A compressed shift schedule: Dealing with some of the problems of shift-work

This study examines some of the psychological and behavioral effects of a 12-hour compressed shift schedule on coal miners in two organizations in Western Canada. It suggests that young, married compressed shift workers are more satisfied with their family relationship. They spend less of their leisure time with spouses when working shifts, and do not spend any more time with them on their days off. They have less time available for many leisure activities on their workdays. The extra time on days off is not reallocated to the leisure activities they were unable to do on their workdays. Some extra leisure time on days off may be spent on personal hobbies. There is no suggestion that the compressed shift schedule has any negative effect on the individual's health.     

Towards mitigation of greenhouse gases by small changes in farming practices: understanding local barriers in Spain

Small changes in agricultural practices have a large potential for reducing greenhouse gas emissions. However, the implementation of such practices at the local level is often limited by a range of barriers. Understanding the barriers is essential for defining effective measures, the actual mitigation potential of the measures, and the policy needs to ensure implementation. Here we evaluate behavioural, cultural, and policy barriers for implementation of mitigation practices at the local level that imply small changes to farmers. The choice of potential mitigation practices relevant to the case study is based on a literature review of previous empirical studies. Two methods that include the stakeholders’ involvement (experts and farmers) are undertaken for the prioritization of these potential practices: (a) Multi-criteria analysis (MCA) of the choices of an expert panel and (b) Analysis of barriers to implementation based on a survey of farmers. The MCA considers two future climate scenarios – current climate and a drier and warmer climate scenario. Results suggest that all potential selected practices are suitable for mitigation considering multiple criteria in both scenarios. Nevertheless, if all the barriers for implementation had the same influence, the preferred mitigation practices in the case study would be changes in fertilization management and use of cover crops. The identification of barriers for the implementation of the practices is based on the econometric analysis of surveys given to farmers. Results show that farmers’ environmental concerns, financial incentives and access to technical advice are the main factors that define their barriers to implementation. These results may contribute to develop effective mitigation policy to be included in the 2020 review of the European Union Common Agricultural Policy.     

Predicting the economic impact of an invasive species on an ecosystem service.

Quantifying the impact of alien invasive species on ecosystem services is an essential step in developing effective practices and policy for invasive species management. Here we develop a stochastic bioeconomic model that enables the economic impact of an invasive pest to be estimated before its arrival, based on relatively poorly specified ecological and economic parameters. We developed the model by using a hypothetical invasion of the varroa bee mite (Varroa destructor) into Australia and the negative flow-on effects that it would have on pollination by reducing honey bee populations, giving rise to a loss of pollination services, reduced crop yields, and additional production costs. If the mite were to continue to be prevented from entering the country over the next 30 years, we estimate that the economic costs avoided would be U.S. $16.4-38.8 million (Aus $21.3-50.5 million) per year. We suggest that current invasion response funding arrangements in Australia, which do not acknowledge these avoided damages, require amendment.     

Accumulation and depuration of mercury in the American oyster Crassostrea virginica

To study the kinetics of mercury uptake in oysters, adult Crassostrea virginica (Gmelin) were held in seawater containing 10 g mercury/l (ppb) or 100 g mercury/l (ppb), added in the form of mercuric acetate, for 60 days. Mercury concentration in tissues was determined by analysis of individually homogenized oyster meats, using wet digestion and flameless absorption spectrophotometry. After 45 days, average mercury tissue concentration was 140,000 g mercury/kg tissue (ppb) and 28,000 g mercury/kg tissue (ppb) in the 100 ppb and 10 ppb experimental groups, respectively. After this time, concentrations dropped sharply, probably due to spawning. Clearance of mercury from tissue was studied by exposing treated adults to estuarine water (with no additions) for 30 days (100 ppb group) and 160 days (10 ppb group). Tissue concentrations in the 100 ppb mercury environment group declined from 115,000 to 65,000 ppb, and those of the 10 ppb group declined from 18,000 to 15,000 ppb, in 18 days; there-after, no further decline occurred in either group. Oysters accumulated mercury 1,400 times and 2,800 times above the environmental concentrations of 100 and 10 ppb mercury, respectively. Total self-purification was not achieved over a 6 month cleansing period.     

Accumulation,tissue distribution and elimination of 203HgCl2 and CH3 203HgCl in the tissues of the American oyster Crassostrea virginica

Oysters (Crassostrea virginica) were exposed for 3 days to mercury-203 labeled HgCl₂ or CH₃HgCl added directly to artificial seawater or added preconcentrated on the marine diatom Phaeodactylum tricornutum. The concentration of mercury in 5 tissues was measured for 45 days after mercury was removed from the ambient water. At the beginning of the depuration period, the highest concentrations of mercury in tissues were attained in: gill>digestive system>mantle>gonad>muscle in oysters exposed to water containing mercury; and in digestive system>gill>mantle> gonad>muscle in oysters fed labeled algae. This same distribution pattern is seen for both chemical forms of mercury. Although the initial pattern of accumulation was identical for both mercury compounds within each exposure group, the fate of the accumulated mercury was very different after 45-days depuration. In oysters accumulating mercury directly from seawater, inorganic mercury residues rapidly declined in gill and digestive tissue, but were slowly reduced in mantle, gonadal, and muscle tissue. This pattern was duplicated by oysters exposed to methyl mercuric chloride in seawater except that gonadal and muscle residues greatly increased during depuration. In oysters ingesting labeled P. tricornutum cells, mercuric chloride and methyl mercuric chloride residues rapidly declined in gill and digestive tissue, remained constant in the mantle, but sharply increased in gonadal and muscle tissue during depuration.     

Beryllium-7 measurements in the Houston and Phoenix urban areas: an estimation of upper atmospheric ozone contributions

Natural radionuclides have been proposed as a means of assessing the transport of ozone (O3) and aerosols in the troposphere. Beryllium-7 (7Be) is produced in the upper troposphere and lower stratosphere by the interaction of cosmogenic particles with atmospheric nitrogen and oxygen. 7Be has a 53.29-day half-life (478 keV gamma) and is known to attach to fine particles in the atmosphere once it is formed. It has been suggested that O3 from aloft can be transported into rural and urban regions during stratospheric-tropospheric folding events leading to increased background levels of O3 at the surface. 7Be can be used as a tracer of upper atmospheric air parcels and the O3 associated with them. Aerosol samples with a 2.5-microm cutoff were collected during 12-hr cycles (day/night) for a 30-day period at Deer Park, TX, near Houston, in August-September of 2000, and at Waddell, AZ, near Phoenix, in June-July of 2001. A comparison of 7Be levels with 12-hr O3 averages and maxima shows little correlation. Comparison of nighttime and daytime O3 levels indicate that during the day, when mixing is anticipated to be higher, the correlation of 7Be with O3 in Houston is approximately twice that observed at night. This is consistent with mixing and with the anticipated loss of O3 by reaction with nitric oxide (NO) and dry deposition. At best, 30% of the O3 variance can be explained by the correlation with 7Be for Houston, less than that for Phoenix where no significant correlation was seen. This result is consistent with the intercept values obtained for 7Be correlations with either O3 24-hr averages or O3 12-hr maxima and is also in the range of the low O3 levels (25 ppb) observed at Deer Park during a tropical storm event where the O3 is attributable primarily to background air masses. That is, maximum background O3 level contributions from stratospheric sources aloft are estimated to be in the range of 15-30 ppb in the Houston, TX, and Phoenix, AZ, area, and levels above these are because of local tropospheric photochemical production.     

Modelling the fate of sulphur-35 in crops. 1. Calibration data

Gas-cooled nuclear power plants in the UK release sulphur-35 during their routine operation. The gas is in the form of COS which can be readily assimilated by vegetation. It is therefore necessary to be able to model the uptake of such releases in order to quantify any potential contamination of the food chain. To develop such models experimental data are required. A series of experiments was undertaken to determine the rate of deposition, the partition and subsequent loss of sulphur-35 in crops exposed to CO(35)S. The mass normalised deposition rate was similar for the range of crops tested, while the partition of the (35)S paralleled the growth of crop components. There was no significant loss of radioactivity other than that expected from radioactive decay.     

Biofilm enhanced geologic sequestration of supercritical CO2

In order to develop subsurface CO₂ storage as a viable engineered mechanism to reduce the emission of CO₂ into the atmosphere, any potential leakage of injected supercritical CO₂ (SC-CO₂) from the deep subsurface to the atmosphere must be reduced. Here, we investigate the utility of biofilms, which are microorganism assemblages firmly attached to a surface, as a means of reducing the permeability of deep subsurface porous geological matrices under high pressure and in the presence of SC-CO₂, using a unique high pressure (8.9 MPa), moderate temperature (32 °C) flow reactor containing 40 millidarcy Berea sandstone cores. The flow reactor containing the sandstone core was inoculated with the biofilm forming organism Shewanella fridgidimarina. Electron microscopy of the rock core revealed substantial biofilm growth and accumulation under high-pressure conditions in the rock pore space which caused >95% reduction in core permeability. Permeability increased only slightly in response to SC-CO₂ challenges of up to 71 h and starvation for up to 363 h in length. Viable population assays of microorganisms in the effluent indicated survival of the cells following SC-CO₂ challenges and starvation, although S. fridgidimarina was succeeded by Bacillus mojavensis and Citrobacter sp. which were native in the core. These observations suggest that engineered biofilm barriers may be used to enhance the geologic sequestration of atmospheric CO₂.