TY - CHAP

T1 - Simulating the fate and release of metazachlor and its transformation products metazachlor oxalic acid and sulfonic acid in a small-scale agricultural catchment

AU - Vollert, Dieter

AU - Gassmann, Matthias

AU - Lange, Jens

AU - Kümmerer, Klaus

AU - Olsson, Oliver

N1 - Conference code: 20

PY - 2018/4

Y1 - 2018/4

N2 - The unwanted release of pesticides after use in agriculture is a known concern for water quality. Thus, a monitoringcampaign was carried out in 2016 and 2017 by the project MUTReWa to determine the release of herbicides fromthe 180 ha area of the Loechernbach catchment. In which the herbicide metazachlor and its transformation products(TPs) metazachlor oxalic acid and sulfonic acid were measured regularly in the base flow and during rainfall-runoffevents even in high concentrations in the Loechernbach catchment. The study area is characterized by vineyardson large terraces and an intensive agricultural use in the valley. A dense road and drainage network accelerates thedrainage of the catchment area.Based on these measurements, the aim of this study was to adapt an existing catchment model, which simulatesthe transport and transformation processes for pesticides in the Loechernbach catchment, for the modeling of theherbicide metazachlor and its TPs oxalic acid and sulfonic acid and to make these available for further simulationstudies.For this purpose, the spatially distributed and process-based catchment area model ZIN-AgriTra was used. Thehydrological sub-model was successfully calibrated for a 6-month high-resolution time series of discharge datafor 2016 (Nash-Sutcliffe efficiency = 0.8). The metazachlor and TPs modeling was done for single rainfall-eventsusing literature parameters for sorption and degradation behavior. The application of metazachlor was adjustedwithin the scope of recommended spray rates to the measured output.The simulation results of outflow and metazachlor concentration fit well with the measurements at the catchmentoutlet. The first event after application causes a strong leaching of metazachlor with maximum concentrations upto 10 µg/L. Thereafter, measurements and simulation results show significantly lower concentrations in the rangeof maximum 200 ng/L. In the model, metazachlor is almost completely degraded in the soil by the end of theapplication period. The results for the simulated transformation products show a maximum concentration of 100ng/L for the sulfonic acid and 400 ng/L for the oxalic acid. The simulated TPs concentration of event and baseoutflows are in the range of the observation. The main discharge path for the TPs is the subsurface flow from thefields, with most of the TPs release being caused by the degradation of the previous year’s application.Concluding, the catchment model ZIN-AgriTra can be seen as a suitable tool for the simulation of the dominantprocesses of the metazachlor release. In addition to the results of the measurement campaign, the model applicationprovided new insights into the behavior and fate of metazachlor and its TPs metazachlor oxalic and sulfonic acids.

AB - The unwanted release of pesticides after use in agriculture is a known concern for water quality. Thus, a monitoringcampaign was carried out in 2016 and 2017 by the project MUTReWa to determine the release of herbicides fromthe 180 ha area of the Loechernbach catchment. In which the herbicide metazachlor and its transformation products(TPs) metazachlor oxalic acid and sulfonic acid were measured regularly in the base flow and during rainfall-runoffevents even in high concentrations in the Loechernbach catchment. The study area is characterized by vineyardson large terraces and an intensive agricultural use in the valley. A dense road and drainage network accelerates thedrainage of the catchment area.Based on these measurements, the aim of this study was to adapt an existing catchment model, which simulatesthe transport and transformation processes for pesticides in the Loechernbach catchment, for the modeling of theherbicide metazachlor and its TPs oxalic acid and sulfonic acid and to make these available for further simulationstudies.For this purpose, the spatially distributed and process-based catchment area model ZIN-AgriTra was used. Thehydrological sub-model was successfully calibrated for a 6-month high-resolution time series of discharge datafor 2016 (Nash-Sutcliffe efficiency = 0.8). The metazachlor and TPs modeling was done for single rainfall-eventsusing literature parameters for sorption and degradation behavior. The application of metazachlor was adjustedwithin the scope of recommended spray rates to the measured output.The simulation results of outflow and metazachlor concentration fit well with the measurements at the catchmentoutlet. The first event after application causes a strong leaching of metazachlor with maximum concentrations upto 10 µg/L. Thereafter, measurements and simulation results show significantly lower concentrations in the rangeof maximum 200 ng/L. In the model, metazachlor is almost completely degraded in the soil by the end of theapplication period. The results for the simulated transformation products show a maximum concentration of 100ng/L for the sulfonic acid and 400 ng/L for the oxalic acid. The simulated TPs concentration of event and baseoutflows are in the range of the observation. The main discharge path for the TPs is the subsurface flow from thefields, with most of the TPs release being caused by the degradation of the previous year’s application.Concluding, the catchment model ZIN-AgriTra can be seen as a suitable tool for the simulation of the dominantprocesses of the metazachlor release. In addition to the results of the measurement campaign, the model applicationprovided new insights into the behavior and fate of metazachlor and its TPs metazachlor oxalic and sulfonic acids.

M3 - Published abstract in conference proceedings

VL - 20

T3 - Geophysical Research Abstracts (GRA)

SP - 19569

BT - Proceedings from the 20th EGU General Assembly

PB - European Geosciences Union (EGU)

T2 - 20th EGU General Assembly - EGU 2018

Y2 - 8 April 2018 through 13 April 2018

ER -