*3.7.4.4 Mass balance models*

Mass balance models quantify phosphorus inputs, outputs, and internal cycling within a water body. They consider sources such as point and non-point pollution, as well as sinks like sedimentation and nutrient uptake by organisms.

#### *3.7.4.5 Reaction kinetics models*

These models describe the rates at which chemical reactions involving phosphorus occur in aquatic systems. They help predict how phosphorus transformations and interactions with other elements change over time.
