Sebastian Kreutzer

The temporal and spatial quantification of Holocene sediment dynamics in a meso-scale catchment in northern Bavaria, Germany

The Aufsess River catchment (97 km2) in northern Bavaria, Germany, is studied to establish a Holocene sediment budget and to investigate the sediment dynamics since the early times of farming in the third millennium BCE. The temporal characterization of the sediment dynamics is based on an intensive dating program with 73 OSL and 14 14C ages. To estimate soil erosion and deposition, colluvial and alluvial archives are investigated in the field by piling and trenching, supported by laboratory analyses. The sediment budget shows that 58% of these sediments are stored as colluvium in on- and foot-slope positions, 9% are stored as alluvium in the floodplains and 33% are exported from the Aufsess River catchment. Colluviation starts in the end-Neolithic (c. 3100 BCE), while first indicators of soil erosion-derived alluviation is recorded c. 2–3 ka later. The pattern of sedimentation rates also displays differences between the colluvial and alluvial system, with a distinct increase in the Middle Ages (c. 1000 CE) for the alluvial system, while the colluvial system records low sedimentation rates for this period. A contrast is also observed since Modern times (c. 1500 CE), with increasing sedimentation rates for the colluvial system, whereas the alluvial system records decreasing rates. The different behavior of the colluvial and alluvial systems clearly shows the non-linear behavior of the catchment’s fluvial system. The results further suggest that human impact is most probably the dominant factor influencing the sediment dynamics of the catchment since the introduction of farming.

Performance tests using the Lexsyg luminescence reader

This study presents test measurements on a Lexsyg luminescence reader, acquired by the Giessen luminescence group. The reader is of the type Standard, hence designed for routine determination of palaeodoses using quartz or K-feldspars. The tests include measurements of the stimulation powers, preheat temperatures, OSL- and TL-curves, as well as dose recovery tests and calibration measurements using highly sensitised calibration quartz. A comparison of De values determined using a Lexsyg reader with single grain De-values, which have been previously obtained on a Risø reader, is also presented. The results imply that the Lexsyg reader is a highly reliable measurement device with high reproducibility, yielding instrumental uncertainties of around 0.3%.

Environmental dose rate determination using a passive dosimeter: Techniques and workflow for α-Al2O3:C chips

Abstract In situ dosimetry (active, passive dosimeters) provides high accuracy by determining environmental dose rates directly in the field. Passive dosimeters, such as α-Al2O3:C, are of particular interest for sites with desired minimum disturbance (e.g., archaeological sites). Here, we present a comprehensive approach obtaining the environmental cosmic and γ-dose rate using α-Al2O3:C chips. Our procedure consists of (1) homemade field containers, (2) a homemade bleaching box, (3) a rapid measurement sequence and (4) software based on R to process the measurement results. Our validation steps include reproducibility, irradiation time correction, cross-talk evaluation and source calibration. We further simulate the effect of the container against the infinite matrix dose rate, resulting in attenuation of ca. 6%. Our measurement design uses a lexsyg SMART luminescence reader equipped with green LEDs. The irradiation is carried out under the closed β-source. The minimum dose that can be determined was estimated with ca. 10 μGy. However, we also show that for the equipment used, an irradiation time correction of ca. 2.6 s is needed and irradiation cross-talk should be taken into account. The suggested procedure is cross-checked with four reference sites at Clermont-Ferrand showing a good γ-dose rate for three out of the four sites. Finally, an application example, including needed analytical steps, is presented for dosimeters buried at the archaeological site of the Sierra de Atapuerca (Spain).

A new fully integrated X-ray irradiator system for dosimetric research.

A fully housed X-ray irradiator was developed for use within lexsyg or Magnettech desktop equipment. The importance of hardening of the low energy photon radiation is discussed, its performance and feasibility is empirically shown and sustained by basic numerical simulations. Results of the latter for various materials are given for different X-ray source settings in order to provide estimates on the required setup for the irradiation of different geometries and materials. A Si-photodiode provides real-time monitoring of the X-ray-irradiator designed for use in dosimetric dating and other dosimetric application where irradiation of small samples or dosemeters is required.