Percent Carbon content from suspended sediment in water samples collected Whale's Tail South marsh tidal creeks in South San Francisco Bay, California, Winter 2021-2022

Water samples were collected 12/3/2021, 12/6/2021 and 1/3/2022 during the king tides using a Niskin bottle. Sampling positions were recorded using a hand-held global navigation satellite system (GNSS) receiver. Samples were placed in cold storage until processed.

The suspended sediment percent carbon measurements were made in the USGS Pacific Coastal and Marine Science Center sediment and carbon labs. The water-sediment samples were centrifuged to remove the water and concentrate the sediment. The sediment was dried and then pulverized into a fine powder. To obtain percent total carbon (TC), approximately 20mg of the pulverized sample was weighed and wrapped in an aluminum tin. A UIC CM 5200 furnace attached to a CM 5017 coulometer was used to incinerate the samples at 950 degree C which converted the produced CO2 into a value to obtain total carbon as percent dry weight. For percent total inorganic carbon (TIC), approximately 20mg of sample was weighed into capsules and placed in glass sample tubes which were loaded into a UIC CM 5230 acid digester attached to a CM 5017 coulometer. The samples were digested with 2mL perchloric acid and the produced CO2 was measured to obtain a total inorganic carbon value as percent dry weight. To determine percent calcium carbonate of a sample, the percent TIC value was multiplied by 8.333. The percent total organic carbon (TOC) value was determined by subtracting the percent TIC value from the percent TC value. Two analyses were run per system and the results were averaged.