Grain size, bulk density, and organic carbon of sediment cores from three locations in the Sacramento-San Joaquin Delta, California, 2017 to 2018

Sediment samples were collected from April, 2017 to March, 2018 during three field activities 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 with the formula: bulk density = (water density * sediment density) / (water density + (sediment density - water density) * water content), where water density is 1 g/cm3 and sediment density is 2.65 g/cm3.

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