Atrazine hydrolysis

Khan, S.U. (1978) Kinetics of hydrolysis atrazine in aqueous fulvic acid solution. Pest. Sci. 9, 39-45. 

Armstrong DE, Chesters G, Harris RF (1967) Atrazine hydrolysis in soil. Soil Sci Soc Am Proc 31 61-66... 

Skipper HD, Gilmour CM, Furtick WR (1967) Microbial versus chemical degradation of atrazine in soils. Soil Sci Soc Am Proc 31 653-656 Sliwinski MK, Goodman RM (2004) Comparison of cienarchaeal consortia inhabiting the rhizosphere of diverse terrestrial plants with those in bulk soil in native environments. Appl Environ Microbiol 70 1821-1826 Stumm W, Morgan JJ (1996). Aquatic chemistry - chemical equlibrium and rates in Natural Waters (3rd edn). Wiley, New York Vega D, Bastide J (2003) Dimethylphthalate hydrolysis by specific microbial esterase. Chemosphere 51 663-668... 

Li and Felbeck (1972) reported that the half-lives for atrazine at 25 °C and pH 4 with and without fulvic acid (2%) were 1.73 and 244 d, respectively. The hydrolysis half-lives in a 5 mg/L fulvic acid solution and 25 °C at pH values of 2.9, 4.5, 6.0, and 7.0 were 34.8, 174, 398, and 742 d, respectively. The only product identified was 2-(ethylamino)-4-hydroxy-6-isopropylamino-5-triazine (Khan, 1978). The primary degradative pathway appears to be chemical (i.e., hydrolysis) rather than microbial (Armstrong et al., 1967 Best and Weber, 1974 Gormley and Spalding, 1979 Geller, 1980 Lowder and Weber, 1982 Skipper et al, 1967). 

Plant. In tolerant plants, atrazine is readily transformed to hydroxyatrazine which may degrade via dealkylation of the side chains and subsequent hydrolysis of the amino groups with some evolution of carbon dioxide (Castelfranco et al, 1961 Roth and Knuesli, 1961 Humburg et al, 1989). In corn juice, atrazine was converted to hydroxyatrazine (Montgomery and Freed, 1964). In both roots and shoots of young bean plants, atrazine underwent monodealkylation forming 2-chloro-4-amino-6-isopropylamino-s-triazine. This metabolite is less phytotoxic than atrazine (Shimabukuro, 1967). 

Chemical/Physical. The hydrolysis half-lives of atrazine in O.lM-HCl, buffer at pH 5.0, and O.lM-NaOH solutions at 20 °C were 9.5, 86, and 5.0 d, respectively. Atrazine degraded to 2-chloro-4-amino-6-isopropylamino-5-triazine (Burkhard and Guth, 1981). 

Chemical/Physical. The hydrolysis half-lives of atrazine in aqueous buffered solutions at 25 °C and pH values of 1, 2, 3, 4, 11, 12 and 13 were reported to be 3.3, 14, 58, 240, 100, 12.5, and 1.5 d, respectively (Armstrong et al., 1967). Atrazine does not hydrolyze in uncatalyzed solutions, even under elevated temperatures. The estimated half-life of atrazine in neutral, uncatalyzed water at pH 6.97 and 25 °C is 1,800 yr. Under acidic conditions, hydrolysis proceeds via mono- and diprotonated forms (Plust et al., 1981). Atrazine is stable in slightly acidic or basic media, but is hydrolyzed to hydroxy derivatives by alkalies and strong mineral acids (Windholz et al., 1983). Atrazine reacts with strong mineral acids forming hydroxyatrazine (Montgomery and Freed, 1964). 

The primary ozonation by-products of atrazine (15 mg/L) in natural surface water and synthetic water were deethylatrazine, deisopropylatrazine, 2-chloro-4,6-diamino-s-triazine, a deisopropylatrazine amide (4-acetamido-4-amino-6-chloro-5-triazine), 2-amino-4-hydroxy-6-isopropylamino-5-triazine, and an unknown compound. The types of compounds formed were pH dependent. At high pH, low alkalinity, or in the presence of hydrogen peroxide, hydroxyl radicals formed from ozone yielded 5-triazine hydroxy analogs via hydrolysis of the Cl-Cl bond. At low pH and low alkalinity, which minimized the production of hydroxy radicals, dealkylated atrazine and an amide were the primary byproducts formed (Adams and Randtke, 1992). 

Atrazine Hydrolysis Al- and H- montmo-rillonite montmo-lillonitic soil clay Ca- and Cu- clays much weaker catalysts... 

Alexander M (1977) Introduction to soil microbiology, 2nd edn. WUey, New York Alexander M (1980) Biodegradation of chemicals of environmental concern. Science 211 132-138 Armstrong DE, Chester G, Harris RF (1967) Atrazine hydrolysis in soil. Soil Sci Soc Am Proc... 

The analytical data for the added pesticides and two of the hydrolysis products, 2,4-D acid and 1-naphthol, were used to formulate the degradation graphs shown in Figures 3-14. Atrazine underwent no degradation either alone or in mixtures and alachlor and trifluralin underwent no degradation in mixtures, so the graphs for these pesticides under these conditions are not shown. 

The hydrolysis reaction is carried out in a sealed test-tube in 1 N hydrochloric acid at 150 °C for 8-16 h. The resulting solution is made basic and the mixture is then dansylated [156]. Triazines such as atrazine, simazine and propazine yield different combinations of free amines on hydrolysis, thus enabling their characterization using the fluorogenic labeling technique. The limits of detection range from 5 to 10 ng per spot. Concentrations of 0.05 ppm in food crops may be determined. 

Prosen, H., and Zupancic-Kralj, L. (2004). Evaluation of photolysis and hydrolysis of atrazine and its first degradation products in the presence of humic acids. Environ. Pollut. 133, 517-529. 

Figure 7.2 Metabolism of atrazine in sugarcane plants by (a) ALdcal kylation of the side chains, (b) hydrolysis of the 2-chloro group followed by JV-dealkylation, and (c) displacement of the 2-chloro by glutathione conjugation (Larson and Ash, 1993).

Transformation of triazines is primarily the result of degradation caused by microorganisms. However, triazines are also subject to a slow chemical degradation process known as hydrolysis. Chemical hydrolysis of atrazine, for example, is a process where the chlorine atom is removed from the atrazine molecule and replaced with a hydroxyl (OH) group. Chemical hydrolysis is relatively fast in acidic and alkaline soils, but it is relatively slow in neutral soils. In neutral soils, the rate of chemical hydrolysis of triazines increases when the triazine is adsorbed on the surfaces of soil particles. Hydroxytriazines, the products of chemical hydrolysis, are very strongly held by soil surfaces and hence move very slowly in soils. The hydroxytriazines have no biological activity. 

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