title: Abiotic partitioning of clothianidin under simulated rice field conditions.
abstract: BACKGROUND
  Clothianidin is registered for pre- and post-flood application in Californian rice fields for control of the rice seed midge, Cricotopus sylvestris, and the rice water weevil, Lissorhoptrus oryzophilus. The objective was to characterize air-water and soil-water partitioning of clothianidin under simulated Californian rice field conditions.
  
  
  RESULTS
  Clothianidin was confirmed to be non-volatile (from water) via the gas purge method, as no loss from the aqueous phase was observed at 22 and 37 °C; an upper-limit KH value was calculated at 2.9 × 10(-11) Pa m(3) mol(-1) (20 °C). Soil-water partitioning was determined by the batch equilibrium method using four soils collected from rice fields in the Sacramento Valley, and sorption affinity (Kd ), sorbent capacity, desorption and organic-carbon-normalized distribution (Koc ) were determined. Values for pH, cation exchange capacity and organic matter content ranged from 4.5 to 6.6, from 5.9 to 37.9 and from 1.25 to 1.97% respectively. The log Koc values (22 and 37 °C) ranged from 2.6 to 2.7, while sorption capacity was low at 22 °C and decreased further at 37 °C. Hysteresis was observed in soils at both temperatures, suggesting that bound residues do not readily desorb.
  
  
  CONCLUSIONS
  Soil-water and air-water partitioning will not significantly reduce offsite transport of clothianidin from flooded rice fields via drainage.
authors.affiliation: Department of Environmental Toxicology, College of Agricultural and Environmental Sciences, University of California, Davis, CA, USA.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Mulligan
authors.affiliation: Department of Land, Air and Water Resources, University of California, Davis, CA, USA.
authors.forename: Sanjai J
authors.initials: SJ
authors.lastname: Parikh
authors.affiliation: Department of Environmental Toxicology, College of Agricultural and Environmental Sciences, University of California, Davis, CA, USA.
authors.forename: Ronald S
authors.initials: RS
authors.lastname: Tjeerdema
mesh_terms: D000393:Air Pollutants / Q000737:chemistry; D000818:Animals; D006146:Guanidines / Q000737:chemistry*; D007300:Insect Control; D007306:Insecticides / Q000737:chemistry*; D000073943:Neonicotinoids; D012275:Oryza / Q000254:growth & development* / Q000469:parasitology; D012989:Soil Pollutants / Q000737:chemistry; D013844:Thiazoles / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry; D048889:Weevils / Q000187:drug effects / Q000502:physiology
chemical_list: D000393:Air Pollutants; D006146:Guanidines; D007306:Insecticides; D000073943:Neonicotinoids; D012989:Soil Pollutants; D013844:Thiazoles; D014874:Water Pollutants, Chemical; C480342:clothianidin
keywords: abiotic pesticide dissipation; air-water partitioning; clothianidin; neonicotinoid insecticides; soil-water partitioning