ppmC

ppmC stands for parts-per-million carbon and is used as a concentration descriptor in a variety of scientific contexts. It denotes the fraction of carbon by mass in a sample, expressed in units of parts per million. In practice, ppmC is often treated as equivalent to milligrams of carbon per liter (mg C/L) in dilute aqueous systems, so that 1 mg/L as C is approximately 1 ppmC.

In environmental chemistry and soil science, ppmC is commonly used to report organic carbon content. For example, dissolved organic carbon (DOC) and total organic carbon (TOC) measurements are frequently discussed in terms of mg C/L or ppmC. Soil organic carbon (SOC) is also described using carbon-based units, especially when comparing carbon stocks across samples or treatments. While ppmC conveys carbon concentration, it does not by itself describe total pollutant load unless carbon is the reference component of interest.

The use of ppmC is not standardized as an SI unit or universal convention; the exact meaning can depend on the analytical method and reporting protocol. When interpreting data labeled as ppmC, it is important to consult the accompanying methodology to understand how carbon content is defined and measured, and how it relates to alternative measures such as TOC, DOC, or total ppm concentrations.

See also: total organic carbon (TOC), dissolved organic carbon (DOC), soil organic carbon (SOC), carbon content.