Occurrence and mobilization of radium in fresh to saline coastal groundwater inferred from geochemical and isotopic tracers (Sr, S, O, H, Ra, Rn)

David S. Vinson, Tarik Tagma, Lhoussaine Bouchaou, Gary S. Dwyer, Nathaniel Richard Warner, Avner Vengosh

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

Salinization in groundwater systems can induce water-rock interaction, including the release of naturally-occurring trace elements of health significance such as radium (Ra), with possible implications for the usability of water resources in addition to the increase of dissolved solids (TDS) concentrations. In general, radium mobility is limited by chemical removal mechanisms including adsorption onto clays and/or Mn and Fe oxides, exchange processes, and coprecipitation with secondary barite. In order to examine the effect of aquifer salinity gradients on the distribution of naturally-occurring Ra in fresh to saline groundwater and the relationship to water-rock interaction and Ra removal mechanisms, two contrasting systems were investigated: the shallow unconfined coastal aquifer in Agadir (southwestern Morocco) and the confined Cretaceous (Cape Fear) and Pliocene (Yorktown) aquifers of the Atlantic Coastal Plain (North Carolina, USA). Geochemical and isotopic indicators of salinity sources (e.g. cation ratios, δ18O, δ2H, Br-/Cl-, δ34S-SO42-,δ18O-SO42-) were used to identify the relative contributions of seawater and other saline waters and subsequent geochemical modification by water-rock interaction. Radium activities (224Ra, 226Ra, 228Ra), radon-222, alkaline earth metal (Mg, Ca, Sr, Ba) concentrations and ratios, and 87Sr/86Sr ratios were analyzed to identify water-rock interaction processes affecting alkaline earth metals including Ra. The Morocco coastal aquifer is generally oxic, exhibits a range of salinity and water types (Cl- 163-2120mg/L, median 932mg/L), and exhibits Ca/Na ratios above the seawater value, typical of monovalent-divalent cation exchange (base-exchange reactions) in coastal aquifers. In contrast, the Atlantic Coastal Plain aquifers are anoxic, sulfate-reducing, cover a wider salinity range (Cl- 5-9890mg/L, median 800mg/L) representing a transition between Na-HCO3- and Na-Cl- waters, and exhibit Ca/Na ratios below that of modern seawater typical of reverse base-exchange reactions. Possible salinity sources in the Morocco coastal aquifer include seawater intrusion, Mesozoic evaporites, other natural saline waters, and/or wastewater, whereas the Atlantic Coastal Plain is primarily affected by old seawater present in the aquifer system. Radium activities are generally low and vary significantly within each aquifer, for example 226Ra ranges from 1.8-27.7mBq/L in the Morocco coastal aquifer (median 8.1mBq/L) and 1.9-214mBq/L in the Atlantic Coastal Plain (median 18.9mBq/L). The highest Ra activities were observed in the most saline wells sampled in the Atlantic Coastal Plain. At total dissolved solids (TDS) concentrations above an apparent threshold of ~5000mg/L, radium activities increase in a generally linear fashion with salinity in the Atlantic Coastal Plain, broadly comparable to previous studies indicating a threshold range of ~3000-10,000mg/L. At lower TDS concentrations, water-rock interaction processes that vary with local aquifer conditions appear to control Ra distribution rather than merely salinity. In the Morocco coastal aquifer, adsorption of Ra and coprecipitation with secondary barite are apparently favorable to control Ra levels in groundwater. Radium removal in the anoxic Atlantic Coastal Plain aquifers appears to be associated with adsorption and/or exchange processes, with the additional possibility of barite precipitation in the Cape Fear aquifer indicated by barite saturation. Overall, the locally-variable factors that can control Ra sources and mobility in fresh to brackish groundwater at near-neutral pH include variation in solid-phase radioactivity, redox state affecting adsorption sites, availability of competing divalent cations, and barite saturation.

Original languageEnglish (US)
Pages (from-to)161-175
Number of pages15
JournalApplied Geochemistry
Volume38
DOIs
StatePublished - Nov 1 2013

Fingerprint

Radium
radium
Aquifers
mobilization
Groundwater
tracer
groundwater
coastal aquifer
Barium Sulfate
Barite
coastal plain
aquifer
water-rock interaction
barite
salinity
Water
Seawater
Rocks
seawater
Alkaline Earth Metals

All Science Journal Classification (ASJC) codes

  • Environmental Chemistry
  • Pollution
  • Geochemistry and Petrology

Cite this

@article{f8aeed8e0e354b3fab87698545e60304,
title = "Occurrence and mobilization of radium in fresh to saline coastal groundwater inferred from geochemical and isotopic tracers (Sr, S, O, H, Ra, Rn)",
abstract = "Salinization in groundwater systems can induce water-rock interaction, including the release of naturally-occurring trace elements of health significance such as radium (Ra), with possible implications for the usability of water resources in addition to the increase of dissolved solids (TDS) concentrations. In general, radium mobility is limited by chemical removal mechanisms including adsorption onto clays and/or Mn and Fe oxides, exchange processes, and coprecipitation with secondary barite. In order to examine the effect of aquifer salinity gradients on the distribution of naturally-occurring Ra in fresh to saline groundwater and the relationship to water-rock interaction and Ra removal mechanisms, two contrasting systems were investigated: the shallow unconfined coastal aquifer in Agadir (southwestern Morocco) and the confined Cretaceous (Cape Fear) and Pliocene (Yorktown) aquifers of the Atlantic Coastal Plain (North Carolina, USA). Geochemical and isotopic indicators of salinity sources (e.g. cation ratios, δ18O, δ2H, Br-/Cl-, δ34S-SO42-,δ18O-SO42-) were used to identify the relative contributions of seawater and other saline waters and subsequent geochemical modification by water-rock interaction. Radium activities (224Ra, 226Ra, 228Ra), radon-222, alkaline earth metal (Mg, Ca, Sr, Ba) concentrations and ratios, and 87Sr/86Sr ratios were analyzed to identify water-rock interaction processes affecting alkaline earth metals including Ra. The Morocco coastal aquifer is generally oxic, exhibits a range of salinity and water types (Cl- 163-2120mg/L, median 932mg/L), and exhibits Ca/Na ratios above the seawater value, typical of monovalent-divalent cation exchange (base-exchange reactions) in coastal aquifers. In contrast, the Atlantic Coastal Plain aquifers are anoxic, sulfate-reducing, cover a wider salinity range (Cl- 5-9890mg/L, median 800mg/L) representing a transition between Na-HCO3- and Na-Cl- waters, and exhibit Ca/Na ratios below that of modern seawater typical of reverse base-exchange reactions. Possible salinity sources in the Morocco coastal aquifer include seawater intrusion, Mesozoic evaporites, other natural saline waters, and/or wastewater, whereas the Atlantic Coastal Plain is primarily affected by old seawater present in the aquifer system. Radium activities are generally low and vary significantly within each aquifer, for example 226Ra ranges from 1.8-27.7mBq/L in the Morocco coastal aquifer (median 8.1mBq/L) and 1.9-214mBq/L in the Atlantic Coastal Plain (median 18.9mBq/L). The highest Ra activities were observed in the most saline wells sampled in the Atlantic Coastal Plain. At total dissolved solids (TDS) concentrations above an apparent threshold of ~5000mg/L, radium activities increase in a generally linear fashion with salinity in the Atlantic Coastal Plain, broadly comparable to previous studies indicating a threshold range of ~3000-10,000mg/L. At lower TDS concentrations, water-rock interaction processes that vary with local aquifer conditions appear to control Ra distribution rather than merely salinity. In the Morocco coastal aquifer, adsorption of Ra and coprecipitation with secondary barite are apparently favorable to control Ra levels in groundwater. Radium removal in the anoxic Atlantic Coastal Plain aquifers appears to be associated with adsorption and/or exchange processes, with the additional possibility of barite precipitation in the Cape Fear aquifer indicated by barite saturation. Overall, the locally-variable factors that can control Ra sources and mobility in fresh to brackish groundwater at near-neutral pH include variation in solid-phase radioactivity, redox state affecting adsorption sites, availability of competing divalent cations, and barite saturation.",
author = "Vinson, {David S.} and Tarik Tagma and Lhoussaine Bouchaou and Dwyer, {Gary S.} and Warner, {Nathaniel Richard} and Avner Vengosh",
year = "2013",
month = "11",
day = "1",
doi = "10.1016/j.apgeochem.2013.09.004",
language = "English (US)",
volume = "38",
pages = "161--175",
journal = "Applied Geochemistry",
issn = "0883-2927",
publisher = "Elsevier Limited",

}

Occurrence and mobilization of radium in fresh to saline coastal groundwater inferred from geochemical and isotopic tracers (Sr, S, O, H, Ra, Rn). / Vinson, David S.; Tagma, Tarik; Bouchaou, Lhoussaine; Dwyer, Gary S.; Warner, Nathaniel Richard; Vengosh, Avner.

In: Applied Geochemistry, Vol. 38, 01.11.2013, p. 161-175.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Occurrence and mobilization of radium in fresh to saline coastal groundwater inferred from geochemical and isotopic tracers (Sr, S, O, H, Ra, Rn)

AU - Vinson, David S.

AU - Tagma, Tarik

AU - Bouchaou, Lhoussaine

AU - Dwyer, Gary S.

AU - Warner, Nathaniel Richard

AU - Vengosh, Avner

PY - 2013/11/1

Y1 - 2013/11/1

N2 - Salinization in groundwater systems can induce water-rock interaction, including the release of naturally-occurring trace elements of health significance such as radium (Ra), with possible implications for the usability of water resources in addition to the increase of dissolved solids (TDS) concentrations. In general, radium mobility is limited by chemical removal mechanisms including adsorption onto clays and/or Mn and Fe oxides, exchange processes, and coprecipitation with secondary barite. In order to examine the effect of aquifer salinity gradients on the distribution of naturally-occurring Ra in fresh to saline groundwater and the relationship to water-rock interaction and Ra removal mechanisms, two contrasting systems were investigated: the shallow unconfined coastal aquifer in Agadir (southwestern Morocco) and the confined Cretaceous (Cape Fear) and Pliocene (Yorktown) aquifers of the Atlantic Coastal Plain (North Carolina, USA). Geochemical and isotopic indicators of salinity sources (e.g. cation ratios, δ18O, δ2H, Br-/Cl-, δ34S-SO42-,δ18O-SO42-) were used to identify the relative contributions of seawater and other saline waters and subsequent geochemical modification by water-rock interaction. Radium activities (224Ra, 226Ra, 228Ra), radon-222, alkaline earth metal (Mg, Ca, Sr, Ba) concentrations and ratios, and 87Sr/86Sr ratios were analyzed to identify water-rock interaction processes affecting alkaline earth metals including Ra. The Morocco coastal aquifer is generally oxic, exhibits a range of salinity and water types (Cl- 163-2120mg/L, median 932mg/L), and exhibits Ca/Na ratios above the seawater value, typical of monovalent-divalent cation exchange (base-exchange reactions) in coastal aquifers. In contrast, the Atlantic Coastal Plain aquifers are anoxic, sulfate-reducing, cover a wider salinity range (Cl- 5-9890mg/L, median 800mg/L) representing a transition between Na-HCO3- and Na-Cl- waters, and exhibit Ca/Na ratios below that of modern seawater typical of reverse base-exchange reactions. Possible salinity sources in the Morocco coastal aquifer include seawater intrusion, Mesozoic evaporites, other natural saline waters, and/or wastewater, whereas the Atlantic Coastal Plain is primarily affected by old seawater present in the aquifer system. Radium activities are generally low and vary significantly within each aquifer, for example 226Ra ranges from 1.8-27.7mBq/L in the Morocco coastal aquifer (median 8.1mBq/L) and 1.9-214mBq/L in the Atlantic Coastal Plain (median 18.9mBq/L). The highest Ra activities were observed in the most saline wells sampled in the Atlantic Coastal Plain. At total dissolved solids (TDS) concentrations above an apparent threshold of ~5000mg/L, radium activities increase in a generally linear fashion with salinity in the Atlantic Coastal Plain, broadly comparable to previous studies indicating a threshold range of ~3000-10,000mg/L. At lower TDS concentrations, water-rock interaction processes that vary with local aquifer conditions appear to control Ra distribution rather than merely salinity. In the Morocco coastal aquifer, adsorption of Ra and coprecipitation with secondary barite are apparently favorable to control Ra levels in groundwater. Radium removal in the anoxic Atlantic Coastal Plain aquifers appears to be associated with adsorption and/or exchange processes, with the additional possibility of barite precipitation in the Cape Fear aquifer indicated by barite saturation. Overall, the locally-variable factors that can control Ra sources and mobility in fresh to brackish groundwater at near-neutral pH include variation in solid-phase radioactivity, redox state affecting adsorption sites, availability of competing divalent cations, and barite saturation.

AB - Salinization in groundwater systems can induce water-rock interaction, including the release of naturally-occurring trace elements of health significance such as radium (Ra), with possible implications for the usability of water resources in addition to the increase of dissolved solids (TDS) concentrations. In general, radium mobility is limited by chemical removal mechanisms including adsorption onto clays and/or Mn and Fe oxides, exchange processes, and coprecipitation with secondary barite. In order to examine the effect of aquifer salinity gradients on the distribution of naturally-occurring Ra in fresh to saline groundwater and the relationship to water-rock interaction and Ra removal mechanisms, two contrasting systems were investigated: the shallow unconfined coastal aquifer in Agadir (southwestern Morocco) and the confined Cretaceous (Cape Fear) and Pliocene (Yorktown) aquifers of the Atlantic Coastal Plain (North Carolina, USA). Geochemical and isotopic indicators of salinity sources (e.g. cation ratios, δ18O, δ2H, Br-/Cl-, δ34S-SO42-,δ18O-SO42-) were used to identify the relative contributions of seawater and other saline waters and subsequent geochemical modification by water-rock interaction. Radium activities (224Ra, 226Ra, 228Ra), radon-222, alkaline earth metal (Mg, Ca, Sr, Ba) concentrations and ratios, and 87Sr/86Sr ratios were analyzed to identify water-rock interaction processes affecting alkaline earth metals including Ra. The Morocco coastal aquifer is generally oxic, exhibits a range of salinity and water types (Cl- 163-2120mg/L, median 932mg/L), and exhibits Ca/Na ratios above the seawater value, typical of monovalent-divalent cation exchange (base-exchange reactions) in coastal aquifers. In contrast, the Atlantic Coastal Plain aquifers are anoxic, sulfate-reducing, cover a wider salinity range (Cl- 5-9890mg/L, median 800mg/L) representing a transition between Na-HCO3- and Na-Cl- waters, and exhibit Ca/Na ratios below that of modern seawater typical of reverse base-exchange reactions. Possible salinity sources in the Morocco coastal aquifer include seawater intrusion, Mesozoic evaporites, other natural saline waters, and/or wastewater, whereas the Atlantic Coastal Plain is primarily affected by old seawater present in the aquifer system. Radium activities are generally low and vary significantly within each aquifer, for example 226Ra ranges from 1.8-27.7mBq/L in the Morocco coastal aquifer (median 8.1mBq/L) and 1.9-214mBq/L in the Atlantic Coastal Plain (median 18.9mBq/L). The highest Ra activities were observed in the most saline wells sampled in the Atlantic Coastal Plain. At total dissolved solids (TDS) concentrations above an apparent threshold of ~5000mg/L, radium activities increase in a generally linear fashion with salinity in the Atlantic Coastal Plain, broadly comparable to previous studies indicating a threshold range of ~3000-10,000mg/L. At lower TDS concentrations, water-rock interaction processes that vary with local aquifer conditions appear to control Ra distribution rather than merely salinity. In the Morocco coastal aquifer, adsorption of Ra and coprecipitation with secondary barite are apparently favorable to control Ra levels in groundwater. Radium removal in the anoxic Atlantic Coastal Plain aquifers appears to be associated with adsorption and/or exchange processes, with the additional possibility of barite precipitation in the Cape Fear aquifer indicated by barite saturation. Overall, the locally-variable factors that can control Ra sources and mobility in fresh to brackish groundwater at near-neutral pH include variation in solid-phase radioactivity, redox state affecting adsorption sites, availability of competing divalent cations, and barite saturation.

UR - http://www.scopus.com/inward/record.url?scp=84886780740&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84886780740&partnerID=8YFLogxK

U2 - 10.1016/j.apgeochem.2013.09.004

DO - 10.1016/j.apgeochem.2013.09.004

M3 - Article

AN - SCOPUS:84886780740

VL - 38

SP - 161

EP - 175

JO - Applied Geochemistry

JF - Applied Geochemistry

SN - 0883-2927

ER -