For grain size distribution of floodplain sediments, sediment samples were first sieved through a 2 mm diameter sieve. Samples less than 2 mm in diameter (10 g) were left overnight in 50 ml of 35 % hydrogen peroxide (H2O2) and heated the next day to remove organic matter. Subsequently, the samples were dispersed using 10 ml of 0.4 N sodium pyrophosphate solution (Na4P2O7) and got ultrasonic treatment for 45 minutes. Grain size analysis was performed for the sand fraction using the dry sieving technique (2000-630 µm: coarse sand, 630-200 µm: medium sand, 200-125 µm: fine sand, 125-63 µm: very fine sand). The finer fractions (63-20 µm: coarse silt, 20-6.3 µm: medium silt, 6.3-2.0 µm: fine silt, 2.0-0.6 µm: coarse clay, 0.6-0.2 µm: medium clay and <0.2 µm: fine clay) were measured by X-ray granulometry (XRG) using a SediGraph III 5120 (Micromeritics). Freely available program GRADISTAT v9.1 was used to calculate D50 (median of grain size), D75/D25 and D75-D25.
Within the framework of the DFG-funded project Archaeological and geoarchaeological investigations at the germanic-roman battlefield site Harzhorn (Northeim, Lower Saxony, Germany), more than 630 samples of the topsoil were taken in relatively high spatial density in order to investigate the relationship between soil parameters and the conservation status of iron objects. The Harzhorn incident took place around the year 235 CE on a Muschelkalk ridge (Harzhorn site) and a neighbouring hill (Kahlberg site) consisting of Jurassic limestone. Upper Buntsandstein and Quaternary loess also occur in some areas. During previous archaeological excavations, the very heterogenuous preservation of iron finds, such as arrow heads, pilae, or shoe nails, was noticed and a correlation with the surface geology/soil properties was assumed. In order to investigate into this relationship, soil samples were taken across the areas at a relatively high density. The sampling was carried out in 2018, the laboratory analyses in the Laboratory for Physical Geography of the Institute for Geographical Sciences at Freie Universität Berlin were finished in 2019.
At the Harzhorn site, the vast majority of archaeological finds were discovered at a depth between 15 - 20 cm. As we were interested in the area-wide in situ soil conditions to evaluate the soil aggressiveness, the soil samples at the Harzhorn site were taken at a depth of 15 cm. At the Kahlberg site, the vast majority of archaeological finds were discovered at a depth between 25 - 30 cm. Thus, at the Kahlberg site the soil samples were taken at a depth of 25 cm. Additionally, in the course of archaeological excavations, we sampled 8 profiles at different depths at the Kahlberg site. All samples were analysed with regard to: pH value (Hanna instruments pH meter, measured in KCl), Electric conductivity (Hanna instruments EC meter, measured in distilled water), and loss on ignition (550°C + 880°C). On a selected number of samples grain size analyses were carried out (laser particle sizer LS 13320 PIDS Beckman Coulter).
We determined grain size distributions of Holocene fluvial sediments from a recovered drilling core from the Weiße Elster floodplain. We left the 2 mm sieved samples (10 g) in 50 ml 35-% hydrogen peroxide (H2O2) overnight and heated them during the next day to remove organic matter. Subsequently, we dispersed the samples using a 10 ml 0.4 N sodium pyrophosphate solution (Na4P2O7) and ultrasonic treatment for 45 minutes. We conducted the grain size analysis of the sand fraction by means of the dry-sieving technique (2000–630 µm: coarse sand, 630–200 µm: medium sand, 200–125 µm: fine sand, 125–63 µm: finest sand). The finer fractions (63–20 µm: coarse silt, 20–6.3 µm: medium silt, 6.3–2.0 µm: fine silt, 2.0–0.6 µm: coarse clay, 0.6–0.2 µm: medium clay and <0.2 µm: fine clay) were measured by X-ray granulometry (XRG) using a SediGraph III 5120 (Micromeritics).