Studies on oxidation of benzo [a] pyrene by sunlight and ozone

The destruction of the carcinogen benzo[a]pyrene (BaP) by light is well known; laboratory workers are routinely advised to cover fluorescent lamps with yellow filters while treating samples containing BaP. However until recently the mechanism of oxidation by sunlight and ozone had not been studied in detail. Concentrations of benzo[a]pyrene in urban air are in the range of 5–10 μg/1000 m³. Oxidant concentrations (predominantly in the form of ozone) are reported to be in the range of 0.01 ppm (22 μg per m³). Thus a sampling system with a filter paper would filter about 22,000 μg of ozone passing through and collect about 5 μg of BaP for analysis. The effect of interactions of such large ozone concentrations with BaP deposited on the filter paper is reported; data for the oxidation rates for benzo[a]pyrene coated on quartz surface and exposed to ozone or sunlight are presented. The oxidation products were analysed by thin-layer chromatography and highpressure liquid chromatography. From about eight products detected in these experiments, three have been identified as quinones based on UV-absorption spectrometry and mass spectrometry. Oxidation rates as high as 100% per hour of exposure are observed when less than 0.1 μg of BaP is coated inside the quartz tubes and exposed to ozone or sunlight. Oxidation rates for benzo[a]pyrene (using tritiated BaP) were determined for two types of experimental conditions. In the first set, tritiated BaP was spotted onto a glass fibre paper and sampling continued for 24 h; the loss of BaP was found to be 88%. In the second set tritiated BaP was spotted at intervals of one hour, for eight hours, while sampling is being carried out and the loss of BaP during the period was estimated to be 50%.     

The spread of fire in corridors

Full- and quarter-scale experimental fires in corridor-room assemblies, using various combinations of floor, wall, and ceiling lining materials, yielded some interesting results. Between the small-and large-scale tests, there were marked differences in the relative effects of floor coverings and ceiling linings. Note: This paper is a contribution from the Division of Building Research, National Research Council of Canada and is published with the approval of the Director of the Division.     

A digital wind gust recorder

The instrument was a byproduct of an undergraduate final year project on wind power which was carried out by the Department of Mechanical Engineering of the University of Liverpool.The windmill test site was on an exposed, rocky island where there was no history of weather recording but a long tradition of violent winds.Field experience during the winter months suggested that corrosion fatigue arising from wind buffeting and salt spray would rank equally with maximum wind pressure as criteria of failure and if modern materials, so convenient for forming aerodynamic surfaces, were to be used then limited life concepts would need to be considered. This called for more knowledge of wind variations at the test site. A complete wind spectrum taken on chart recording instruments would have been ideal but since such such refined devices were not available the instrument to be described was designed.The only wind measuring instrument which was available was a rotating cup anemometer. This supplied an alternating voltage proportional to its rotational speed. It also operated a gear driven microswitch which could give an integrated “miles of wind” reading on an electromagnetic counter.Briefly the e.m.f. generated by the anemometer (Fig. 1) was matched against a pre-set voltage corresponding to the required gust velocity. When this was exceeded an appropriate counter was operated. Only the rising e.m.f. was significant. The subsequent fall was ignored. Initially three stages were incorporated which reported the gusts rising through forty, fifty and sixty knots, respectively. These recorded on separate counters. All basic settings were based on pitot-static speed determinations in a wind tunnel.     

Organochlorines in egg samples from Norwegian birds of prey: congener-, isomer- and enantiomer specific considerations

The content of chlorinated persistent organic pollutants was determined in a total of 44 egg samples from 8 different raptor species collected throughout Norway in the period 1991-1997. The content of 8 chlorinated bornanes, 9 chlorinated pesticides, and 15 polychlorinated biphenyl congeners (PCB) were determined. The highest average concentrations for PCB were found for eggs from White-tailed Sea Eagle and Peregrine Falcon (average sum PCB concentration: 8.9 and 9.1 microg/g wet weight (w.w.), respectively). Merlin and Sparrowhawk eggs were the highest contaminated with chlorinated pesticides (average sum pesticide concentration: 3.0 and 4.3 microg/g w.w.). For the first time, the content of chlorobornanes was determined in Norwegian birds of prey eggs. However, only minor contamination compared to PCBs and conventional chlorinated pesticides was found. The highest sum concentration was determined for White-tailed Sea Eagle eggs (0.09 microg/g w.w.). No chlorobornane contamination was found in Osprey and Merlin eggs. No spatial and regional specific trends or pattern distribution were found for organochlorine contamination in the egg samples analysed. In order to gain information about enantiomer specific bioaccumulation and biotransformation capacity of the organism, enantioselective analyses was performed for the chiral contaminants trans-chlordane, oxy-chlordane and the chlorobornane B9-1679 (Parlar #50). Indications for species-dependent deviation from the racemic distribution (enantiomeric ratio = 1) were found. Peregrine Falcon and Merlin eggs were characterised with an extremely high enantiomeric excess of the (-)-trans-chlordane (enantiomeric ratio (ER) <0.01). For Golden Eagle, Goshawk and Sparrowhawk eggs, the ERs were between 0.1 and 0.22 demonstrating also here that the (-)-trans-chlordane was the most abundant enantiomer. For the distribution of oxy-chlordane and B9-1679 enantiomers no species-dependent differences were found. For all species the ER values between 0.3 and 0.8 were determined. Thus, also for oxy-chlordane and B9-1679, the (-)-enantiomers are the most dominating stereoisomers in the birds of prey eggs analysed.     

Application of GaN-based ultraviolet-C light emitting diodes--UV LEDs--for water disinfection

GaN-based ultraviolet-C (UV-C) light emitting diodes (LEDs) are of great interest for water disinfection. They offer significant advantages compared to conventional mercury lamps due to their compact form factor, low power requirements, high efficiency, non-toxicity, and overall robustness. However, despite the significant progress in the performance of semiconductor based UV LEDs that has been achieved in recent years, these devices still suffer from low emission power and relatively short lifetimes. Even the best UV LEDs exhibit external quantum efficiencies of only 1-2%.The objective of this study was to investigate the suitability of GaN-based UV LEDs for water disinfection. The investigation included the evaluation of the performance characteristics of UV LEDs at different operating conditions as well as the design of a UV LED module in view of the requirements for water treatment applications. Bioanalytical testing was conducted using Bacillus subtilis spores as test organism and UV LED modules with emission wavelengths of 269 nm and 282 nm.The results demonstrate the functionality of the developed UV LED disinfection modules. GaN-based UV LEDs effectively inactivated B. subtilis spores during static and flow-through tests applying varying water qualities. The 269 nm LEDs reached a higher level of inactivation than the 282 nm LEDs for the same applied fluence. The lower inactivation achieved by the 282 nm LEDs was compensated by their higher photon flux. First flow-through tests indicate a linear correlation between inactivation and fluence, demonstrating a well designed flow-through reactor. With improved light output and reduced costs, GaN-based UV LEDs can provide a promising alternative for decentralised and mobile water disinfection systems.     

Measurement of the intrinsic process zone in rock using acoustic emission

Laboratory specimens with a smooth boundary (no notch) were fabricated from four different rock types (grain sizes from 0.1–10 mm) and were tested in three-point bending. The locations of acoustic emission that occurred around peak load were used to characterize the dimensions of the region of localized microcracking, the so-called intrinsic process zone. The size of this zone was found to vary significantly between the rock types, but was not found to vary significantly for different size beams of the same material. An approximately linear relation was found between the width of the intrinsic process zone and the logarithm of the grain size. An explanation of size effect evolves naturally by considering the intrinsic process zone as a material characteristic. Two different models were used to analyze stress at failure. The first treated the intrinsic process zone as a mathematical crack, an infinite stress raiser, from which a K_IC value was calculated. The second model assumed the intrinsic process zone was a cohesive notch, a finite stress raiser, from which the theoretical tensile strength was defined. The second method seemed somewhat better at predicting size effect on nominal peak stress.     

Trace-metal concentrations in normal human liver: methods to cope with marked variability

Concentrations of trace elements in human tissues characteristically vary widely, and the distributions of most concentrations are skewed to the right. Examination of some of the factors which contribute to the marked variability and skewness of the concentrations revealed that: (1) distributions of concentrations are satisfactorily normal (Gaussian) after logarithmic transformation, (2) ash weight is the best frame of reference in which to report results, (3) the distributions of metal concentrations are not further normalized by adjustments which assume that tissue lipid or collagen contains a fixed fraction of the metal found in the parenchyma, and (4) the choice of sample site within the liver is of minimal significance.     

Job accessibility impacts of intensive and multiple land-use scenarios for the Netherlands’ Randstad Area

This paper examines job accessibility impacts of intensive and multiple land-use scenarios in the Netherlands’ Randstad Area for the period 1996–2030. The scenarios involve a heavy increase in the density and diversity of activities around railway stations. Accessibility impacts are examined using location-based accessibility measures and utility-based accessibility benefit measures within a high-resolution land-use/transport interaction modelling framework, taking into account the regional demand for economic activities and possible market responses. It is concluded that extreme concentrations of economic activities at central urban locations well served by public transport are not to be preferred over less heavy concentrations of economic activities at more locations. Heavy concentrations of new firms may firstly repel existing firms in the neighbourhood and secondly result in decreasing marginal returns of accessibility benefits for public transport users.     

Microanalysis of anionic surfactants in waste water by infrared spectroscopy

Infrared spectroscopy was applied to identify and determine microamounts of anionic surfactants contained in sewage or river waters. The surfactants tested were linear alkylbenzene sulfonate (LAS), branched alkylbenzene sulfonate (ABS), alpha olefine sulfonate (AOS), fatty alcohol sulfate (AS) and fatty alcohol ethoxy sulfate (AES).Anionic surfactants in waters were extracted by chloroform as methylene blue complexes and sulfate type surfactants, i.e. AS and AES were then removed by subsequent hydrolysis. Residual sulfonate type surfactants were first released from methylene blue complexes by ion exchange technique and then changed to sulfonyl chloride derivatives for infrared spectroscopy. Key bands for the identification of sulfonate type surfactants are 640, 618 and 524 cm⁻¹ for LAS, ABS and AOS, respectively. Sulfate type surfactants was calculated from the difference of methylene blue active substance contents before and after hydrolysis.     

Seismic methods for study of soil building properties

Bulletin of Engineering Geology and the Environment - Information about distribution of elastic wave propagation velocities Vp, Vs in the subsurface zone of a soil mass can be obtained rapidly and...