Ionic liquids (ILs) are called "green" solvents, which are due to their unique physicochemical properties and potential applications in various areas. However, the toxicity of ILs has attracted increasing attention from scientific researchers. The present paper studied the toxic effects of 1-octyl-3-methylimidazolium hexafluorophosphate ([C8mim]PF6) on wheat seedlings at 0, 1, 2, 4, 6, and 8 mg l(-1) on days 7, 10 and 13. The present results showed that the growth of wheat seedlings was seriously inhibited when the concentration was higher than 2 mg l(-1) and the inhibitory effect enhanced with increasing concentration and time. The EC50 values for germination, shoot length, root length and dry weight were 11.104, 5.187, 4.380 and 6.292 mg l(-1), respectively. [C8mim]PF6 could cause an increase in the production of ROS, which led to the oxidative damage and lipid peroxidation. Furthermore, these toxic effects on wheat seedlings were irreversible.

Fomesafen is a diphenyl ether herbicide that has an important role in the removal of broadleaf weeds in bean and fruit tree fields. However, very little information is known about the effects of this herbicide on soil microbial community structure and activities. In the present study, laboratory experiments were conducted to examine the effects of different concentrations of fomesafen (0, 10, 100, and 500 μg/kg) on microbial community structure and activities during an exposure period of 60 days, using soil enzyme assays, plate counting, and denaturing gradient gel electrophoresis (DGGE). The results of enzymatic activity experiments showed that fomesafen had different stimulating effects on the activities of acid phosphatase, alkaline phosphatase, and dehydrogenase, with dehydrogenase being most sensitive to fomesafen. On the tenth day, urease activity was inhibited significantly after treatment of different concentrations of fomesafen; this inhibiting effect then gradually disappeared and returned to the control level after 30 days. Plate counting experiments indicated that the number of bacteria and actinomycetes increased in fomesafen-spiked soil relative to the control after 30 days of incubation, while fungal number decreased significantly after only 10 days. The DGGE results revealed that the bacterial community varied in response to the addition of fomesafen, and the intensity of these six bands was greater on day 10. Sequencing and phylogenetic analyses indicated that the six excised DGGE bands were closely related to Emticicia, Bacillus, and uncultured bacteria. After 10 days, the bacterial community exhibited no obvious change compared with the control. Throughout the experiment, we concluded that 0-500 μg/kg of fomesafen could not produce significant toxic effects on soil microbial community structure and activities.

Widespread use of pesticides has caused serious environmental concern. In order to evaluate the fate of organic pesticides in the atmosphere, rate constants for gas phase reactions of OH radicals with dichlorvos, carbaryl, chlordimeform, and 2,4-D butyl ester were measured using the relative rate method at ambient temperature and 101 kPa total pressure. On-line FTIR spectroscopy was used to monitor the concentrations of pesticides as a function of time. The reaction rate constants with OH radicals (in units of cm 3 molecule −1 s −1 ) have been determined as (2.0 ± 0.4) × 10 −11 for dichlorvos, (3.3 ± 0.5) × 10 −11 for carbaryl, (3.0 ± 0.7) × 10 −10 for chlordimeform, and (1.5 ± 0.2) × 10 −11 for 2,4-D butyl ester. These rate constants agree well with those estimated based on the structure-activity relationship. The group rate constant for N C group (k (N C) ) was estimated as 2.7 × 10 −10 cm 3 molecule −1 s −1 . Dimethyl phosphite has been tentatively identified as a product of the reaction of dichlorvos with OH radicals. Atmospheric lifetimes due to the reactions with OH radicals were also estimated (in units of h): 14 ± 3 for dichlorvos, 8 ± 1 for carbaryl, 1.0 ± 0.3 for chlordimeform, and 19 ± 3 for 2,4-D butyl ester. These short atmospheric lifetimes indicate that the four organic pesticides degrade rapidly in the atmosphere, and they themselves are unlikely to cause persistent pollution. Further studies are needed to identify the potential hazard of their degradation products. C 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: [755][756][757][758][759][760][761][762] 2005

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