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Partitioning of etofenprox under simulated California rice‐growing conditions
Author(s) -
Vasquez Martice E,
Gunasekara Amrith S,
Cahill Thomas M,
Tjeerdema Ronald S
Publication year - 2010
Publication title -
pest management science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.296
H-Index - 125
eISSN - 1526-4998
pISSN - 1526-498X
DOI - 10.1002/ps.1826
Subject(s) - soil water , chemistry , environmental chemistry , fugacity , partition coefficient , volatilisation , paddy field , environmental science , saturation (graph theory) , agronomy , soil science , chromatography , biology , organic chemistry , mathematics , combinatorics
BACKGROUND: The pyrethroid insecticide etofenprox is of current interest to rice farmers in the Sacramento Valley owing to its effectiveness against the rice water weevil, Lissorhoptrus oryzophilus Kuschel. This study aimed to describe the partitioning of etofenprox under simulated rice field conditions by determining its Henry's law constant ( H ) (an estimate of volatilization) and organic carbon‐normalized soil–water distribution coefficient ( K oc ) at representative field temperatures. A comparison of etofenprox and λ‐cyhalothrin is presented using a level‐1 fugacity model. RESULTS: Experimental determination of H revealed that etofenprox partitioned onto the apparatus walls and did not significantly volatilize; the maximum value of H was estimated to be 6.81 × 10 −1 Pa m 3 mol −1 at 25 °C, based on its air and water method detection limits. Calculated values for H ranged from 5.6 × 10 −3 Pa m 3 mol −1 at 5 °C to 2.9 × 10 −1 Pa m 3 mol −1 at 40 °C, based on estimated solubility and vapor pressure values at various temperatures. Log K oc values (at 25 °C) were experimentally determined to be 6.0 and 6.4 for Princeton and Richvale rice field soils, respectively, and were very similar to the values for other pyrethroids. Finally, temperature appears to have little influence on etofenprox sorption, as the log K oc for the Princeton soil at 35 °C was 6.1. CONCLUSION: High sorption coefficients and relatively insignificant desorption and volatilization of etofenprox suggest that its insolubility drives it to partition from water by sorbing to soils with high affinity. Offsite movement is unlikely unless transported in a bound state on suspended sediments. Copyright © 2009 Society of Chemical Industry