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.
Walse
Spencer S
SS
Department of Chemistry and Biochemistry, University of South Carolina, Columbia, South Carolina 29208, USA.
Morgan
Stephen L
SL
Kong
Li
L
Ferry
John L
JL
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