# 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:

&#x20;        $$\Delta pst_{lkwtr}=pst_{in}- (pst_{sol,o}+ p st_{sorb,o})-pst_{deg,wtr} -pst_{vol,wtr}- pst_{stl,wtr}+pst_{rsp,wt r}\pm pst_{dif}$$

&#x20;                                                                                                                      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)
