No description available.

Halle, Wittenberg, Universiẗat, Diss., 2003.

No description available.

Abstract This dissertation describes a study of the treatment of wastewater using the flocculation process. Wastewater samples from Barloworld Plascon paints were used for the research. Environmental pressure has necessitated the introduction of a new generation of low-solvent paints. The behaviour of these in coagulation and flocculation treatment processes has not been investigated previously. The optimum flocculent dosage for these paints was investigated. It was found that for paint wastewater to be flocculated, the effect of the dispersants needs to be counteracted, which destabilizes the colloidal suspension, enabling flocculation and settling to occur. Results showed a correlation between the solid content of wastewater and flocculent dosage. Changes in redox potential have been found to be associated with good flocculation. In this work, redox potential was evaluated as an indicator for destabilisation of the dispersants. It was shown that redox potential can be used as an indicator of good flocculation at low dispersant concentrations. Owing to the importance of the hydrolysis reactions of Al3+ in flocculation, which are affected by pH, the pH range in which good flocculation occurs was determined. Results show that optimal flocculation occurred between pH 4 and 5. A strong relationship between flocculent dosage and particle nucleation and growth was observed. Results also showed that mixing improves flocculation kinetics.

No description available.

Parasitoid insects face the fundamental problem of finding a suitable host in environments filled with competing stimuli. Many are deft sensors of olfactory cues emitted by other insects and the plants they live on, and use these cues to find hosts. Using olfactory cues from host-plants is effective because plants release volatile organic compounds (VOCs), in response to herbivory or oviposition, that contain information about the presence of hosts. However, plant-produced cues can also be misleading because they are influenced by a variety of stimuli (abiotic variation, infection and multiple sources of induction via herbivory or oviposition). Flexible behavior is one strategy that parasitoids may use to cope with variation in olfactory cues. We examine the innate and learned responses of a natural population of wasp egg parasitoids (Trichogramma deion and Trichogramma sathon) using a series of laboratory and field Y-olfactometer experiments. Wasps typically attack eggs of the hawkmoth Manduca sexta and Manduca quinquemaculata on native Datura wrightii plants in the southwestern United States. We show that Trichogramma wasps responded innately to VOCs produced by D. wrightii and could distinguish plants recently attacked by M. sexta from non-attacked plants. Furthermore, adult Trichogramma wasps were able to learn components of the VOC blend given off by D. wrightii, though they did not learn during exposure as pupae. By further exploring the behavioral ecology of a natural population of Trichogramma, we gain greater insight into how egg parasitoids function in tri-trophic systems.

Los organismos vivos intercambian gases con la atmósfera. Estos gases llamados Compuestos Orgánicos Volátiles Biogénicos (COVBs) son muy importantes para la química de la troposfera y el ciclo global del carbono. Las plantas producen una gran variedad de hidrocarburos de los cuales el grupo más representativo y abundante son los isoprenoides. El isopreno, los monoterpenos y sesquiterpenos representan una pequeña proporción de esta gran diversidad de productos vegetales dentro del grupo de los isoprenoides. Además de isoprenoides, las plantas emiten otros compuestos orgánicos volátiles, por ejemplo, el metanol, metil jasmonato, etileno y muchos compuestos orgánicos oxigenados de carbono. Existen muchos procesos de retroalimentación entre la biosfera y la atmósfera. Por un lado las plantas juegan un papel importante en la química de la zona baja de la atmósfera. La foto-oxidación atmosférica de las emisiones de COVs produce dos productos importantes en la baja atmósfera, el ozono y los aerosoles orgánicos. Ambos tienen importantes consecuencias para la calidad del aire y el clima. Por otro lado, el clima, es decir, los cambios en la variabilidad o estado medio de la atmósfera a través del tiempo, está afectando a su vez las actividades de la biosfera. Por lo tanto, es de gran importancia estimar los flujos biogénicos COVs a la atmósfera y sus variaciones en el contexto del cambio climático, especialmente ante las predicciones, por parte de modelos climáticos y ecofisiológicos, de un aumento de la sequía durante las próximas décadas.La mayor parte de la investigación acerca de los flujos de COVs (sin incluir el metano) se ha centrado en los flujos de las partes aéreas de las plantas a diferentes niveles, desde la cubierta foliar hasta flores y tallos. Sin embargo, hasta los últimos años, la información sobre los flujos COV procedentes las partes subterráneas de las plantas, por ejemplo las raíces, era muy escasa. En esta tesis nos hemos interesado por el intercambio de gases traza diferentes al metano biogénico: CO2 y COVs. El principal método utilizado para medir los flujos de gases del suelo en este trabajo es una variante del método de cámara cerrada. El modo de funcionamiento en este caso es dinámico. Un flujo continuo de aire se bombea a través de la cámara, y el gas emitido desde el suelo se mide directamente en la corriente de aire o es adsorbido en un material adecuado para la captura y posterior análisis de la emisión del suelo.Los objetivos generales de esta tesis doctoral fueron: 1) caracterizar el contenido y el intercambio de COVs en suelos Mediterráneos, en particular monoterpenos por su importante papel en la ecología, la fisiología vegetal y la química atmosférica, y también de otros compuestos orgánicos volátiles, y 2) evaluar los posibles cambios en el intercambio de COVs y CO2 del suelo ante la perspectiva de un cambio ambiental global hacia unas condiciones más áridas y secas en la región Mediterránea. Las principales conclusiones son las siguientes: Las tasas de intercambio de COVs totales y de monoterpenos entre la superficie del suelo y la atmósfera son muy bajas. La contribución de las emisiones del suelo por unidad de superficie al total de emisiones monoterpenos de origen biogénico a la atmósfera, es relativamente baja. Las tasas absorción de COVs y monoterpenos del suelo son también bajas, sin embargo, son comparables con algunas tasas de absorción foliar de monoterpenos. Se requieren más estudios para corroborar estos resultados y la posible importancia del suelo como un sumidero de COVs en el los modelos químico-climáticos. Los resultados sugieren que la reducción en la disponibilidad de agua y el incremento de las temperaturas previstos para las próximas décadas podría afectar de manera importante las tasas de intercambio de COVs del suelo con la atmósfera, sin embargo se necesitan estudios a largo término para determinar con exactitud esta respuesta frente al cambio climático.En este trabajo hemos encontrado que la sequía y las altas temperaturas tienden a incrementar las tasas de emisión de COVs del suelo. Los resultados sugieren que las causas podrían ser más bien debidas al efecto físico de la sequía y las altas temperaturas en las características del suelo y la volatilidad de los COVs, más que un efecto en las actividad de las raíces y los microorganismos del suelo. Sin embargo, los resultados también muestran que la sequía reduce el flujo de CO2 del suelo, mientras que las altas temperaturas los aumentan. Así pues, la sequía y el calentamiento están afectando diversos procesos biológicos que se desarrollan en las partes aéreas y subterráneas del ecosistema, los cuales podrían afectar el intercambio de COVs del suelo. El efecto final del cambio climático no es, por tanto, claro, ya que es probable que las factores que afectan el intercambio de COVs del suelo estén produciendo diferentes efectos de manera desacoplada. / Living organisms exchange trace gases with the atmosphere. These gases named biogenic volatile organic compounds (BVOCs) are very important for the global tropospheric chemistry and the global carbon cycle (Fehsenfeld et al, 1992; Singh and Zimmerman, 1992). Plants produce a variety of hydrocarbons of which the most representative and abundant group is isoprenoids. Isoprene, monoterpenes and sesquiterpenes represent a small proportion of the diverse group of isoprenoid plant products. In addition to isoprenoids, several other volatile organic compounds are emitted by plants, for example methanol, methyl jasmonate, ethylene and many organic oxygenated carbon compounds. Biosphere and atmosphere show multiple regulation feedbacks in their processes. On one hand plants play an important role in the low atmosphere chemistry. The atmospheric photo-oxidation of the emitted VOCs leads to two important products in the lower atmosphere, ozone and organic aerosol, which have important consequences for air quality and climate. On the other hand, the earth's global climate, i. e. the changes in the variability or average state of the atmosphere over time, is affecting biosphere activities in turn. Hence, it is important to estimate biogenic VOC fluxes to the atmosphere and their variations under the climate warming and the increased drought projected for the next decades by climatic and ecophysiological models. Most of the research about non methane VOC fluxes has focused on fluxes from the above-ground part of the plants at different levels, from canopy to foliar/flower/stem level. However, until the last years, information about VOC fluxes from the below-ground parts of the plants was very scarce.We were interested in the soil atmosphere trace gas exchange of CO2 and non methane biogenic VOCs. The principal method used to measure soil fluxes in this work is a variant of the enclosure method. The mode of operation was dynamic. A steady stream of air is pumped though the chamber, and the gas emitted from the soil is measured directly in the air stream or adsorbed in a suitable trapping material for subsequent release and analysis.The general objectives of this PhD thesis were 1) to characterize Mediterranean soil VOC contents and exchange, particularly monoterpenes because of their important role on ecology, plant physiology and atmospheric chemistry, but also other VOCs, and 2) to assess the possible changes in soil VOC and CO2 exchange rates under the global environmental change towards more arid and warm conditions in the Mediterranean region.The major conclusions are the following ones: Total VOC and monoterpene exchange rates from soil surfaces are low. There is relatively low soil emissions contribution to total biogenic monoterpene emissions to the atmosphere on a land area basis. Soil VOC and monoterpene uptake rates were also low, though comparable with some foliar uptake rates. Further studies are needed to corroborate these results and the possible importance of the soil VOCs sink in chemistry-climate models.Results suggest that the water availability reduction and the increase of temperature expected in the next decades might greatly affect soil VOC exchange rates to the atmosphere, but longer-term studies are needed to discern the response of soil VOC exchange rates to climate change. We found that drought and high temperatures tended to increase soil VOC emission rates. Results suggest the causes may be more the physical effects on soil features and VOCs volatility than the effects on soil roots and microorganisms activities. However, results also showed that drought reduced soil CO2 fluxes, while high temperature increased them. Thus, drought and warming are affecting several biological below-ground and above-ground processes which could affect soil VOCs exchange. The final effect of climate change is not clear but uncoupling effects to different processes are thus likely to occur.

Measurements of ambient volatile organic compounds (VOCs) by proton transfer reaction mass spectrometry (PTR-MS) are reported from recent airborne and surface based field campaigns. The Southeast Texas Tetroon Study (SETTS) was a project within the TEXAQS 2005 field campaign, conducting airborne measurements that investigated the nocturnal Lagrangian transport of industrial plumes downwind of the Houston, Texas metropolitan area. On the evening of July 26-27, a polluted air mass with elevated mass 43, mass 45 and mass 57 VOCs along with elevated O3, CO, and NOx was tracked from the Houston metropolitan area to an area northwest of Shreveport, LA, a distance of over 200 miles. This campaign demonstrated that the PTRMS is capable of tracking a VOC plume over large distances and these measurements indicate that transport of VOCs, particularly light alkenes and their oxidation products, out of the Houston metropolitan area may need to be considered by areas downwind of the Houston area when they are determining how to attain their air quality goals. During the MILAGRO field campaign in March 2006 VOCs were measured by PTR-MS instrumentation on a rooftop in the urban mixed residential and industrial area north northeast of downtown Mexico City. Diurnal profiles of weekday and weekend/holiday aromatic VOC concentrations clearly show the influence of vehicular traffic during the morning rush hour time period and during the afternoon hours although a separate late afternoon peak is not seen. Plumes of toluene elevated as much as 216 parts per billion by volume (ppbv) and ethyl acetate elevated as much as 183 ppbv above background levels were observed during the late night and early morning hours. These plumes indicate the probability of significant industrial sources of these two compounds in the region. The high levels of toluene measured by our PTR-MS exceed levels that would be predicted by examination of the Mexico City Metropolitan Area (MCMA) emission inventory and when these VOC measurements are integrated with measurements conducted throughout the MCMA a better understanding of both the overall spatial pattern of VOCs in the MCMA as well as its variability will be attained.

Houston-Galveston-Brazoria area is in severe non-attainment status for ozone compliance. Source-oriented mechanistic modeling was used to determine the major sources of VOCs that contributes to ozone formation during the Texas Air Quality Study (TexAQS) from August 16, 2000 to September 7, 2000. Environmental Protection Agency (EPA)?s Community Scale Air Quality Model (CMAQ) version 4.6 was used as a host model to include a revised Statewide Air Pollution Research Center (SAPRC99) photochemical mechanism with source-oriented extensions to track the contributions of Volatile Organic Compounds (VOCs) emissions from diesel engines, biogenic sources, highway gasoline vehicles, fuel combustion, off-highway gasoline engines, solvent utilization and petrochemical industries to ozone formation in the atmosphere. Source-oriented emissions needed to drive the model were generated using a revised Sparse Matrix Operator Kernel Emissions (SMOKE) model version 2.4. VOC/NOx ratios are found to be a critical factor in the formation of ozone. Highest ozone formation rates were observed for ratios from 5-15. The contributions of VOC to ozone formation were estimated based on the linear relationship between the rate of NO to NO2 conversion due to radicals generated from VOC oxidation and the rate of net ozone formation. Petroleum and other industrial sources are the largest anthropogenic sources in the urban Houston region and contribute to 45% of the ozone formation in the HGB area. Highway gasoline vehicles make contributions of approximately 28% to ozone formation. Wildfires contribute to as much 11% of ozone formation on days of high wildfire activity. The model results show that biogenic emissions account for a significant amount of ozone formation in the rural areas. Both highway and off-highway vehicles contribute significantly to ozone formation especially in the downwind region. Diesel vehicles do not contribute significantly to ozone formation due to their low VOC emissions.

The subject of this thesis is divided into two parts: (1) Treatment of 2-ethyl hexanol (2-EH) in an air stream by a pilot-scale biotrickling filter, and (2) Treatment of gaseous VOC emissions from a resin manufacturing plant by a full-scale biotrickling filter. Treatment of 2-Ethyl Hexanol in An Air Stream by A Pilot-Scale Biotrickling Filter 2-Ethyl Hexanol (2-EH) may release from the thermal breakdown of di-isooctyl phthalate (DOP), a commonly-used plasticizer, in the curing stage when manufacturing PVC synthetic leather and gloves. This paper reports the results of studies using a biotrickling filter (BTF) with blast-furnace slag packings (sizes = 2-4 cm and specific surface area = 120 m2/m3) for treatment of 2-EH in an air stream. The experimental setup consisted of a set of two-stage-in-series biotrickling filters. Each stage of the biotrickling filter was constructed from a 19.5-cm x 200-cm (ID x H) acrylic column packed with slags of 125 cm in height. The operation started with the conditions of recirculation liquid pH = 8.0 and rate (VL) = 8.83 m3/m2.h, a steady nutrient (ammonia nitrogen and phosphate phosphorus) addition, and without a special microbial seeding. Results indicate that, yellowish-brown biofilms on the surface of packing slags could be observed in one week and well developed in two weeks after the start-up operation. The effects of volumetric 2-EH loading (L) and superficial gas velocity (U0) on the 2-EH elimination capacity (K) and the removal efficiency (K/L) were tested. Long-term experimental results show that, in the conditions of influent 2-EH concentration C0 = 250 mg/m3, U0 = 162 m3/m2.h, and gas empty-bed-retention time EBRT = 55 s, K/L could be correlated by the equation K/L = 71.9/(72.4+L) with a correlation coefficient (R) of 0.9988. The 2-EH elimination rate was mass-transfer controlled when L<16 g/m3.h and reaction-controlled when L>16 g/m3.h. Results also indicate that nutrient addition and liquid recirculation were important for the normal operation of the BTF in eliminating the influent 2-EH. Treatment of Gaseous VOC Emissions from A Resin-Manufacturing Plant by A Full-Scale Biotrickling Filter A resin and chemical company located in Tainan County, Taiwan engages in the manufacture of PU (poly urethane), PVAC (poly vinyl acetate), PS (poly styrene), and PMMA (poly methyl methacrylate) resins from various chemical stocks. Gaseous volatile organic compounds (VOCs) emitted from the reactors include toluene, methyl ethyl ketone (MEK), acetone, vinyl chloride, styrene, butyl acetate, 2-ethyl hydroxyl acetate, and methyl methacrylate. These VOCs should be properly eliminated before discharging the reactor vents to the atmosphere. This paper reports the performance results of using a biotrickling filter (BTF) with wood packings (sizes = 2-12 cm and specific surface area = 97 m2/m3) for treating the reactor vents with a total flowrate of 80 m3/min at 20-30¢J. The BTF was constructed from a 7.0 m x 6.0 m (ID x H) SUS 304 column with wood packings of 4.0 m in height. The operation started with the conditions of recirculation liquid pH = 7.0-8.0 and rate (VL) = 1.56 m3/m2.h, a steady nutrient (urea and phosphate phosphorus) addition, and without a special microbial seeding. Results indicate that, yellowish-brown biofilms on the surface of packings could be observed in one week and well developed in two weeks after the start-up operation. Long-term operation results show that, in the conditions of influent VOC concentration C0 = 200-10000 ppm (expressed in terms of methane), U0 = 125 m3/m2.h, and gas empty-bed-retention time EBRT = 115 s, K/L could be correlated by the equation K/L = 345/(467+L) with a correlation coefficient (R) of 0.9913. The VOC elimination rate was mass-transfer limited when L<45 g/m3.h, with the mass of VOCs expressed as that of methane. Results also indicate that the liquid recirculation might be interrupted for a hour without influencing the performance. Toluene was the most difficult one to eliminate among the VOCs in the gas stream.