Diffusion-advection process modeling of organochlorine pesticides in rivers

This paper deals with the diffusion-advection process modeling of organochlorine pesticides (OCPs) dissolved in a topical river. The novelty consists of proposing mathematical expressions to estimate the physical coefficients (molecular diffusion, advective diffusion, partition) and biochemical coefficients (substrate utilization rate) of OCPs advection-diffusion processes combined to OCPs biochemical transformation processes. The OCPs involved were DDTs (p.p'-DDT, o.p'-DDT, p.p'-DDD, p.p'-DDE, o.p'-DDE) and DRINs (Aldrin, Dieldrin and Endrin). Four scenarios for simulating the OCPs transport were calibrated: (1) molecular diffusion, (2) biochemical transformation, (3) advection-diffusion and (4) a combination of advection-diffusion, biochemical transformation and sorption/desorption processes. The evaluated scenarios predicted with a good approach to the OCPs's spatio-temporal distribution with a prediction capability within an interval until 1.5 standard deviation with respect to the mean of difference between observed and simulated OCPs The scenario N degrees 4 associated to a coupled model offered a suitable prediction of processes for a tropical river.