# Mass Balance

The processes described above can be combined into mass balance equations for the well-mixed water body and the well-mixed sediment layer:

         $$\Delta pst\_{lkwtr}=pst\_{in}- (pst\_{sol,o}+ p st\_{sorb,o})-pst\_{deg,wtr} -pst\_{vol,wtr}- pst\_{stl,wtr}+pst\_{rsp,wt r}\pm pst\_{dif}$$

                                                                                                                       8:4.3.1

$$\Delta pst\_{lksed}=pst\_{deg,sed}+pst\_{stl,wtr}-pst\_{rsp,wtr }-pst\_{bur}\pm pst\_{dif}$$        8:4.3.2

where $$\Delta pst\_{lkwtr}$$ is the change in pesticide mass in the water layer (mg pst),  $$\Delta pst\_{lksed}$$ is the change in pesticide mass in the sediment layer (mg pst), $$pst\_{in}$$ is the pesticide added to the water body via inflow (mg pst), $$pst\_{sol,o}$$ is the amount of dissolved pesticide removed via outflow (mg pst), $$p st\_{sorb,o}$$ 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), $$pst\_{rsp,wt r}$$ 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)