Degradation and Transport of the Chiral Herbicide S-Metolachlor at the Catchment Scale: Combining Observation Scales and Analytical Approaches

• DOI: 10.1021/acs.est.7b02297
• Publication Date: 2017-10-23T15:08:13Z
• Authors: Lefrancq Marie; Payraudeau Sylvain; Guyot Benoit; Millet Maurice; Imfeld Gwenaël
• Keywords: Metolachlor; Degradation; Topsoil

Evaluating pesticide degradation and transport in the soil-surface water continuum remains challenging at catchment scale. Here we investigated dissipation of chiral herbicide S-metolachlor (SM) soil relation to its runoff. Analyses SM, transformation products (TPs, i.e., MESA MOXA), enantiomers were combined determine SM plot scales. Assisted by modeling, found that main pathways scale (71%), volatilization (5%), leaching (8%) runoff (3%), while 13% persisted topsoil. This highlights relevance processes. TPs could trace different discharge contributions: MOXA prevailed water, whereas was associated with slower flowpaths. At outlet, 11% applied exported dissolved or particulate phases as (in mass equivalent). A single event 1 week after application 96% which underlined potential importance severe rainfall on seasonal export. Enantioselective enriched R-enantiomer over longer periods may be Altogether, combining observation scales analytical approaches enabled quantify identify how controls export