Partitioning of polycyclic aromatic hydrocarbons between dissolved and particulate phases in natural waters

Quantities of polycyclic aromatic hydrocarbons (PAH), some of which are carcinogens, enter natural waters in effuents of coke production and other high-temperature industrial pyrolysis processes. Because of their low water solubilities. PAH compounds are generally considered to occur in particulate form in lakes and rivers. However, present studies of ¹⁴C-anthracene adsorption by autoclaved yeast cells indicated that significant fractions of both dissolved and particulate forms of PAH may exist in natural waters. Quantities of anthracene adsorbed exceeded values for PAH adsorption onto mineral surfaces by more than an order of magnitude: suspended organic material may thus be more important than mineral particles in adsorption of PAH compounds. Adsorption was highly dependent upon the yeast cell concentration, and varied widely through the range of suspended organic solids normally encountered in natural waters. The heat of adsorption (5.2 kcal/mole) was characteristic of a physical adsorptive process. Because ecological effects and pathways of dissolved and particulate PAH may differ, adsorptive partitioning may be important in determining PAH hazards to higher organisms in aquatic food chains, and ultimately to man.     

In situ dialysis for the determination of the state of trace elements in natural waters

A new method is described which enables determination of the concentration of truly dissolved forms of trace elements in natural waters without substantial influence of adsorption on the walls of apparatus and vessels. The method also simplifies further analysis of the ionic and molecular forms of trace elements. It consists in immersing a dialysis bag, filled with pure water, directly into the natural water in situ and allowing the dialysis and adsorption equilibriu to be established. Conditions for the use of this method are discussed and results of the determination of the dissolved fraction of 20 elements in river water, as compared with the results by filtration and ultrafiltration are presented. Neutron activation analysis was used for the elemental determinations.     

Thermorheological model of a frozen-soil continuum

A method of evaluating the stress-strain state of frozen soils, which takes into account the existence of elastoviscoplastic and temperature deformations over time under variable external effects, is described. Translated from Osnovaniya, Fundamenty i Mekhanika Gruntov, No. 4, pp. 10–13, July–August, 1997.     

The bacterial population of piggery-waste anaerobic digesters

A survey was made of the anaerobic and facultatively anaerobic bacteria present in piggery waste, digesting piggery waste and domestic anaerobic sludge sludge used to start a piggery waste digester. An influence of the input waste was shown in that streptococci, the predominant facultatively anaerobic bacteria in the piggery waste, were the predominant bacteria in the digesting waste, and they replaced Enterobacter, predominant in the domestic sludge, when a piggery waste digestion had been established from this latter material. Cellulolytic or methanogenic bacteria could not be detected in the piggery waste but populations of these, and other hydrolytic bacteria, became established at different times during the buildup of digestion by gradual addition of piggery waste to water. The bacteria concerned in degradation of the waste constituents were all anaerobes.Production of methane from H₂/CO₂, formate and butyrate could be detected in mixed cultures from dilutions of digester contents, but the only methanogenic bacterium that could be isolated in pure culture was Methanobacterium formicicum, which uses H₂/CO₂ or formate only.     

Large bending of pipes

The computer model developed has been used successfully for studying the large pipe-bending problem frequently encountered in offshore structural engineering. The pipe-soil interaction is modelled by using the Coulomb friction law. The modified finite element approach coupled with a modified tangent stiffness procedure is used to handle the nonlinearities (geometric and material, etc.) in the problem. The material nonlinearity has been considered both by the plastic-hinge method and by an elastic-plastic method. Before studying the practical problems, sufficient check problems were analysed and a good agreement was found between theoretically exact solutions and the results obtained from the developed computer model.     

Experimental studies on the weatherability of the capivara dam basalts,rio paranapanema,brazil

The weatherability of the basalts in the Capivara Dam site, Rio Paranapanema, São Paulo State, Brazil, has been studied by means of saturation-drying tests. A great number of samples have disaggre — gated intensively with production of fines. The behavior of these rocks is related to their petrography, especially to their content in expansive clay minerals. These studies were performed in order to obtain data for the utilization of this material as rock fill, including ripraps.     

The Italian national survey of indoor radon exposure

An investigation is being developed by the Camitato Nazionale per la Ricerca e per lo Sviluppo dell'Energia Nucleare e delle Energie Alternative, ENEA, to assess the indoor exposure of the Italian population. The programme, which started in 1982, includes regional and local surveys in all the administrative districts and intensive investigations of factors which influence indoor radon levels. The survey is organized by statistical areas of sampling to obtain representative samples of houses. The definition of the areas takes into account basic parameters e.g. geolithological environments, radon soil gas from underlying soils and rocks, specific activities of local building materials, climatic and seasonal variations, building technology, types of houses and town planning. The collected data may also be used for the compilation of radon risk maps to plan special monitoring and remedial actions if needed. Preliminary results concerning the above items are discussed.     

Smoke development at different energy flux levels in an NBS smoke density chamber

An automatically controlled high-energy flux heater has been developed and utilized in an NBS Smoke Density Chamber.     

Ultraviolet light inactivation of protozoa in drinking water: a Bayesian meta-analysis

To assess the dose of UV light needed to achieve specified levels of Giardia spp. cysts and Cryptosporidium spp. oocysts inactivation in drinking water, a Bayesian meta-analysis is used to analyze experimental data from several studies. Of the 20 studies identified by an extensive data collection effort, 14 (five reported experiments on Giardia and nine on Cryptosporidium) were selected for analysis based on a set of criteria. A substantial amount of the log inactivation data are reported as greater than a given inactivation level (i.e., censored data). The Bayesian hierarchical modeling approach used in this study not only properly addresses the common concerns in a meta-analysis but also provides a robust method for incorporating censored data. Different statistical models will result in different estimates of the UV doses needed to achieve a specific inactivation level. The Bayesian approach allows us to present the uncertainty in terms of risk, which is better suited for supporting US EPA in developing regulations.