Phenoxyalkanoic acid herbicides

Buser H-R, MD Muller (1997) Conversion reactions of various phenoxyalkanoic acid herbicides in soil. 2. Elucidation of the enantiomerization process of chiral phenoxy acids from incubation in a DjO/soil system. Environ Sci Technol 31 1960-1967. 

Gintautas PA, SR Daniel, DL Macalady (1992) Phenoxyalkanoic acid herbicides in municipal landfill leachates. Environ Sci Technol 26 517-521. 

Phenoxyalkanoic acid herbicides are not amenable to direct gas chromatographic determination because of the high polarity or low volatility of the compounds and must be converted to their... 

There are several routes for nitrosamine contamination in pesticides use of contaminated chemicals during synthesis, side reactions, use of nitrite as a preservative and corrosion inhibitor of metal containers and by reactions with environmental nitrosating agents. Over 300 formulations were shown to be contaminated with nitrosamines however, the main contamination was confined to 2,6-dinitroaniline herbicides, dimethylamino salts of phenoxyalkanoic acid herbicide, diethanolamine and triethanolamine salts of acid... 

Phenoxyalkanoic acid herbicides are not amenable to direct gas chromatographic determination because of the high polarity or low volatility of the compounds and must be converted to their more volatile derivatives. The sensitivity of the electron capture detector towards alkyl esters of 4-chloro-2-methylphenoxy acetic acid, 4-chloro-2-methylphenoxy butyric acid, etc., is very poor. The methyl ester of 4-chloro-2-methylphenoxy acetic acid was 100 times less sensitive to electron affinity detection than the 2,4-D-methyl ester [396]. 

Lindane is relatively non-persistent, especially under anaerobic conditions, and although its more highly chlorinated residues may present the same problems as those of polychlorophenols, the less chlorinated residues should follow pathways similar to those established for the microbial degradation of the chlorinated phenoxyalkanoic acid herbicides. Recent evidence (46) indicates that certain microbes can dechlorinate DDT anaerobically, thereby making available intermediates which may undergo further aerobic attack, leading in principle to total degradation. The ultimate fate of the hexachloronorbornene nucleus of cyclodienes is still uncertain and this question continues to attract attention. 

Miiller, M.D. Buser, H.-R., Conversion reactions of various phenoxyalkanoic acid herbicides in soil. 1. Enantiomerization and enantioselective degradation of the chiral 2-phenoxypropionic acid herbicides Environ. Sci. Technol 1997, 31, 1953-1959. 

Effects of Long-Term Phenoxyalkanoic Acid Herbicide Field Applications on the Rate of Microbial Degradation... 

The phenomenon of cross-enhancement, or the ability of soils pretreated with specific herbicides to degrade other structurally related herbicides more rapidly than in untreated control soils, has been known for nearly 40 years. Both enhanced degradation and cross-adaptation have been observed under field conditions for phenoxyalkanoic acid herbicides (3-5). ... 

The objectives of this review are to briefly summarize the various factors influencing the breakdown of the phenoxyalkanoic acid herbicides in soils of North America and Europe, and then to discuss the effects of their repeated field usage on the rate of their microbial degradation. 

Since the phenoxyalkanoic acid herbicides are degraded in the soil by biological processes, factors that affect microbial activity will directly affect their breakdown. Soil pH, soil type, soil organic matter, herbicide formulation, and herbicide concentration can all influence the rate of microbial decomposition ( 4, 5). Greater effects are experienced with moisture and temperature, since these factors have a profound influence on microbial activity and thus on herbicide breakdown (4 5). It has been concluded ( 5), that soil temperature above 10°C and moistures above the wilting point are necessary for biological degradation of phenoxyalkanoic acids. 

Field studies with single applications of phenoxyalkanoic acid herbicides have indicated that breakdown is rapid under temperature and moisture conditions that favour microbiological activity (5). Enhanced degradation of these herbicides, under field conditions, was first noted in the late 1940s. The use of plant bioassay procedures, led to the discovery that the persistence of 2,4-D, but not 2,4,5-T, was decreased,by pretreatment of the soil with 2,4-D (26, 27). This enhanced breakdown was later confirmed using (14C)2,4-D and radiochemical analytical techniques (29). The breakdown of the (14C)2,4-D being more rapid in soil from the treated plots, tested 8 months after the last field application, than in soil from plots treated for the first time. 

Patsias, J., Papadakis, E. N., and Papadopoulou-Mourkidou, E., Analysis of phenoxyalkanoic acid herbicides and their phenolic conversion products in soil by microwave assisted solvent extraction and subsequent analysis of extracts by online SPE-liquid chromatography, J. Chromatogr. A, 959, 153-161, 2002. 

Eelding, G., Braude Sprensen, J., Btigel Mogensen, B., and Christian Hansen, A., Phenoxyalkanoic acid herbicides in mnoff, Sci. Total Environ., 175, 207-218, 1995. 

Phenoxyalkanoic acid herbicides, i.e. 2-(2,4-dichlorophenoxy)-propionic acid (2,4-DP) and 2-(4-chloro-2-methylphenoxy)-propiotric acid (MCPP) Plant and soil samples Chirobiotic T Chiroptical detector 22... 

Some groups of herbicides depend upon phloem translocation to reach their sites of action. For example, the phenoxyalkanoic acid herbicides, which act on cell growth and development, and glyphosate, which inhibits the biosynthesis of aromatic amino acids, are translocated from leaves to all sites of active growth within the plant. Similarly, the sulfonylureas and imidazolinones, which inhibit acetolactate synthase, are, when applied postemergence, translocated in the phloem to all parts of the plant. 

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