Grain size and bulk density from Little Holland Tract and Liberty Island, Sacramento-San Joaquin Delta, California, 2015 to 2019 (ver. 3.0, April 2023)

Sediment samples were collected from 2015 to 2019 using a Ponar grab or push core sampler. Sampling positions were recorded using a handheld 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.

Additional samples from 2018 and 2019 were processed using the above steps. From January 2017 until October 2019, the Pacific Coastal and Marine Science Center sediment lab's Beckman Coulter LS 13 320 particle size analyzer had a low sensitivity issue, resulting in under-reporting of the coarse silt range from 4 to 5.5 phi, and slightly skewed distribution of the mud grain size parameters. Samples from that time period were re-analyzed during 2020, and the updated results are presented in version 2.0 of the data.

Edited metadata to add keywords section with USGS persistent identifier as theme keyword. No data were changed.

Performed minor edits to the metadata to correct typos. No data were changed.

Additional samples from FAN 2018-673-FA were included in the data file. Corrected the dates for samples from FAN 2018-626-FA.