Pesticides decomposition

The family of hazardous pollutants also includes phenol and its nitro and chloro derivatives. They enter the aquatic environment through waste-waters from many industries, such as petroleum processing and production of plastics, dyes, cellulose, pharmaceuticals, etc., or as the products of pesticides decomposition. Phenols may also arise in drinking water from the reaction of natural humic and fulvic acids with chlorinating disinfectants. Even at non-toxic levels, they deteriorate the taste and odor of drinking water. To address the steady increase in water contamination with phenolic compounds and pesticides, the US Environmental Protection Agency (EPA) has included 26 phenoHc compounds and 32 pesticides and their metaboHtes in the list of priority contaminants. In accordance with regulatory requirements, the allowed tolerance hmit of these pollutants must not exceed O.lpg/L for individual species and 0.5 Xg/L... 

Desorption is the reverse of the sorption process. If the pesticide is removed from solution that is in equdibrium with the sorbed pesticide, pesticide desorbs from the sod surface to reestabUsh the initial equdibrium. Desorption replenishes pesticide in the sod solution as it dissipates by degradation or transport processes. Sorption/desorption therefore is the process that controls the overall fate of a pesticide in the environment. It accomplishes this by controlling the amount of pesticide in solution at any one time that is avadable for plant uptake, degradation or decomposition, volatilization, and leaching. A number of reviews are avadable that describe in detad the sorption process (31—33) desorption, however, has been much less studied. 

The performance of microwave-assisted decomposition of most difficult samples of organic and inorganic natures in combination with the microwave-assisted solution preconcentration is illustrated by sample preparation of carbon-containing matrices followed by atomic spectroscopy determination of noble metals. Microwave-assisted extraction of most dangerous contaminants, in particular, pesticides and polycyclic aromatic hydrocarbons, from soils have been developed and successfully used in combination with polarization fluoroimmunoassay (FPIA) and fluorescence detection. 

Possible exposure to pesticide-derived N,-nitroso compounds depends on environmental processes that influence formation, movement, and degradation of the compounds. Although laboratory studies have shown the feasibility of environmental nitrosamine formation, there has been little evidence that it is an important process. Nitrosamines vary greatly in their environmental stabilities, but all seem to be susceptible to one or more modes of decomposition including photolysis, microbiological degradation, and plant metabolism. 

A variety of phosphoric acid triesters and their derivatives are used as pesticides. Although there are no natural phosphorotriesters, those artificial ones undergo decomposition in the soil, implying that some microorganisms exist which are capable of hydrolysing them. The first report on a stereoselective enzymatic phos-photriester hydrolysis was pubhshed in 1973, when Dudman and Zerner succeeded... 

The best way to test the practicability of the multi-residue approach is to start with the GC determination step. Most often the inability to vaporize the intact compound means that it is not possible to include a new pesticide in the multi-residue scheme. In the case of common moiety methods, a decomposition step is needed to produce the common analyte. Often for that step, modification of the reaction conditions (such as pH and temperature) are necessary, which would lead to a significant deviation from standard multi-residue procedures. 

In addition to the chemicals included on the other lists, the CDC also included heavy metals such as arsenic, lead, and mercury volatile solvents such as benzene, chloroform, and bromoform decomposition products such as dioxins and furans polychlorinated biphenyls (PCBs) flammable industrial gases and liquids such as gasoline and propane explosives and oxidizers and all persistent and nonpersistent pesticides. Agents included in this volume are limited to those that are most likely to pose an acute toxicity hazard. 

The most likely cause of the incident was the decomposition of bulk sacks of the pesticide, which had been placed too close to a hot compressor discharge pipe, and the release of flammable vapors (USEPA-OSHA, 1999). This case history illustrates that severe reactive incidents can occur even at companies engaged in the simple storage and handling of chemicals. The facility was not covered by OSHA PSM, and AZM50W does not have an NFPA rating. 

Di-ra-octylphthalate is produced as a decomposition product of the pesticide dinocap (HSDB 1995). 

Chlorocatechols, known intermediates in the decomposition of 2,4-D,2,4,5-T, and other pesticides, were shown to be incorporated by enzymatic polymerization into HA when reacted with purified horseradish peroxidase. 

Rice, C.P., Sikka, H.C.,and Lynch, R.S. Persistence ofdichlobenil in a farm pond, / Agric. FoodChem., 22(3) 533-535,1974. Rice, F.O. and Murphy, M.T. The thermal decomposition of five-membered rings, / Am. Chem. Soc., 64(4) 896-899,1942. Richard. Y. and Brener. L. Removal of pesticides from drinking water by ozone, in Handbook of Ozone Technology and Applications, Volume II. Ozone for Drinking Water Treatment, Rice, A.G. and Netzer, A.. Eds. (Montvale, M A Butterworth Publishers, 1984), pp. 77-97. 

Gerstl Z, Yaron B (1983) Behavior of bromacU and napropamide in soils. 11. Distribution after application from a point source. Amer J Soil Sci 47 478 83 Gerstl Z, B Yaron, Nye PH (1979a) Diffusion of a biodegradable pesticide as affected by microbial decomposition. Soil Sci Soc Am J 43 843-848... 

Thermal degradation studies might be required to determine the decomposition characteristics of of the subject pesticide vAien heated alone or In the presence of oxidizers and/or binders In both closed and open systems and at various temperatures. 

Figure 6. Degradation of 2,4-D ester plus the 2,4-D acid hydrolysis decomposition product with time in the presence of five other formulated pesticides. amount in soil and water 0, amount in water.

Table I Summary of the Effect of Ambient Conditions, Aeration at 1 L/min, Peptone Nutrient at 0.1 Wt. %, Concentration, and the Presence of 5 Other Pesticides (Mix) on the Degradation of Six Pesticides and Two Decomposition Products... 

The pH measurements of the mixed contents were made immediately after taking the soil and liquid samples. The presence of a very large amount of suspended sediment affected the accuracy and reproducibility of these pH measurements. The average values for each container are summarized in Table II. The deposited pesticides, the formulating agents and the decomposition products did not change the pH from that observed for ambient water except for... 

A two-step laboratory thermal-decomposition analytical system involving vaporization and thermal destruction was developed in 1975 by the University of Dayton Research Institute for EPA (6). Vaporization of pure pesticide occurred at 200 to 300°C and was followed by decomposition in a quartz tube at temperatures exceeding 900 C. The destruction efficiencies for DDT, Kepone, and mirex exceeded 99.99% at 2-s residence time and greater than 900 C. 

Decomposition of farm-generated pesticide wastewater was demonstrated with a mobile 66-lamp ultraviolet (UV) unit and ozone. Aqueous solutions of 2,4-D (1086 ppm) and atrazine (4480 ppm) were degraded more than 80% in about 2-3 h, while paraquat (1500 ppm) was degraded more slowly. 

Whether such disposal is intentional or incidental, significant quantities of pesticides and pesticide wastes end up in natural and artificial aquatic systems. Thus, any consideration of the disposal of this broad category of anthropogenic chemicals must include an understanding of the reaction mechanisms and principal pathways for degradation of pesticides in aquatic systems. Of the degradative pathways relevant to such systems, hydrolysis reactions are perhaps the most important type of chemical decomposition process ( 1 7 ). 

Pesticides (14, 85), polychlorinated biphenyls (86, 87) and herbicides (88) are usually separated by this technique also. In analytic work, however, the detection sensitivity of the selective detectors used in gas chromatography could not be achieved (59). Nevertheless, sUch substances can be separated by liquid chromatography with no attendant decomposition problems and no derivatization, making the procedure significantly simpler. i... 

This technology can remove oily sludges, pesticides, herbicides, pentachlorophenol, polychlorinated biphenyls (PCBs), coal by-products, wood treating compounds, dioxins, and furans. It is often used in conjunction with the company s base-catalyzed decomposition (BCD) process. The BCD process is designed to treat chlorinated compounds. 

The principal source of 4-chloro-ort/zo-toluidine in the enviromnent was as an impurity and as a decomposition (metabolic) product of chlorodimeform. This pesticide is no longer produced (WHO, 1998). 

Sovocool GW, Harless RL, Bradway DE, et al. 1981. The recognition of diazinon, an organophosphorus pesticide, when found in samples in the form of decomposition products. Analy Toxicol 5 73-80. 

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