The biological degradation of volatile halogenated hydrocarbons (chlorocarbons (VCCs) and chlorofluorocarbons (CFCs)) was investigated under simulated conditions of landfills in laboratory test digesters. Fully halogenated VCCs (tetrachloroethylene, 1,1,1-trichloroethane, tetrachloromethane and dichloromethane) and CFCs (trichlorofluoromethane (R11), dichlorodifluoromethane (R12) and 1,1,2-trichlorotrifluoroethane (R113)) were degraded under anaerobic conditions in addition to the methanogenic bacteria in municipal solid waste (MSW) and organic wastes. These substances showed different degradation reactions in the simulated acid and methanephases of MSW landfills. It is assumed that R11 and R113 could be decomposed completely under methanogenic conditions. Dichlorofluoromethane (R21) was oberved as the reductive degradation product of R11 and was further degraded during the methanephase, but hardly at all under acid conditions. Chlorodifluoromerhane (R22) as a degradation product of R12 was not degraded, even not in the methanephase. In the acidphase, R11 was the only CFC to be dechlorinated, although only in small quantities. The degradation products of tetrachloroethylene differed under the various environmental conditions. In the acidphase, 1,1-dichloroethylene was detected as the only dichloroethylene, whereas in particular cis-1,2-dichloroethylene but also trans-1,2-dichloroethylene, 1,1-dichloroethylene and vinyl chloride could be detected as metabolites in the methanephase. Dichloromethane and chloroethane, as metabolites of 1,1,1-trichloroethane, could hardly be degraded at all in the acidphase. The degradation of VCCs and CFCs is largely independent of the substrate used. The investigations have demonstrated that the measured biodegradation rates (0.3–15 mg/m³ ₘₐₜₑᵣᵢₐₗ ᵥₒₗ./h) cannot be improved considerably since they are limited by the inhibiting effect of the substances and their degradation products.

The supercritical fluid extraction liquid phase oxidation (SELPhOx) process is being developed as a highly flexible means of remediating and destroying both high and low concentrations of light aliphatic to heavy aromatic contaminants from solid matrices. The process employs two distinct technologies: extraction of organic contaminants with supercritical carbon dioxide and wet air oxidation (WAO) destruction of the extracted contaminants. A separation step links the two process stages. Supercritical fluid extraction tests are conducted over wide ranges of temperature, pressure, and CO2/contaminant ratios with soils from a wood treatment plant and two manufacturing gas plant sites. Extraction of polynuclear aromatic hydrocarbons (PAHs) from these soil samples are studied experimentally. The addition of methanol as an extraction modifier was also explored. At comparable CO2-to-contaminant ratios and extraction conditions of 48 degrees C and 137 atm, the total PAHs removed from the three soils ranged from 76.9 to 97.9 percent with CO2 alone and from 88.4 to 98.6 percent with methanol added. Results of these tests are presented and analysed. A skid-mounted Field Test Unit (FTU) based on the laboratory bench-scale test results is being constructed which allows on-site testing of the integrated SELPhOx process with contaminated soils.

Terpenes in citrus oil must be removed to stabilize the products and to dissolve it in aqueous solution. Supercritical fluid extraction has been investigated for the terpeneless citrus oil processing as a lower temperature process. In order to achieve higher yield and higher separation selectivity, a continuous countercurrent extraction with reflux was studied at a temperature of 333 K and a pressure of 8.8 MPa. Cold-pressed orange oil from Brazil and a model mixture of 80% limonene and 20% linalool, where limonene and linalool are principal constituent of terpenes and oxygenated compounds in orange oil, were used as feed and carbon dioxide was used as solvent. Operation at total reflux was carried out to calculate the minimum number of plates required to achieve a separation between limonene and linalool. Effects of the solvent-to-feed ratio, reflux ratio, and feed inlet position on the yield and selectivity were investigated for continuous operation. The selectivity increased with the increase in the solvent-to-feed ratio. Terpeneless citrus oil was obtained on the operation at the higher solvent-to-feed ratio and longer stripping section.

Supercritical carbon dioxide and supercritical propane were found to be effective solvents in extracting stickies and trace chlorinated organics, including dioxins, from recycled fibers. These undesirable components are not effectively removed with current recycled fiber processing techniques. It was also found that endogenous yeast and mold spores on the fibers were inactivated with supercritical carbon dioxide. An economic analysis was performed for a recycled paper pretreatment process which utilizes semi-batch supercritical fluid extraction. Matrix effects were ignored owing to lack of data. Results are encouraging, estimating cost ranges of 7-17 cents per pound of fibers treated -- costs well within reasonable price targets to pretreat premium paper and tissue products.

The internal barrier of rotation (Erot) was calculated for all 209 polychlorinated biphenyls (PCBs) by using a semi-empirical method, viz. the Austin Model 1 (AMI) Hamiltonian. The difference in total energy between a forced planar state and an optimised twisted structure was defined as Erot. The Erot values were in the range of 8.33 to 483 kj/mol, and were significantly influenced by the number of chlorine atoms inortho position. An additional structural characteristic of the PCBs influencing Erot ofortho substituted congeners was substitution by chlorine atoms in vicinalmeta positions, which is assumed to prevent outward bending ofortho substituents. This so-called buttressing effect contributed with 4 to 31 kj/mol per added chlorine atom. In conclusion, the internal barrier of rotation, calculated for all 209 PCBs, provides an important structure dependent physico-chemical parameter for multivariate modelling of future quantitative structure-activity and structure-property relationships (QSARs/QSPRs).

In the tradition of the study of materials flows through society, the Substance Flow Analysis (SFA) method is presented. SFA aims at providing the relevant information for a country’s overall management strategy regarding single substances or coherent groups of substances. This article is dedicated to the presentation of a threestep general framework for SFA-type studies, and elaborates on its first step the systems definition. Attention is given to the definition of the external and internal system boundaries, the categorization of the system’s elements, aspects of materials choice, time, and space, and how these depend on the aim of the conducted study. Moreover, a broader discussion is started on the need for standardization of materials flow studies in general.In the tradition of the study of materials flows through society, the Substance Flow Analysis (SFA) method and its software tool SFINX are presented. SFA aims at providing the relevant information for a country’s overall management strategy regarding single substances or coherent groups of substances. Three modelling techniques and their possibilities and limitations are discussed: Bookkeeping, static modelling, and dynamic modelling. The computer program SFINX can be used for varoius purposes: (1) to obtain an overview of stocks and flows of a substance in, out and through a nation’s economy and environment for a specific year, (2) to trace the origins of specific pollution problems, and (3) to estimate the effectiveness of certain abatement measures. Each application has its own requirements with regard to data and modelling.

A two-step analytical method is developed for the isolation and characterization of polycyclic aromatic hydrocarbons (PAHs) in crude oil contaminated soil. In the first step, those crude oil components were isolated which are easily mobilized with water from the contaminated soil (determination of groundwater pollution potential). In the second step, the fraction containing the remaining crude oil compounds was extracted using toluene. After the cleanup of the fractions, both fractions were analyzed using high-performance liquid chromatography (HPLC).The HPLC of the toluene extracted fraction shows that along with the sixteen priority pollutants from the US-EPA list, many other polycyclic aromatic hydrocarbons (PAHs) are present as well. It is evident from the chromatograms that a significant amount of PAHs are present as is also the case in the fractions eluted by water.The described method allows the determination of total organic pollutants from crude oil, some of them being potential groundwater contaminants. The major part of the total pollutants could not be mobilized by water and therefore remains in the soil, which was extracted in the second step.

Daily total ozone observations made during 1985–1993 by both the Total Ozone Mapping Spectrometer (TOMS) flown on the Satellite Nimbus-7 and the Dobson Spectrophotometer have been used in order to investigate the fluctuations of the daily broad-band and spectral solar ultraviolet radiation reaching the ground. This investigation has been performed by employing a recently developed parametric algorithm for the estimation of the spectral and broad-band solar ultraviolet radiation which takes the total ozone variations into consideration. Total ozone reductions during the summertime from 1985 to 1993 over Athens, Greece (37.6° N, 23.4° E), cause an increase in the ultraviolet irradiance which reaches the ground of 0.54 %, 0.98 %, 2.60 % and 0.79 % per decade for the months of July at 300 nm, 312 nm, 320 nm and UVB (280-320 nm), respectively.