DOI: 10.15480/882.13237
title: Time-dependent density profiles of cohesive sediment samples from the Port of Hamburg

description: The data set was collected within the context of the research project ELMOD - “Simulation and analysis of the hydrological and morphological development of the Tidal Elbe for the period from 2013 to 2018”. The aim was to: i) obtain information on the settling and consolidation behavior of the site-specific coehsive sediment and ii) create a data set for the calibration of numerical models. The dataset consists of time-dependent density profiles of six cohesive sediment samples, collected in the Elbe estuary in the area of the Port of Hamburg. The sediment of three samples each was collected on the "Suederelbe" (SE) and the "Norderelbe" (NE). The exact sampling positions are shown in Figure 1 in the following related publication: https://doi.org/10.3389/fmars.2024.1386081. The grain size distributions (GSD) of the sediment samples are included in the dataset. The sediment samples were diluted in the laboratory to densities between 1035 kg/m³ and 1080 kg/m³. The samples were thoroughly homogenized in a 20 cm diameter settling column, by mixing the suspension for 10 minutes with a stirring machine. After 15 minutes of settling the first density profile was taken. For this purpose, a small amount of suspension (~5 ml) was extracted from defined heights in the settling column (every 5 cm). This procedure was performed by inserting thin alloy tubes from the top of the suspension and aspirating the suspension with a syringe from the desired depth. Since this procedure disturbs the sediment sample/suspension above the extraction depth, the subsamples are taken from top to bottom. The densities of the subsamples are measured using an Anton Paar DMA 35 density meter. After the density measurement the subsamples are returned to the settling column. Since the whole sample is disturbed after a complete density profile has been taken, the sample is homogenized again using the same procedure (10 minutes stirring) and the next profile can be taken after e.g. 30 minutes of settling. The described procedure was first presented in https://doi.org/10.3389/feart.2022.916056. In order to improve the data quality, slight modifications of the procedure have been introduced for the collection and evaluation of the presented data set: From the suspension/water surface to the lutocline, the density is set to the measured water density, since the variations in this area are &lt; 1 g/l. To capture the area of the lutocline, where the largest gradients of the density profiles occur, the first subsample was taken 1 cm below the lutocline for each profile. Subsequent subsamples were taken at the fixed depths, 5 cm apart. For the updated version of the dataset, the profiles for 24h settling time for NE-sediment with initial densities of 1050 kg/m³ and 1065 kg/m³ have been repeated and corrected. The results of the previous version suggested irregularities in the recording of these two single profiles, since the integration of the measured densities over the settling column height showed an unusual deviation, compared to the other profiles of the same density. To test the repeatability of the results, the measurement of the 24h profile of sample NE1-8 with an initial density of ~1042 kg/m³ was repeated five times (sample homogenized and allowed to settle for 24h each time). The file NE1-8_1042_24h_Repetitions_DensityProfiles.csv contains the single density profiles of the five repetitions. Examplary explanation of the nomenclature of the files: GSD_NE1-8.txt -&gt; Grain size distribution data for sample NE1-8 (NE1-8 indicates the eighth sample taken during campaign NE1) NE1-8_1035_DensityProfiles.csv -&gt; Time-dependent density profiles of sample NE1-8 with an initial density of 1035 kg/m³. The initial height of the suspension is given in the .csv file (70-80 cm). NE1-8_1042_24h_Repetitions_DensityProfiles.csv -&gt; Repetitions of the density profile of sample NE1-8 with an initial density of ~1042 kg/m³ after 24 hours of settling/consolidation.