- Email: [email protected]
gas interface
Chemosphere 45 (2001) 875±880
www.elsevier.com/locate/chemosphere
Dissipation of triadimefon on the solid/gas interface J.P. Da Silva *, Abõlio M. Da Silva, I.V. Khmelinskii FCT, Universidade do Algarve, 8000 Faro, Portugal Received 6 October 2000; received in revised form 28 February 2001; accepted 22 March 2001
Abstract The dissipation of triadimefon, as pure solid and in the Bayleton 5 commercial formulation, was studied under controlled and natural conditions. Volatilization and photodegradation were shown to be the main dissipation processes. The volatilization results can be described by an empirical model assuming exponential decay of the volatilization rate. The ®ller of the commercial formulation is determinant for the volatilization but has little eect on the photodegradation rates. The main photoproducts were identi®ed and a reaction mechanism proposed. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: Pesticides; Models; Volatilization; Photodegradation
1. Introduction Dissipation of pesticides is of major importance from the agronomic, economic and environmental points of view. Since pesticides are mainly localized at the solid/ gas interface (Parler, 1992), any description of their behavior in the environment requires the description in these systems. Triadimefon (Fig. 1), {1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl) butanone}, is a widely used systemic fungicide (Kuck, 1987), known to be very ecient against powdery mildew and rust fungi (Buchnauer, 1977). Results on its vapor pressure have been reported (Da Silva and Da Silva, 1997) and a comparative study of its dissipation in greenhouse and ®eld conditions has also been made (Da Silva and Da Silva, 1998). It was proposed that dissipation from leaf surface occurs mainly by volatilization and photodegradation. The results were described by a model including an initial fast phase due to exponential decay of the volatilization rates, followed by a second slower
phase where ®rst-order processes predominate. Although the model describes the experiment satisfactorily, no study of the contribution of the volatilization and photodegradation processes to dissipation has ever been made in well-controlled conditions. The triadimefon photolysis kinetics and its photodegradation products in water were studied (Moza et al., 1995). The photoproducts were also determined in several organic solvents (Nag and Dureja, 1997). However, neither the role of photodegradation nor the product distribution on the solid/gas interface are known. The present work describes volatilization and photodegradation of triadimefon in controlled conditions. The initial fast dissipation phase was con®rmed to be caused by volatilization. We studied the eect of temperature and wind speed on dissipation. The main photoproducts were determined at the solid/gas interface and a reaction mechanism proposed.
2. Experimental *
Corresponding author. Tel.: +351-289-800900; fax: +351289-819403. E-mail address: [email protected] (J.P. Da Silva).
Triadimefon (oered by Bayer Portugal in its highest purity grade); Bayleton 5 (wettable powder with 5% (w/w) of triadimefon); clean-up cartridges (Adsorbex
0045-6535/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 5 - 6 5 3 5 ( 0 1 ) 0 0 0 9 9 - 6
876
J.P. Da Silva et al. / Chemosphere 45 (2001) 875±880 Table 1 Residue of triadimefon lg=sample, upon volatilization at 40°C (wind speed: 0.5 m/s)
Fig. 1. Triadimefon.
RP-18 400 mg, Merck); acetonitrile (Merck, LiChrosolv); deionized and distilled water were used without further treatment. The samples were prepared using aqueous suspensions of Bayleton 5 (1.25 g/l) and aqueous solutions of pure triadimefon (62.5 mg/l). Seven drops 10 ll of each solution were applied onto glass surfaces (Petri dish). The temperature was controlled using a water bath. The wind speed was controlled using an electric fan and monitored with an anemometer. The experiments were conducted both in darkness and under solar radiation. Three separate samples were analyzed for each experimental point against three controls kept in the dark. Triadimefon was extracted with acetone and analyses were performed on a Merck-Hitachi 655A-11 liquid chromatograph with a 655A-22 UV detector. The analysis conditions were published elsewhere (Da Silva and Da Silva, 1997). The products of photodegradation were obtained in a merry-go-round photoreactor at 313 nm (400 W medium-pressure Hg lamp with an appropriate ®lter solution) (Murov, 1973). Irradiated samples were passed through RP-18 100 mg cartridges (Merck) to concentrate the photoproducts. The photoproducts were eluted with 1 ml of acetonitrile, and then separated by preparative HPLC. The separated products were concentrated using RP-18 cartridges. Mass spectra were obtained using a Hewlett Packard 5890 Series II gas chromatograph with a 5971 series mass selective detector. Samples were reanalyzed at each step of the concentration and separation procedure to detect any dark transformations of the photoproducts.
3. Results and discussion Volatilization is the only triadimefon dissipation process in the dark. The evolution of pesticide residue, caused by volatilization at 40°C and 0.5 m/s wind speed is given in Table 1. This temperature is easily achieved on soil and plant surfaces in Algarve, south of Portugal, in spring and summer, when the pesticide is mainly used. The volatilization losses of pure solid triadimefon in the dark show an initial linear section, as expected for pure compounds. The volatilization accounts for about 80%
Time (h)
Pure triadimefon
Bayleton 5
0.00 0.25 0.50 1.00 2.00 3.00 5.00 8.00 11.0 16.0
4.38 3.49 2.69 1.62 0.90 0.77 0.57 0.39 0.26 0.21
4.38 3.54 3.05 2.49 1.81 1.33 0.96 0.87 0.70 0.73
losses of the pure pesticide and for 60% of the commercial formulation in the initial 2 h, although the vapor pressure of triadimefon at this temperature is only 2:37 10 3 Pa (Da Silva and Da Silva, 1997). Da Silva and Da Silva (1998) proposed that the amount of pesticide M per sample could be described by the equation dM dt
k1 e
k2 t
M
k3 M;
1
where the ®rst term corresponds to volatilization losses, the second term corresponds to degradation, k1 ; k2 and k3 being the reaction rate constants. With the degradation negligible, the equation becomes dM dt
k1 e
k2 t
M:
2
Integrating (2), we obtain ln
M k1 e M0 k2
k2 t
1;
3
where M0 is the amount of applied pesticide. Residue data were ®tted using Eq. (3), by least-squares optimization. Values of ln M=M0 as function of t are plotted in Fig. 2 jointly with the ®tted curve. The constants and correlation coecients at dierent temperatures are presented in Table 2. The results con®rm that the initial fast decay of triadimefon in its commercial formulation Bayleton 5, observed by Da Silva and Da Silva (1998) is due to volatilization losses. Such behavior was attributed to water evaporation, leading to formation of a thin crust that prevents pesticide diusion to the surface, and making more adsorption positions available to the pesticide (Da Silva and Da Silva, 1998). The rate constant activation energies were estimated using the results obtained at 30°C and 40°C. Their values are 118 and 78:7 kJ=mol
J.P. Da Silva et al. / Chemosphere 45 (2001) 875±880
877
Fig. 2. Remaining residue of triadimefon upon volatilization at 40°C: (r) experimental values; ± model.
for k1 and k2 , respectively. These results could be used to predict dissipation under dierent environmental conditions. An initial fast dissipation and volatilization phase, followed by a second slower phase has also been found in soil (Nash and Hill, 1990), thus the model discussed is applicable to the biphasic behavior on soil surfaces. This behavior has been described considering an evaporation system composed of two or more com-
Table 2 Constants of the model Temperature (°C)
k1 h 1
k2 h 1
Corr. Coef.
25 30 40
0:11 0:05 0:15 0:02 0:67 0:05
0:045 0:018 0:14 0:02 0:38 0:03
0.995 0.996 0.995
Table 3 Initial volatilization rates at dierent conditions Conditions
Initial rate lg=h sample
Temperature °C
Wind speed (m/s)
Pure triadimefon
Bayleton 5
25 30 30 30 30 40
0.5 0.0 0.1 0.5 1.0 0.5
0:74 0:03 0:26 0:06 0:43 0:05 0:9 0:3 0:73 0:02 3:4 0:1
0:49 005 0:58 0:03 2:7 0:4
partments, allowing volatilization from each and mass transfer between them (Nash and Hill, 1990). Our results suggest that the use of such models cannot describe the biphasic behavior correctly, since the pesticide is distributed uniformly in the commercial formulation and there is no migration of the compound between compartments. The initial volatilization rates are presented in Table 3 in function of temperature and wind speed. Volatilization losses increase with temperature due to increasing vapor pressure. The volatilization rate increases with the wind speed caused by decreasing boundary layer thickness. Our results also suggest that wind speeds over 1 m/s do not signi®cantly increase the volatilization losses. Table 4 shows initial volatilization rates of triadimefon in the dark and exposed to solar radiation. Photodegradation is an important process of triadimefon dissipation on the solid/gas interface. As seen from the initial dissipation rates of the commercial formulation, the solid ®ller has little eect on the photodegradation rates. In fact, assuming that photodegradation and volatilization act in parallel, the subtraction of the initial rates observed in the dark from those observed under solar radiation gives the same photodegradation rate for the pure pesticide and the commercial formulation. Photochemical studies simulating natural conditions should be made using solar radiation or a wavelength interval of solar spectrum at the ground level. Irradiating at 313 nm ful®lls this condition, as the UV absorption spectrum of the compounds studied superimposes
878
J.P. Da Silva et al. / Chemosphere 45 (2001) 875±880
Table 4 Initial dissipation rates lg=h sample of triadimefon at 14°C Conditions
Pure triadimefon
Bayleton 5
Dark Under solar radiation
0:40 0:01 0:73 0:04
0:12 0:01 0:50 0:06
the solar radiation spectrum at ground level in this wavelength region. Three main photoproducts were observed at this wavelength (Table 5), a number much lower than that in solution (Nag and Dureja, 1997). This result can be attributed to lower molecular mobility due to adsorption, hence lower probability of secondary reactions. The main photoproducts suggest two photodegradation paths for triadimefon on the solid/gas interface: one that involves cleavage of the C±O bond in the b position to the carbonyl group (Fig. 3(a)) and Table 5 Main photodegradation products
other that leads to the cleavage of the a C±C bond (Fig. 3 (b)). Path A was earlier proposed in solution (Nag and Dureja, 1997) while the path B is proposed for the ®rst time. The elimination of carbon monoxide, path B, was also observed for other carbonyl compounds at the solid/gas interface (Quinkert et al., 1971; Gao and Hill, 1996). The nature of photoproducts is very important from the environmental point of view, since some degradation products may be more toxic than the parent compound (Moore and Moore, 1976). The results in solution are dierent from those on the solid/gas interface, suggesting that studies of pesticides should be made in conditions as similar as possible to those observed in natural systems. We also found that photodegradation leads to organochlorine compounds, like 4-chlorophenol, also an important xenobiotic (Oudjehani and Boule, 1992).
J.P. Da Silva et al. / Chemosphere 45 (2001) 875±880
879
Fig. 3. Proposed mechanism for the photochemical reaction of tradimefon on the solid/gas interface.
Acknowledgements We are grateful to Bayer Portugal for the sample of triadimefon. This work was supported by Junta Nacogica (JNICT), ional de Investigacß~ao Cientõ®ca e Tecnol grant PRAXIS XXI/BD/3617/94. References Buchnauer, H., 1977. Mode of action of triadimefon in Ustilago avenae. Pestic. Biochem. Physiol. 7, 309±320.
Da Silva, J.P., Da Silva, A.M., 1997. Vapor pressure of triadimefon by the gas saturation method. J. Chem. Eng. Data 42 (3), 538±540. Da Silva, J.P., Da Silva, A.M., 1998. Comparative study of the dissipation of triadimefon in greenhouse and ®eld conditions. Toxicol. Environ. Chem. 66, 229±236. Gao, M., Hill, R.H., 1996. The mechanism of the photoreaction of uranyl 1,3-diketonate complexes as thin ®lms on silicon surfaces. J. Photochem. Photobiol. A 97, 73±79. Kuck, K.H., 1987. Studies on the uptake of Bayletonâ in wheat leaves. P¯anzenschutz-Nachr. Bayer 40, 1±28. Moore, J.W., Moore, E.A., 1976. Environmental Chemistry. Academic Press, New York.
880
J.P. Da Silva et al. / Chemosphere 45 (2001) 875±880
Moza, P.N., Hustert, K., Feich, E., Kettrup, A., 1995. Comparative rates of photolysis of triadimefon in aqueous solution in the presence of humic and fulvic acids. Chemosphere 30, 605±610. Murov, S.L., 1973. Handbook of Photochemistry. Marcel Dekker, New York. Nag, S.K., Dureja, P., 1997. Photodegradation of azole fungicide triadimefon. J. Agric. Food Chem. 45, 294±298. Nash, R.G., Hill, B.D., 1990. Modeling pesticide volatilization and soil decay under controlled conditions. In: Kurtz, D.A. (Ed.), Long Range Transport of Pesticides. Lewis Publishers, pp. 17±28.
Oudjehani, K., Boule, P., 1992. Photoreactivity of 4-chlorophenol in aqueous solution. J. Photochem. Photobiol. A 68, 363±373. Parler, H., 1992. Mechanisms for the behavior of pesticides on surfaces. In: Chemistry of Plant Protection. Springer, Berlin, Heidelberg, pp. 107±134. Quinkert, G., Palmowski, J., Lorenz, H.-P., Wiersdor, W.-W., Finke, M., 1971. Non-chelotropic photodecarbonylation of 1,2-diphenyl-substituted 2-indanone derivates. Angew. Chem. Int. Ed. 10 (3), 198±199.
www.elsevier.com/locate/chemosphere
Dissipation of triadimefon on the solid/gas interface J.P. Da Silva *, Abõlio M. Da Silva, I.V. Khmelinskii FCT, Universidade do Algarve, 8000 Faro, Portugal Received 6 October 2000; received in revised form 28 February 2001; accepted 22 March 2001
Abstract The dissipation of triadimefon, as pure solid and in the Bayleton 5 commercial formulation, was studied under controlled and natural conditions. Volatilization and photodegradation were shown to be the main dissipation processes. The volatilization results can be described by an empirical model assuming exponential decay of the volatilization rate. The ®ller of the commercial formulation is determinant for the volatilization but has little eect on the photodegradation rates. The main photoproducts were identi®ed and a reaction mechanism proposed. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: Pesticides; Models; Volatilization; Photodegradation
1. Introduction Dissipation of pesticides is of major importance from the agronomic, economic and environmental points of view. Since pesticides are mainly localized at the solid/ gas interface (Parler, 1992), any description of their behavior in the environment requires the description in these systems. Triadimefon (Fig. 1), {1-(4-chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl) butanone}, is a widely used systemic fungicide (Kuck, 1987), known to be very ecient against powdery mildew and rust fungi (Buchnauer, 1977). Results on its vapor pressure have been reported (Da Silva and Da Silva, 1997) and a comparative study of its dissipation in greenhouse and ®eld conditions has also been made (Da Silva and Da Silva, 1998). It was proposed that dissipation from leaf surface occurs mainly by volatilization and photodegradation. The results were described by a model including an initial fast phase due to exponential decay of the volatilization rates, followed by a second slower
phase where ®rst-order processes predominate. Although the model describes the experiment satisfactorily, no study of the contribution of the volatilization and photodegradation processes to dissipation has ever been made in well-controlled conditions. The triadimefon photolysis kinetics and its photodegradation products in water were studied (Moza et al., 1995). The photoproducts were also determined in several organic solvents (Nag and Dureja, 1997). However, neither the role of photodegradation nor the product distribution on the solid/gas interface are known. The present work describes volatilization and photodegradation of triadimefon in controlled conditions. The initial fast dissipation phase was con®rmed to be caused by volatilization. We studied the eect of temperature and wind speed on dissipation. The main photoproducts were determined at the solid/gas interface and a reaction mechanism proposed.
2. Experimental *
Corresponding author. Tel.: +351-289-800900; fax: +351289-819403. E-mail address: [email protected] (J.P. Da Silva).
Triadimefon (oered by Bayer Portugal in its highest purity grade); Bayleton 5 (wettable powder with 5% (w/w) of triadimefon); clean-up cartridges (Adsorbex
0045-6535/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII: S 0 0 4 5 - 6 5 3 5 ( 0 1 ) 0 0 0 9 9 - 6
876
J.P. Da Silva et al. / Chemosphere 45 (2001) 875±880 Table 1 Residue of triadimefon lg=sample, upon volatilization at 40°C (wind speed: 0.5 m/s)
Fig. 1. Triadimefon.
RP-18 400 mg, Merck); acetonitrile (Merck, LiChrosolv); deionized and distilled water were used without further treatment. The samples were prepared using aqueous suspensions of Bayleton 5 (1.25 g/l) and aqueous solutions of pure triadimefon (62.5 mg/l). Seven drops 10 ll of each solution were applied onto glass surfaces (Petri dish). The temperature was controlled using a water bath. The wind speed was controlled using an electric fan and monitored with an anemometer. The experiments were conducted both in darkness and under solar radiation. Three separate samples were analyzed for each experimental point against three controls kept in the dark. Triadimefon was extracted with acetone and analyses were performed on a Merck-Hitachi 655A-11 liquid chromatograph with a 655A-22 UV detector. The analysis conditions were published elsewhere (Da Silva and Da Silva, 1997). The products of photodegradation were obtained in a merry-go-round photoreactor at 313 nm (400 W medium-pressure Hg lamp with an appropriate ®lter solution) (Murov, 1973). Irradiated samples were passed through RP-18 100 mg cartridges (Merck) to concentrate the photoproducts. The photoproducts were eluted with 1 ml of acetonitrile, and then separated by preparative HPLC. The separated products were concentrated using RP-18 cartridges. Mass spectra were obtained using a Hewlett Packard 5890 Series II gas chromatograph with a 5971 series mass selective detector. Samples were reanalyzed at each step of the concentration and separation procedure to detect any dark transformations of the photoproducts.
3. Results and discussion Volatilization is the only triadimefon dissipation process in the dark. The evolution of pesticide residue, caused by volatilization at 40°C and 0.5 m/s wind speed is given in Table 1. This temperature is easily achieved on soil and plant surfaces in Algarve, south of Portugal, in spring and summer, when the pesticide is mainly used. The volatilization losses of pure solid triadimefon in the dark show an initial linear section, as expected for pure compounds. The volatilization accounts for about 80%
Time (h)
Pure triadimefon
Bayleton 5
0.00 0.25 0.50 1.00 2.00 3.00 5.00 8.00 11.0 16.0
4.38 3.49 2.69 1.62 0.90 0.77 0.57 0.39 0.26 0.21
4.38 3.54 3.05 2.49 1.81 1.33 0.96 0.87 0.70 0.73
losses of the pure pesticide and for 60% of the commercial formulation in the initial 2 h, although the vapor pressure of triadimefon at this temperature is only 2:37 10 3 Pa (Da Silva and Da Silva, 1997). Da Silva and Da Silva (1998) proposed that the amount of pesticide M per sample could be described by the equation dM dt
k1 e
k2 t
M
k3 M;
1
where the ®rst term corresponds to volatilization losses, the second term corresponds to degradation, k1 ; k2 and k3 being the reaction rate constants. With the degradation negligible, the equation becomes dM dt
k1 e
k2 t
M:
2
Integrating (2), we obtain ln
M k1 e M0 k2
k2 t
1;
3
where M0 is the amount of applied pesticide. Residue data were ®tted using Eq. (3), by least-squares optimization. Values of ln M=M0 as function of t are plotted in Fig. 2 jointly with the ®tted curve. The constants and correlation coecients at dierent temperatures are presented in Table 2. The results con®rm that the initial fast decay of triadimefon in its commercial formulation Bayleton 5, observed by Da Silva and Da Silva (1998) is due to volatilization losses. Such behavior was attributed to water evaporation, leading to formation of a thin crust that prevents pesticide diusion to the surface, and making more adsorption positions available to the pesticide (Da Silva and Da Silva, 1998). The rate constant activation energies were estimated using the results obtained at 30°C and 40°C. Their values are 118 and 78:7 kJ=mol
J.P. Da Silva et al. / Chemosphere 45 (2001) 875±880
877
Fig. 2. Remaining residue of triadimefon upon volatilization at 40°C: (r) experimental values; ± model.
for k1 and k2 , respectively. These results could be used to predict dissipation under dierent environmental conditions. An initial fast dissipation and volatilization phase, followed by a second slower phase has also been found in soil (Nash and Hill, 1990), thus the model discussed is applicable to the biphasic behavior on soil surfaces. This behavior has been described considering an evaporation system composed of two or more com-
Table 2 Constants of the model Temperature (°C)
k1 h 1
k2 h 1
Corr. Coef.
25 30 40
0:11 0:05 0:15 0:02 0:67 0:05
0:045 0:018 0:14 0:02 0:38 0:03
0.995 0.996 0.995
Table 3 Initial volatilization rates at dierent conditions Conditions
Initial rate lg=h sample
Temperature °C
Wind speed (m/s)
Pure triadimefon
Bayleton 5
25 30 30 30 30 40
0.5 0.0 0.1 0.5 1.0 0.5
0:74 0:03 0:26 0:06 0:43 0:05 0:9 0:3 0:73 0:02 3:4 0:1
0:49 005 0:58 0:03 2:7 0:4
partments, allowing volatilization from each and mass transfer between them (Nash and Hill, 1990). Our results suggest that the use of such models cannot describe the biphasic behavior correctly, since the pesticide is distributed uniformly in the commercial formulation and there is no migration of the compound between compartments. The initial volatilization rates are presented in Table 3 in function of temperature and wind speed. Volatilization losses increase with temperature due to increasing vapor pressure. The volatilization rate increases with the wind speed caused by decreasing boundary layer thickness. Our results also suggest that wind speeds over 1 m/s do not signi®cantly increase the volatilization losses. Table 4 shows initial volatilization rates of triadimefon in the dark and exposed to solar radiation. Photodegradation is an important process of triadimefon dissipation on the solid/gas interface. As seen from the initial dissipation rates of the commercial formulation, the solid ®ller has little eect on the photodegradation rates. In fact, assuming that photodegradation and volatilization act in parallel, the subtraction of the initial rates observed in the dark from those observed under solar radiation gives the same photodegradation rate for the pure pesticide and the commercial formulation. Photochemical studies simulating natural conditions should be made using solar radiation or a wavelength interval of solar spectrum at the ground level. Irradiating at 313 nm ful®lls this condition, as the UV absorption spectrum of the compounds studied superimposes
878
J.P. Da Silva et al. / Chemosphere 45 (2001) 875±880
Table 4 Initial dissipation rates lg=h sample of triadimefon at 14°C Conditions
Pure triadimefon
Bayleton 5
Dark Under solar radiation
0:40 0:01 0:73 0:04
0:12 0:01 0:50 0:06
the solar radiation spectrum at ground level in this wavelength region. Three main photoproducts were observed at this wavelength (Table 5), a number much lower than that in solution (Nag and Dureja, 1997). This result can be attributed to lower molecular mobility due to adsorption, hence lower probability of secondary reactions. The main photoproducts suggest two photodegradation paths for triadimefon on the solid/gas interface: one that involves cleavage of the C±O bond in the b position to the carbonyl group (Fig. 3(a)) and Table 5 Main photodegradation products
other that leads to the cleavage of the a C±C bond (Fig. 3 (b)). Path A was earlier proposed in solution (Nag and Dureja, 1997) while the path B is proposed for the ®rst time. The elimination of carbon monoxide, path B, was also observed for other carbonyl compounds at the solid/gas interface (Quinkert et al., 1971; Gao and Hill, 1996). The nature of photoproducts is very important from the environmental point of view, since some degradation products may be more toxic than the parent compound (Moore and Moore, 1976). The results in solution are dierent from those on the solid/gas interface, suggesting that studies of pesticides should be made in conditions as similar as possible to those observed in natural systems. We also found that photodegradation leads to organochlorine compounds, like 4-chlorophenol, also an important xenobiotic (Oudjehani and Boule, 1992).
J.P. Da Silva et al. / Chemosphere 45 (2001) 875±880
879
Fig. 3. Proposed mechanism for the photochemical reaction of tradimefon on the solid/gas interface.
Acknowledgements We are grateful to Bayer Portugal for the sample of triadimefon. This work was supported by Junta Nacogica (JNICT), ional de Investigacß~ao Cientõ®ca e Tecnol grant PRAXIS XXI/BD/3617/94. References Buchnauer, H., 1977. Mode of action of triadimefon in Ustilago avenae. Pestic. Biochem. Physiol. 7, 309±320.
Da Silva, J.P., Da Silva, A.M., 1997. Vapor pressure of triadimefon by the gas saturation method. J. Chem. Eng. Data 42 (3), 538±540. Da Silva, J.P., Da Silva, A.M., 1998. Comparative study of the dissipation of triadimefon in greenhouse and ®eld conditions. Toxicol. Environ. Chem. 66, 229±236. Gao, M., Hill, R.H., 1996. The mechanism of the photoreaction of uranyl 1,3-diketonate complexes as thin ®lms on silicon surfaces. J. Photochem. Photobiol. A 97, 73±79. Kuck, K.H., 1987. Studies on the uptake of Bayletonâ in wheat leaves. P¯anzenschutz-Nachr. Bayer 40, 1±28. Moore, J.W., Moore, E.A., 1976. Environmental Chemistry. Academic Press, New York.
880
J.P. Da Silva et al. / Chemosphere 45 (2001) 875±880
Moza, P.N., Hustert, K., Feich, E., Kettrup, A., 1995. Comparative rates of photolysis of triadimefon in aqueous solution in the presence of humic and fulvic acids. Chemosphere 30, 605±610. Murov, S.L., 1973. Handbook of Photochemistry. Marcel Dekker, New York. Nag, S.K., Dureja, P., 1997. Photodegradation of azole fungicide triadimefon. J. Agric. Food Chem. 45, 294±298. Nash, R.G., Hill, B.D., 1990. Modeling pesticide volatilization and soil decay under controlled conditions. In: Kurtz, D.A. (Ed.), Long Range Transport of Pesticides. Lewis Publishers, pp. 17±28.
Oudjehani, K., Boule, P., 1992. Photoreactivity of 4-chlorophenol in aqueous solution. J. Photochem. Photobiol. A 68, 363±373. Parler, H., 1992. Mechanisms for the behavior of pesticides on surfaces. In: Chemistry of Plant Protection. Springer, Berlin, Heidelberg, pp. 107±134. Quinkert, G., Palmowski, J., Lorenz, H.-P., Wiersdor, W.-W., Finke, M., 1971. Non-chelotropic photodecarbonylation of 1,2-diphenyl-substituted 2-indanone derivates. Angew. Chem. Int. Ed. 10 (3), 198±199.