Dissolved organic carbon definition

Dissolved organic carbon (DOC) is by definition the organic carbon content of a sample which was prefiltered through a 0.45 pm filter, whereas total organic carbon (TOQ is the carbon content of an... 

The nomenclature of organic carbon is described in detail in Chapter 2 and in the Glossary. While there is a difference in definition between total organic carbon (TOQ and dissolved organic carbon (DOC), which is that the DOC is that part of TOC which passes through a 0.45 om filter, in this thesis the terms are used interchangeably. 

Total carbon includes dissolved organic material (called total organic carbon, TOC) and dissolved COf and HCOJ (called inorganic carbon, IC). By definition, TC = TOC + IC. To distinguish TOC from IC, the pH of a fresh sample is lowered below 2 to convert COl and HCO J into CO2, which is purged from (bubbled out of) the solution with N2. After IC has been removed, combustion analysis of the remaining material measures TOC. IC is the difference between the two experiments. 

Almost all of the reactions that the practicing inotganic chemist observes in the laboratory take place in solution. Although water is the best-known solvent, it is not the only one of importance to the chemist. The organic chemist often uses nonpolar solvents sud) as carbon tetrachloride and benzene to dissolve nonpolar compounds. These are also of interest to Ihe inoiganic chemist and, in addition, polar solvents such as liquid ammonia, sulfuric acid, glacial acetic acid, sulfur dioxide, and various nonmctal halides have been studied extensively. The study of solution chemistry is intimately connected with acid-base theory, and the separation of this material into a separate chapter is merely a matter of convenience. For example, nonaqueous solvents are often interpreted in terms of the solvent system concept, the formation of solvates involve acid-base interactions, and even redox reactions may be included within the (Jsanovich definition of acid-base reactions. 

All natural waters contain some carbonaceous material. Even rainwater has been shown to include about 1 mg C/L (Thurman, 1985). Some of this organic material is in the form of truly dissolved, soluble compounds, whereas other fractions consist of colloidal or particulate organic matter. The definitions of dissolved and particulate carbon that have been more or less established by convention among aquatic scientists are somewhat elastic and arbitrary one criterion that is widely used sets the boundary between the two at 0.45 /tM (the pore size of some common filter media). These demarcations tend to disguise the fact that there is a continuum of organic particles in water that ranges in relative size from molecules to microorganisms. 

According to the definition we will use here, a chemical species represent expressis verbis the molecular arrangement of a particular metal or metal compound. This may include free aquated ions, distinct chemical compounds (such as dissolved inorganic salts and acids, or solid oxides, sulfides, and carbonates), as well as thermodynamically unstable aggregates (like dissolved and solid organic complexes, colloids or coprecipitates) either naturally available or as a result of man s activity. 

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