Degradative transformation

Organophosphate flame retardants and plasticisers Perfluorinated compounds Pharmaceuticals and personal care products Polar pesticides and their degradation/transformation products Surfactants and their metabolites... 

Broad analyte coverage and integrity (no analyte degradation, transformation)... 

Phytoremediation of organic xenobiotics is generally based on mineralization or more frequently on degradation/transformation of the xenobiotics to environmentally less dangerous compounds, which are fixed in cell compartments or stored in the vacuole as soluble products or exuded back to the environment. Affection of the metabolic pathway by suppression or enhancement of expression of enzyme leading particular... 

Hexa- and other higher brominated biphenyls are expected to be present in the particle-adsorbed state in the atmosphere. These PBBs photolyze in solution and in soil (Hill et al. 1982 Ruzo and Zabik 1975 Trotter 1977). Since PBBs present in surface soil are known to photolyze, particle-sorbed PBBs present in the atmosphere may also undergo photolysis. The importance of the photochemical reaction under sunlight illumination conditions for the degradation/transformation of PBBs in air cannot be evaluated due the lack of information. 

Several productive degradative transformations of chlorophyll a and b depend upon the ready oxidation of the ring E /3-keto ester. The so-called phase test involves aerial oxidation of the enolate anion produced by treatment of the ring e keto ester with alkali. One molecule of oxygen is consumed in this allomerization reaction to produce a hydroperoxide (111) which can fragment to give (112) after acidification, the unstable chlorin (113) is obtained, and this can be transformed into purpurin-18 (114) by evaporation, or into purpurin-7 trimethyl ester (115) by esterification with diazomethane. 

Fig. 7 Conceptual representation of processes influencing the atmospheric transport and fate of POPs. (1) Primary emissions of POPs to the atmosphere, (2) atmospheric deposition and photochemical degradation/transformation, (5) re-volatilisation from secondary sources in the different environmental compartments and burial in sediments, (4) bioaccumulation and biotic transport, (5) accumulation in glaciers and ice caps, with probable releases due to melting...

A section on methodology provides some background on relevant degradation/transformation processes, influential factors, data characteristics, and availability. 

A third section on algorithms and software attempts to overview the currently available, preferably computerized, predictive degradation/transformation models, as well as their applicability and reliability. Any recommendations for particular programs are dependent on the suitability of the program for specific questions (e.g., specific compounds and transformation), and also continuous improvements and new developments. 

Abiotic degradation transforms organic compounds by chemical reactions such as oxidation, reduction, hydrolysis, and photodegradation. Abiotic degradation processes do not usually achieve a complete breakdown of the chemical (mineralization). 

Conversely, some substances are transported relatively slowly to their site of degradation, transformation, or excretion, so that the rate of diffusion limits their rate of removal from the system. Substances of this nature are best described by noncompartmental models and power functions. 

Noncompartmental models were introduced as models that allow for transport of material through regions of the body that are not necessarily well mixed or of uniform concentration [248]. For substances that are transported relatively slowly to their site of degradation, transformation, or excretion, so that the rate of diffusion limits their rate of removal from the system, the noncompartmental model may involve diffusion or other random walk processes, leading to the solution in terms of the partial differential equation of diffusion or in terms of probability distributions. A number of noncompartmental models deal with plasma time-concentration curves that are best described by power functions of time. 

Half-life Time it takes to degrade, transform, or eliminate a chemical to 50% of its initial concentration. 

The Michaelis-Menten equation is often employed in soil-water systems to describe kinetics of ion uptake by plant roots and microbial cells, as well as microbial degradation-transformation of organics (e.g., pesticides, industrial organics, nitrogen, sulfur, and natural organics) and oxidation or reduction of metals or metalloids. Derivation of the Michaelis-Menten equation(s) is demonstrated below. 

Degradative Transformation of Poly(vinyl chloride) under Mild Oxidative Conditions... 

No study was located that reported the abiotic degradation/transformation of dinitrophenols in soil. It has been speculated that 2,4-DNP in soil may be reduced to 2-amino-4-nitrophenol by sunlight in the presence of a reductant, such as ferrous ions and a sensitizer, such as chlorophyll (Kaufman 1976 Overcash et al. 1982 Shea et al. 1983). Considering, however, that sunlight would not penetrate below the surface layer of soil, photolysis would not be significant at subsurface levels. 

The degradation products 6 and 17 were identical to the compounds in the reported (lb) and synthetic materials (1 la) in all respects. Thus, we prepared suitably protected synthetic intermediate 17 from 1 in a 26% overall yield (6 steps). An efficient degradative transformation of 1 into the synthetic intermediate 17 could be utilized for the synthesis of various analogues of this antibiotic. 

Special interest in these polymers is stipulated by intensive progress in computer technology. In the last 5-10 years, a great list of publications concerning structure and properties of LCP was presented. However, there is little information on thermoresistance and specific features of ECP degradative behaviour. Authors have studied degradative transformations... 

The activity measures in environmental sciences concern ecotoxicological effects as well as fate- and exposure-related parameters such as partitioning between the water, air and soil phases, or degradation/transformation. Because of the different nature of these endpoints, different techniques may be appropriate for the respective structure-activity analyses. Nevertheless, whichever sophisticated method is applied, it has to be stressed repeatedly that the basis of any QSAR modelling is the experimental data, and that their quality (i.e. variability) determines the reliability and soundness of the derived models. 

Perhaps no other part of the measurement process affects the resulting data more significantly than the ionization step. Unless originally in the gas phase, analytes need to be vaporized from a solid or liquid phase, ionized, and transferred into the vacuum system of the mass analyzer. This vaporization process, often called desorption (sputtering), can be fairly energetic and can degrade/transform the analytes before they are characterized. 

Polar pesticides and their degradation—transformation products. 

Fate is the whereabouts of a chemical in the environment it can distribute between soil, air, water, sediment and organisms there it can be fully degraded i.e. mineralized to inorganic chemicals or only incompletely degraded ( transformed ) or accumulate in soil, water, sediment or organisms and may hereby enter the food chain. 

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