@phdthesis{TianKunze2001, author = {Tian-Kunze, Xiangshan}, title = {Experimental and theoretical study of S(IV)/S(VI) ratio in rain and cloud events}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-000000093}, school = {BTU Cottbus - Senftenberg}, year = {2001}, abstract = {Production of atmospheric sulfate from SO2 emitted into the troposphere is the key question we have to answer for assessing main problems like acid rain, forest decline and negative climate forcing which is believed to counteract the green house effect. About one decade ago many researchers agreed that sulfate formation occurs dominantly (80-90 \%) via the aqueous phase chemical transformation, where the SO2 dissociation is the first step. However, there is still a high uncertainty on the amount of sulfite (dissolved SO2) being oxidized and on that removed by wet deposition in the reduced form S(IV) (sulfite). This important question, whose answer gives climate modellers an essential input on the percentage of emitted SO2 converted into sulfate, was the aim of this work. This work presents experimental and theoretical results from studies of the ratio sulfite/sulfate in rainwater and cloudwater to assess the contribution of S(IV) to the total sulfur amount in the aqueous phase. The wet deposition of S(IV) in rainwater was studied by collecting rainwater samples from two different levels using a 324 m high tower. The increase of S(IV) wet deposition flux from the 324 m level to the ground level via sub-cloud scavenging of SO2 is significant. 13-51 \% (36 \% in average) of sulfur in rainwater on the ground level was found to be in the form of S(IV). The result that S(IV) is an important form of sulfur in rainwater was further confirmed by our theoretical study using a one-dimensional time-dependant physical-chemical cloud model. Model calculations show that most of sub-cloud scavenged SO2 will remain as free S(IV) in rainwater. In highly polluted areas the ratio can be as high as 0.9. This ratio in cloudwater is much less than that in rainwater according to our field experiment carried out at Mt. Brocken. Neverthless, under some special conditions, this ratio can be as high as 0.2, which means that the role of S(IV) in cloudwater is not ignorable. Thus, this study has confirmed the very few S(IV) measurements found in literature, suggesting the importance of S(IV) wet deposition. Our findings suggest that considerable part of emitted SO2 will not be transformed to sulfate especially in the sub-cloud layer. Therefore, the production of climate affecting sulfate aerosol via aqueous phase transformation of dissolved SO2 is more limited than believed by climate modellers.}, subject = {Berlin-Frohnau; Regen; Sulfite; Sulfate; Brocken; Wolke; Wasser; S(IV); S(IV)/S(VI) ratio; sub-cloud scavenging; cloud chemistry; cloud modelling}, language = {en} } @phdthesis{Rusumdar2013, author = {Rusumdar, Ahahmad Jhony}, title = {Treatment of non-ideality in the multiphase model SPACCIM and investigation of its influence on tropospheric aqueous phase chemistry}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-28190}, school = {BTU Cottbus - Senftenberg}, year = {2013}, abstract = {The troposphere is a complex multiphase and multicomponent environment with simultaneously occurring gas and aqueous phase as well as heterogeneous chemical transformations, which can potentially alter the physico-chemical composition of aerosols. In this multicomponent system, phase transfer processes take place, which can influence the particle and droplet formation as well as particle growth. In the modeling of such multiphase processes it is necessary to consider non-ideal conditions in deliquescent particles. Such, highly concentrated solutions are typical when small amounts of water available in aqueous aerosol particles. The behavior of this non-ideal mixed solvent-electrolyte solutions including inorganic and organic chemistry is not yet described satisfyingly in existing multiphase models. In light of this, a modeling framework has been developed in the context of multiphase air parcel model to treat the kinetic description of phase transfer processes considering complex multiphase chemistry and an extended description of non-ideal solutions for the aqueous phase chemistry by means of activity coefficient models. Activity coefficient models, such as AIOMFAC, mod. LIFAC and Pitzer-ion interaction models were implemented in this work. The current available activity coefficient models developed for electrolyte-organic-water mixtures are evaluated in the first part of the thesis. For that, the model investigations cover a scale, ranging from very simple to complex simulations. The implemented module can use different combinations of mixing rules and activity coefficient models flexibly. In the second part of the thesis, the extended activity coefficient model was implemented in the parcel model framework SPACCIM, in order to investigate the influence of treatment of non-ideality on multiphase chemistry. The effect of considering non-ideal solutions was studied for two different aerosol types (remote, urban) regarding complex multiphase chemistry. The advanced model simulations have shown under which circumstances it is important to consider non-ideal solutions and how they will affect the simulated particle/droplet growth and chemical transformations. The modeled activity coefficients and their pattern, which decides the multiphase chemical transformations, were investigated for inorganic and organic systems. The present results have shown that, the inclusion of the treatment of non-ideality can substantially extend our ability to model complex multiphase chemistry especially in the particle phase.}, subject = {Wolke; Aerosol; Phasenumwandlung; Modellierung; Multiphasenmodellierung; Aerosol-Wolken-Wechselwirkung; Phasentransfer; Nicht-ideale L{\"o}sungen; Aktivit{\"a}tskoeffizienten; Multiphase modeling; Aerosol-cloud-interactions; Phase transfer; Non-ideal solutions; Activity coefficients}, language = {en} } @phdthesis{Mehrjouei2012, author = {Mehrjouei, Mohammad}, title = {Advanced oxidation processes for water treatment : reactor design and case studies}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-26619}, school = {BTU Cottbus - Senftenberg}, year = {2012}, abstract = {The aim of this work was to study in detail the physical-chemical aspects of water and wastewater treatment using different so-called "advanced oxidation systems". Our target was to construct an annular multiphase falling film reactor with a fixed photocatalyst (TiO2) and to compare its performance with that of a planar reactor in different chemical oxidation regimes. The annular design of the falling film reactor was prepared for heterogeneous photocatalytic oxidation systems by combining three different phases (solid fixed photocatalyst, falling liquid wastewater and an ozone/oxygen gaseous mixture). UVA light sources were employed for irradiation of the photocatalyst surface. In the first step, the design, construction and characterisation of the reactor was performed. The next step was the assessment of the performance of the falling film reactor in the decomposition of selected organic chemicals as model compounds. Six different oxidation methods were evaluated for the degradation of model compounds. Photo-oxidation (UVA/O2), photo-ozonation (UVA/O3), ozonation (O3), catalytic ozonation (TiO2/O3), photocatalytic oxidation (TiO2/UVA/O2) and photocatalytic ozonation (TiO2/UVA/O3) processes were investigated in this study. It was shown that due to the synergetic effects between ozone molecules and the irradiated surface of TiO2, photocatalytic ozonation was the most effective oxidation process for the decomposition of model compounds. Oxalic acid, dichloroacetic acid, citric acid, terephthalic acid, p-chlorobenzoic acid, methyl tert-butyl ether, ethyl tert-butyl ether, tert-amyl ethyl ether and tert-butanol were chosen as model compounds. Two different immobilisation techniques were employed and evaluated for fixing TiO2 nanoparticles onto the reactor walls. The immobilisation of photocatalysts was performed on borosilicate glass and polymethylmethacrylate. It was observed that the photoactivity of fixed TiO2 particles on borosilicate glass was higher than that on polymethylmethacrylate. The stability of immobilised photocatalysts on both substrates was good. The influences of different experimental parameters, such as the initial concentration of model compounds, ozone concentration, solution pH, temperature and solution recycling rate on the degradation rate and efficiency of the oxidation systems were studied and discussed. In terms of the characterisation of the falling film reactor, different aspects were studied. The thickness and distribution pattern of falling films, the gas washing effects of falling films, the absorption of ozone in the falling films, the adsorption of organic pollutants on the photocatalyst surface, the effect of UVA irradiation on ozone decomposition, etc. were studied in detail. The concentration of model compounds was determined by ion chromatography (IC), high performance liquid chromatography (HPLC) and headspace techniques. Chemical oxygen demand (COD) was applied to quantify the quality of wastewaters and total organic carbon (TOC) measurements were employed for the determination of model compound mineralisation. At the end of this study, treatment of real wastewater was performed by means of the falling film reactor as a case study. The real wastewater was produced in a pyrolysis process. More than 30 organic and inorganic compounds were included in the composition of this wastewater. The application of ozone-based advanced oxidation processes showed good results in terms of colour and odour removal of pyrolysis wastewater as well as in terms of decreasing its COD.}, subject = {Wasseraufbereitung; Photokatalyse; Ozonisierung; Moderne Oxidationprozesse; Fallfilmreaktor; Wasseraufbereitung; Photokatalyse; Photokatalytische Ozonisierung; Advanced oxidation processes; Falling film reactor; Water treatment; Photocatalysis; Photocatalytic ozonation}, language = {en} } @phdthesis{Sehili2005, author = {Sehili, Aissa Mounir}, title = {Coupling between complex multiphase chemistry and detailed microphysics in a size resolved cloud model}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-000000938}, school = {BTU Cottbus - Senftenberg}, year = {2005}, abstract = {The target of the present work was to develop, implement and test a coupling strategy between a complex multiphase chemistry and a size resolved microphysics in order to accurately simulate the multiphase processes taking place in a cloud. The coupling scheme provides time-interpolated meteorological variables and time-averaged mass fluxes over a defined coupling time interval for chemistry. The resulting ODEs are large, non-linear and extremely stiff. Implicit time integration schemes based on the BDF and on the second order Rosenbrock methods associated with direct sparse solvers were used to solve the resulting systems. The coupled model SPACCIM (Spectral Aerosol Cloud Chemistry Model) was evaluated for various case studies. Comparison with measured values from a field experiment showed a good agreement and proofed that the coupling strategy is robust and reliable. Moreover, the model is capable to handle different microphysical approaches and to deal with different reacting mechanisms under various types of dynamics with high flexibility.}, subject = {Atmosph{\"a}re / Chemie; Atmosph{\"a}re; Physik}, language = {en} } @phdthesis{Koch2003, author = {Koch, Bernhard}, title = {Atmospheric traces monitoring using cavity ringdown spectroscopy}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-000000363}, school = {BTU Cottbus - Senftenberg}, year = {2003}, abstract = {Cavity Ringdown laser Spectroscopy has been applied to develop a novel in-situ monitoring device for atmospheric trace gases. The study has been dedicated to the detection of NO2 and HONO compounds which play an important role in atmospheric chemistry. The system, based on a Nd-YAG pumped UV-VIS OPO laser, has performed field experiments under harsh conditions showing high reliability and a detection limit in the 500 ppt range. Longer term measurements performed from the laboratory of the institute for air chemistry (BTU Cottbus) in Berlin-Adlershof in autumn and winter 2001/2002 showed very good coincidence with the results of the Berliner Luftg{\"u}te Meßnetz (BLUME). Present limitations in the performance have been elucidated putting in to evidence the effect of the aerosol content of the atmosphere. On the other hand, the possibility of quantitative aerosol analysis could be demonstrated.}, subject = {Atmosph{\"a}re; Spurengas; Stickstoffoxide; Cavity-Ring-Down-Spektroskopie; In situ; Cavity ringdown spectroscopy; CROS; Optical parametric oscillator; OPO; Nitrogen dioxide}, language = {en} }