H. Jungner

Persistent luminescence of Eu2+ doped alkaline earth aluminates, MAl2O4:Eu2+

Abstract The polycrystalline Eu2+ and RE3+ (rare earth) doped alkaline earth aluminates MAl2O4:Eu2+,RE3+ (M=Ca and Sr) were prepared by a solid state reaction starting from the corresponding oxides (Al, RE) and carbonates (Ca, Sr). The UV-excited photoluminescence, persistent luminescence (afterglow) and thermoluminescence of these materials was studied and compared. The two spectra (band position and width) were very similar indicating that the luminescent centre is an Eu2+ ion in both cases. A slight blue shift was observed in the afterglow emission in some cases. The RE3+ co-doping had no effect on the position and shape of the persistent luminescence band but the Nd3+ and Dy3+ ions enhanced the most the afterglow and thermoluminescence of the CaAl2O4:Eu2+ and SrAl2O4:Eu2+ materials, respectively. Easily reducible rare earth ions such as Sm3+ and Yb3+ suppressed both the afterglow and thermoluminescence of MAl2O4:Eu2+. Based on these observations, the mechanism of RE3+ co-doping is discussed.

Recent and ancient fluvial deposition systems in the Amazonian foreland basin, Peru

Still active Sub-Andean foreland deformation is suggested to have syndepositionally modified the fluvial depositional environments in the Peruvian Amazonian foreland basin throughout Neogene-Quaternary time. Modern fluvial aggradation continues to proceed on a large scale ( c . 120 000 km 2 ) in two differing depositional systems. Firstly, various multistoried floodbasin deposits are derived from the meandering and anastomosing rivers within the subsiding intraforeland basins. Secondly, in the northern part of the Pastaza-Maranon basin the largest known Holocene alluvial fan-like formation ( c . 60 000 km 2 ) composed of reworked, volcaniclastic debris derived from active Ecuadorian volcanoes, has been identified. The widespread, poorly known, dissected surface alluvium ( terra firme ) which covers the main part of the Peruvian Amazonian foreland basin shows further evidence of long-term foreland deformation, and terraces indicate both the effects of tectonism and Pleistocene climatic oscillations. In northern Peru, the surface alluvium was deposited by a Tertiary fluvial system with palaeocurrents to the west and northwest into the Andean foreland basin. In southern Peru, the respective surficial alluvium was part of a post-Miocene fluvial system flowing northeast into the main Amazon basin. Both systems were gradually abandoned when the eastward migrating Andean foreland deformation led to the more distinctive partitioning of the intraforeland basins, and the modern drainage system was created.

The Last Interglacial-Glacial cycle in NE Fennoscandia: a nearly continuous record from Sokli (Finnish Lapland)

Abstract Boreholes from the Sokli basin in Finnish Lapland have recovered a unique sequence of diamicts interlayered with fine-grained sediments that are rich in fossils. The diamicts are interpreted as till beds deposited by the Fennoscandian Ice-Sheet. The fine-grained intercalations seem to represent a series of warm stages that include one interglacial and three interstadials. The interglacial is characterized by a mixed taiga pollen assemblage and corresponds to a distinct diatom gyttja bed. The interstadials show progressively colder floras from open birch forest to arctic forest limit to shrub tundra. Their sediments comprise gyttja interlayered with wood and sand (interstadial 1); sands grading into sandy gyttja (interstadial 2); and sands overlain by laminated silt and clay (interstadial 3). The interstadial 2 and 3 deposits are underlain by diamict and are interpreted as deglaciation sequences. Silts with a tundra pollen assemblage separate the interglacial and interstadial 1 deposits. Luminescence dating evidence indicates that the interglacial bed most probably represents the NW European mainland Eemian Interglacial (marine isotope stage (MIS) 5e). The interstadial 1, 2 and 3 deposits are tentatively correlated with the Early Weichselian Brorup and Odderade Interstadials and an interstadial of Middle Weichselian age, respectively (MIS 5c, 5a and 3, respectively). The correlation implies that the easternmost part of the ice-divide zone of the Fennoscandian continental ice-sheet was deglaciated during part of MIS 3.

New radiocarbon dates from Finnish mammoths indicating large ice-free areas in Fennoscandia during the Middle Weichselian

New radiocarbon dates from Finnish subfossil mammoth material (Mammuthus sp.), transported by glacial ice, range in age from ca. 32000 to ca. 22500 yr BP. These results suggest that there was a larger ice-free area in Fennoscandia during the Middle Weichselian than previously assumed. In addition, two dates are also presented for bones found in clay with a different transport history. Copyright

Temperature sensitivity of soil carbon fractions in boreal forest soil.

Feedback to climate warming from the carbon balance of terrestrial ecosystems depends critically on the temperature sensitivity of soil organic carbon (SOC) decomposition. Still, the temperature sensitivity is not known for the majority of the SOC, which is tens or hundreds of years old. This old fraction is paradoxically concluded to be more, less, or equally sensitive compared to the younger fraction. Here, we present results that explain these inconsistencies. We show that the temperature sensitivity of decomposition increases remarkably from the youngest annually cycling fraction (Q10 < 2) to a decadally cycling one (Q10 = 4.2-6.9) but decreases again to a centennially cycling fraction (Q10 = 2.4-2.8) in boreal forest soil. Compared to the method used for current global estimates (temperature sensitivity of all SOC equal to that of the total heterotrophic soil respiration), the soils studied will lose 30-45% more carbon in response to climate warming during the next few decades, if there is no change in carbon input. Carbon input, derivative of plant productivity, would have to increase by 100-120%, as compared to the earlier estimated 70-80%, in order to compensate for the accelerated decomposition.

Three-dimensional reconstruction of carbon accumulation and CH4 emission during nine millennia in a raised mire

A three-dimensional model, based on numerous vertical and horizontal 14C datings and GIS simulation from a concentrically domed mire in southern Finland, demonstrates considerable variation in actual (net) rate of carbon accumulation (ARCA) through time. Lateral growth between 9000 and 3000 yr ago accounts for only 25% of the total carbon sequestration, whereas bog formation after ombrotrophication is responsible for the remaining 75%. On the other hand, the most rapid increase in landscape CH4 flux occurred between 4500 and 3000 yr ago, the period of the fastest horizontal growth. In addition to autecological factors, a climatic shift towards cooler and wetter conditions is a plausible mechanism for maintaining accelerated carbon accumulation.

Variation with depth of dose distributions in single grains of quartz extracted from an irradiated concrete block

Abstract Most attempts to apply retrospective dosimetry using luminescence methods to building materials have made use of heated (sensitised) items such as brick or tile ceramic. Unfired materials, such as mortar and concrete, are much more widespread in the industrial environment, but unfortunately these cannot be assumed to contain a negligible dose at the time of construction. We have analysed the dose distributions derived from optically stimulated luminescence (OSL) measurements of single grains of quartz extracted from two industrially produced concrete blocks, one unirradiated and the other irradiated normal to one face in the laboratory using 137 Cs gamma photons. The OSL dose-depth profile for the irradiated block was determined by measuring the dose distributions from single quartz grains extracted from slices taken across the block and compared with that predicted using Monte Carlo calculations. Despite measured doses in grains extracted from the unirradiated concrete of up to 140 Gy , we show that it is possible to detect accrued doses of about 100 mGy from grains extracted from the bulk concrete, and about 50 mGy in grains extracted from the surface of the block.

Using the OSL single-aliquot regenerative-dose protocol with quartz extracted from building materials in retrospective dosimetry

We report on the application of the single-aliquot regenerative-dose (SAR) protocol to the optically stimulated luminescence signal from quartz extracted from fired bricks and unfired mortar in retrospective dosimetry. The samples came from a radioactive materials storage facility, with ambient dose rates of about 0.1 mGy/h. A detailed dose-depth profile was analysed from one brick, and compared with dose records from area TL dosemeters. Small-aliquot dose-distributions were analysed from the mortar samples; one associated with the exposed brick, and one from a remote site exposed only to background radiation. We conclude that unfired materials have considerable potential in retrospective dosimetry.

AMS 14C DATING OF LIME MORTAR

Abstract A method for refining lime mortar samples for 14 C dating has been developed. It includes mechanical and chemical separation of mortar carbonate with optical control of the purity of the samples. The method has been applied to a large series of AMS datings on lime mortar from three medieval churches on the Aland Islands, Finland. The datings show convincing internal consistency and confine the construction time of the churches to AD 1280–1380 with a most probable date just before AD 1300. We have also applied the method to the controversial Newport Tower, Rhode Island, USA. Our mortar datings confine the building to colonial time in the 17th century and thus refute claims of Viking origin of the tower. For the churches, a parallel series of datings of organic (charcoal) inclusions in the mortar show less reliable results than the mortar samples, which is ascribed to poor association with the construction time.

Absorbed dose evaluations in retrospective dosimetry: methodological developments using quartz

Abstract Dose evaluation procedures based on luminescence techniques were applied to 50 quartz samples extracted from bricks that had been obtained from populated or partly populated settlements in Russia and Ukraine downwind of the Chernobyl NPP. Determinations of accrued dose in the range ∼30–300 mGy were obtained using TL (210°C TL and pre-dose) and OSL (single and multiple aliquot) procedures. Overall, good inter-laboratory concordance of dose evaluations was achieved, with a variance (1 σ ) of ∼±10 mGy for the samples examined.