Ala Aldahan

A review on speciation of iodine-129 in the environmental and biological samples

As a long-lived beta-emitting radioisotope of iodine, (129)I is produced both naturally and as a result of human nuclear activities. At present time, the main part of (129)I in the environment originates from the human nuclear activity, especially the releases from the spent nuclear fuel reprocessing plants, the (129)I/(127)I ratios have being reached to values of 10(-10) to 10(-4) in the environment from 10(-12) in the pre-nuclear era. In this article, we review the occurrence, sources, inventory, and concentration level of (129)I in environment and the method for speciation analysis of (129)I in the environment. Measurement techniques for the determination of (129)I are presented and compared. An overview of applications of (129)I speciation in various scientific disciplines such as radiation protection, waste depository, and environmental sciences is given. In addition, the bioavailability and radiation toxicity (dose to thyroid) of (129)I are discussed.

A 600‐year annual 10Be record from the NGRIP ice core, Greenland

Understanding the link between the Sun and climate is vital in the current incidence of global climate change, and 10Be in natural archives constitutes an excellent tracer for this purpose. As cosmic rays enter the atmosphere, cosmogenic isotopes like 10Be and 14C are formed. Variations in solar activity modulate the amount of incoming cosmic rays, and thereby cosmogenic isotope production. Atmospherically produced 10Be enters natural archives such as sediments and glaciers by wet and dry deposition within about a year of production. 10Be from natural archives therefore provides information on past solar activity, and because these archives also contain climate information, solar activity and climate can be linked. One remaining question is to what degree 10Be in natural archives reflects production, and to what extent the local and regional environment overprints the production signal. To explore this, 10Be was measured at annual resolution over the last 600 years in a Greenland ice core. Measurement potentials for these samples benefited from the development of a new laboratory method of co-precipitating 10Be with niobium. To diversify geographic location and archive media type, a pioneer study of measuring 10Be with annual resolution in varved lake sediments from Finland was conducted, with samples from the entire 20th century. Pathways of 10Be into lake sediments are more complex than into glacial ice, inferring that contemporary atmospheric conditions may not be recorded. Here, it is shown for the first time that tracing the 11-year solar cycle through lake sediment 10Be variations is possible. Results also show that on an annual basis, 10Be deposition in ice and sediment archives is affected by local environmental conditions. On a slightly longer timescale, however, diverse 10Be records exhibit similar trends and a negative correlation with solar activity. Cyclic variability of 10Be deposition persisted throughout past grand solar minima, when little or no sunspot activity was recorded. 10Be levels indicate that although solar activity has been high during the 20th century, levels are not unprecedented in the investigated 600 years. Aerosol 10Be/7Be values indicate possible influence of stratosphere-troposphere exchange on isotope abundance and the production signal.

Alteration of detrital Fe-Ti oxides in sedimentary rocks

Scanning electron microscope study has revealed that in Proterozoic sandstones, shales, and carbonate rocks of the Visingso Group in southern Sweden, detrital Fe-Ti oxides have undergone alteration by dissolution and/or replacement mainly by titanium oxides, hematite (reddish rocks), or pyrite (greenish sandstones, shales, and carbonate rocks). The titanium oxides occur as either poorly crystalline masses, cryptocrystalline aggregates, or discrete, euhedral crystals of anatase, brookite, and rutile that attain a variety of crystal habits. Microprobe analyses have shown that the alteration of ilmenite occurs through several intermediate phases, each successively enriched in titanium and depleted in iron, to an almost pure form of TiO 2 . Some of the iron and titanium which is released during alteration of the Fe-Ti oxides is incorporated in associated clay minerals.

Multiradionuclide evidence for the solar origin of the cosmic-ray events of ᴀᴅ 774/5 and 993/4

The origin of two large peaks in the atmospheric radiocarbon (14C) concentration at AD 774/5 and 993/4 is still debated. There is consensus, however, that these features can only be explained by an increase in the atmospheric 14C production rate due to an extraterrestrial event. Here we provide evidence that these peaks were most likely produced by extreme solar events, based on several new annually resolved 10Be measurements from both Arctic and Antarctic ice cores. Using ice core 36Cl data in pair with 10Be, we further show that these solar events were characterized by a very hard energy spectrum with high fluxes of solar protons with energy above 100 MeV. These results imply that the larger of the two events (AD 774/5) was at least five times stronger than any instrumentally recorded solar event. Our findings highlight the importance of studying the possibility of severe solar energetic particle events.

Atmospheric interactions at northern high latitudes from weekly Be-isotopes in surface air

We present weekly 7Be (from 1972 to 1995), and weekly/seasonal 10Be (for 1994) data in surface air from ground level stations in Sweden with a coverage of most of the northern high latitudes (56 degrees-68 degrees N). Our Be data are regionally representative and reveal seasonal variation and coupling with tropospheric air mass from middle-low latitudes. The Be data also suggests a few percent, and sometimes episodic, incursion of stratospheric air mass. Frequent precipitation depletes the Be isotopes in the air, but cyclone events contribute to enrichments. A strong coherence between the 7Be record and short-term (monthly-seasonal) change in solar activity is observed which introduces a new mechanism for driving the amplitude of seasonal variation.

Atmospheric impact on beryllium isotopes as solar activity proxy

Reconstructing solar activity variability beyond the time scale of actual measurements provides invaluable data for modeling of past and future climate change. The 10 Be isotope has been a primary ...

DISTRIBUTION OF BERYLLIUM BETWEEN SOLUTION AND MINERALS (BIOTITE AND ALBITE) UNDER ATMOSPHERIC CONDITIONS AND VARIABLE PH

Abstract Biotite and albite grains having a size range from 20 to 124 μm were suspended in Be-bearing solutions at pH 2 to 9 for periods of 30 min to 20 days. The amount of Be sorbed onto biotite is up to 40 times higher than onto albite under the same conditions and pH≤7. At pH≤6, the distribution of Be between solution and solids is related to sorption but at pH>6, the solute concentration is strongly controlled by solubility of Be(OH) 2-solid . Because of this solubility control, the calculation of a distribution coefficient ( K d = S / C , where S is Be sorbed at equilibrium per mass or specific surface area of sorbent, and C is the Be concentration in solution at equilibrium) seems to be valid only at pH≤6. The K d increases with decreasing suspended particle concentration (from 0.2 to 2.0 g l −1 ) for both minerals. For biotite the K d also increases with the fine (20–63 μm) relative to the coarse (63–124 μm) size fraction even upon normalization to specific surface area. The relatively small amount of Be sorbed onto albite at pH 2 and 4 limited extensive evaluation and comparison. The rate of Be sorption onto biotite follows a logarithmic function and ranges from 0.8 to 1.0×10 −11 mol cm −2 s −1 in pH 2 and 6 solutions, respectively. The time-variation of sorbed Be onto albite was insignificant with increasing pH. The sorption of Be onto biotite partly relates to the kinetics of cation release. The results of experiments are discussed with respect to some examples of the distribution of Be isotopes in continental aquatic systems.

Petrological modifications in granitic rocks from the siljan impact structure: evidence from cathodoluminescence

Abstract Cathodoluminescence (CL) and microprobe analyses were performed on quartz, plagioclase and K-feldspar from granitic rocks in the Siljan impact area, central Sweden. In the upper 2200 m and in the vicinity of the Gravberg-1 well, secondary reddish luminescing quartz and brownish luminescing albite (Ab > 98%) and K-feldspar (Or > 95%) are the dominant minerals. Primary magmatic quartz, plagioclases (oligoclase-andesine) and K-feldspar show blue, yellowish and bluish luminescence colours, respectively. The reddish luminescence colour of quartz is interpreted to have been induced by the shock heating episode of the impact and subsequent elevated temperature in the granites. The impact shock pressure effects, as shown by shatter cones and planar features, were retained within granite dominated by blue luminescing quartz. Most alteration of the feldspar took place during the cooling episode that followed the impact heating. Post-impact fracturing facilitated the infiltration of meteoric water, which has further enhanced alteration of feldspars.

Iodide and iodate (129I and 127I) in surface water of the Baltic Sea, Kattegat and Skagerrak.

Despite the common incorporation of iodine in the biological cycle and occurrence of huge contamination of the radioactive isotope (129)I in the Baltic Proper, Skagerrak and Kattegat, there is no data on chemical speciation of iodine in these waters. We here present first time data on iodine isotopes (129)I and (127)I species as iodide and iodate in surface seawater samples collected from 16 locations in August 2006 and 19 locations in April 2007 in the Baltic Proper, Skagerrak and Kattegat. After extensive separation methods, the isotopes concentrations were determined using accelerator mass spectrometry (AMS) technique for the (129)I and inductively coupled plasma mass spectroscopy (ICP-MS) for (127)I. High concentrations of both isotopes species were found in the Skagerrak-Kattegat basins, whereas the values in the Baltic Proper are low for both species. The ratios of (129)I(-)/(129)IO(3)(-) and (127)I(-)/(127)IO(3)(-) significantly increase from south to central Baltic Sea, and iodide (both isotopes) appears as the predominant inorganic iodine species along the Baltic Sea. The results show insignificant change in (129)I and (127)I speciation and suggest that reduction of iodate and oxidation of iodide in Skagerrak and Kattegat may be a slow process. Additionally, the positive correlation between salinity and iodide and iodate (both isotopes) may reflect effective control of Skagerrak water mass on iodine distribution in surface water of the Baltic Sea.

A high-resolution Be-10 profile from deep sea sediment covering the last 70 ka: Indication for globally synchronized environmental events

We present a high-resolution Be-10 profile from deep sea sediments (sampled from Hole 502B in the Caribbean sea) that strongly resembles the 10Be record in ice core profiles, particularly the Vosto ...