Mobilization of actinides by dissolved organic compounds at the Nevada Test Site

Zhao, Pihong; Zavarin, Mavrik; Leif, Roald N.; Powell, Brian A.; Singleton, Michael; Lindvall, Rachel E.; Kersting, Annie B.

doi:10.1016/j.apgeochem.2010.12.004

Cited by 51 publications

(35 citation statements)

References 42 publications

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“…Pu(IV) sorption on goethite decreased by 30% in the presence of 240 mg/L natural DOC [36], consistent with observed effects of DOC on Pu(IV) sorption in the presence of zeolitized tuff [44]. In addition, increasing concentrations of carbonate ligands to 100 meq/L (total alkalinity) had little effect on Pu(IV) or Pu(V) sorption to goethite.…”

Section: Effects Of Carbonate Speciessupporting

confidence: 85%

Sorption coefficients and molecular mechanisms of Pu, U, Np, Am and Tc to Fe (hydr)oxides: A review

Kaplan

2012

Journal of Hazardous Materials

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Section: Effects Of Carbonate Speciessupporting

confidence: 85%

Sorption coefficients and molecular mechanisms of Pu, U, Np, Am and Tc to Fe (hydr)oxides: A review

Kaplan

2012

Journal of Hazardous Materials

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“…Activities associated with underground nuclear testing and tunnel construction on Rainier Mesa have altered the tunnel water geochemistry, resulting in much higher dissolved organic matter (DOM) content (15-19 mg C/L) than local spring water (0.2 mg C/L) (Zhao et al 2011). The source of the DOM is believed to be tunnel lagging, wood debris, drilling fluids, and their microbial decomposition products.…”

Section: U12 Tunnel Systemmentioning

confidence: 99%

Colloid-Facilitated Transport of Plutonium at the Nevada Test Site, NV, USA

Kersting

Zavarin

2011

Actinide Nanoparticle Research

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Increasing observations of subsurface actinide transport has reinforced the need for a basic geochemical and hydrologic understanding of how these contaminants are transported in groundwater. At the Nevada Test Site, NV, USA, low-levels of plutonium have been shown to migrate on the scale of kilometers. At all but one sampling location the Pu is associated with the colloidal fraction (<1 mm) consisting predominantly of clays and zeolites. The majority of the Pu ($70%) is associated with the smallest nanoparticle (e.g., colloid) size fraction of 10-100 nm and in one case was identified as associated with a clay colloid. At one unique sampling site, Pu is predominantly associated with dissolved organic matter. Monitoring at over 20 contaminated groundwater sites at the NTS suggests that low-levels of Pu can be mobilized either via colloid-facilitated transport in fractured rock or as a result of aqueous Pu stabilization by anthropogenic levels of dissolved organic matter. Nevertheless, activities above the EPA's Maximum Contaminant Level (MCL) for alpha-emitting radionuclides (15 pCi/L, 0.56 Bq/L) have been measured at only two locations at the NTS.

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“…Dissolved organic matter (DOM) is the main vehicle of organic carbon (OC) and nutrient transport to the subsoil (Kaiser and Kalbitz, 2012;Kalbitz et al, 2000). There it stimulates key biogeochemical processes including heterotrophic microbial activity (Fontaine et al, 2007), mineral transformation and organic and inorganic nutrient and contaminant mobilization (Chorover et al, 2007;Polubesova and Chefetz, 2014;Zhao et al, 2011). Interactions with subsoil surfaces act to stabilize DOM against advective transport and microbial degradation (Eusterhues et al, 2014;Kalbitz et al, 2000;Lutzow et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Wet-dry cycles impact DOM retention in subsurface soils

Olshansky¹,

Root²,

Chorover³

2017

Preprint

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Abstract. Transport and reactivity of carbon in the critical zone are highly controlled by reactions of dissolved organic matter (DOM) with subsurface soils, including adsorption, transformation and exchange. These reactions are dependent on frequent wet-dry cycles common to the unsaturated zone, particularly in semi-arid regions. To test for an effect of wet-dry cycles on DOM interaction and stabilization in subsoils, samples were collected from subsurface (Bw) horizons of an Entisol and an Alfisol from the Catalina-Jemez Critical Zone Observatory and sequentially reacted (four batch steps) with DOM extracted from the corresponding soil litter layers. Between each reaction step, soils either were allowed to air dry (<q>wet-dry</q> treatment) before introduction of the following DOM solution or were maintained under constant wetness (<q>continually-wet</q> treatment). Microbial degradation was the dominant mechanism of DOM loss from solution for the Entisol subsoil, which had higher initial organic C content, whereas sorptive retention predominated in the lower C Alfisol subsoil. For a given soil, bulk dissolved organic C losses from solution were similar across treatments. However, a combination of Fourier transform infrared (FTIR) and near edge X-ray absorption fine structure (NEXAFS) spectroscopic analyses revealed that wet-dry treatments enhanced the interactions between carboxyl functional groups and soil particle surfaces and scanning transmission X-ray microscopy (STXM) data suggested that cation bridging by Ca2+ was the primary mechanism for carboxyl association with soil surfaces. STXM data also showed that spatial fractionation of adsorbed OM on soil organo-mineral surfaces was diminished relative to what might be inferred from previously published observations pertaining to DOM fractionation on reaction with specimen mineral phases. This study provides direct evidence of the role of wet-dry cycles in affecting sorption reactions of DOM to a complex soil matrix. In the soil environment, where wet-dry cycles occur at different frequencies from site to site and along the soil profile, different interactions between DOM and soil surfaces are expected and needs to be consider for the overall assessment of carbon dynamics.

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Mobilization of actinides by dissolved organic compounds at the Nevada Test Site

Cited by 51 publications

References 42 publications

Sorption coefficients and molecular mechanisms of Pu, U, Np, Am and Tc to Fe (hydr)oxides: A review

Sorption coefficients and molecular mechanisms of Pu, U, Np, Am and Tc to Fe (hydr)oxides: A review

Colloid-Facilitated Transport of Plutonium at the Nevada Test Site, NV, USA

Wet-dry cycles impact DOM retention in subsurface soils

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