Pollutants models

What are the major limitations in modeling pollutant transformations in urban areas ... 

The comparisons in Table 1 using anthracene as the model pollutant showed that the dialysis and sorption techniques compare well. For both Boonton Humic Acid and Pakim Pond Humic Acid the results were not significantly different. 

The reactivity of Ti02 with alcohols is important in a number of technological applications. For example, alcohols can be used as energy carriers in renewable sources and they are also employed as model pollutants so that environmental cleaning strategies can be tested. 

Ramaswami A, Milford JB, Small MJ (2005) Integrated environmental modeling. Pollutant transport, fate, and risk in the environment Wiley, New York... 

Keywords Basin management, Climate change impacts, Downscaling, Hydrological modelling, Pollutants... 

Modeling pollutant concentration between source and worker prediction of small-scale dispersion of contaminants using data collected with a high-resolution three-axis sonic anemometer. The ultimate goal is to convert information collected by the anemometer into eddy diffusion coefficients, which can be used to estimate contaminant concentrations at any point within indoor environments. 

The Statistical Model. The residue levels of the individual specimens in a particular subpopulation (e.g., a given Census Division and age, sex, race category) are assumed to follow a lognormal distribution. Previous studies on NHATS data have found the lognormal distribution to be appropriate and goodness of fit tests performed on the collected data verified that the assumption is still reasonable. The lognormal model assumes only non-negative values and allows the variances of the different subpopulation distributions to increase with the mean levels. This distribution is commonly used to model pollutant levels in the environment. 

Synthetic wastewater containing organic model pollutant was prepared using two different concentrations, 20 and 80 mgL , of the commercial dye Cibacron Marine P2R-01, C.l. Reactive Blue 137 (RB137) obtained from Ciba-Geigy, and deionezed water pH 7, conductivity less than 1 pS cm. Other chemicals (H2O2, 30 % sulfuric acid, >95 % and sodimn hydroxide, p.a.) were supplied by Kemika, Croatia. 

Figure 6-2 Typical change in DOC remaining after ozonation (1) and biodegradable (2) as a function of the specific ozone dose / for the ozonation of model pollutant M and subsequent biodegradation of its oxidation products in a batch system.

Liu D-L, Nazaroff W (2001) Modeling pollutant penetration across building envelopes. Atmos Environ 35 4451 1462... 

Reviewed previous SCWO research with model pollutants and demonstrated that phenolic compounds are the model pollutants studied most extensively under SCWO conditions Studied supercritical water oxidation of aqueous waste Explored reaction pathways in SCWO of phenol Studied catalytic oxidation in supercritical water Explored metal oxides as catalysts in SCWO Studied decomposition of municipal sludge by SCWO Investigated the SCWO kinetics, products, and pathways for CH3- and CHO-substituted phenols Determined oxidation rates of common organic compounds in SCWO... 

Phenolic compounds are the model pollutants studied most extensively under SCWO conditions. Equation (10.8) and Equation (10.9) describe the formation of free radicals in the absence of initiators. They are formed by the reaction of oxygen with the weakest C-H bonds of the organic compound ... 

To gain insight into kinetics, reaction pathways, and reaction end products, laboratory investigations were performed by Rahman and Agrawal (1997). Sodium nitrate and sodium nitrite were selected as model pollutants. Reactions were carried out at room temperature in the dark with untreated [Fe°] = 69.4 g/L. In some cases, Fe° was treated with 10% HC1 (v/v) for nearly 2 min and then washed with deionized water four to six times prior to reaction. The nitrate and nitrite stock solution was nearly 0.16 mM, and mixing was achieved at 40 rpm. 

Cunningham J, Al-Sayyed G, Srijaranai S. Adsorption of model pollutants onto Ti02 particles in relation to photoremediation of contaminated water. In ... 

Photocatalytic systems became a subject of many detailed studies and improvements. A need to compare photocatalytic activity of various materials enforced selection of a model pollutant . Perhaps the most commonly chosen is 4-chloroph-enol (4-CP) [56, 57]. The route of 4-CP oxidation in the presence of excited Ti02 was described in many original and review papers [58-64], The oxidative pathway includes attack of hydroxyl radicals or direct oxidation with a hole leading to... 

The main advantage of this model is that it does not include any adjustable parameters. Hence, the behavior of the system can be predicted if the experimental conditions (applied current intensity, solution flow rate, and mass-transfer coefficient) are known. The good agreements obtained between model and experimental data validate all the assumptions made in the development of this model. This validation has been carried out with a wide variety of model pollutants including aromatics, nitroaromatics, cloroaromatics, carboxylic acids, alcohols, etc. 

Contaminants such as phenol, whose toxic effects on human health are well documented, have been widely used as a model pollutant to elucidate the complex PC reaction mechanisms and to evaluate the performance of... 

CREC researchers have addressed recently the application of Fe cations as additives to enhance the performance of PC reactions employing inexpensive procedures. This was sought owing to the characteristic properties and behavior of Fe cations in a PC reaction. Phenol and similar aromatics were selected as model pollutants given their refractory nature in water treatment and health problems associated with their presence in drinking water. 

In this respect, the effect of Fe cations on bofh the oxidation rate and complete mineralization rate of phenol and alike aromatic compounds was considered. Optimum conditions were reviewed to use Fe cations as reaction enhancers (henceforth PC reactions involving optimum Fe concentrations are called Fe-assisted PC reactions). This also involved the assessment of effect and mechanism of Fe ions on fhe PC reaction of phenol and other selected aromatic species. A systematic comparison between the kinetic reaction schemes for both unpromoted PC and Fe-assisted PC reactions for the selected model pollutants was also a primary emphasis. Last, the estimation of the enhancement through efficiency factor calculations was described. 

The next set of experiments involved the Fe-assisted PC oxidation of p-DHB and 1,4-BQ as the model pollutants. In these cases, similar patterns were observed leading to the conclusion that these two compoimds behave in a similar way to phenol and o-DHB with both exhibiting a series-parallel reaction scheme (Ortiz-Gomez et al., 2008)... 

The underlying assumption in this reaction scheme is that all chemical species behave the same as a model pollutant or as an intermediate. To exemplify, o-DHB is an intermediate in the Fe-assisted oxidation of phenol and when used as a model reactant, o-DHB forms p-DHB. It is h)q)othesized therefore that o-DHB as an intermediate in phenol Fe-assisted PC conversion forms p-DHB. Hence, the same assumptions for the development of the overall reaction scheme in the unpromoted PC reaction are considered for the Fe-assisted PC system. 

THB as a model pollutant (results not shovm here), its reaction rate was very fast compared with the oxidation of the other aromatics. Moreover, the Fe-assisted PC reaction of 1,2,4-THB was even faster than the impromoted PC reaction. Thus, it can be expected that if 1,2,4-THB is formed in the Fe-assisted oxidation of p-DHB, it will disappear very quickly as well, keeping its concentration below the detectable limit. 

Ramaswami, A. Milford, J.B. Small, M.J. Integrated Environmental Modeling—Pollutant Transport, Fate, and Risk in the Environment John Wiley New York, 2005. 

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