Behavior of fenhexamid in soil and water.
A study was conducted to investigate fenhexamid (FEX) behavior in soil and in water. FEX proved to be rather stable at acid pH but showed slight degradation at neutral and alkaline pH. After 101 days of FEX spiking of a soil sample, 94% at pH 4, 12% at pH 7 and 23% at pH 9 of the active ingredient was still present. In natural water the rate of FEX disappearance appeared to be slow which may be due to abiotic rather than biotic processes. The soil degradation tests showed low persistence of the active ingredient if a good microflora activity is guaranteed (DT(50) about 1 day). Moreover, in absence of microorganisms, FEX proved to be stable. Humidities of 25 and 50% of Water Holding Capacity (WHC) influenced in equal measure the rate of degradation. From the same soil, a bacterium was isolated and identified as Bacillus megaterium, which was able to metabolize FEX with the hydroxylation of the cyclohexane ring. Moreover, FEX showed an elevated affinity for humic acid (73%), smectite (31%), and ferrihydrite(20%) and low affinity for vermiculite (11%) and kaolinite (7%).
Abbate
Cristina
C
Dipartimento di Scienze Agronomiche, University of Catania, Catania, Italy. cristina.abate@unict.it
Borzì
Daniela
D
Caboni
Pierluigi
P
Baglieri
Andrea
A
Gennari
Mara
M
D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry; D000577:Amides / Q000737:chemistry*; D001410:Bacillus megaterium / Q000378:metabolism*; D002853:Chromatography, Liquid; D005290:Ferric Compounds / Q000737:chemistry; D006801:Humans; D006812:Humic Substances / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007616:Kaolin / Q000737:chemistry; D013058:Mass Spectrometry; D010575:Pesticides / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry; D012988:Soil Microbiology; D012989:Soil Pollutants / Q000737:chemistry*; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000737:chemistry*
D000538:Aluminum Silicates; D000577:Amides; D005290:Ferric Compounds; D006812:Humic Substances; D010575:Pesticides; D017640:Silicates; D012989:Soil Pollutants; D014874:Water Pollutants, Chemical; C003760:vermiculite; D007616:Kaolin; C092844:ferric oxyhydroxide; C033214:Smectite; C451426:N-(2,3-dichloro-4-hydroxyphenyl)-1-methylcyclohexanecarboxamide