Total Organic Carbon (TOC)

Status and Trends

Organic matter plays a major role in transferring energy in aquatic systems. Some of these pathways include biogeochemical processes, nutrient cycling, biological availability and chemical transport interactions. It also has direct implications in the planning of wastewater treatment and drinking water treatment.

Organic matter content is typically measured as total organic carbon and dissolved organic carbon, which are essential components of the carbon cycle. Organic matter in water mass consist of many components, including macroscopic particles such as algal cells, colloids, dissolved macromolecules, and organic compounds.

Median TOC concentrations ranged from 1.3 mg/L at Braddock Run to 5.6 mg/L on the North Branch Potomac at US 220. Highest median concentrations (TOC > 3.3 mg/L) of total organic carbon occurred at 31% of all stations. Lowest median concentrations occurred at 30% of all stations and stations with intermediate TOC median concentrations occurred at 39% of all stations.

TOC concentration increased at 22% of all stations. Trends in TOC were increasing in the Ohio River Basin, the western most Upper Potomac Basin, at the upper two stations in the Patuxent Basin, on the Susquehanna River and on the Choptank River. Total organic carbon concentration significantly decreased at the two lowest stations on Antietam Creek.

TOC was weakly correlated (i. e. PCC < 0.64) with CHLA at 38% of all stations where CHLA is sampled.

Total Organic Carbon (TOC) data for sampled locations are summarized in these plots.

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This page was updated on 12/5/2005