Triazine degradation pathways

Jutzi K, AM Cook, R Hutter (1982) The degradative pathway of the 5-triazine melamine. Biochem J 208 679-684. 

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). 

Pelizzetti, E., Minero, C., Carlin, V, Vincenti, M., Pramauro, E., and Dolci, M. Identification of photocatal34ic degradation pathways of 2-Cl-s-triazine herbicides and detection of their decomposition intermediates, Chemosphere, 24(7) 891-910,1992. 

The difficulty of elucidating mechanisms and pathways for the degradation of. v-triazine compounds is illustrated by the continuous effort over more than 40 years to define the respective roles of biotic versus abiotic degradation pathways. As early as the 1960s it was evident that the capacity of soil microbial populations to release C02 from. v-triazincs was variable. Degradation depended on the microbial composition of the soil (diversity and biomass) and on soil conditions (i.e., soil type, temperature, humidity, pH, additional energy sources, etc.) (Knusli et al., 1969 Walker, 1987). 

This section discusses the occurrence of the degradation products of atrazine, cyanazine, simazine, propazine, prom-etryn, and prometon, as well as their degradation pathways from soil into surface water. More detailed discussion of triazine degradation can be found in several other chapters of this book. 

In Table 19.3, the total gas evolved for different species was obtained by integrating the instantaneous values in time. In nitrogen, the amount of H20 evolved increases with the inclusion of the NC when PA6 is compared with PA6 + NC and PA6 + FR with PA6 + FR + NC. This is likely caused by the liberation of water from clay. The same trend is observed for NH3 while the opposite trend is apparent for C02. In the case of PA6 + FR + NC, the increase in NH3 might be partly caused by the evolution of water and consequent hydrolysis of the triazine ring, which in subsequent steps produces cyanuric acid and finally ammonia and carbon dioxide. The decreased levels of C02 might be related to a difference in the degradation pathways and possibly trapping of hydrocarbons and production of an aromatic char structure [12]. In the air, the fractions will depend on oxidation... 

A seven year smdy on the groundwater in the Paris region of France, revealed DEA was present at a concentration above that of its parent compound. The atrazine degradation pathway and the higher solubility of DEA in water may explain this finding. Recent work showed that photolysis of triazines and acetanilides followed pseudo first order kinetics, and the photodegradation in soils was accelerated as the content of organic matter increased. Another study showed that humic substances enhanced terbutylazine photolysis. ... 

The use of LC-MS and LC-UV allowed determination of the degradation pathway of cyromazine under irradiation, with or without Ti02. The formation of CYA prevented the complete mineralisation of cyromazine as previously observed for atrazine and other r-triazines by oxidative methods <2001JPH79>. 

Pelizzetti, E., C. Minero, V Carhn, M. centi, E. Pramauro, and M. Dolci. Identification of Photocatalytic Degradation Pathways of 2-Cl-x-Triazine Herbicides and Detection of Their Decomposition Intermediates, Chemosphere, 24(7) 891-910 (1992). 

Degradation of a herbicide by abiotic means may be divided into chemical and photochemical pathways. Herbicides are subject to a wide array of chemical hydrolysis reactions with sorption often playing a key role in the process. Chloro-j -triazines are readily degraded by hydrolysis (256). The degradation of many other herbicide classes has been reviewed (257,258). 

ChemicaPPhysical. Mascolo et al. (1995) studied the reaction of prometryn (100 mM) with sodium hypochlorite (10 mM) at 25 °C and pH 7. Degradation followed the following pathway prometryn 2,4-(A/A -diisopropyl)diamino-6-methylsulfinyl-s-triazine 2,4-(N,W-disopropyl)-diamino-6-methylsulfonyl-1,3,5-triazine 2,4- (N, W-diisopropyl) diamino-6-methanesulfonate ester 5-triazine 2,4-(N,A -diisopropyl)diamino-6-hydroxy-s-triazine. 

Montgomery and Freed (1964) reviewed the early research metabolism of triazine herbicides by plants and concluded that there was a good correlation between resistance in plants and the extent of their metabolism. A common pathway of degradation for these chemicals was indicated by the presence of 2-hydroxy analogs. 

The third metabolic pathway discovered for degradation of triazine herbicides in plants was first reported by Shimabukuro et al. (1970) and involved conjugation of atrazine with glutathione in corn nutrient uptake, excised leaves, and leaf disc experiments. This new degradation mechanism was postulated to be the primary factor in the... 

---