# Heavy Metal Routing Heavy metals are pollutants that are increasingly under scrutiny. Most heavy metals can exist in a number of different valence states and the solubility of a heavy metal is often dependent on the valence state it is in. The complexity of the processes affecting heavy metal solubility make modeling these processes directly unrealistic. At this time, SWAT+ allows heavy metal loadings to be added to the stream network in point source loading inputs. SWAT+ currently routes the heavy metals through the channel network, but includes no algorithms to model in-stream processes. Simple mass balance equations are used to determine the movement of heavy metals through the river network. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://swatplus.gitbook.io/io-docs/theoretical-documentation/section-7-main-channel-processes/heavy-metal-routing.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.