Mass Balance

The processes described above can be combined into mass balance equations for the well-mixed reach segment and the well-mixed sediment layer: $\Delta pst_{rchwtr}=pst_{in}-(pst_{sol,o}+pst_{sorb,o})-pst_{deg,wtr}-pst_{vol,wtr}-pst_{stl,wtr}+pst_{rsp,wtr}\pm pst_{dif}$​

7:4.3.1

$\Delta pst_{rchsed}=-pst_{deg,sed}+pst_{stl,wtr}-pst_{rsp,wtr}-pst_{bur}\pm pst_{dif}$ 7:4.3.2

where $\Delta pst_{rchwtr}$ is the change in pesticide mass in the water layer (mg pst), $\Delta pst_{rchsed}$ is the change in pesticide mass in the sediment layer (mg pst), $pst_{in}$ is the pesticide added to the reach segment via inflow (mg pst), $pst_{sol,o}$ is the amount of dissolved pesticide removed via outflow (mg pst), $pst_{sorb,o}$ is the amount of particulate pesticide removed via outflow (mg pst), $pst_{deg,wtr}$ is the amount of pesticide removed from the water via degradation (mg pst), $pst_{vol,wtr}$ is the amount of pesticide removed via volatilization (mg pst), $pst_{stl,wtr}$ is the amount of pesticide removed from the water due to settling (mg pst), $pst_{rsp,wtr}$ is the amount of pesticide removed via resuspension (mg pst), $pst_{dif}$ is the amount of pesticide transferred between the water and sediment by diffusion (mg pst),$pst_{deg,sed}$ is the amount of pesticide removed from the sediment via degradation (mg pst), $pst_{bur}$ is the amount of pesticide removed via burial (mg pst).