Persistence
The length of time a pollutant remains in the environment before degradation or removal.
Formula
Half-life (t½) = 0.693 / k (where k = degradation rate constant)
Real World
DDT was banned in the UK in 1984, yet it is still detected in Arctic wildlife today — its 15-year half-life means meaningful concentrations persist decades after application ceased.
Exam Focus
Always link persistence to bioaccumulation risk; examiners expect you to explain why persistent pollutants pose greater ecological hazard than degradable ones.
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