Table 1. Comparison of pesticides reactivity towards OH radicals in gas phase and in partficle phase (rate constants and half-lives) and partitioning of pesticides in particle phase with the effective rate constants.
Pesticide | estimated in gas-phasea (cm3 molecule−1 s−1) | Estimated half-lives in gas phaseb (days) | in particle phases (cm3 molecule−1 s−1) | Partitioning in particle phasecΦpesticide | in gas and particle phases (cm3 molecule−1 s−1) | Atmospheric half-lives in gas and particle phasesb (days) |
---|---|---|---|---|---|---|
Pendimethalin | 3.0 · 10−11 | 0.4 | (4.3 ± 2.2) · 10−13 | 0.01 | 3.0 · 10−11 | 0.4 |
Cyprodinil | 2.0 · 10−10 | 0.1 | (9.7 ± 2.9) · 10−13 | 0.07 | 1.9 · 10−10 | 0.1 |
Tetraconazole | 1.1 · 10−11 | 1.0 | <<(4.3 ± 2.2) · 10−13 | 0.38 | <<7.0 · 10−12 | >>1.5 |
Oxadiazon | 2.4 · 10−11 | 0.5 | <<(4.3 ± 2.2) · 10−13 | 0.62 | <<9.4 · 10−12 | >>1.1 |
Fipronil | 9.6 · 10−11 | 0.1 | <<(4.3 ± 2.2) · 10−13 | 0.84 | <<1.6 · 10−11 | >>0.7 |
Deltamethrin | 2.3 · 10−11 | 0.5 | (6.9 ± 2.8) · 10−13 | 0.91 | 2.7 · 10−12 | 4.0 |
Permethrin | 2.3 · 10−11 | 0.5 | (5.5 ± 2.2) · 10−13 | 0.97 | 1.2 · 10−12 | 8.9 |
Difenoconazole | 2.2 · 10−11 | 0.5 | <<(4.3 ± 2.2) · 10−13 | 0.99 | <<6.5 · 10−13 | >>16.5 |
aEstimated rate constants by modeling using AOPWIN program.
bHalf-lives for an average concentration [OH(g)] = 1.5 · 106 cm−3 and for an exposure of 12 h by day.
cPartitioning in the particle phase estimated by AEROWIN software using the Junge-Pankow adsorption mode.