> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/introduction-1/aquifers/aquifer.aqu/ptl_n.md).

# carbon

The carbon content in the aquifer is used to compute a pesticide's Kd value, or distribution coefficient, which is a measure of how tightly a pesticide binds to soil particles. Kd values are important for understanding how pesticides move through the environment.

A higher carbon value increases the pesticide partition coefficient Kd, which increases retardation/sorption behavior and generally reduces pesticide movement with aquifer flow and seepage.