Photodecomposition du bioxyde de chlore et des ions chlorite par irradiation u.v. en milieu aqueux-partie II. Etude cinetique

The decomposition of ClO₂ and ClO₂⁻ by u.v. radiation leads to the production of chlorate, chloride and oxygen as end-products via complex reactions which are initiated by the products generated by the primary reactions of photolysis (Buxton and Subhani, 1972a; Mialocq et al., 1973; Karpel Vel Leitner et al., 1992). As far as the rate of decomposition is concerned, Bowen and Cheung (1932) and Zika et al. (1985) have shown that the quantum yield of photodecomposition of chlorine dioxide (overall reaction) increases when the wavelength decreases [Zika et al. (1985): φ = 0.46 at 366 nm and 1.4 at 296.7 nm]. However, the values of the quantum yield of photodecomposition of ClO₂ and ClO₂⁻ at 253.7 nm as well as the quantum yields for the primary reactions of photolysis of ClO₂ and ClO₂⁻ at different wavelengths are not given in the literature.The aim of this work was to study the kinetics of photodecomposition of chlorine dioxide and of chlorite by u.v. irradiation.     

Blue mountains sewage transfer scheme: a review of tunnelling

To preserve the natural surroundings of the Blue Mountains of New South Wales while simultaneously serving the needs of the region's growing population, the Sydney Water Board has developed an improved, but complex, sewage transfer scheme for the area. This paper traces the development of the scheme, with particular attention to the geology of the area, the equipment used to construct the tunnels for the project, and elements of the directional drilling that connects the sewer areas to the tunnel.     

Radon concentration in houses over a closed Hungarian uranium mine

High radon concentration (average 410 kBq m-3) has been measured in a tunnel of a uranium mine, located 15-55 m below the village of Kovágószolos, Hungary. The mine was closed in 1997; the artificial ventilation of the tunnel was then terminated and recultivation works begun. In this paper, a study has been made as to whether the tunnel has an influence on the radon concentration of surface dwellings over the mining tunnel. At different distances from the surface projection of the mining tunnel, radon concentration, the gamma dose, radon exhalation and radon concentration of soil gas were measured. The average radon concentration in the dwellings was 483 Bq m-3. Significantly higher radon concentrations (average 667 Bq m-3) were measured in houses within +/-150 m from the surface projection of the mining tunnel +50 m, compared with the houses further than the 300-m belt (average 291 Bq m-3). The average radon concentration of the soil gas was 88.8 kBq m-3, the average radon exhalation was 71.4 Bq m-2 s-1 and higher values were measured over the passage as well. Frequent fissures crossing the passage and running up to the surface and the high radon concentration generated in the passage (average 410 kBq m-3) may influence the radon concentration of the houses over the mining tunnel.     

Influence de la taille des mottes et du mode de compactage sur la perméabilité des sols

In the domain of impervious barriers, many factors influence the permeability of compacted soil layers. These factors can lead to discrepancy between the permeability results in the laboratory andin situ. In this context, a laboratory study showed the influence of the size of clods and the method of compaction on permeability of highly plastic marl, compacted dynamically with standard Proctor energy and statically at different stresses, under the same conditions of water content and dry density. This paper also presents the results of a comparative study which has been conducted on the influence of the method of compaction on the permeability of the marl and that of a low plastic silt.     

Lead in glasgow street dirt and soul

The levels of lead in city street dirt and in soil from various locations in Glasgow were investigated during spring 1976. Lead concentrations in street dirt ranged from 150–2300 ppm, mean 960 ppm, and were significantly elevated with respect to the observed “natural” level of 78 ppm. Lead derived from anti-knock compounds in petrol and introduced to the environment via automobile exhausts was clearly implicated as the main source of lead pollution in a series of soil lead measurements at the centre and periphery of eight Glasgow parks.Various chemical leaching techniques were employed and compared. Less than 5% of street dirt and soil lead was found to be associated with the organic phase.     

Cigarette characteristics,smoker characteristics,and the relationship to cigarette fires

Data were collected from eight cities on a wide range of cigarette and smoker characteristics for a sample of smokers. Of these, 564 smokers had had fires and were identified through fire department response to those fires, while the other 1,611 smokers had not had fires and were identified through a telephone sample survey of the communities. The characteristics analyzed included those that had shown evidence of a relationship to the risk of a cigarette-initiated fire, either in laboratory studies or in previous statistical analyses of fire experience.The smoker characteristics analyzed were household income, education, age, gender, and race. The cigarette characteristics analyzed were filter, tobacco column length, filter length, circumference, density, amount of tobacco, menthol, citrate, porosity, and pack type. In addition, a variable was used to control for the smoker's city.After controlling for all smoker characteristics and city, logistic regression modeling showed four cigarette characteristics to be significant: filter, filter length, porosity, and type of pack. Filter, filter length, and porosity all affect air intake, which, therefore, appears to be an important physical element in the combustion process associated with risk. Analysis limited to filtered cigarettes only showed the same characteristics to be significant, plus tobacco column length. Extension of the analysis to two-way interaction terms did not change any of the conclusions on which cigarette characteristics are important, but it did indicate that the role of pack type was different for men and women.Sensitivity analyses, shown in the appendix, supported the main conclusions that cigarette characteristics are significant after controlling for smoker characteristics and that the four specific cigarette characteristics—filter, filter length, porosity, and pack—are the ones that are significant. These analyses checked the impact of cluster sampling, sensitivity to missing data on smoker characteristics, and sensitivity to nonfire smoker cases with responses by people other than the smokers themselves.All this means that there are already cigarettes commercially available that exhibit a reduced propensity for ignition when one controls for smoker characteristics.This report was originally written as the final report in June 1993 as part of CPSC-P-91-1147 Contract Cigarette Fire Incident Study that the National Fire Protection Association conducted for the U.S. Consumer Product Safety Commission.Harwood, formerly with the Consumer Product Safety Commission, is retired.     

Assessment of nitrification in groundwater filters for drinking water production by qPCR and activity measurement

In groundwater treatment for drinking water production, the causes of nitrification problems and the effectiveness of process optimization in rapid sand filters are often not clear. To assess both issues, the performance of a full-scale groundwater filter with nitrification problems and another filter with complete nitrification and pretreatment by subsurface aeration was monitored over nine months. Quantitative real-time polymerase chain reaction (qPCR) targeting the amoA gene of bacteria and archaea and activity measurements of ammonia oxidation were used to regularly evaluate water and filter sand samples. Results demonstrated that subsurface aeration stimulated the growth of ammonia-oxidizing prokaryotes (AOP) in the aquifer. Cell balances, using qPCR counts of AOP for each filter, showed that the inoculated AOP numbers from the aquifer were marginal compared with AOP numbers detected in the filter. Excessive washout of AOP was not observed and did not cause the nitrification problems. Ammonia-oxidizing archaea grew in both filters, but only in low numbers compared to bacteria. The cell-specific nitrification rate in the sand and backwash water samples was high for the subsurface aerated filter, but systematically much lower for the filter with nitrification problems. From this, we conclude that incomplete nitrification was caused by nutrient limitation.     

Spatial and temporal evolution of trihalomethanes in three water distribution systems

Spatial and seasonal changes in trihalomethane (THM) concentrations were investigated in three distribution systems of Quebec (Canada) which are supplied by different surface waters and which use a variety of physicochemical treatment strategies. The investigation was based on an intensive 25-week sampling programme, undertaken at a time of year when the temperature of southern Quebec surface waters exceeds 4 degrees C (April-November). THMs and other water quality and operational parameters were monitored at points along the distribution system--between the treatment plant and the system extremities--which represented variable residence times of water. Results showed that THM concentrations vary significantly (from 1.5 to 2 times, depending on the utility) between finished waters as they leave the plant and water at the system extremities. When water temperature exceeds 15 degrees C, spatial THM variations are particularly high (from 2 to 4 times, depending on the utility). The development of multivariate regression models showed that water temperature was a better predictor of THM seasonal variability than chlorine dose, surrogates of natural organic matter and pH. Also, initial THM formation (in finished waters leaving the plant) was a good predictor of THM levels at distribution system extremities.     

Toxicity, accumulation and elimination studies of α-hexachlorocyclohexane (α-HCH) with freshwater organisms of different trophic levels

A short- and long-term toxicity study with α-hexachlorocyclohexane (α-HCH) was carried out with freshwater organisms of different trophic levels (algae, crustaceae and fishes). In this study mortality, immobilization, growth, reproduction, histopathologic changes and enzyme activities were chosen as criteria.Furthermore accumulation and elimination processes were investigated in separate organisms as well as the uptake of α-HCH by one organism and through a food-chain.Finally a tentative method for deriving an “ecological limit” for χ-HCH in surface water is described.     

Lead,cadmium, and arsenic residues in animal tissues in relation to those in their surrounding habitat

The relationships of the residues of lead, cadmium, and arsenic in animal tissues to those in surrounding vegetation and soil were determined in a natural habitat representing a wide range of such residues. The samples studied were selected from 18 different locations. Analyses were performed on a total of 113 animals, 332 plant specimens (representing 33 species), and 408 soil samples (taken at different depths). For the purpose of evaluating relationships, the samples from each location were averaged and reported as parts per million on a dry weight basis. The average lead residues from different locations ranged from 1.4–9.2 ppm in the liver, 45–195 in bones, 4–283 in vegetation, and 15–1399 in soil samples. The cadmium contents ranged from 1–27 ppm in the liver, 3–77 in bones, 0.5–5 in vegetation, and 1–10 in soil. The arsenic contents in different components of the ecosystem varied with an average of 1–9 ppm in liver, 0.6–94 in vegetation, and 7–655 in soil samples. The soil residues varied considerably according to the depth of sampling. Little variation was noted in different species of vegetation or in soil and vegetation samples according to the time and year of sampling.Statistical analyses performed on the averages indicated a significant correlation between vegetation and soil residues for all three elements, and also between animal to vegetation and animal to soil cadmium residues. Multiple linear correlations for all elements in soil, vegetation, and animal tissues were determined. The results indicated a possibility of an increase in cadmium in animal tissues depending upon the increased residues of this metal in the environment.