Keld A. Jensen

Release of VOCs and Particles During Use of Nanofilm Spray Products

Here, we present emission data on VOCs and particles emitted during simulated use of four commercial nanofilm spray products (NFPs) used for making easy-to-clean or self-cleaning surfaces on floors, ceramic tiles, and windows. The aim was to characterize the emitted VOCs and to provide specific source strength data for VOCs and particles released to the airduring use of the products. Containers with NFP were mounted on a spray-stand inside a closed stainless steel chamber with no air exchange. NFPs were sprayed in amounts corresponding to 1 m2 surface toward a target plate at a distance of 35 cm. Released VOCs were measured by a combination of air sampling on Tenax TA adsorbent followed by thermal desorption GC/MS and GC/FID analysis and real time measurements using a miniature membrane inlet mass spectrometer. Particles were measured using a fast mobility particle sizer and an aerosol particle sizer. A number of VOCs were identified, including small alcohols, ketones and ethers, chlorinated acetones, a perfluorinated silane, limonene, and cyclic siloxanes. The number of generated particles was on the order of 3 x 10(8) to 2 x 10(10) particles/m3 per g sprayed NFP and were dominated by nanosize particles.

The Okélobondo natural fission reactor, southeast Gabon: Geology, mineralogy, and retardation of nuclear-reaction products

Nuclear fission reactors occur in the Oklo-Okelobondo uranium deposit in southeast Gabon. The Okelobondo reactor zone (RZOKE, ∼310 m depth) was the last reactor zone to be excavated before mining was terminated in December 1997. RZOKE is situated at the base of a 2.5 m deep and 2.7 m wide reactor synform located between the FA sandstone and hydrothermally altered black shales—argile de pile—of the FB Formation. The reactor synform developed by hydrothermal dissolution of the FA sandstone during criticality at ca. 2 Ga. The core of RZOKE is up to ∼55 cm thick and contains ≤90 vol% uraninite (≤91.24 ± 0.91 wt% UO 2 and ≤7.22 ± 0.53 wt% PbO) embedded in a matrix of Si-rich illite (6.08 to 7.91 Si per formula unit [p.f.u.]). The argile de pile (typically ≤60 cm) consists mainly of donbassitic chlorite (7.84 to 8.07 octahedrally coordinated Al p.f.u.) cut by fine illite veinlets. Fe-rich chlorite (0.708 to 1.427 Fe p.f.u.) is abundant at the edges of the reactor zone. Organic matter in both the reactor zone and near-field surroundings played an important role in the enhancement of porosity and stabilization of U during formation and operation of RZOKE. Fissiogenic Zr, Ce, Nd, and Th (daughter of 240 Pu and 236 U generated by neutron-capture reactions) are well retained in uraninite and (U,Zr)-silicate. The (U,Zr)-silicate formed during local migration of Zr, Sr, U, Pu, and lanthanide fission products during reactor criticality. Fissiogenic Ru, including 99 Ru—a daughter of 99 Tc, was mainly retained as ruthenium arsenide (± Pb, Co, Ni, and S). Although RZOKE generally appears well preserved, partially dissolved galena and uraninite, as well as the presence of accessory anglesite(?) and lead-uranyl sulfate hydroxide hydrate, suggest that recently observed deep, oxidized groundwaters have begun to interact with RZOKE.

REE mobility in groundwater proximate to the natural fission reactor at Bangombé (Gabon)

The natural nuclear fission reactor at Bangombe is located at a depth of approximately 12 m and has undergone supergene weathering and chemical exchange with groundwater under moderately oxidizing conditions. This reactor has been studied as an analogue for the migration of radionuclides in a geologic repository. Five water samples were taken from a drill hole in the reactor zone and from drill holes that are situated along the direction of the groundwater flow. Dissolution of phosphates in the weathering profile provided an important mechanism for the mobilization of phosphorous and REE. This phosphorous allowed the formation of secondary minerals, e.g., phosphatian coffinites and Fe-uranyl phosphate hydroxide hydrates. The filtered groundwaters (dissolved phase) obtained directly from the reactor zone had anomalous 143Nd/146Nd, 145Nd/146Nd and 149Sm/147Sm isotope ratios of 0.7235, 0.4933 and 0.843, respectively, confirming mixing between a fissiogenic and normal REE component. In this dissoved phase, a small fraction of the Nd (2.3 at.%) is of fissiogenic origin. The suspended loads (filtered particulates) of the same groundwater from within the reactor show similar isotopic anomalies with a fissiogenic Nd contribution of 3.2 at.%. Similar fissiogenic Nd contributions are observable for groundwater samples from outside the reactor zone (3 m distance). Both dissolved and suspended load samples from the more distant well (25 m) have normal isotopic ratios. Thus, the prevailing physico-chemical conditions within this groundwater system allow the migration of the fissiogenic REE over at least 3 m but less than 25 m. Although REE phases are abundant in the reactor zone, the REE concentrations of the water in contact with the sediments of this zone are very low (<17 ppt). The most important lanthanide- and actinide-bearing phases are uraninite, coffinites and Fe-uranyl phosphate hydroxide hydrate. The presence of all of these phases retards the mobility of the fissiogenic lanthanides and actinides.

Time-response relationship of nano and micro particle induced lung inflammation. Quartz as reference compound

An increasing number of engineered particles, including nanoparticles, are being manufactured, increasing the need for simple low-dose toxicological screening methods. This study aimed to investigate the kinetics of biomarkers related to acute and sub-chronic particle-induced lung inflammation of quartz. Mice were intratracheal instilled with 50 µg of microsized or nanosized quartz. Acute inflammation was assessed 1, 2, 4, 8, 16 or 48 hours post exposure, whereas sub-chronic inflammation was investigated 3 months after exposure. Markers of acute inflammation in the bronchoalveolar lavage fluid (BALF) were neutrophils (PMN), tumor necrosis factor-alfa (TNF-α), interleukin (IL)-1β, macrophage inflammatory protein-2 (MIP-2), keratinocyte derived chemokine (KC) and total protein, which were all close to maximum 16 hours post instillation. No major differences were seen in the time-response profiles of nano- and micro-sized particles. The potency of the two samples cannot be compared; during the milling process, a substantial part of the quartz was converted to amorphous silica and contaminated with corundum. For screening, BALF PMN, either TNF-α or IL-1β at 16 hours post instillation may be useful. At 3 months post instillation, KC, PMN and macrophages were elevated. Histology showed no interstitial inflammation three months post instillation. For screening of sub-chronic effects, KC, PMN, macrophages and histopathology is considered sufficient.

U6+ phases in the weathering zone of the Bangombé U-deposit: observed and predicted mineralogy

Summary The mineralogy of the supergene-weathered Bangombé natural fission reactor (RZB) and surrounding uranium deposit has been analyzed and compared with the thermodynamically predicted minerals based on groundwater compositions. The primary U-minerals are uraninite UO2+x and minor coffinite (U[SiO4]·nH2O); sometimes with phosphorous. The U6+ minerals include fourmarierite Pb1−x[(UO2)4O3−2x(OH)4+2x]·4(H2O), bassetite (Fe1−x2+Fex3+[(UO2)(PO4)]2(OH)x·8−xH2O); possibly associated with U(HPO4)2·2H2O and/or chernikovite ((H3O)2[(UO2)(PO4)]2·6H2O); torbernite (Cu[(UO2)(PO4)]2· 8-12H2O), Ce-françoisite-(Nd) (REE(UO2)3O(OH)(PO4)2· 6H2O), and uranopilite ((UO2)6(SO4)O2(OH)6(H2O)6·8H2O). Autunite (Ca[(UO2)(PO4)]2·10-12H2O) has also been reported. Thermodynamic equilibrium modeling was completed using Geochemists Workbench¯ with an expanded data base and the groundwater composition (−112 mV ≤ Eh ≤ 143 mV; pH = 5.96) at the base of RZB in drill-hole BAX03. The new ΔG0f,298.15 data were obtained from the literature or estimated using the polyhedral contribution method. Based on the updated database, Eh-pH diagrams predict that coffinite, U(HPO4)2·H2O and UOF2·H2O are the only stable U4+ phases and that uranopilite, torbernite and bassetite will become stable during oxidative alteration. Except from UOF2·H2O, this is in accord with mineralogical observations. The role of Cu was predicted from log aCu-pH diagrams, which predicts that torbernite is stable at log aCu=3.98×10−14 and pH≥2.2 at Eh=143 mV in BAX03 groundwaters. At Eh = −112 mV, torbernite is stable at pH>5.5. Soddyite ((UO2)2SiO4·2H2O) was predicted to form at the expense of coffinite, but soddyite has not been identified at Bangombé. Previous blind prediction modeling, often omitting P and S, had only predicted soddyite and haiweeite (Ca(UO2)2[Si5O12(OH)2]·4-5H2O) and hence, failed to predict the U6+ minerals observed at Bangombé. The results stress the importance of SO42− and PO43− resulting from dissolution of accessory apatite, monazite and sulfides in the retardation of U owing to the formation of U6+ sulfates and phosphates.

Crandallites and Coffinite: Retardation of Nuclear Reaction Products at the Bangombé Natural Fission Reactor

Various REE-Sr-(Pb)-crandallites, uraninite, and coffinite in the near-field of the 2 Ga old super-gene-altered Bangombe U-deposit and its natural fission reactor (RZB) have been examined. The crandallite minerals may have formed during syncriticality host-rock alteration, continous alteration of phosphates, episodic Pb-loss and/or supergene weathering. Coffinitization with P 2 O 5 and SO 4 -substitution has occurred immediately below RZB and resulted in extensive loss of U (≤ 46%) and enrichment of Ce (≤ 190%) and Nd (≤ 780%). Additional loss of U during coffinitization also may have occurred due to dissolution. Current alteration under oxidizing conditions has resulted in partial dissolution of uraninite and coffinite and the formation of uranyl phases. Despite supergene alteration, the hydrogeochemistry (3.09 ppt U [ 235 U/ 238 U = 0.7012 to 0.7019%], 4.96 ppt Ce, and 1.92 ppt Nd) suggests a remarkable retardation of lanthanides and depleted uranium by REE-Sr-(Pb)-crandallites, uraninite, coffinite, and uranyl phases at RZB.

Oxygen isotopic composition of nano-scale uraninite at the Oklo-Okélobondo natural fission reactors, Gabon

Abstract High spatial resolution (10-30 μm), in situ oxygen isotopic analyses by secondary ion mass spectrometry (SIMS), coupled with high-resolution transmission electron microscopy (HRTEM), were used to show that uraninite from the Oklo-Okélobondo natural fission reactors that occur in near surface environments, have low δ18O values and nanotextures that are consistent with interaction with ground water. These low δ18O values (-14.4 to -8.5‰) suggest that the minerals exchanged with meteoric groundwater. In contrast, reactor zones that occur at depth have largely retained their original O isotopic composition (-10.2 to -5.6‰) and uraninites are well-crystallized and essentially defect-free. These observations clearly demonstrate that by combining both HRTEM and in situ O isotopic analyses by SIMS, it is possible to characterize the nano-scale porosity and postdepositional alteration of U-bearing phases.

In Situ Isotopic Analysis of Uraninite Microstructures from the Oklo-Okélobondo Natural Fission Reactors, Gabon

Uranium deposits can provide important information on the long-term performance of radioactive waste forms because uraninite (UO 2+X ) is similar to the UO 2 in spent nuclear fuel. The Oklo-Okelobondo U-deposits, Gabon, serve as natural laboratory where the long-term (hundreds to billions of years) migration of uranium and other radionuclides can be studied over large spatial scales (nm to km). The natural fission reactors associated with the Oklo- Okelobondo U-deposits occur over a range of depths (100 to 400 m) and provide a unique opportunity to study the behavior of uraninite in near surface oxidizing environments versus more reducing conditions at depth. Previously, it has been difficult to constrain the timing of interaction between U-rich minerals and post-depositional fluids. These problems are magnified because uraninite is susceptible to alteration, it continuously self-anneals radiation damage, and because these processes are manifested at the nm to μm scale. Uranium, lead and oxygen isotopes can be used to study fluid-uraninite interaction, provided that the analyses are obtained on the micro-scale. Secondary ionization mass spectrometry (SIMS) permits in situ measurement of isotopic ratios with a spatial resolution on the scale of a few μm. Preliminary U-Pb results show that uraninite from all reactor zones are highly discordant with ages aaproaching the timing of fission chain reactions (1945±50 Ma) and resetting events at 1180±47 Ma and 898±46 Ma. Oxygen isotopic analyses show that uraninite from reactors that occur in near surface environments (δ 18 O= −14.4‰ to −8.5‰) have reacted more extensively with groundwater of meteoric origin relative to reactors located at greater depths (μ 18 O= −10.2‰ to −7.3‰). This study emphasizes the importance of using in situ high spatial resolution analysis techniques for natural analogue studies.

Toxicity of pristine and paint-embedded TiO2 nanomaterials:

Little is known on the toxicity of nanomaterials in the user phase. Inclusion of nanomaterials in paints is a common nanotechnology application. This study focuses on the toxicity of dusts from sanding of paints containing nanomaterials. We compared the toxicity of titanium dioxide nanomaterials (TiO2NMs) and dusts generated by sanding boards coated with paints with different amounts of two different types of uncoated TiO2NMs (diameters:10.5 nm and 38 nm). Mice were intratracheally instilled with a single dose of 18, 54 and 162 µg of TiO2NMs or 54, 162 and 486 µg of sanding dusts. At 1, 3 and 28 days post-instillation, we evaluated pulmonary inflammation, liver histology and DNA damage in lung and liver. Pulmonary exposure to both pristine TiO2NMs and sanding dusts with different types of TiO2NMs resulted in dose-dependently increased influx of neutrophils into the lung lumen. There was no difference between the sanding dusts from the two paints. For all exposures but not in vehicle controls, mild histological lesions were observed in the liver. Pulmonary exposure to pristine TiO2NMs and paint dusts with TiO2NMs caused similar type of histological lesions in the liver.