title: Reduced metribuzin pollution with phosphatidylcholine-clay formulations.
abstract: BACKGROUND
  Metribuzin is a widely used herbicide that has been identified as a groundwater contaminant. In this study, slow-release formulations of metribuzin were designed by encapsulating the active ingredient in phosphatidylcholine (PC) vesicles and adsorbing the vesicles onto montmorillonite.
  
  
  RESULTS
  The maximum active ingredient content in the slow-release formulations was 246 g kg(-1) . Infrared spectroscopy results revealed that the hydrophobic interactions between metribuzin and the alkyl chains on PC were necessary for encapsulation. In addition, water bridges connecting the herbicide and the PC headgroup enhanced the solubility of metribuzin in PC. Adsorption experiments in soils were performed to evaluate the relationship between sorption and leaching. Funnel experiments in a sandy soil revealed that the herbicide was not irreversibly retained in the formulation matrix. In soil column experiments, PC-clay formulations enhanced herbicide accumulation and biological activity in the top soil layer relative to a commercial formulation. PC-clay formulations also reduced the dissipation of metribuzin by a factor of 1.6-2.5.
  
  
  CONCLUSIONS
  A reduction in the recommended dose of metribuzin can be achieved by employing PC-clay formulations, which reduces the environmental risk associated with herbicide applications. Moreover, PC and montmorillonite are non-toxic and do not negatively affect the environment.
authors.affiliation: Institute of Natural Resources and Agrobiology (CSIC), Seville, Spain. undabeyt@irnase.csic.es
authors.forename: Tomás
authors.initials: T
authors.lastname: Undabeytia
authors.forename: Esther
authors.initials: E
authors.lastname: Recio
authors.forename: Celia
authors.initials: C
authors.lastname: Maqueda
authors.forename: Esmeralda
authors.initials: E
authors.lastname: Morillo
authors.forename: Eulalia
authors.initials: E
authors.lastname: Gómez-Pantoja
authors.forename: Trinidad
authors.initials: T
authors.lastname: Sánchez-Verdejo
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry*; D000077215:Clay; D004784:Environmental Monitoring; D006540:Herbicides / Q000737:chemistry; D010713:Phosphatidylcholines / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry; D014227:Triazines / Q000737:chemistry*
chemical_list: D000538:Aluminum Silicates; D006540:Herbicides; D010713:Phosphatidylcholines; D012989:Soil Pollutants; D014227:Triazines; D012822:Silicon Dioxide; C009235:metribuzin; D000077215:Clay