# Degradation

Pesticides in both the particulate and dissolved forms are subject to degradation. The amount of pesticide that is removed from the water via degradation is:

                   $$pst\_{deg,wtr}= k\_{p,aq}\*pst\_{rchwtr}\*TT$$                                                          7:4.1.6

where $$pst\_{deg,wtr}$$ is the amount of pesticide removed from the water via degradation (mg pst), $$k\_{p,aq}$$ is the rate constant for degradation or removal of pesticide in the water (1/day), $$pst\_{rchwtr}$$ is the amount of pesticide in the water at the beginning of the day (mg pst), and $$TT$$ is the flow travel time (days). The rate constant is related to the aqueous half-life:

                  $$k\_{p,aq}=\frac{0.693}{t\_{1/2,aq}}$$                                                                                             7:4.1.7

where $$k\_{p,aq}$$ is the rate constant for degradation or removal of pesticide in the water (1/day), and $$t\_{1/2,aq}$$ is the aqueous half-life for the pesticide (days).