Hydrolysis abiotic

Abiotic hydrolysis generally accomplishes only a single step in the ultimate degradation of the compounds that have been used for illustration. The intervention of snbseqnent biotic reactions is therefore almost invariably necessary for their complete mineralization. 

Beltran E, H Eenet, JE Cooper, CM Coste (2000) Kinetics of abiotic hydrolysis of isoxaflutole influence of pH and temperature in aqueous mineral buffered medium. J Agric Eood Chem 48 4399-4403. 

Hydrolysis is easily predicted, provided that the rate constants for a compound are known. The rate of abiotic hydrolysis is given by... 

Katagi T (2002) Abiotic hydrolysis of pesticides in the aquatic environment. Rev Environ Contain Toxicol 175 79-261... 

The three processes responsible for the transformation and degradation of disulfoton in water are abiotic hydrolysis, photosensitized oxidation, and biodegradation. Disulfoton is most stable towards... 

A relatively small proportion of heptachlor epoxide was formed. Heptachlor epoxide was never found to be greater than 10% of the total C in the water sample. The authors concluded that the major pathway of heptachlor in aquatic systems is rapid abiotic hydrolysis of heptachlor to 1-hydroxychlordene followed by metabolism to 1-hydroxychlordene epoxide (Lu et al. 1975). 

Abiotic hydrolysis of pollutants in subsurface waters is pH dependent. The predominant pathways are acid-catalyzed, base-mediated, and neutral (pH-independent) hydrolysis. The acid-catalyzed hydrolysis reaction rate is dependent on proton concentration increases with a decrease in pH. This behavior occurs because the proton is not consumed in the reaction. 

Parathion (0,0-diethyl 0-/7-nitrophenyl phosphorothioate) is degraded in the near subsurfaee aerobie environment via hydrolysis, where two degradation products are observed, diethylthiophosphoric acid and p-nitrophenol, according to the schematic pathway described in Fig. 16.35. Abiotic hydrolysis of parathion in the subsurface is a result of a surface-mediated transformation (see Sect. 16.1) or a biodegradation process. 

Loos MA (1975) Phenoxyalkanoic acids. In Kemey PC, Kaufman DD (eds) Herbicides chemistry, degradation and mode of action, vol 1. Marcel Dekker New York, pp 1-128 Lovley DR (1993) Dissimilatory metal reduction. Annual Review of Microbiology 47 263-290 Macalady DL, Wolfe NL (1983) New perspectives on the hydrolytic degradation of the organo-phosphorothionate insecticide chloropyrifos. J Agric Food Chem 31 1139-1147 Macalady DL, Wolfe NL (1985) Effects of sediment sorption and abiotic hydrolysis. J Agric Food Chem 33 167-173... 

It is the purpose of this article to summarize the present status of our understanding of the factors governing the rates of hydrolysis of pesticides which are sorbed to sediments. The work reported herein deals specifically with abiotic hydrolysis reactions, which for some pesticides, may be as important or more important than biologically mediated hydrolysis reactions (], . ... 

MACALADY AND WOLFE Abiotic Hydrolysis of Sorbed Pesticides... 

Abiotic hydrolysis, sorbed pesticides, 221-43 Acetanilide herbicide, groundwater contamination, 299 Acid-catalyzed hydrolysis aldlcarb by RIEX, 257f kinetics, disappearance rate, 223 Acid hydrolysis, sorbed pesticides, 242... 

Although diazinon has been detected in groundwater samples in both the United States and Canada (Cohen 1986 EPA 1989a Frank et al. 1987, 1990b HazDat 1996), no studies were identified concerning diazinon transformation and degradation processes within aquifers. Based on theoretical considerations, abiotic hydrolysis mechanisms would be expected to degrade diazinon within a few months (Chapman and Cole 1982 Cowart etal. 1971). 

Chemical (abiotic) hydrolysis has been well studied by organic chemists for many years, frequently under environmentally relevant conditions (in water at ambient temperature and pH 5-9) [25]. Testing is sometimes carried out at elevated... 

Comparison of kh with the calculated k,ot = 0.15 d 1 shows that abiotic hydrolysis is the most important removal mechanism for BzC in the pond ( 75%>) thus, you have to worry about the transformation product benzyl alcohol (Fig. 12.1). About 7% is removed by flushing (kw = VIQ = 0.01 d"1), and the rest by other processes. Considering the properties of benzyl chloride (e.g., Kj0Vi, Ajaw, see Appendix C), the most likely additional elimination processes are gas exchange and biotransformation (see later chapters). 

After a fire in a chemical storehouse at Schweizerhalle, Switzerland, in November 1986, several tons of various pesticides, solvents, dyes, and other raw and intermediate chemicals were flushed into the Rhine River (Capel et al., 1988 Wanner et al., 1989). Among these chemicals was the insecticide disulfoton, of which 3500 kg were introduced into the river water (11°C, pH 7.5). During the 8 days travel time from Schweizerhalle to the Dutch border, 2500 kg of this compound were eliminated from the river water. Somebody wants to know how much of this elimination was due to abiotic hydrolysis. Since in the literature you do not find any good kinetic data for the hydrolysis of disulfoton, you make your own measurements in the laboratory. Under all selected experimental conditions, you observe (pseudo)first-order kinetics, and you get the results given below. 

First-order rate constant of abiotic hydrolysis of DCP at 25°C kA/B -0.06 d-1 (independent of pH) Atmospheric concentrations of DCP and CPO are negligible. 

Due to an accident, rMA = 30 kg of the pesticide cis-1,3-dichlor-l-propene (DCP) finds its way into a small, well-mixed pond. (1) You are asked to estimate how long it will take until the DCP concentration has fallen below 1 pg L-1. You also worry about the buildup of cis-3-chloro-2-propene-l-ol (CPO), the product of abiotic hydrolysis of DCP. (2) What maximum concentration of CPO do you expect in the pond and (3) what is its concentration at the time when the concentration of the original pollutant (DCP) has fallen below 1 pg L-1 ... 

The abiotic hydrolysis of triazines in soil environments is catalyzed by acidic sites on the surfaces of both organic and inorganic soil constituents. The surfaces of soil constituents have both Lewis acid sites (which accept electron pairs) and Bronsted acid sites (which donate protons). However, triazines are not competitive with water and OH groups for complexation with Lewis acid sites, so in soil environments hydrolysis is catalyzed primarily by Bronsted acid sites. Four types of Bronsted acid sites are found on soil surfaces (Mortland, 1970) ... 

Although hydrolysis of the triazine herbicides is temperature and pH dependent, these herbicides are considered to be hydrolytically stable under the pH and temperature conditions encountered in natural waters. However, the relatively slow hydrolysis rates in natural waters may be enhanced somewhat by the presence of dissolved organic carbon (DOC) (in the form of fulvic acids and a variety of low-molecular-weight carboxylic acids and phenols) that has been shown to catalyze the hydrolysis of several triazine herbicides. Although microbial degradation is probably the most important mechanism of dissipation of the triazine herbicides in soils, abiotic hydrolysis of these herbicides also occurs. Hydrolysis in soils is affected by the pH, organic matter (humic acid) content, and the type and content of clay in the soil. 

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