Dataset: Watershed concentrations of dissolved inorganic carbon, dissolved organic carbon, and particulate organic carbon in the York River Estuary sampled in 2019-2021.

Three of the four stations were accessed by land.  The two USGS gauge sites (Pamunkey Gauge, PG; Mattaponi Gauge, MG) were sampled by lowering a bucket from the bridges crossing the rivers at the gauge locations.  The other site (Walkerton Landing Bridge, WLB) was sampled from a floating dock.  The White House station (WH) was not accessible from the road; this station is a long-term monitoring site of the Chesapeake Bay National Estuarine Research Reserve in Virginia (CBNERRVA) and was sampled for us by CBNERRVA staff.  Sample dates were the same except for two dates when WH was sampled one day before or after the other sites.  Samples were collected from the surface at all stations.  Water temperature and salinity were measured in the field with a YSI EXO2 datasonde.  Carbon samples were collected in triplicate and filtered immediately in the field at PG, MG, and WLB; samples from WH were kept on ice and returned to the lab for filtration.  DIC samples were filtered through 0.2 um polycarbonate filters into 8-mL hungate tubes and refrigerated underwater until analysis on an Apollo SciTech AS-C3 analyzer coupled to a LI-COR LI-7000 infrared gas analyzer.  DOC samples were filtered through 0.45 um polyethersulfone filters and frozen prior to analysis on a Shimadzu TOC-V organic carbon analyzer.  POC samples were filtered onto pre-combusted 0.7 um glass fiber filters, dried at 60°C, and stored in a dessicator prior to analysis.  Beginning in August 2019, samples were fumed with HCl to remove any inorganic carbon.  Samples through June 2019 were measured on a Thermo 1110 CHN Analyzer; subsequent samples were measured on a Costech 4010 CHN Analyzer.  A series of blank filters were also measured to correct for background POC concentrations.