A technique for estimating one-dimensional diffusion coefficients in low-permeability sedimentary rock using X-ray radiography: comparison with through-diffusion measurements

The measurement of diffusive properties of low-permeability rocks is of interest to the nuclear power industry, which is considering the option of deep geologic repositories for management of radioactive waste. We present a simple, non-destructive, constant source in-diffusion method for estimating one-dimensional pore diffusion coefficients (D(p)) in geologic materials based on X-ray radiography. Changes in X-ray absorption coefficient (Deltamicro) are used to quantify changes in relative concentration (C/C(0)) of an X-ray attenuating iodide tracer as the tracer solution diffuses through the rock pores. Estimated values of D(p) are then obtained by fitting an analytical solution to the measured concentration profiles over time. Measurements on samples before and after saturation with iodide can also be used to determine iodide-accessible porosity (phi(I)). To evaluate the radiography method, results were compared with traditional steady-state through-diffusion measurements on two rock types: shale and limestone. Values of D(p) of (4.8+/-2.5)x10(-11) m(2).s(-1) (mean+/-standard deviation) were measured for samples of Queenston Formation shale and (2.6+/-1.0)x10(-11) m(2).s(-1) for samples of Cobourg Formation limestone using the radiography method. The range of results for each rock type agree well with D(p) values of (4.6+/-2.0)x10(-11) m(2).s(-1) for shale and (3.5+/-1.8)x10(-11) m(2).s(-1) for limestone, calculated from through-diffusion experiments on adjacent rock samples. Low porosity (0.01 to 0.03) and heterogeneous distribution of porosity in the Cobourg Formation may be responsible for the slightly poorer agreement between radiography and through-diffusion results for limestones. Mean values of phi(I) for shales (0.060) and limestones (0.028) were close to mean porosity measurements made on bulk samples by the independent water loss technique (0.062 and 0.020 for shales and limestones, respectively). Radiography measurements offer the advantage of time-saving for diffusion experiments because the experiment does not require steady-state conditions and also allows for visualization of the small-scale heterogeneities in diffusive properties within rocks at the mm to cm scale.     

Crusting of stored dairy slurry to abate ammonia emissions: pilot-scale studies

Storage of cattle slurry is a significant source of ammonia (NH3) emissions. Emissions can be reduced by covering slurry stores, but this can incur significant costs, as well as practical and technical difficulties. In this pilot-scale study, slurry was stored in small tanks (500 L) and the effectiveness of natural crust development for reducing NH3 emissions was assessed in a series of experiments. Also, factors important in crust development were investigated. Measurements were made of crust thickness and specially adapted tank lids were used to measure NH3 emissions. Slurry dry matter (DM) content was the most important factor influencing crust formation, with no crust formation on slurries with a DM content of <1%. Generally, crusts began to form within the first 10 to 20 d of storage, at which time NH3 emission rates would decrease. The formation of a natural crust reduced NH3 emissions by approximately 50%. The type of bedding used in the free stall barn did not influence crust formation, nor did ambient temperature or air-flow rate across the slurry surface. There was a large difference in crust formation between slurries from cattle fed a corn (Zea mays L.) silage-based diet and those fed a grass silage-based diet, although dietary differences were confounded with bedding differences. The inclusion of a corn starch and glucose additive promoted crust formation and reduced NH3 emission. The maintenance of a manageable crust on cattle slurry stores is recommended as a cost-effective means of abating NH3 emissions from this phase of slurry management.     

Official reporting and newspaper coverage of road crashes: A case study

This paper describes a case study in Flanders–Belgium on the reporting rate of road crashes. Crash data from three sources were compared: official crash data, data retrieved from an insurance company and newspaper articles. A sample of 140 injury crashes with motorcyclists from an insurance company was used as the reference category. The purpose was to explore factors that contribute to the likelihood of crashes (not) to be reported in official statistics and newspapers. Logistic regression analyses and chi-square tests were used to reveal differences in reporting rate according to some variables. About 80% of the crashes with severe injuries were reported in the official statistics whereas the reporting rate for crashes with slightly injured was about 55%. Newspapers covered about 50% of crashes with severe injuries. The reporting rate in both official statistics and newspapers increased with the severity of the crash.     

Characteristics of natural salt licks located in the Colombian Amazon foothills

Salt licks are key places for the ecological dynamics of wildlife communities around the world and are locations where animals develop geophagical behaviours. Geophagy is a method for animals to supplement their diets or facilitate their digestive processes and is related to the health of individuals and populations. This study characterises a series of salt licks located in the Colombian Amazon foothills and describes their structural, mineralogical and physicochemical properties, as well as the fauna that visit these locations. The results are analysed in reference to the geological characteristics of the study area and in relation to the role of the salt lick in the nutritional ecology of the Amazonian fauna. Located in the study area are two types of salt licks that are significantly different in composition. These salt licks are located in an area where young geological materials have been exposed. The characteristics of the salt licks supports the hypothesis that they are used to solve nutritional problems that result from herbivorous diets. The clear importance of salt licks in the ecology of several Amazonian animal species emphasises the need to prioritise conservation areas by maximising the complementarities of salt lick sites.     

Numerical Study of Physical and Biogeochemical Processes Controlling Dissolved Oxygen in an Urbanized Subtropical Estuary: Vitória Island Estuarine System,Brazil

Environmental Modeling & Assessment - Subtropical estuaries such as the Vitória Island Estuarine System (VIES), located on the central coast of Brazil, are under strong anthropic pressure....     

Outbound offending: The journey to crime and crime sprees

Studies on crime and mobility primarily focus on local crime patterns. The city has long played an important role, whether analysing the offence or the offender. This paper goes beyond city boundaries and discusses ‘outbound offenders’, whose crime trips start in a city, but end outside. It is argued that a substantial proportion of crime trips follow this pattern, indicating that areas other than cities also provide interesting opportunities for property crime. We link outbound offending to a number of features that may explain crime travelling, including the target’s features and offender/offence features. We find that outbound offending mostly occurs towards affluent target regions and near motorways, as such confirming findings from previous research. We also find crime sprees to be indicative for mobile offending. Thus, mobile property offenders tend to compensate for travelled distances, not only by targeting affluent areas and using fast transportation means, but also by committing several successive offences, hereby reducing their relative transportation cost for each offence.     

Carotenoid maintenance handicap and the physiology of carotenoid-based signalisation of health

Despite a reasonable scientific interest in sexual selection, the general principles of health signalisation via ornamental traits remain still unresolved in many aspects. This is also true for the mechanism preserving honesty of carotenoid-based signals. Although it is widely accepted that this type of ornamentation reflects an allocation trade-off between the physiological utilisation of carotenoids (mainly in antioxidative processes) and their deposition in ornaments, some recent evidence suggests more complex interactions. Here, we further develop the models currently proposed to explain the honesty of carotenoid-based signalisation of heath status by adding the handicap principle concept regulated by testosterone. We propose that under certain circumstances carotenoids may be dangerous for the organism because they easily transform into toxic cleavage products. When reserves of other protective antioxidants are insufficient, physiological trade-offs may exist between maintenance of carotenoids for ornament expression and their removal from the body. Furthermore, we suggest that testosterone which enhances ornamentation by increasing carotenoid bioavailability may also promote oxidative stress and hence lower antioxidant reserves. The presence of high levels of carotenoids required for high-quality ornament expression may therefore represent a handicap and only individuals in prime health could afford to produce elaborate colourful ornaments. Although further testing is needed, this ‘carotenoid maintenance handicap’ hypothesis may offer a new insight into the physiological aspects of the relationship between carotenoid function, immunity and ornamentation.     

Some Interpolation Estimators in Environmental Risk Assessment for Spatially Misaligned Health Data

Ecological regression studies are widely used in geographical epidemiology to assess the relationships between health hazard and putative risk factors. Very often, health data are measured at an aggregate level because of confidentiality restrictions, while putative risk factors are measured on a different grid, i.e., independent (exposure) variable and response (counts) variable are spatially misaligned. To perform a regression of risk on exposure, one needs to realign the spatial support of the variables. Bayesian hierarchical models constitute a natural approach to the problem because of their ability to model the exposure field and the relationship between exposure and relative risk at different levels of the hierarchy, taking proper account of the variability induced by the covariate estimation. In the current paper, we propose two fully Bayesian solutions to the problem. The first one is based on the kernel-smoothing technique, while the second one is built on the tessellation of the study region. We illustrate our methods by assessing the relationship between exposure to uranium in drinkable waters and cancer incidence, in South Carolina (USA).