DDT IN A FRESHWATER MARSH: A SIMULATION STUDY.

A computer simulation model has been constructed t o represent t h e dynamics of chlorine-36 labelled DDT i n a Lake Erie marsh, An exponent i a l l y decreasing input function (representing release of DDT from t h e granular formulati on i n w h i ch it was appli ed) determi nes concentration i n m t e r , from which one-or two-compartment models represent t h e concent r a t i o n i n various forms of f l o r a and fauna.Observational data on 10 plant speci e s , 6 invertebrates, and 3 vertebrate species were modelled, Five species (a plant, an invertebrate speefes, and t h e 3 vertebrates) were used f o r a food-chain simulation, The overall r e s u l t s generally suggest t h a t simple models, of t h e kind used t o study radionuclide transf e r through food chains, w i l l provide reasonably good representations of t h e behavior of DDT i n food chains, It i s suggested %hat controlled experiments a r e needed t o properly identify t h e components of a model, and t h a t a number of questions about sampling methodology remain unanswered.