Modeling the vertical distribution of carbendazim in sediments

Abstract

Abstract-The sorption, fate, and vertical distribution of the fungicide Derosal with active ingredient carbendazim in sediments were investigated in indoor freshwater microcosms. Carbendazim penetration in the sediment was measured as a function of time and depth. Freundlich sorption parameters were determined by batchwise equilibration of carbendazim in a sediment suspension. Freundlich parameters were K f ϭ 258 g (1Ϫn) L n /kg and n ϭ 0.78. Analysis of different layers of sediment cores showed a slow penetration of carbendazim in the first 6 cm of the sediment in 60 d. The penetration was successfully simulated with a multilayer model accounting for sorption to organic matter (using the measured isotherm), molecular diffusion, biodegradation, and bioturbation. The calibrated model was most sensitive to the parameters for molecular diffusion and sorption in the sediment. Bioturbation did not affect the carbendazim profiles because of carbendazim toxicity for bioturbators. So there was a direct feedback between carbendazim toxicity and fate. The calibrated model was validated using a dataset obtained from another freshwater microcosm.

Positioning activated carbon amendment technologies in a novel framework for sediment management

“…It has been shown that the application of AC without mixing is nearly as effective as application with initial brief mixing (Sun and Ghosh ; Hale et al ). A high effectiveness of the PAC treatment after only initial mixing in field scale bioaccumulation experiments has been observed (Kupryianchyk et al ) indicating that subsequent mixing by bioturbation (Matisoff ; Koelmans and Jonker ; Kupryianchyk et al 2013a; Lin et al ), turbulent dispersion due to wind induced pressure gradients (Koelmans et al ), or direct wind‐induced resuspension were able to ascertain sufficient mixing of AC. For bioturbation, it has been shown that the presence of bioturbators tolerant to AC addition, may on the one hand enhance mixing and facilitate HOC mass transport to AC particles, whereas on the other hand increase sediment‐to‐water fluxes of HOCs and thus reduce the effectiveness of AC in lowering overlying water concentrations (Cornelissen et al ; Kupryianchyk et al 2013a; Lin et al ).…”

A Mechanistic Model for Simulation of Carbendazim and Chlorothalonil Transport through a Two-Stage Vertical Flow Constructed Wetland

“…The log K ow and K oc affect the sorption process considerably, since they regulate the distribution, mobility and availability of pesticides in different compartments [35]. The target pesticides have a moderate hydrophobic property (2 < log K ow < 3) [13,18]. Chlorothalonil is considered as lowly mobile (K oc > 500) [36]; hence, it is easily adsorbed onto the substrate, while carbendazim is more mobile and continuously transported inside the system.…”

“…The use of vertical flow constructed wetlands for pesticide treatment has been studied recently [14][15][16][17], which has shown great promise towards efficient removal of pesticides. A lot of these studies usually describe the removal efficiency of the pesticides from wastewater; however, very few manage to conduct a more detailed study of pesticide concentration dynamics as the wastewater passes through the substrate bed [18].…”

The TOXSWA model version 3.3 for pesticide behaviour in small surface waters : description of processes

“…Bioturbation is associated with considerable increase in the vertical transport due to bioactivity. Bioturbation was implemented as a particle dispersion process (Koelmans et al, 2000) in TOXSWA 3.4. The implementation is not yet fully tested and documented.…”