Grain size and bulk density of sediment cores from Little Holland Tract and Liberty Island, Sacramento-San Joaquin Delta, California, 2014 (ver. 2.0, March 2025)

Sediment samples were collected on August 25 and 26, 2014 using a push core sampler. Sampling positions were recorded using a hand-held global navigation satellite system (GNSS) receiver.

The grain-size distributions of samples were determined in the USGS Pacific Coastal and Marine Science Center sediment lab. Approximately 20 g of sediment was sub-sampled and 10 mL of 35 percent hydrogen peroxide was added to remove organic material in the sample. The sample was heated at 250 degrees C to remove any remaining hydrogen peroxide and was placed in an ultrasonic bath to liberate the fine fraction. Subsequently, the sample was centrifuged for 1.5 hours to remove soluble salts. Samples were funneled through a 2 mm and a 63 um sieve to separate the gravel (greater than 2 mm), sand (63 um to 2 mm), and mud (less than 63 um). The sand and gravel fractions were dried in an 80 degree C oven and weighed. Five mL of sodium hexametaphosphate was added to the mud fraction and a 20 mL aliquot was taken from a 1 L graduated cylinder to determine the weight of the mud. The particle-size distribution of the mud and sand fractions was analyzed separately using a Beckman Coulter LS 13 320, and the gravel, sand, and mud results were integrated into a single grain-size distribution for each sample. Where used, phi sizes are equal to the negative log base 2 of millimeter size.

Bulk density was calculated by weighing the sample bag, the wet sample in the bag, and the dry sample in the bag. Measurements were made in the USGS Pacific Coastal and Marine Science Center sediment lab. The bulk density reported here was calculated as: water density (1 g/cm3) times sediment density (2.65 g/cm3) divided by water density plus the product of sediment density minus sediment density and water content of the sample.

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CARBON ANALYSIS: A total of 5 samples were analyzed for percent carbon. Carbon analysis was performed by the PCMSC carbon lab employing a coulometric titration technique described in Engleman and others (1985) and UIC operating manuals for the UIC CM5200 autosampler furnace, the UIC CM5230 acidification module, and the UIC CM5017 coulometer. Total carbon (TC), total inorganic carbon (TIC), total organic carbon (TOC) and percent calcium carbonate (CaCO3) are reported as percent dry weight. Approximately 5 grams of sediment were dried in an 80 degrees Celsius oven. Samples were then pulverized, redried, and placed in a desiccator. For TC analysis, approximately 20 milligrams of the pulverized sample were weighed and wrapped in an aluminum capsule then combusted at 950 degrees Celsius in an UIC CM5200 autosampler furnace attached to an UIC CM5017 coulometer. The carbon dioxide (CO2) produced by combusting the sample was then converted to TC by the UIC CM5017 coulometer. For TIC, approximately 20 milligrams of sample were weighed and loaded into an UIC CM5230 acidification module attached to an UIC CM5017 coulometer. The samples were then digested in a perchloric acid solution, and the CO2 generated was measured and converted to TIC. Two analyses per sample were run and the results were averaged. TOC was calculated by subtracting TIC from TC. The TIC value was then multiplied by 8.333 (the molar stochiometric ratio of CaCO3 to C) to convert TIC to percent CaCO3.