Organic sorbents as barriers to decrease the mobility of herbicides in soils.

49 páginas, 5 tablas, 3 figuras, 2 figuras suplementarias. -- The definitive version is available at http://www.elsevier.comNumerous organic sorbents have been introduced in recent years to develop technologies aimed at preventing the pollution of soil and water by pesticides. This work set out to study and compare the effect on the mobility of ethofumesate and terbutryn in a soil of five low-cost organic residues (grape marc, pine wastes, urban solid wastes, sewage sludge, and spent mushroom substrate), and two organoclays (swelling and non-swelling clays modified with octadecyltrimethylammonium). Herbicide leaching experiments were conducted under water saturated flow in hand-packed soil columns in which sorbents were incorporated as barriers. The breakthrough curves obtained were fitted to the one-dimensional transport model CXTFIT. The leaching of ethofumesate and terbutryn in the soil recorded figures of 96.0% and 66.9%, respectively, and when a barrier of organic residues or organoclays was incorporated into the column these amounts decreased for ethofumesate to 65.7–84.6% and 3.35–5.99%, and for terbutryn to 0.28–13.8% and 1.11–0.79%. The effect of the organoclay barriers was more significant for ethofumesate, while the effect of organoclays for terbutryn was close to that of certain organic residues. The barrier's impact was also observed in the variation of the retardation coefficients (Rexp), which increased by 3–202 or 3–40 times those coefficients for soil without a barrier. Distribution coefficients (K) increased 72–147 and 3771–9461 times (ethofumesate), and 46–986 and 264–747 times (terbutryn) for amended soils with both organic residues and organoclays, respectively. Significant inverse correlations were found for ethofumesate between sorption coefficients and leached amounts due to the relevant effect of the OC content of organic sorbents in these processes, although this was not the case for terbutryn whose behavior was linked to the OC nature of organic sorbents. The herbicide leaching data were well described by CXTFIT (mean square error, MSE < 1.2 · 10− 6) for most of the treatments, although it fell short with high sorption capacity barriers. Information from this study may be used to select an efficient method based on the use of sorbent barriers designed to prevent water contamination by pesticides.This work was funded by the “Agencia Española de Cooperación Internacional para el Desarrollo (AECID)” as a part of the Project 60/04/P/E and by MINECO/FEDER UE (Project AGL2015-69485-R).Peer reviewe