A Porous Flow Model for Steady State Transport of Radium in Groundwater

Davidson, Malcolm R.; Dickson, B.L.

doi:10.1029/wr022i001p00034

Cited by 70 publications

(47 citation statements)

References 27 publications

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“…Radon-222 activity in water may be interpreted as recoil flux from mineral surfaces (Krishnaswami et al, 1982) or more complexly as a combination of recoil and diffusion of Rn from microfractures resulting from a higher effective surface area for Rn relative to Ra (Rama and Moore, 1984;Davidson and Dickson, 1986;Andrews et al, 1989). In this study, 222 Rn is strongly associated with rock type, and in particular, groundwater from the Rolesville Granite exhibits approximately one order of magnitude higher median 222 Rn (Table 3).…”

Section: Radon-222mentioning

confidence: 84%

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Relationships between radium and radon occurrence and hydrochemistry in fresh groundwater from fractured crystalline rocks, North Carolina (USA)

et al. 2009

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a b s t r a c t a r t i c l e i n f oNaturally-occurring radionuclides (uranium, radium, and radon), major dissolved constituents, and trace elements were investigated in fresh groundwater in 117 wells in fractured crystalline rocks from the Piedmont region (North Carolina, USA). Chemical variations show a general transition between two water types: (1) slightly acidic (pH 5.0-6.0), oxic, low-total dissolved solids (TDS) waters, and (2) near neutral, oxic to anoxic, higher-TDS waters. The uranium, radium, and radon levels in groundwater associated with granite (Rolesville Granite) are systematically higher than other rock types (gneiss, metasedimentary, and metavolcanic rocks). Water chemistry plays a secondary role on radium and radon distributions as the 222 Rn/ 226 Ra activity ratio is correlated with redox-sensitive solutes such as dissolved oxygen and Mn concentrations, as well as overall dissolved solids content including major divalent cations and Ba. Since 224 Ra/ 228 Ra activity ratios in groundwater are close to 1, we suggest that mobilization of Ra and Rn is controlled by alpha recoil processes from parent nuclides on fracture surfaces, ruling out Ra sources from mineral dissolution or significant long-distance Ra transport. Alpha recoil is balanced by Ra adsorption that is influenced by redox conditions and/or ion concentrations, resulting in an approximately one order of magnitude decrease (~20,000 to~2000) in the apparent Ra distribution coefficient between oxygensaturated and anoxic conditions and also across the range of dissolved ion concentrations (up to~7 mM). Thus, the U and Th content of rocks is the primary control on observed Ra and Rn activities in groundwater in fractured crystalline rocks, and in addition, linked dissolved solids concentrations and redox conditions impart a secondary control.

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Section: Radon-222mentioning

confidence: 84%

“…Thus, 226 Ra would be more available due to the recoil effect placing it closer to the mineral surface (Davidson and Dickson, 1986); (2) U, being more soluble than Th, could be mobilized by weathering or the groundwater system to provide additional 226 Ra precursors to adsorption sites (e.g. Michel, 1984).…”

mentioning

confidence: 99%

Relationships between radium and radon occurrence and hydrochemistry in fresh groundwater from fractured crystalline rocks, North Carolina (USA)

et al. 2009

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“…Rama and Moore, 1984;Davidson and Dickson, 1986;Tricca et al, 2001). In particular, the activities of radon and radium isotopes are usually high in groundwater as a result of the decay of their parent nuclides in the host aquifer solids (e.g.…”

Section: Introductionmentioning

confidence: 99%

Application of radon and radium isotopes to groundwater flow dynamics: An example from the Dead Sea

et al. 2015

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“…Input from decay of dissolved parent isotopes is generally negligible for Ra because Th isotopes are nearly insoluble in ground water (Langmuir and Herman, 1980), but Ra input from Th decay on aquifer surface coatings can be signi®cant (Davidson and Dickson, 1986;Krishnaswami et al, 1982). Input of Ra into pore¯uid by alpha-recoil depends on the activity and location of the parent isotope relative to the solid±¯uid interface.…”

Section: Radium Geochemistry In Rock±water Systemsmentioning

confidence: 99%

Radium geochemistry of ground waters in Paleozoic carbonate aquifers, midcontinent, USA

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Binz

et al. 2001

Applied Geochemistry

114

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The purpose of this study was to elucidate the processes controlling the distribution and behavior of the longerlived Ra isotopes in continuous Paleozoic carbonate aquifers of parts of Missouri, Kansas, and Oklahoma. Activities of ( 228 Ra) and ( 226 Ra) were analyzed in fresh and saline ground waters, brines, and rocks. The¯uids have a wide salinity range (200±250,000 mg l À1 total dissolved solids). The ( 226 Ra) activity ranges from 0.66±7660 dpm kg À1 and correlates with salinity and other alkaline earth element (Ca, Sr, and Ba) concentrations. The range of ( 228 Ra:226 Ra) ratios in the¯uids (0.06±1.48) is similar to that in the aquifer rocks (0.21±1.53). The relatively low mean¯uid ( 228 Ra: 226 Ra) ratio (0.30) re¯ects the low Th:U ratio of the predominant carbonate aquifer rock. Radium occurs mostly (r77%) as Ra 2+ species in the¯uids. Salinity-dependent sorption±desorption processes (with log K values from 10 0 ±10 4 and negatively correlated with salinity), involving Th-enriched surface coatings on aquifer¯ow channels, can explain the rapid solid±¯uid transfer of Ra isotopes in the system and the correlation of Ra with salinity. 7

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A Porous Flow Model for Steady State Transport of Radium in Groundwater

Cited by 70 publications

References 27 publications

Relationships between radium and radon occurrence and hydrochemistry in fresh groundwater from fractured crystalline rocks, North Carolina (USA)

Relationships between radium and radon occurrence and hydrochemistry in fresh groundwater from fractured crystalline rocks, North Carolina (USA)

Application of radon and radium isotopes to groundwater flow dynamics: An example from the Dead Sea

Radium geochemistry of ground waters in Paleozoic carbonate aquifers, midcontinent, USA

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