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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Indoor and outdoor dust in Damaturu Nigeria : composition, exposure and risk to human health

Mohammed, Fatima Sule January 2013 (has links)
Harmattan and Dust (sand) storms together with anthropogenic activities including the use of firewood and kerosene as fuel for cooking, and diesel/petrol generators for electricity generation are potential sources of particulate and gaseous pollutants in homes in Damaturu town, Nigeria. Other activities like the burning of locally produced incense and mosquito coils as well as the use of aerosol sprays are further possible sources of indoor pollution, which may result in exposure of people to a range of pollutants through inhalation, by ingestion of settled dusts as well as dermal contact. Local people associate occurrence of dust events with adverse health effects and hence there is a need for an understanding of the composition of the settled and airborne dusts in order to assess the possible associated health risks. The first phase of the study involved selection and development of methods of dust sampling and analysis. For validation of the methods employed and to establish a broad understanding of the characteristics of the settled dusts, an initial survey study was conducted involving the application of thermal desorption/gas chromatography/mass spectrometry (TD/GC/MS) analysis for organic compound analysis, scanning electron microscopy (SEM), inductively coupled plasma-mass spectrometry (ICP-MS) for analysis of metals, and microbiological analysis. Airborne samples were also collected using sorbent tubes to determine organic compounds in air during activities such as cooking with kerosene, gas, and firewood as well as during electricity generation with fossil fuels. Carbon monoxide (CO) and ultrafine particles (UFPs) monitored simultaneously during some of the household activities. The study involved a novel method of extracting organic chemical emissions from dust by heating of the dusts directly in a micro chamber (μ-CTETM) and collection of emissions on sampling tubes. The method provided a relatively quick way of collecting chemical emissions from dusts that are readily available for release. The sampled tubes were analysed by TD/GC/MS. The conventional solvent extraction of the dusts was also carried out and the extracts were analysed by liquid injection-GC/MS and results of the two methods compared. The study determined a number of constituents (metals, SVOCs, phthalates and physical properties) of dusts collected from households in Damaturu during different weather events and from different indoor/outdoor locations; and compared with some UK samples. The samples investigated include dusts deposited; during two notable dusty-weather events (Harmattan and Storm) as well as when there was no notable dust event; during human activities; and dusts from different types of buildings (modern and traditional homes) as well as inside and outside homes. A standard reference material for organic chemicals (SRM 2585) was also analysed. The physical characterization of the settled house dust samples analysed revealed the various shapes and sizes, and elemental composition of the constituents, which included respirable particles. The microbial analysis also indicated the presence of the spores of a host of fungi and bacterial species; and the possible contributions of household activities to the increased production of pollutants (UFP and CO) ascertained. The μ-CTE extraction of the house dusts by heating with TD/GC/MS analysis of the emissions as well as the solvent extraction-GC/MS revealed the presence of many organic chemical compounds with different analytical retention times and varying concentrations in the dust samples. Chemicals of interest quantified: benzene, hexanal, nonanal, diethyl phthalate (DEP), diisobutylphthalate (DIBP), dibutylphthalate (DBP), and diethylhexylphthalate (DEHP). A host of other chemicals commonly present in the analysed samples identified using the NIST library associated with the MS system software. These chemicals included naphthalene and C10-C16 aliphatic and aromatic hydrocarbons, which would need confirmation by running the pure compound samples. There was an observed higher concentration of the chemicals in the solvent extracts than the μ-CTE extracted dust. The higher concentration of the chemicals in the solvent extracts expected due to the aggressive removal of the chemicals by the organic solvent whereas in the case of thermal extraction only the readily available chemicals (loosely bound to the matrix) released by increases in temperature were removed. Generally, the concentrations of the chemicals found were higher in the indoor than in the outdoor dust samples. In the analysis of the dusts collected during weather events; higher chemical concentrations observed in the samples collected during Harmattan period than the other periods. The Harmattan dust period may pose increased exposures to dust and possible health risks. More exposure is expected to occur in the traditional homes compared with the modern homes due to the higher concentrations of the chemicals in both the indoors and the outdoors and this may be especially important to women and children who spend most of their times at home. Metal analysis involved microwave-assisted digestion of the dust samples followed by ICP-MS analysis. The total quant method of metal analysis for a general profiling indicated the presence of more than 50 elemental contaminants in house dust. The results of the quantitative analysis for six target metals: Cd, Cr, Cu, Ni, Pb, and Zn showed their presence in all indoor and the outdoor dust samples. The mean concentrations showed that the metals were in higher concentrations in the indoor dusts than in the outdoor dusts. The quantitative analysis carried out indicated higher metal contents in the storm dusts than the dusts during the other periods. Results of the dusts collected from modern and traditional homes indicated the presence of the metals in higher concentrations in the dusts from traditional homes than the dusts from the modern homes. The estimated mean concentrations of the metals and phthalates inadvertently ingested as a constituent of dust indicated that some of the pollutants could exceed the tolerable daily intake (TDI) due to high exposures to dust expected to be the case in Damaturu. The results of the investigation of the dust composition, combined with information on exposure to dust and pollutants, show that dusts are a risk to the health of people in the Damataru community. Recommendations are made for more studies to provide a better understanding of dust ingestion and exposure to some phthalates and heavy metals in particular and the possible health risks. To the best of my knowledge, this is the first ever research study of airborne and settled dusts undertaken in North-Eastern Nigeria.
22

Kinetic Study on Degradation of Gas-phase 1, 3-Butadiene and Propylene Glycol Monomethyl Ether Acetate (PGMEA) by UV/O3

Huang, Bo-Jen 24 October 2005 (has links)
This study investigates the rate kinetics for BD and PGMEA oxidation by UV/O3 process. The reactor constructs of a 100 cm x 20 cm x 85 cm (L x W x H) stainless steel chamber, in which four vertical steel plates (20 cm x 65 cm, W x H) were inserted to establish a plug flow path for the flowing gas. The reactor has a total effective volume of 170 L. Each of the five compartments of the reactor is equipped with an individual UV irradiation system with a 3.0-cm x 15-cm (ID x L) quartz sheath that housed an UV lamp, and two electric UV power inputs of 0.147 or 0.294 W/L were obtained. The gas flows perpendicularly to the UV lamps in the reactor. The influent tested VOC concentration was adjusted to about 50 ppm, and the gas flows were controlled at the individual flow rate of 60 and 120 L/min. The effects of moisture content (relative humidity, RH), ozone dosage (initial molar ratio of ozone to the tested VOC, m) and UV volumetric electric power input on the removal of the tested VOCs are investigated in the study. Also, kinetic models of the tested VOCs by photolysis, ozonation and UV/O3 have been developed and confirmed with reference to the experimental data. According to the kinetic models, both photolysis rate and oxidation rate by UV/O3 are following the first order behavior with respect to the tested VOC concentrations which are low. The result reveals the absorbance for the reactions is weak absorbance under UV irradiation. The reaction rates are proportional to the UV electric power inputs in UV-initiated reactions. And the parameter, £i, which represents the ratio of OH radical consumption rate by the tested VOC to the total OH radical consumption rate, can be obtained by simulating the performance of experimental data of OH reactions. The experimental results reveal that for BD oxidation with a gas space time of 85 sec and RH = 40 ¡V 99%, BD photolysis did not occur at wavelength of 185 nm with UV electric power inputs of 0.147 and 0.294 W/L. The ozonation efficiency of BD reached 90% at m = 3.5, and RH had no influence on the removal efficiency of BD. The removal efficiencies by UV/O3 process reached 90% with m = 2.2 and 1.6 for UV power inputs of 0.147 and 0.294 W/L, respectively. The addition of ozone apparently encouraged BD removal efficiency by UV/O3 process. And the enhancement of ozone dosage (m = 0.5 ¡V 4.4) would promote the decomposition of BD more effectively than the enhancements of UV power input (from 0.147 to 0.294 W L-1) and RH (from 40 to 99%). For PGMEA photolysis in a batch reactor with volume of 1.188 L, the photolysis occurred at wavelength of 185 nm under UV irradiation. And the photolysis rate follows the first order behavior with respect to the concentration of PGMEA. But PGMEA photolysis did not occurred at UV wavelength of 254 nm. PGMEA ozonation was performed in the same batch reactor; and the removal efficiency of only 50% at m = 3.96 would take 35 min. So, PGMEA ozonation in the plug flow reactor did not be observed at the conditions of the gas space time of 85 sec and RH = 15 ¡V 99%. Besides, the photolysis of PGMEA was carried out at the above conditions. The removal efficiency of PGMEA by UV/O3 could reach 90% at the conditions of the gas space time of 170 sec, UV volumetric electric power input of 0.294 W/L and m = 2.9. And the enhancement of UV power input (from 0.147 to 0.294 W L-1) would promote the decomposition of PGMEA more effectively than the addition of ozone dosage (m = 1.05 ¡V 15.63) and RH = 15 ¡V 99%.
23

Study on the Biological Treatment of Air-borne VOCs by Sieve-plate Absorption Tower Combined with Activated Sludge Aeration Tank

Chang, Hsiao-Yu 24 October 2005 (has links)
Bioprocesses for air pollution control can generally be categorized as bioscrubber, biofilter, and biotrickling filter systems. These processes have been proven to be economical and effective for control of volatile organic compounds (VOCs) with concentrations of <1,000 mg C m-3 in gas streams. First, an activated sludge aeration tank (W x L x H = 40 x 40 x 300 cm) with a set of 2 mm orifice air spargers was utilized to treat gas-borne VOCs (toluene, p-xylene, and dichloromethane) in air streams. The effects of liquid depth (Z), aeration intensity (G/A), the overall mass transfer rate of oxygen in clean water (KLaO2), the Henry¡¦s law constant of the tested VOC (H), and the influent gaseous VOC concentration (C0) on the efficiency of removal of VOCs were examined and compared with a literature-cited model. Results show that the measured VOC removal efficiencies and those predicted by the model were comparable at a G/A of 3.75 ¡V 11.25 m3 m-2 hr-1 and C0 of around 1,000 ¡V 6,000 mg m-3. Experimental data also indicate that the designed gas treatment reactor with KLaO2 = 5 ¡V 15 hr-1, could achieve > 85% removal of VOCs with H = 0.24 ¡V 0.25 at an aerated liquid depth of 1 m, and > 95% removal of dichloromethane with H = 0.13 at a 1 m liquid depth. The model predicts that, for gas treatment in common activated sludge tanks, with KLaO2 = 5 ¡V 10 hr-1, depth = 3 ¡V 4.5 m, G/A = 9 ¡V 18 m3 m-2 hr-1, > 92% VOC removal can be achieved with operating parameters of Z of 3.0 m and KLaVOC/(G/A) of about 0.28 m-1, for VOCs with H < 0.3, such as most oxygen-containing hydrocarbons with low molecular weights, and benzene, toluene, ethylbenzene, and dichloromethane. Second, an activated sludge aeration tank and a sieve-plate column with six sieve plates were utilized to treat gas-borne VOCs in air streams. The tank was used for the biodegradation of the absorbed VOCs from the column which utilized the activated mixed liquor drawn from the tank as a scrubbing liquor. This research proposed a model for VOC absorption to a down-flow activated sludge liquor in a sieve-plate column. The experimental setup consisted of a pilot-scale activated-sludge tank and a sieve-plate tower, as demonstrated. The sieve-plate tower was constructed from a 25 x 25 x 162 cm (W x L x H) acrylic column with six custom-made sieve plates. Each plate has 382 holes which are 3 mm in diameter arranged on a square pitch. The holes give an open area of 3.82% of the whole plate area for gas flow. Two 25 mm-i.d. down-comer pipes were also equipped to allow for the downflow of the activated sludge liquor. Ports were provided at the column inlet, outlet, and each plate for gas and liquid sampling. Experiments were conducted and the model verified based on the results of tests on the removal efficiencies of isopropyl alcohol (IPA), toluene and p-xylene in the system operated at a range of influent VOC concentrations, air application rates, and liquid/gas flow ratios (L/G). The model developed by a material balance for the gaseous- and liquid-VOC over each plate of the column was developed and experimentally verified in this study. Superficial gas velocity over the column plate (U), number of plates (N), volumetric liquid-phase VOC-transfer coefficient (KLaVOC), aerated liquid depth over the plate (Z), volumetric liquid/gas flow-rate ratio (L/G), dimensionless Henry¡¦s law coefficient of the VOC to be absorbed (H), VOC content of the influent scrubbing liquor (xN+1), and the biodegradation rate constant of the VOC in the activated sludge mixed liquor (k) are among the affecting parameters to the effectiveness of the VOC removal. Model application by the model for effects of affecting parameters on the VOC removal effectiveness indicates that L/G, plate number N, biodegradation rate constant k, Henry¡¦s law constant of VOC H are among the important ones. A L/GH of greater than 2 and N of around 6 are enough for the effective (>90%) removal of the influent VOCs with H < 0.01 if no biodegradation occurred in the column. However, a N of over 16 is required for the influent VOCs with H of around 0.2. Biodegradation with a rate constant of around 100 hr-1 in the column greatly improves the column performance.
24

Oxidation characteristics of fluorine-, nitrogen-, and sulfur-containing organic compounds by UV/O3

Chang, Ken-Lin 10 September 2007 (has links)
DMSO (dimethyl sulfoxide) is a liquid with a high boiling point (189 oC) that has been extensively utilized in various industries owing to its ability to dissolve various organic and inorganic compounds. DMSO is increasingly being adopted as a detergent or a photo-resistant stripping solvent in manufacturing semiconductors and liquid crystal displays (LCD). Therefore, DMSO is now a major component of wastewater. The biological treatment of DMSO-containing wastewater generates noxious DMS (dimethyl sulfide) and other compounds that may cause odor problems. Also having a high water solubility and a moderate boiling point (110 oC), tetrafluoro propanol (TFP) has been extensively applied in the manufacture of CD-R and DVD-R, due to its ability to dissolve organic dyes. The spin coating process produces a large amount of wastewater containing TFP. No reports have been written on the biodegradability of TFP to the authors¡¦ knowledge. Additionally, HMDS (hexamethyldisilazane) has been extensively used in life science microscopy and material science. For instance, the semiconductor industry employs HMDS to promote the adhesion of photo-resistant material to oxide(s). HMDS is classified as a carcinogen, and has an ammonia odor. Condensing incinerators have been found to be unsuitable for treating HMDS-containing waste gases, because of the formation of silicon dioxide, which blocks porous adsorbents. Biological treatment also appears to be unpromising due to its low water solubility and limited biodegradability. This investigation evaluates the feasibility, effectiveness and oxidation characteristics of aqueous DMSO, TFP and gaseous HMDS (hexamethyldisilazane) by UV/O3 processes. A reactor made entirely of acrylic plastic with an effective volume of 10 L was employed for the reactions. The tested VOCs concentrations were adjusted to 400¡V890mg/L and 772¡V887 mg/L for DMSO and TFP, respectively, and the gas (ozone-enriched air) flow rate was controlled at 3L/min. The effects of various solution pH values (acidic, alkaline, uncontrolled), solution temperatures (26 oC, 37 oC, 48 oC and 60 oC), and UV wavelengths (254 nm and 185+254 nm) on the removal of tested VOCs were studied . Additionally, the operation costs of treating DMSO and TFP by UV/O3 were estimated. Experimental results demonstrate that acidic conditions (pH = 3.6) favored the degradation of DMSO, and that the removal efficiency could reach 95% at a volumetric UV intensity P/V of 2.25 W/L and a reaction time of 120 min. However, alkaline conditions (pH = 9.5) favored the decomposition of TFP, with the removal efficiency reaching 95% at P/V = 2.5 W/L and a reaction time of 60 min. Both DMSO and TFP exhibited zero-order degradation kinetics when sufficient ozone was supplied. Raising the oxidation temperature did not increase the UV/O3 oxidation of TFP in the tested concentration and temperature ranges. Operation costs of the UV/O3 per unit volume of wastewater with DMSO or TFP are comparable to those of the methods described in the literature. For the gaseous HMDS oxidation, two batch reactors with effective volumes of 1.2 and 5.8 L were used employed with the decomposition occurred under UV (185+254 nm) irradiation and UV (254 nm)/O3 processes. Tests were performed with initial HMDS concentrations of 32¡V41mg/m3 under various initial ozone dosages (O3 (mg)/HMDS (mg) =1¡V5), atmospheres (N2, O2, and air), temperatures (28 oC, 46 oC, 65 oC and 80 oC), relative humilities (20%, 50%, 65% and 99%) and volumetric UV power inputs (0.87 W/L, 1.74 W/L, 4.07 W/L and 8.16 W/L) to assess their effects on the HMDS degradation rate. Results of this study demonstrate that the decomposition rates for the UV (185+254 nm) irradiation exceeded those for the UV (254 nm)/O3 process for all conditions. UV (185+254 nm) decompositions of HMDS displayed apparent first-order kinetics. A process with irradiation of UV (185+254 nm) to HMDS in air saturated with water at temperatures of 46¡V80 oC favors the HMDS degradation. With the above conditions and a P/V of around 8 W/L, k≈ 0.20 s−1, and over 90% of the initial HMDS was degraded in a time of 12s. The main mechanisms for the HMDS in wet air streams irradiated with UV (185+254 nm) were found to be caused by OH free radical oxidation produced from photolysis of water or O (1D) produced from photolysis of oxygen. Economic evaluation factors of UV (185+254 nm) and UV (254 nm)/O3 processes at various UV power inputs were also estimated.
25

Influence of bioremediation on the chemical and nutritional composition of produce from crude oil-polluted sites

Odukoya, Johnson Oluwaseun January 2015 (has links)
The influence of crude oil-contaminated and remediated sites on agrifood production is not clearly understood. To address this knowledge gap, the research was divided into two stages involving: (1) assessment of the efficiency of two bioremediation strategies to support hydrocarbons degradation as well as agrifood production with the initial analysis of the experimental materials, and (2) evaluation of the effect of different crude oil remediation intervention values (CRIV) on selected vegetables (Brassica juncea, Brassica oleracea, Lactuca sativa and two different cultivars of Solanum lycopersicum). Results from the first stage showed that the crude oil used had a pristane/phytane ratio of 0.98 (within the 0.8 – 3.0 range of most crude oils), higher concentrations of C10 – C14, C15 – C20 and C21 – C27 alkanes than the C28 – C36 alkanes including higher concentrations of two of the US EPA priority pollutant polycyclic aromatic hydrocarbons (PAHs) - phenanthrene and anthracene. Four treatments were prepared in which weekly tillage enhanced the degradation of C15 – C20 and C21 - C27 alkanes in the Remediation by Enhanced Natural Attenuation (RENA) treatment. The two bioremediation strategies (RENA and bioaugmentation) enhanced PAHs degradation compared with the remediation-study control treatment while only RENA application among the two approaches supported the growth of B. juncea. Although there was no statistical significant difference (p > 0.05) between the major dietary mineral contents of samples from the various treatments compared with the control treatment samples, RENA application affected the Cr, Zn and Pb contents. Meanwhile, the Ca/P (> 1.0) and Na/K (< 0.60) ratios of all the harvested samples imply that they provide a good source of these minerals for bone formation and would not contribute to high blood pressure. The crude oil used also deterred the attack of juvenile caterpillars of cabbage white butterfly. Findings from the second stage revealed that the yield of the green leafy vegetables including one of the selected tomato cultivars (Micro-Tom), was in most cases impaired at CRIV ≥ 3,000 mg/kg total petroleum hydrocarbon (TPH). Compared with the control treatment samples’ composition, crude oil stress at 10,000 mg/kg TPH enhanced the concentration of K, Mn and crude protein of B. oleracea and L. sativa as well as the sucrose, total sugars, total phenolics and total flavonoids contents of the latter vegetable. Sucrose was also only detected in M82 tomato cultivar samples from the crude oil-containing treatments. The Cd content of B. oleracea, Pb contents of: L. sativa and M82 tomato harvested samples were all below the FAO/WHO Codex Alimentarius Commission 2015 recommended maximum levels. However, tartaric acid was only detected in B. oleracea and L. sativa samples from the 10,000 mg/kg TPH treatment as well as in M82 tomato cultivar samples from the treatment involving CRIV of 5,000 mg/kg TPH. Generally, the yield of these crops in response to crude oil contamination varied in which B. juncea had the least tolerance to crude oil stress among the green leafy vegetables tested. Most of the quality parameters in the two tomato cultivars were not affected by CRIV between 750 - 5,000 mg/kg TPH with p-xylene having the greatest toxic potential among the VOCs emitted from the 5,000 mg/kg TPH treatment. The research findings, under the experimental conditions, indicated the effectiveness of RENA for the degradation of low molecular weight PAHs and its agricultural benefits. They also suggest that crude oil-contaminated sites at ≤ 3,000 mg/kg TPH present a similar growing environment to a clean site for agrifood production and the possibility that crude oil stress at 10,000 mg/kg TPH could enhance crop quality. Nonetheless, the contribution of bio- accumulated PAHs in these crops to the food chain demands further investigation.
26

Electrical Impedance Spectroscopic Studies On Bread Staling : Sensors And Instrumentation

Bhatt, Chintan M 06 1900 (has links) (PDF)
Quality control is essential in food industry and efficient quality assurance is becoming increasingly important. The assessment of food quality still centers on its sensory properties (appearance, aroma and texture). Bread is one of the most consumed food item all over the world. Bakery product manufacturers expect that the bread should retain all of its attributes during storage and consumers expect their bread to be ‘fresh’. Unfortunately, it remains truly ‘fresh’ for only a few hours after it leaves the oven because the ingredients of the bread undergo series of physical and chemical changes that eventually lead to deterioration, referred as “staling”, of bread quality. Bread staling is classified in two categories: crust (outer portion of bread) staling and crumb (center portion of bread) staling. Crust staling is associated to the moisture migration from crumb to crust during storage. This moisture migration leads to a phenomenon called glass transition at crust. This phenomenon changes the mechanical and dielectric properties of bread crust. Crumb staling is mainly associated to the physicochemical changes in starch. During storage, amorphous starch regains its crystallinity, which increases the firmnesss and dryness of bread crumb. Thus, the knowledge of moisture content, starch recrystallization and the glass transition helps in understanding the bread staling mechanism. There are some volatiles produced from the bread during storage, which forms the characteristic flavor or aroma of the bread. The loss of this characteristic flavor during storage also gives the information about the loss of freshness and staling. Thus, there is a need for detection and monitoring the loss of these volatiles to determine the characteristic flavor during storage. Hence, the present investigations are focused on these issues and developed a measurement facility to monitor the above physicochemical changes in bread during storage. As a part of experimental investigations, two separate test facilities have been developed. A multichannel ring electrodes with suitable instrumentation based on impedance spectroscopy technique is developed for simultaneous measurement of electrical properties of bread at crust and crumb during storage in the frequency range from 50 Hz to 100 kHz. The detailed investigations have been conducted on wheat bread. The variation in capacitance showed that the glass transition phenomenon, at room temperature, in bread crust occurs after 96 h of storage with 18% of moisture in it. The resistance changes at bread crumb showed the starch recrystallization during staling. The electrical property results are justified with the results obtained from the conventional differential scanning calorimmetery (DSC) studies. The impedance measurement at crust and crumb estimates the moisture content at the respective zones of bread. Thus the test facility is used for the simultaneous measurement of moisture content, starch recrystallization and glass transition at crumb and crust respectively without destructing the bread loaf. A few experiments are conducted on maida bread and the obtained results are compared with the wheat bread results. Another test facility has been developed for the detection of volatiles produced from the wheat bread during storage. The gas chromatography and mass spectroscopy (GC-MS) experimentations are conducted to identify the volatiles produced from the bread during storage. The major volatiles produced from wheat bread are found to be 1-Heptanol, 1-Pentanol, 1-Octanol, Furan and Hydroperoxyde. A conducting polymer based gas sensor is designed and developed to sense these volatiles and the changes in its electrical property is monitored with a suitable instrumentation based on impedance spectroscopy technique in the frequency range from 10 Hz to 2MHz. Experimental investigations are carried out in an in-house air tight closed test chamber. The bread sample and the designed sensor are kept inside the test chamber and closed tightly so that only bread volatile can interact with the sensor. The sensor response is monitored by measuring the changes in its capacitance upon exposure to organic volatiles produced from bread during storage. It is observed that the capacitance of the sensor changes with the quantitative changes of the above volatiles. Thus, the test facility is found quite suitable for the detection and monitoring the bread volatiles produced during storage, which finally affects the aroma property. Thus, the developed experimental test facilities with suitable sensors and instrumentation based on impedance spectroscopy technique are found quite suitable to monitor the changes in physicochemical properties and aroma of bread during storage. The correlation between the measured electrical properties and the changes in the textural and flavor properties of bread during storage has been established. The results obtained with the developed test facilities are in good agreement with the results obtained from the standard traditional techniques like DSC and GC-MS.
27

Recovery of petrol vapour at a bulk storage facility

Venter, Cornelia 28 March 2008 (has links)
Please read the abstract in the section, 00front of this document / Dissertation (MEng (Environmental Engineering))--University of Pretoria, 2008. / Chemical Engineering / MEng / Unrestricted
28

Senzorické vlastnosti organických materiálů / Sensoric Properties of Organic Materials

Tmejová, Kateřina January 2009 (has links)
The first part of the work is aimed to the study of changes of electrical properties of substituted phthalocyanines under the influence of humidity. Thin films were prepared by spin coating technique. During the influenece of humidity electrical conductivity increases. Sorption and desorption and the changes in electrical properties under the repated humidity exposure were investigated as well. Impedance spectroscopy was used for the studies. The second part of this work consists of optical studies and changes of optical parametrsunder the influence of different alcohols (methanol, ethanol, 2-propanol) exposures. The investigated samples were prepared by vacuum evaporation a glow-discharge-induced sublimation. The changes of optical reflectances of the films upon exposure to alcoholvapour-containg atmospheres were studied as a function of alcohol concetration and exposure time.
29

Part I. From the Lab to the Field - Recent Developments in Polymer Coated ATR Sensing for the Determination of Volatile Organic Compounds ; Part II. From the Field to the Lab - Investigating IR Signatures for Remote Sensing Applications

Karlowatz, Manfred 22 June 2004 (has links)
Part I: Successful transition of polymer coated, ATR-FTIR sensor devices from a laboratory environment to real world field applications for detecting and quantifying VOCs in water is shown. Simultaneous, quantitative detection of BTX mixtures in water during enrichment into polymer coated ZnSe ATR elements has been performed. The obtained results showed accurate detection and quantification to the low ppb concentration region. Fiber-optic evanescent field measurement campaigns have been conducted at simulated field conditions during which concentration gradients of various VOCs in the mg/L range have been monitored successfully. The first test of an ATR based, polymer coated sensor system under real world field conditions, the chlorobenzene concentration in groundwater at mg/L levels was determined. An interesting aspect of these measurements was the experimental proof for the dependence of analyte extraction dynamics on the flow conditions of the sample matrix surrounding the extractive polymer membrane. The obtained results demonstrate that MIR evanescent field sensors are suitable for in-situ analysis at real world field conditions for environmental monitoring applications. PART II: Recently, measurements of disturbed soils have shown different spectral contrast in comparison to undisturbed soils. In this work first measurements at controlled laboratory conditions have been performed to investigate individual minerals of the soil matrix and their spectral characteristics under various environmental conditions. ATR spectroscopy has been applied to investigate multi-disperse quartz sand and mono-disperse soda lime glass spheres samples. For the investigation of spectral differences between pristine and disturbed quartz sand, a wetting/drying procedure with subsequent sample aerating has been developed. In addition to established differences in spectral contrast of disturbed and undisturbed soil, a strong spectral shift of absorption features was observed. When probed with s- or p-polarized light, both samples showed strong LO-TO mode splitting. The studies also reveal that the main reason for spectral differences of pristine and disturbed soils is caused by water facilitated changes of the particle size distribution in the probed volume. The presented results advance the variety of spectral characteristics useful for the detection of disturbed soils (i.e. possible landmine sites) with MIR imaging systems.
30

Seasonal Variation of Ambient Volatile Organic Compounds and Sulfur-containing Odors Correlated to the Emission Sources of Petrochemical Complexes

Liu, Chih-chung 21 August 2012 (has links)
Neighboring northern Kaohsiung with a dense population of petrochemical and petroleum industrial complexes included China Petroleum Company (CPC) refinery plant, Renwu and Dazher petrochemical industrial plants. In recent years, although many scholars have conducted regional studies, but are still limited by the lack of relevant information evidences (such as odorous matters identification and VOCs fingerprint database), while unable to clearly identify the causes of poor ambient air quality. By sampling and analyzing VOCs, we will be able to understand the major sources of VOCs in northern Kaohsiung and their contribution, and to provide the air quality management and control countermeasures for local environmental protection administration. In this study, we sampled and analyzed the speciation of VOCs and sulfur-containing odorous matters (SOMs) in the CPC refinery plants, Renwu and Dazher petrochemical complexes simultaneously with stack sampling. The sampling of VOCs and SOMs were conducted on January 7th, 14th, and 19th, 2011 (dry season) and May 6th, 13rd, and 23rd, 2011 (wet season). We established the emission source database, investigated the characteristics of VOC fingerprints, and estimate the emission factor of each stack. It helps us understand the temporal and spatial distribution of VOCs and ascertain major sources and their contribution of VOCs. Major VOCs emitted from the stacks of the CPC refinery plant were toluene and acetone. It showed that petroleum refinery processes had similar VOCs characteristics and fingerprints. The fingerprints of stack emissions at Renwu and Dashe industrial complexes varied with their processes. Hydrogen sulfide was the major sulfur-containing odorous matter in all petrochemical plants. Compared to other petrochemical complexes, Renwu industrial complex emitted a variety of SOMs species as well as relatively high concentrations of sulfur-containing odorous matters. The petrochemical industrial complexes in the industrial ambient of VOCs analysis results showed that isobutane, butane, isopentane, pentane, propane of alkanes, propene of alkenes, toluene, ethylbenzene, xylene, styrene of aromatics, 2-Butanone (MEK), acetone, of carbonyls are major species of VOCs. In addition, ethene+acetylene+ethane (C2), 1,2-dichloroethane, chloromethane, dichloromethane, MTBE were also occasionally found. Sulfur-containing odorous matter (SOMs) analytical results showed that major odorous matters included hydrogen sulfide, methanethiol, dimethyl sulfide, and carbon disulfide. The highest hydrogen sulfide concentration went up to 5.5 ppbv. In this study, the species of VOCs were divided into alkanes, alkenes, aromatics, carbonyls, and others. The temporal and spatial distribution of various types of VOCs strongly correlated with near-surface wind direction. The most obvious contaminants were alkanes, aromatics, and carbonyls of the dispersion to the downwind. Generally, the ambient air surrounding the petrochemical industrial complexes was influenced by various pollutants in the case of high wind speeds. It showed that stack emission and fugitive sources had an important contribution to ambient air quality. TSOMs and hydrogen sulfide emitting mainly from local sources resulted in high concentration of TSOMs and hydrogen sulfide surrounding the petrochemical industrial complex. Principal component analysis (PCA) results showed that the surrounding areas of petrochemical industrial complexes, regardless of dry or wet seasons, were mainly influenced by the process emissions and solvent evaporation. The impact of traffic emission sources ranked the second. Chemical mass balance receptor modeling showed that stack emissions from the CPC refinery plants contributed about 48 %, while fugitive emission sources and mobile sources contributed about 30 % and 11%, respectively. The stack emissions from Renwu industrial complex contributed about 75 %, while fugitive emission sources and mobile sources contributed about 17 % and 5 %, respectively. The stack emissions from Dazher industrial complex contributed about 68 %, while fugitive emission sources and mobile sources contributed about 21 % and 2 %, respectively.

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