Decomposition of DDT

Experimental studies of PCBs and DDT transformation in marine waters showed that PCBs inhibited decomposition of DDT at the concentration ratio of DDT to PCBs of 1 100-1 200 that may lead to prolongation of circulation time and toxic effect of this compound at water ecosystem (Tuteliyan and Lashneva, 1988). It is also known that in the past, PCBs were often added to HCH to increase the longevity of the insecticide (Mel nikov, 1974). 

Burge, W.D. Anaerobic Decomposition of DDT in soil. Acceleration by volatile components of alfalfa, J. Agrlc. Food Chem., 19(2) 375-378, 1971. 

Lopez Gonzales, J.De D. and Valenznela-Calahorro, C. Associated decomposition of DDT to DDE in the diffnsion of DDT on homoionic clays, J. Agric. Food Chem., 18(3) 520-523, 1970. 

An example of a few of these reactions that occur in our environment with several commonly used pesticides is illustrated in Figures 7-11. Fleck (15) has illustrated in Figure 7 that ultraviolet light catalyzes the decomposition of DDT. In the presence of air, one of the decomposition products is 4,4 -dichlorobenzophenone. However, when air is absent, 2,3-dichloro-l,l,4,4-tetrakis-(p-chlorophenyl)-2-butene is formed. This compound, through subsequent oxidation, may be converted into 4,4 -dichlorobenzophenone. In mammals 2,2-bis(p-chloro-phenyl) acetic acid (DDA) has been identified and shown to be excreted in the feces and urine. The mechanism of formation of DDA is believed to be an initial dehydrochlorination to DDE, which is then hydrolyzed to DDA as shown in Figure 8. Mattson et ah (29) found both DDT and DDE in most samples of human fat, and Walker et ah (44) noted low levels of these same compounds in restaurant meals. 

It is convenient to draw together various developments. Packed columns have been largely replaced by capillary columns that are available for a wide range of applications. Attention is drawn to the decomposition of DDT at the GC inlet that could result in unacceptable errors in the concentration of DDT metabolites and therefore in the persistence of DDT (Foreman and Gates 1997). The generality of this phenomenon is unknown. 

The decomposition of DDT induced by photolysis of diethylanaline produced DDD, DDE, and dichlorobenzophenone. All have been suggested as products of anaerobic degradation of DDT. 

Using CuTSPc as component of the microemulsion lowered the overpotential for the reduction of o-chlorophenol by 1 V, hence showed promise for catalytic decomposition of DDT . ... 

Using these systems, the thermal decomposition of DDE, DDT, diazinon, endrin, hexachlorobenzene, Kepone, mirex, and penta-chloronitrobenzene was studied, and in several instances stable intermediate products of incomplete destruction were observed. Kepone at 400 to 500°C yielded hexachlorocyclopentadiene, hexachlorobenzene, and an unidentified chlorinated hydrocarbon, all... 

Humic substances (HS) are polymeric oxidation products that result from the decomposition of plant and animal residues. As a consequence of their colloidal state in natural waters, they play an important role in the transport of organic pollutants. Thus hydrophobic organic pollutants such as polycyclic aromatic hydrocarbons, DDT, and PCBs are known to bind well to humic substances, thereby enhancing the former s water solubility. One important characteristic of... 

Besides the preliminary stability study, regular checks should be carried out over the entire lifetime of the material. In some rare situations, over the certification projects conducted under the BCR activities, examples of instability of substances was demonstrated at certain storage temperatures. Figures 4.12a-b on organochlorine pesticides in animal feed (confirmed in fish oil) and 4.13a-b for polycyclic aromatic hydrocarbons illustrate such examples. For p,p -TDE the increase in content is generated by the decomposition of p,p -DDT. A similar effect is noticed for o,p -DDT which fully disappears over a period of six months at +40 C [12,14]. For benzo(a)pyrene it could not be demonstrated whether the decrease in content noticed was due to a decomposition of the PAH or to a decrease in its extractability due to the change of the physical stage in the matrix [46,47]. These materials looked stable at lower temperatures usually already at +20°C. Consequently they are stored at temperatures of +4 C or less. 

Cracking Decomposition of petroleum with heat, steam, or other agents EDDT All DDT analogs combined... 

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. 

IV. Characteristics of Steady Detonation V, Initiation Behavior VI. Deflagration-to-Detonation Transition (DDT) and Combustion VII. Decomposition and Kinetics VIII. Analytical Methods IX. Waste Disposal X. Toxicity XI. RDX Detonators XII. Military Specifications and XIII. References. Major emphasis will be placed on Sections IV, V, and VI... 

Two common pesticides Endrin and DDT are susceptible to decomposition on dirty injection port. The former oxidizes to Endrin aldehyde and Endrin ketone, while the latter degrades to 4,4 -DDE and 4.4 -DDD. If degradation of either of these analytes exceeds 20%, corrective action should be taken before performing calibration. The percent breakdown is calculated as follows ... 

---