Radiolyijyn määritys sedimenttien ajoitusta varten

Osa uraanisarjaan kuuluvan Ra-226:n hajotessa muodostuvasta Rn-222:sta tihkuu maasta ilmakehään. Rn-222:n hajotessa edelleen muodostuu radiolyijyä (Pb-210), joka päätyy laskeumassa maahan ja vesistöihin. Vesistöissä Pb-210 sitoutuu sedimentoituviin partikkeleihin ja päätyy sedimenttiin. Sedimentin radiolyijy koostuu tukeutuneesta sedimentin Ra-226:n hajotessa syntyvästä radiolyijystä sekä tukeutumattomasta radiolyijystä, joka on peräisin laskeumasta. Tukeutumatonta radiolyijyä voidaan käyttää sedimenttien ajoitukseen aina noin 150 vuoden päähän. Radiolyijyajoituksessa käytetään malleja, joissa oletetaan vakioksi sedimentoitumisnopeus ja radiolyijyn vuo sedimenttiin, tukeutumattoman radiolyijyn aktiivisuus sedimentin pinnalla tai pelkästään radiolyijyvuo. Radiolyijy on määritetty perinteisesti alfaspektrometrisesti tyttärentyttärensä Po-210:n kautta. Tämä menetelmä vaatii työlään radiokemiallisen erottelun. Nykyisin myös gammaspektrometriaa voidaan hyödyntää radiolyijyn määritykseen suoraan sedimenttinäytteestä, mutta radiolyijyn alhaisella gammaenergialla gammasäteilyn itseabsorptio näytteeseen voi olla merkittävää ja vaihdella näytteen alkuainekoostumuksen mukaan. Radiolyijyn gammaenergia on alhainen ja intensiteetti pieni, mikä vaikeuttaa gammaspektrometrista määritystä. Lisäksi tunnetaan useita menetelmiä, joissa radiolyijy määritetään tyttärensä Bi-210:n tai sen omien beetahiukkasten kautta. Myös näiden menetelmien radiokemialliset erottelut ovat työläitä. Pro gradu -työn kokeellisessa osassa määritettiin radiolyijy Umbozeron ja Pitkälammen sedimenteistä alfa- ja gammaspektrometrisesti ja tehtiin sedimenteille radiolyijyajoitus. Gammaspektrometriassa tutkittiin itseabsorptiota Cutshallin menetelmällä. Työn tavoitteena oli kehittää radiolyijyn määrittämiseksi uusi menetelmä, joka olisi vähemmän työläs kuin alfaspektrometria mutta herkempi kuin gammaspektrometria. Uudessa menetelmässä hyödynnetään 3 M Emporen valmistamaa kiinteäfaasiuuttosuodatinta Strontium Diskiä, joka uuttaa strontiumin laimeasta typpihappoliuoksesta kvantitatiivisesti. Radiolyijyn havaittiin pidättyvän Strontium Diskiin. Radiolyijy mitattiin Strontium Diskeistä nestetuikelaskennalla. Strontium Diskiä hyödyntävässä uudessa menetelmässä saatiin useimmilla näytteillä pienemmät radiolyijypitoisuudet kuin alfaspektrometrisesti määritettynä, mikä voi johtua vaimenemisesta tai siitä, ettei radiolyijy pidättynyt Strontium Diskiin kvantitatiivisesti. Menetelmä vaatii vielä kehittelyä, mutta sen etuna on nestetuikelaskennan korkea efektiiviisyys radiolyijylle ja alfaspektrometristä määritystä pienempi työmäärä. Alfa- ja gammaspektrometrian tulokset vastasivat hyvin toisiaan. Itseabsorptio ei ollut gammaspektrometriassa merkittävää työssä mitatuilla enintään noin 5 gramman sedimenttinäytteillä. Umbozeron sedimentille saatiin alfaspektrometrisesti ja uudella menetelmällä tuloksia, jotka vastasivat aiemmin julkaistuja. Pitkälammen sedimentti oli sekoittunut, eikä sitä voitu ajoittaa

Sorption of inorganic radiocarbon on iron oxides

The sorption of inorganic radiocarbon on goethite, hematite and magnetite was studied as a function of carbon concentration, pH and ionic strength. It was discovered that the sorption of radiocarbon on magnetite was negligible in all studied conditions. The distribution coefficients of radiocarbon on hematite and goethite decreased with increasing pH whereas the ionic strength had only a slight decreasing effect on radiocarbon sorption. The sorption on goethite and hematite was modelled with PhreeqC using a generalized double-layer surface complexation model.Peer reviewe

Behaviour of Metals during Bioheap Leaching at the Talvivaara Mine, Finland

The behaviour of base metals Ni, Zn, Cu, Co, Fe, and Mn, potentially toxic metals Pb, Cr, and Cd, and the radioactive elements, U and Th, in the Talvivaara mining process, Finland has been studied by tracing metal concentrations from the black schist ore, through ores subjected to bioheap leaching of varying duration, to pregnant leach solution (PLS), and solid process waste material deposited on site in gypsum waste ponds. It is apparent that Zn, Cu, Co, and Cd are leached from the ore in a similar manner and recovered efficiently in the PLS; however, Ni, though leached, was also found in the gypsum pond at relatively high concentrations. Relatively little Pb is released from the ore, but the small fraction that is mobilised accumulates in the gypsum pond. Of the radioactive constituents, Th is essentially immobile, whereas U is readily leached from the ore, again accumulating in gypsum pond waste. In addition, a laboratory-based sequential leach test was applied to assess the future leaching potential of metals from residual ore and process waste material under different environmental conditions.Peer reviewe

Radionuclide and heavy metal redistribution at the former pilot-scale apatite plant in Sokli, northern Finland

A new phosphate mine is being planned at Sokli in northern Finland. In the late 1970s, pilot-scale mining and mineral processing took place at the site. The mobilisation of radionuclides and heavy metals from the mill tailings was examined in order to assess the potential environmental impact of past and future mining activities. Given the considerable amount of apatite still present, the waste material does not represent true tailings. Variations in abundance probably represent material discharges to the tailings rather than mobilization of the elements from the tailings themselves. No indication of heavy-metal migration was found. Extraction results suggest that only a small proportion of cadmium is in exchangeable form. Elements that are partly soluble under weakly-acidic conditions include copper, zinc, cadmium, uranium and lead. However, most of the elements are tightly bound to the sample matrix and therefore not easily released to the environment.Peer reviewe

Physical activity and health-related quality of life among high-risk women for type 2 diabetes in the early years after pregnancy

Background Previous studies have shown that physical activity (PA) correlates positively with health-related quality of life (HRQoL) in the general population. Few studies have investigated associations between device-measured PA and HRQoL among premenopausal women at risk for type 2 diabetes (T2D). In addition to physical well-being, general well-being improved by PA has been suggested to strengthen PA's benefits in reducing metabolic diseases. The aim of this study was to examine the associations between PA and HRQoL (general and dimensions) among high-risk women in the early post-pregnancy years when T2D risk is highest and to estimate whether current obesity or prior gestational diabetes (GDM) modified these associations. Methods This cross-sectional study of high-risk women [body mass index (BMI) >= 30 kg/m(2) and/or prior GDM)]4-6 years after delivery measured sleep, sedentary time, daily steps, and light (LPA), moderate-to-vigorous (MVPA), and vigorous PA (VPA) with the SenseWear ArmbandTM accelerometer for seven days and HRQoL with the 15D instrument. Results The analyses included 204 women with a median (IQR) age of 39 (6.0) years and a median BMI of 31.1 kg/m(2) (10.9). 54% were currently obese (BMI >= 30 kg/m(2)), and 70% had prior gestational diabetes (GDM+). Women with obesity had lower PA levels than women with normal weight or overweight (p = 30 kg/m(2)), the associations remained significant only in women without obesity. Among them, sleep, total steps, MVPA, and VPA were positively associated with 15D. Conclusions Higher PA levels are associated with better HRQoL among high-risk women with normal weight and overweight but no differences were found among women affected by obesity in the early years after pregnancy. Trial registration Ethics committees of Helsinki University Hospital (Dnro 300/e9/06) and South Karelian Central Hospital (Dnro 06/08).Peer reviewe

Lifestyle and glycemic health 5 years postpartum in obese and non-obese high diabetes risk women

Aim Women with prior gestational diabetes (GDM) are at increased diabetes risk. This study aimed to assess whether lifestyle is associated with glycemic health of high-risk women 5 years postpartum, taking into account the pre-pregnancy BMI. Methods The RADIEL study enrolled before or in early pregnancy 720 women with pre-pregnancy BMI >= 30 kg/m(2)and/or prior GDM. The follow-up visit 5 years postpartum included questionnaires and measurements of anthropometrics, blood pressure, and physical activity (PA) as well as analyses of glucose metabolism, lipids, and inflammatory markers. We measured body composition (Inbody) and calculated a Healthy Food Intake Index (HFII) from Food Frequency Questionnaires (FFQ). ArmBand measured PA, sedentary time, and sleep. To take into account the diverse risk groups of GDM, we divided the women based on pre-pregnancy BMI over/under 30 kg/m(2). Results Altogether 348 women attended the follow-up. The obese and non-obese women showed similar prevalence of glycemic abnormalities, 13% and 19% (p = 0.139). PA levels were higher among the non-obese women (p <0.05), except for step count, and their HFII was higher compared to the obese women (p = 0.033). After adjusting for age, education, and GDM history, PA and HFII were associated with glycemic health only among obese women. When both lifestyle factors were in the same model, only PA remained significant. PA associated with other markers of metabolic health also among the non-obese women, excluding HbA1c. Conclusion Lifestyle 5 years postpartum was associated with better glycemic health only among the obese high-risk women. PA, however, is essential for the metabolic health of all high-risk women.Peer reviewe

Radionuclide and heavy metal redistribution at the former pilot-scale apatite plant in Sokli, northern Finland

A new phosphate mine is being planned at Sokli in northern Finland. In the late 1970s, pilot-scale mining and mineral processing took place at the site. The mobilisation of radionuclides and heavy metals from the mill tailings was examined in order to assess the potential environmental impact of past and future mining activities. Given the considerable amount of apatite still present, the waste material does not represent true tailings. Variations in abundance probably represent material discharges to the tailings rather than mobilization of the elements from the tailings themselves. No indication of heavy-metal migration was found. Extraction results suggest that only a small proportion of cadmium is in exchangeable form. Elements that are partly soluble under weakly-acidic conditions include copper, zinc, cadmium, uranium and lead. However, most of the elements are tightly bound to the sample matrix and therefore not easily released to the environment

Behaviour of radionuclides during microbially-induced mining of nickel at Talvivaara, Eastern Finland

The Talvivaara mine in Eastern Finland utilizes microbe-induced heap leaching to recover nickel and other valuable metals (Zn, Cu, Co) from a black schist ore. In addition to the target metals, the ore contains uranium at a concentration of 17 mg/kg, incorporated as uraninite (UO2). Uranium oxidizes from the U(IV) to U(VI) state during leaching and dissolves as the uranyl ion (UO22+) in the acidic pregnant leach solution. Mobilisation of uranium has caused sufficient concern that plans have been developed for uranium recovery. The aim of this study is to generate new data leading to a better understanding of the fate of its radiotoxic daughter nuclides, primarily 226Ra, 210Pb and 210Po, in the mining process. It is shown that uranium daughters mostly remain in the heaps during the leaching process and are associated with secondary minerals, including jarosite, goethite and gypsum. Thorium and progeny (232Th plus 228Th, 228Ra) are also mainly retained. High sulphate concentrations in the acidic solutions limit the solubility of radium by incorporation in the crystal lattices of precipitated secondary sulphates. Electron probe microanalysis shows that goethite in the heaps is uraniferous, resulting from the adsorption of U(VI). After recovery of target metals, the pregnant leach solution is neutralized to further remove metal contaminants and the resulting slurries stored in a bunded tailings pond. The activity concentrations of thorium, radium, lead and polonium isotopes are generally low in the pond owing to prior retention by secondary minerals in the heaps. However, 238U activity concentrations range up to 3375 Bq/kg, which exceeds the permitted value (1000 Bq/kg) for natural radionuclides of the 238U series