks is released by weathering, cycled through vegetation and animals, and eventually enters the oceans, primarily by rivers. Strontium leaves the oceans, the largest reservoir of dissolved Sr, primarily by deposition in marine carbonate. A small amount of Sr is also transferred directly from the oceans to the atmosphere and transferred to the continents in precipitation.

The Sr isotopic composition of the Earth's rivers reflects the nature of the exposed crust undergoing

Analytical methods

The application of Sr isotopes as an ecosystem tracer requires the determination of the isotopic composition of the components of the system as well as the sources to the system. Isotopic analysis of different components in a terrestrial system can require different sampling and extraction techniques. Characterization of a soil system often involves several steps: leaching cations with an exchange reagent, removal of carbonate with acetic acid and dissolution of the silicate residue in

Strontium isotope tracers of terrestrial processes

Once the isotopic compositions of the sources of strontium to the soil–atmosphere–biosphere system are known, ⁸⁷Sr/⁸⁶Sr ratios in soil, precipitation, dust, and vegetation can track the geochemical cycling of Sr within and between components. This provides insight into the terrestrial processes that affect the budget of Sr and other elements. The range of Sr isotopic variation in each component determines the resolution of the method.

Summary

Strontium isotopes can be a powerful tool in ecosystem studies, both as a tracer of nutrient sources and as a monitor of the weathering process. In many cases, isotopic characterization of sources to an ecosystem allows quantification of the relative contributions of in situ weathering and atmospheric inputs to soil and vegetation. The ⁸⁷Sr/⁸⁶Sr ratio of dust can indicate the source of atmospheric input, with implications for local climate patterns. Strontium isotope analyses, when combined

Acknowledgements

This paper was improved by the careful reviews and insightful comments of Ariel Anbar and Larry Wilding. We also thank Jean Hsieh, Gene Kelly, Chuck Whipkey and GEOL 3960 for helpful discussions. Lance Lugar provided invaluable library research assistance. This work was funded in part by NSF grant EAR-9614875 and a University of Pittsburgh Central Research and Development grant to R.C. Capo and NASA–JPL Mission to Planet Earth grants to O.A. Chadwick.

References (99)

G. Åberg et al.
Weathering rates and ⁸⁷Sr/⁸⁶Sr ratios: An isotopic approach
J. Hydrol.
(1989)
G. Åberg et al.
Strontium isotopes in trees as an indicator for calcium availability
Catena
(1990)
P. Andersson et al.
Major element chemistry, δ²H, δ¹⁸O and ⁸⁷Sr/⁸⁶Sr in a snow profile across central Scandinavia
Atmos. Environ.
(1990)
J.D. Blum et al.
⁸⁷Sr/⁸⁶Sr ratios of Sierra Nevada stream waters: Implications for relative mineral weathering rates
Geochim. Cosmochim. Acta
(1993)
G.W. Brass
The effect of weathering on the distribution of strontium isotopes in weathering profiles
Geochim. Cosmochim. Acta
(1975)
G.W. Brass
The variation of the marine ⁸⁷Sr/⁸⁶Sr ratio during Phanerozoic time: Interpretation using a flux model
Geochim. Cosmochim. Acta
(1976)
T. Bullen et al.
Chemical weathering of a soil chronosequence on granitoid alluvium, II. Mineralogic and isotopic constraints on the behavior of strontium
Geochim. Cosmochim. Acta
(1997)
O.A. Chadwick et al.
From a black box to a gray box — a mass balance interpretation of pedogenesis
Geomorphology
(1990)
E.J. Dasch
Strontium isotopes in weathering profiles, deep-sea sediments, and sedimentary rocks
Geochim. Cosmochim. Acta
(1969)
D.J. DePaolo et al.
Rb–Sr, Sm–Nd, K–Ca, O, and H isotopic study of Cretaceous–Tertiary boundary sediments, Caravaca, Spain: Evidence for an oceanic impact site
Earth Planet. Sci. Lett.
(1983)

L.A. Derry et al.

Sedimentary cycling and environmental change in the Late Proterozoic: Evidence from stable and radiogenic isotopes

Geochim. Cosmochim. Acta

(1992)

H. Elderfield

Strontium isotope stratigraphy

Palaeogeogr., Palaeoclimatol., Palaeoecol.

(1986)

P.D. Fullagar et al.

Chemical weathering and Rb–Sr whole rock ages

Geochim. Cosmochim. Acta

(1975)

S.S. Goldich et al.

Effects of weathering on the Rb–Sr and K–Ar ages of biotite from the Morton Gneiss, Minnesota

Earth Planet. Sci. Lett.

(1966)

S.L. Goldstein et al.

The Nd and Sr isotope systematics of river water dissolved material: Implications for the source of Nd and Sr in sea water

Chem. Geol. (Isot. Geosci. Sect.)

(1987)

S.L. Goldstein et al.

Nd and Sr isotopic systematics of river water suspended material: implications for crustal evolution

Earth Planet. Sci. Lett.

(1988)

B. Herut et al.

Strontium in rainwater from Israel: Sources, isotopes and chemistry

Earth Planet. Sci. Lett.

(1993)

D.A. Hodell et al.

Variation in the strontium isotopic composition of seawater (8 Ma to present): Implications for chemical weathering rates and dissolved fluxes to the oceans

Chem. Geol. (Isot. Geosci. Sect.)

(1990)

S. Krishnaswami et al.

Strontium isotopes and rubidium in the Ganga–Brahmaputra river system: Weathering in the Himalaya, fluxes to the Bay of Bengal and contributions to the evolution of oceanic ⁸⁷Sr/⁸⁶Sr

Earth Planet. Sci. Lett.

(1992)

M.T. McCulloch et al.

Strontium isotope variations in single ostracod valves from the Gulf of Carpentaria, Australia: A palaeoenvironmental indicator

Geochim. Cosmochim. Acta

(1989)

D.R. Muhs et al.

Geochemical evidence of Saharan dust parent material for soils developed on Quaternary limestones of Caribbean and western Atlantic islands

Quat. Res.

(1990)

D.W. Müller et al.

Origin and age of the Mediterranean Messinian evaporites: implications from Sr isotopes

Earth Planet. Sci. Lett.

(1991)

S. Nakai et al.

Provenance of dust in the Pacific Ocean

Earth Planet. Sci. Lett.

(1993)

B.K. Nelson et al.

Effects of diagenesis on strontium, carbon, nitrogen and oxygen concentration and isotopic composition of bone

Geochim. Cosmochim. Acta

(1986)

A.M. Olivarez et al.

Geochemistry of eolian dust in Pacific pelagic sediments: Implications for paleoclimatic interpretations

Geochim. Cosmochim. Acta

(1991)

M.R. Palmer et al.

The strontium isotope budget of the modern ocean

Earth Planet. Sci. Lett.

(1989)

M.R. Palmer et al.

Controls over the strontium isotope composition of river water

Geochim. Cosmochim. Acta

(1992)

J. Quade et al.

Strontium and carbon isotope tracers and the origins of soil carbonate in South Australia and Victoria

Palaeogeogr., Palaeoclimatol., Palaeoecol.

(1995)

D.K. Rea et al.

Asian aridity and the zonal westerlies: Late Pleistocene and Holocene record of eolian deposition in the northwest Pacific Ocean

Palaeogeogr., Palaeoclimatol., Palaeoecol.

(1988)

F.M. Richter et al.

Sr isotope evolution of seawater: the role of tectonics

Earth Planet. Sci. Lett.

(1992)

J. Veizer et al.

⁸⁷Sr/⁸⁶Sr in Late Proterozoic carbonates: Evidence for a `mantle event' at 900 Ma ago

Geochim. Cosmochim. Acta

(1983)

M.A. Wadleigh et al.

Strontium and its isotopes in Canadian rivers: Fluxes and global implications

Geochim. Cosmochim. Acta

(1985)

L.T. West et al.

Differentiation of pedogenic and lithogenic carbonate forms in Texas

Geoderma

(1988)

T. Wickman et al.

Base cation nutrition for pine stands on lithic soils near Stockholm, Sweden

Appl. Geochem., Suppl.

(1993)

C. Yang et al.

Chemical dynamics of the `St. Lawrence' riverine system: δD_H2O, δ¹⁸O_H2O, δ¹³C_DIC, δ³⁴S_sulfate, and dissolved ⁸⁷Sr/⁸⁶Sr

Geochim. Cosmochim. Acta

(1996)

G. Åberg

The use of natural strontium isotopes as tracers in environmental studies

Water Air Soil Pollut.

(1995)

G. Åberg et al.

Strontium isotope ratios in mussel shells as indicators of acidification

Ambio

(1995)

R.L. Armstrong

Glacial erosion and the variable isotopic composition of strontium in seawater

Nature

(1971)

W.T. Baisden et al.

Elemental concentrations in fresh snowfall across a regional transect in the northeastern U.S.: Apparent sources and contribution to acidity

Water Air Soil Pollut.

(1995)

J.L. Banner et al.

Tracing groundwater evolution in a Pleistocene limestone aquifer using Sr isotopes: Effects of multiple sources of dissolved ions and mineral-solution reactions

Geology

(1994)

R.A. Berner

A model for atmospheric CO₂ over Phanerozoic time

Am. J. Sci.

(1991)

P.E. Biscaye et al.

Rb/Sr, ⁸⁷Sr/⁸⁶Sr isotope systems as an index of provenance of continental dusts in open Atlantic Ocean

J. Rech. Atmos.

(1974)

Bohn, H.L., McNeal, B.L., O'Connor, G.A., 1979. Soil Chemistry. Wiley, New York, 329...

M.L. Bottino et al.

Effects of weathering on whole rock Rb–Sr ages of granitic rock

Am. J. Sci.

(1968)

G.H. Brimhall et al.

Deformational mass transport and invasive processes in soil evolution

Science

(1991)

Brimhall, G.H., Donovan, J., Singh, B., 1994. Provenance and discordance mechanism of zircons in the Australian...

W.H. Burke et al.

Variation of seawater ⁸⁷Sr/⁸⁶Sr throughout Phanerozoic time

Geology

(1982)

Cahill, T.A., Ashbaugh, L.L., Eldred, R.A., Feeney, P.J., Kusko, B.H., Flocchini, R.G., 1981. Comparisons between...

R.C. Capo et al.

Partitioning of atmospheric and silicate weathering sources in the formation of desert soil carbonate using strontium isotopes

EOS, Trans. Am. Geophys. Union

(1993)

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Strontium isotopes as tracers of ecosystem processes: theory and methods

Abstract

Introduction

Section snippets

Rubidium–strontium mineral chemistry

The strontium cycle

Analytical methods

Strontium isotope tracers of terrestrial processes

Summary

Acknowledgements

J. Hydrol.

Catena

Atmos. Environ.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geomorphology

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Geochim. Cosmochim. Acta

Palaeogeogr., Palaeoclimatol., Palaeoecol.

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Chem. Geol. (Isot. Geosci. Sect.)

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Chem. Geol. (Isot. Geosci. Sect.)

Earth Planet. Sci. Lett.

Geochim. Cosmochim. Acta

Quat. Res.

Earth Planet. Sci. Lett.

Earth Planet. Sci. Lett.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Earth Planet. Sci. Lett.

Geochim. Cosmochim. Acta

Palaeogeogr., Palaeoclimatol., Palaeoecol.

Palaeogeogr., Palaeoclimatol., Palaeoecol.

Earth Planet. Sci. Lett.

Geochim. Cosmochim. Acta

Geochim. Cosmochim. Acta

Geoderma

Appl. Geochem., Suppl.

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The use of natural strontium isotopes as tracers in environmental studies

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Strontium isotope ratios in mussel shells as indicators of acidification

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