In order to clarify the effect of Potamogeton crispus L.(P.crispus)on bioavailability and biodegradation activity of pyrene in aged and unaged sediments,model calculation based on experimental results was carried out.During a 36-day experiment,the dissipation ratio of pyrene was increased by planting but decreased by aging.P.crispus improved the dissipation more significantly in aged sediments(45.9%)than in unaged sediments(17.6%).Results derived from a two-compartment desorption model showed that the decrease of rapidly desorbing fraction of pyrene was in the order of aged sediments without plant(A)> unaged sediments without plant(U)> unaged sediments with plant(UP)> aged sediments with plant(AP).Moreover,the results of biodegradation kinetic model showed that the first-order biodegradation coefficient was in the order of AP > UP > U and A,which was consistent with that of sediment redox potential.These modeling results indicated that planting could enhance the bioavailability(73.9%)and biodegradation activity(277%)of pyrene more significantly in aged sediments as compared to unaged sediments(13.1%and 150%,respectively),which should be the key reasons leading to more significant dissipation increment of pyrene in aged sediments by P.crispus.