Sediment size distributions from San Pablo Bay and China Camp Marsh, California

Surface sediment was collected on 19 days between December 3, 2013 and June 21, 2016 using a small ponar, or 'grab', sampler from the R/V Parke Snavely. Some sediment samples were collected from sediment that accumulated on instruments. A handheld global satellite navigation system (GNSS) receiver was used to determine the locations of sediment samples.

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.

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

Entity and Attribute section was edited for clarity. No data were changed. (rtakesue@usgs.gov)