Role of dissolved organic matter, nitrate, and bicarbonate in the photolysis of aqueous fipronil.
A multivariate kinetic model of aqueous fipronil photodegradation was developed as a function of dissolved organic matter (DOM), bicarbonate, and nitrate at concentrations that bracketthose commonly observed in natural waters (ca. 0-10 mg/L). Several pathways were available for fipronil photodegradation in this system, including direct photolysis and indirect photooxidation by species produced during the illumination of natural waters (e.g., 3NOM*, 1O2*, *OH, *CO3(1-), *OOR, *OOH, e(aq)-, O2(*-)). Product studies indicated thatfipronil was quantitatively converted to fipronil desulfinyl, a product that is associated with direct photolysis alone. DOM was the only variable that affected fipronil degradation; it decreased the rate of fipronil photodegradation primarily through competitive light absorption (i.e., attenuation) and the quenching of fipronil*. The addition of sodium chloride (30 percent per thousand) resulted in a more rapid rate (approximately 20%) of fipronil loss in comparison to equivalent experiments performed without sodium chloride, implying that fipronil may be more photolabile in marine environments.
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA.
Spencer S
SS
Walse
Stephen L
SL
Morgan
Li
L
Kong
John L
JL
Ferry
D001639:Bicarbonates / Q000737:chemistry*; D008956:Models, Chemical; D009566:Nitrates / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D010777:Photochemistry; D011720:Pyrazoles / Q000032:analysis* / Q000528:radiation effects; D012995:Solubility; D014466:Ultraviolet Rays; D014874:Water Pollutants, Chemical / Q000032:analysis* / Q000528:radiation effects
D001639:Bicarbonates; D009566:Nitrates; D009930:Organic Chemicals; D011720:Pyrazoles; D014874:Water Pollutants, Chemical; C082360:fipronil