Ephemeral Organic Carbon Fluxes to the Chesapeake Bay from Agricultural Runoff on the Virginia Coastal Plain

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Caverly, Emma Katherine
thesis / dissertation description
Dissolved organic carbon (DOC) and particulate organic carbon (POC) play a critical role in nutrient cycling, contaminant transport and the global carbon cycle, but total organic carbon (TOC) fluxes are not well constrained across different land uses and environments. We use automated high resolution sampling of agricultural storm runoff and stream height to quantify DOC and POC fluxes and dynamics in an ephemeral channel on the coastal plain of Virginia. DOC and POC were characterized using specific UV absorbance (SUVA254). During a two week period when a hurricane and tropical storm passed over the region, we measured a DOC flux of 22 kg ha-1 and a POC flux of 11.3 kg ha-1. SUVA254 values indicated that the aromatic portion of DOC ranged from a minimum 18.6% at the beginning of the first event to a maximum of 44.0% during the second event; this represents an increase in soil derived DOC. Hysteresis plots and SUVA254 indicated that plant derived aliphatic DOC was depleted while soil sourced aromatic DOC was readily available. Ephemeral can facilitate the export of large quantities of organic carbon during flashy, storm generated flows.