Atrazine mineralization

Photolytic. Pelizzetti et al. (1990) studied the aqueous photocatalytic degradation of prometon and other s-triazines (ppb level) using simulated sunlight (7, >340 nm) and titanium dioxide as a photocatalyst. Prometon rapidly degraded forming cyanuric acid, nitrates, the intermediate tentatively identified as 2,4-diamino-6-hydroxy-7V,A -bis(l-methylethyl)-s-triazine, and other intermediate compounds similar to those found for atrazine. Mineralization of cyanuric acid to carbon dioxide was not observed. 

McMahon, P.B., Chapehe, F.H., and Jagucki, M.J. Atrazine mineralization potential of alluvial-aquifer sediments under aerobic conditions. Environ. Sci. Technol, 26(8) 1556-1559, 1992. 

Nair, D.R. and Schnoor, J.L. Effect of two electron acceptors on atrazine mineralization rates in soil. Environ. Sci. Technol, 26(ll) 2298-2300, 1992. 

Pseudomonas spp. strain DSM 93-99 (YAYA6) Atrazine Mineralization Yanze-Kontchou and Gschwind (1995)... 

Of the more than 200 bacterial colonies isolated from an atrazine-mineralizing mixed culture, none were found to individually degrade atrazine however, when mixed together, their degradation ability was restored (Mandelbaum etal., 1993a). 

Despite extensive efforts over 40 years, it was not until 1993 that a pure culture of an atrazine-mineralizing bacterium was isolated, patented (Mandelbaum and Wackett, 1996), and deposited in the American Type Culture Collection (ATCC 55464). Interestingly, within a short time several other pure bacterial cultures that could mineralize atrazine were also described (Yanze-Kontchou and Gschwind, 1994 Mandelbaum et al., 1995 Radosevich et al., 1995a Mandelbaum and Wackett, 1996 Moscinski et al. 1996 Boundy-Mills et al., 1997 Bouquard et al., 1997 Struthers etal., 1998). 

Radosevich et al. (1995a) studied atrazine mineralization by indigenous microbial communities inoculated with a Ralstonia pickettii (previously strain M91-3 (Stamper et al., 1997)) in surface soil and subsurface zones. The authors found that the mineralization rate constants (k) and overall mineralization (P-max) were higher in microcosms that were not sterilized prior to inoculation, indicating that the native microbial populations in the sediments were contributing to the overall release of 14C02 from (U-14C -ring)-atrazine and (14C -ethyl)-atrazine. They also concluded... 

Masaphy and Mandelbaum (1997) indicated that long-term irrigation with treated wastewater increased organic matter in soil but decreased the overall mineralization rate of atrazine. The authors indicated that initial atrazine mineralization was greater in soils irrigated with treated wastewater, but after a few days of interaction between the soil and the applied herbicide, mineralization rates decreased as a result of decrease in bioavailability. 

Alvey, S. and D.E. Crowley (1996). Survival and activity of an atrazine mineralizing bacterial consortium in rhizosphere soil. Environ. Sci. Technol., 30 1596-1603. 

Masaphy, S. and R.T. Mandelbaum (1997). Atrazine mineralization in slurries from soils irrigated with treated wastewater. Appl. Soil Ecol., 6 283-291. 

Ostrofsky, E.B., S.J. Traina, and O.H. Tuovinen (1997). Variation in atrazine mineralization rates in relation to agricultural management practice. J. Environ. Qual., 26 647-657. 

Topp, E., L. Tessier, and E.G. Gregorich (1996). Dairy manure incorporation stimulates rapid atrazine mineralization in an agricultural soil. Can. J. Soil Sci., 76 403 109. 

Other representative pesticides that have also been shown to be mineralized include glyphosate, parathion, carbaryl, EPTC, isofenphos, and propachlor. Pesticides that are susceptible to mineralization are not typically found in, or considered to be a threat to, groundwater suppHes because of their rapid degradation, ie, nonpersistence. Microorganisms can evolve, that is, develop metaboHc pathways for the mineralization of previously persistent compounds. For example, there have been several reports documenting the existence of atrazine-mineralizing microoiganisms (21). 

Figure 1. Upper atrazine biodegradation pathway in all known atrazine-mineralizing bacteria showing hydrolytic conversion of atrazine to cyanuric acid. Dehalogenation of atrazine to 2-hydroxyatrazine is catalyze by the gene product of atzA. 2-Hydroxyatrazine is then sequentially AT-deaUcylated to produce cyanuric acid by enzymes encoded by atzB and atzC,...

Based on these results, it appears that atrazine mineralization rates and the density of culturable atrazine-degrading bacteria are not linked i.e., the exposure to atrazine stimulates the activity of a population that was present in soil but was not detectable by the MPN assay. 

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