page_title: Dissolved organic carbon
section_title: Overview
hierarchical_section_title: Dissolved organic carbon / Overview
caption_attribution_description: English: Colour differences in filtered coastal waters Filtered (0.2 μm) coastal marine waters collected at various locations in the United Kingdom. The differences in color is due to the range of soil-derived carbon input to the coastal water, with dark brown (left) indicating a high soil-derived carbon contribution and near-clear water (right) indicating a low soil-derived carbon contribution
context_page_description: Dissolved organic carbon is the fraction of total organic carbon operationally defined as that which can pass through a filter pore size that typically ranges in size from 0.22 and 0.7 micrometers. The fraction remaining on the filter is called particulate organic carbon.
  Dissolved organic matter is a closely related term often used interchangeably with DOC. DOC refers specifically to the mass of carbon in the dissolved organic material, while DOM refers to the total mass of the dissolved organic matter. Thus, in addition to carbon, DOM includes the mass of the other elements in the organic matter, such as nitrogen, oxygen and hydrogen. In this sense DOC is a component of DOM and there is typically about twice as much DOM as DOC. Many statements that can be made about DOC apply equally to DOM, and much of what is said in this article about DOC could equally have been said of DOM.
  DOC is abundant in marine and freshwater systems and is one of the greatest cycled reservoirs of organic matter on Earth, accounting for the same amount of carbon as the atmosphere and up to 20% of all organic carbon.
context_section_description: DOC is a basic nutrient, supporting growth of microorganisms and plays an important role in the global carbon cycle through the microbial loop. In some organisms (stages) that do not feed in the traditional sense, dissolved matter may be the only external food source. Moreover, DOC is an indicator of organic loadings in streams, as well as supporting terrestrial processing (e.g., within soil, forests, and wetlands) of organic matter. Dissolved organic carbon has a high proportion of biodegradable dissolved organic carbon (BDOC) in first order streams compared to higher order streams. In the absence of extensive wetlands, bogs, or swamps, baseflow concentrations of DOC in undisturbed watersheds generally range from approximately 1 to 20 mg/L carbon.  Carbon concentrations considerably vary across ecosystems. For example, the Everglades may be near the top of the range and the middle of oceans may be near the bottom. Occasionally, high concentrations of organic carbon indicate anthropogenic influences, but most DOC originates naturally. 
  The BDOC fraction consists of organic molecules that heterotrophic bacteria can use as a source of energy and carbon.  Some subset of DOC constitutes the precursors of disinfection byproducts for drinking water. BDOC can contribute to undesirable biological regrowth within water distribution systems.
  The dissolved fraction of total organic carbon (TOC) is an operational classification. Many researchers use the term "dissolved" for compounds that pass through a 0.45 μm filter, but 0.22 μm filters have also been used to remove higher colloidal concentrations.
  A practical definition of dissolved typically used in marine chemistry is all substances that pass through a GF/F filter, which has a nominal pore size of approximately 0.7 μm (Whatman glass microfiber filter, 0.6–0.8 μm particle retention). The recommended procedure is the HTCO technique, which calls for filtration through pre-combusted glass fiber filters, typically the GF/F classification.
caption: Colour differences in DOC collected from coastal waters Filtered (0.2 μm) coastal marine waters collected at various locations around the United Kingdom. The differences in colour is due to the range of soil-derived carbon input to the coastal water, with dark brown (left) indicating a high soil-derived carbon contribution and near-clear water (right) indicating a low soil-derived carbon contribution.[7]
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