Reactivity of hydroxyl radicals with neonicotinoid insecticides: mechanism and changes in toxicity.
The reactivity of hydroxyl radicals (HO ) towards three neonicotonoid insecticides, namely imidacloprid, thiacloprid and acetamiprid was investigated. These radicals were generated by photolysis of H(2)O(2) solutions. Flash photolysis experiments were used to determine the rate constants of 5.5 x 10(10) M(-1)s(-1), 6 x 10(10) M(-1)s(-1), and 7.5 x 10(10) M(-1)s(-1), for the reactions of HO with acetamiprid, imidacloprid, and thiacloprid, respectively. Continuous irradiation experiments in the absence and presence of H(2)O(2) allowed the identification and toxicity evaluation of the primary photo- and oxidation products of the insecticides. In all cases, the less toxic 6-chloronicotinic acid was found to be the major product at higher degrees of oxidation. The results reported here indicate that the half life of the insecticides due to their reaction with HO radicals in natural aquatic reservoirs may vary between 5 h and 19 days, and therefore the hydroxyl radical-mediated oxidation may be a significant abiotic elimination route. However, elimination of the insecticide under such conditions might not improve the quality of the contaminated water, as the primary products of degradation still show considerable toxicity to Vibrio fischeri assays.
Dell'arciprete
María L
ML
Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas (INIFTA), Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Casilla de Correo 16, Sucursal 4 (1900), La Plata, Argentina.
Santos-Juanes
Lucas
L
Sanz
Antonio Arques
AA
Vicente
Rafael
R
Amat
Ana M
AM
Furlong
Jorge P
JP
Mártire
Daniel O
DO
Gonzalez
Mónica C
MC
D048908:Aliivibrio fischeri / Q000166:cytology / Q000187:drug effects*; D006861:Hydrogen Peroxide / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry / Q000633:toxicity; D007306:Insecticides / Q000737:chemistry* / Q000633:toxicity*; D008826:Microbial Sensitivity Tests; D000073943:Neonicotinoids; D009574:Nitro Compounds / Q000737:chemistry / Q000633:toxicity; D010782:Photolysis; D011725:Pyridines / Q000737:chemistry / Q000633:toxicity; D013843:Thiazines / Q000737:chemistry / Q000633:toxicity
D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D011725:Pyridines; D013843:Thiazines; D017665:Hydroxyl Radical; C082359:imidacloprid; C464485:acetamiprid; D006861:Hydrogen Peroxide; C417209:thiacloprid