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The Environmental Fate of Trifloxystrobin

Trifloxystrobin (TFS) is a recently introduced mesostemic fungicide of the strobilurin group with an oxime-ether side chain (Fig. 7). The combination of the methyl and substituted phenyl substituents in the oximether moiety and the presence of a trifluoromethyl group in the side chain of the phenyl ring provide broad fungicidal efficacy against fungal diseases that mostly attack fruit, vegetable and crops.

126_trifloxystrobin

Structural formula of trifloxystrobin (EE isomer)

 

Aim

This research project was undertaken to investigate the fate of TFS in soil environment with the following objectives

  1. to study the rate of degradation of TFS in soils of different physicochemical properties and geographic origins and find its effect on soil biological properties
  2. to study the adsorption/desorption of TFS on soils of different physicochemical properties
  3. to study the photolytic degradation of TFS in aquatic system.


Approach

'''The degradation experiment in soil'''

Fate of trifloxystrobin (TFS) was studied under in-vitro condition. TFS was applied in 3 soils (USDA classification: Typic Ustochrepts, Vertic Ustropepts and Typic Cambudolls) with different physico-chemical properties and geographical origins from India and Germany and the kinetics of biological degradation was studied according to the international protocols of EC, SETAC, BBA and FDA. The degradation experiment was carried out for 90 days and the samples were analyzed at regular intervals for TFS (EE conformation), its 3 isomers (EZ, ZE and ZZ) and also the acid metabolites of all the 4 above-mentioned isomers (EE-acid, EZ-acid, ZE-acid and ZZ-acid) by LC-MS/MS.

'''Adsorption-Desorption'''

The adsorption and desorption rate kinetics and isotherms were studied according to the US-EPA method on all the test soils.

'''Photolytic degradation in water '''

The photolysis studies employed three different liquid media, namely pure acetone, water/methanol (9/1 v/v) and water/methanol (9/1 v/v) and humic acid 10 mg/L was used. At 12 different geographic locations between the latitudes of 20° and 60° N
the photolytic environmental half time was calculated for the months of March, June, September and December.

Results

Degradation kinetics

The biodegradation of TFS in darkness could best be explained by first + first-order rate kinetics with half-lives ranging between 1.8 and 2.3 days. Hydrolysis was found to be the major pathway of degradation resulting in the formation of the acid metabolite, TFS-acid with EE conformation.

Sorption study

The adsorption rate of both TFS and TFS-acid followed linear or Freundlich isotherms. The extent of adsorption was directly correlated with organic matter and clay contents, whereas desorption had a negative correlation. In case of the TFS-acid, however, the adsorption was weaker. Hence, if its further degradation is slow, it may contaminate lower soil horizons and there exists a potential risk for groundwater contamination.

Photolytic degradation in water

In all photolysis studies, the main pathway was isomerization. The data of the theoretical environmental half-lives indicate that in summer, the half-life of TFS is 0.7 - 1.3 days irrespective of the latitude. The half-life extends with the seasonal change from spring to winter. These findings indicate that TFS is susceptible to rapid photolysis.

 

Funding

Ministry of Science & Technology, Govt. of India
BOYSCAST

 

Publications

  1. Banerjee, K.; Ligon, A.; Spiteller, M. (2007):
    "Spectral elucidation of the acid metabolites of four geometric isomers of trifloxystrobin" Analytical and Bioanalytical Chemistry, 388, (8), 1831-1838.

  2. Banerjee, K.; Ligon, A. P.; Spiteller, M. (2006):
    "Environmental Fate of Trifloxystrobin in Soils of Different Geographical Origins and Photolytic Degradation in Water" Journal of Agriculture and Food Chemistry, 54 (25), 9479-9487.

  3. Banerjee, K.; Ligon, A.P.; Spiteller, M. (2005):
    "Photoisomerization kinetics of trifloxystrobin" Analytical and Bioanalytical Chemistry, 382 (7), 1527-1533.



Sub content

Contact

Prof. Dr. Dr. h.c. Michael Spiteller
Tel.: 0231 755-4080

Dr. rer. nat. Kaushik Banerjee

Phone: +20 (0)2691-4245

kbgrape@yahoo.com