Nitrogen fluxes on an intensive investigation plot in the North Tyrolean limestone Alps

In the framework of this study, nitrogen fluxes on a limestone site are investigated. The major goals are the assessment of the nitrogen status, the estimation of the nitrogen budget and the evaluation of the nitrogen saturation. The investigation area, the intensive investigation plot and the research equipment are described.     

Monitoring the impact of sulphur with the Austrian Bioindicator Grid

In Austria, the impact of sulphur has been assessed since 1985 with the help of the Austrian Bioindicator Grid on 760 sample plots with Picea abies as the main tree species (90%). The annual sampling allows a precise evaluation of the temporal and regional development of the impact of sulphur on the basis of legal standards. Despite the reduction of SO2 emissions in Austria, the legal standard is still exceeded on 8% of the plots. These plots are mainly located near large Austrian emittors, but also in areas affected by transboundary sulphur emissions from neighbouring countries. The present paper describes how the Bioindicator Grid can be applied for the control of legal requirements to enact effective clean air measures in Austria and take supportive measures that reduce the impact of sulphur from emittors in neighbouring countries.     

Regeneration of a compost biofilter degrading high loads of ammonia by addition of gaseous methanol

The long-term stability of a biofilter loaded with waste gases containing NH3 concentrations larger than 100 ppmv was studied in a laboratory-scale compost reactor. At an empty bed residence time (tau) of 21 sec, elimination capacities of more than 300 g NH3/m3/day were obtained at elimination efficiencies up to 87%. Because of absorption and nitrification, almost 80% of the NH3-N eliminated from the waste gas could be recovered in the compost as NH4(+)-N or NO2-/NO3(-)-N. The high elimination capacities could be maintained as long as the NH4+/ NOX- concentration in the carrier material was less than 4 g NH4+/NOx(-)-N/kg wet compost. Above this critical value, osmotic effects inhibited the nitrifying activity, and the elimination capacity for NH3 decreased. To restore the biofilter performance, a carbon source (methanol) was added to reduce NH4+/NOx- accumulated in the compost. Results indicate that methylotrophic microorganisms did convert NH4+/NOx- into biomass, as long as the NO3- content in the compost was larger than 0.1 g NO3(-)-N/kg compost. Removal efficiencies of CH3OH of more than 90% were obtained at volumetric loads up to 11,000 g CH3OH/ m3/day. It is shown that addition of CH3OH is a suitable technique for regenerating the compost material from osmotic inhibition as a result of high NH3 loading. The biofilter was operated for 4 months with alternating load ing of NH3 and CH3OH.     

Effect of surface coatings, grain size, and ionic strength on the maximum attainable coverage of bacteria on sand surfaces

The injection of bacteria in the subsurface has been identified as a potential method for in situ cleanup of contaminated aquifers. For high bacterial loadings, the presence of previously deposited bacteria can result in decreased deposition rates--a phenomenon known as blocking. Miscible displacement experiments were performed on short sand columns (approximately 5 cm) to determine how bacterial deposition on positively charged metal-oxyhydroxide-coated sands is affected by the presence of previously deposited bacteria. Approximately 8 pore volumes of a radiolabeled bacterial suspension at a concentration of approximately 1 x 10(9) cells ml-1 were introduced into the columns followed by a 2-pore-volume flush of cell-free buffer. It was found that the presence of Al- and Fe-coated sand increased both deposition rates and maximum fractional surface coverage of bacteria on the sediment surfaces. The effect of grain size on maximum bacterial retention capacity, however, was not significant. Decreasing ionic strength from 10(-1) to 10(-2) M KCl resulted in noticeable decreases in sticking efficiency (alpha) and maximum surface coverage (thetamax) for clean silica sand--results consistent with DLVO theory. In columns containing positively charged Al- and Fe-coated sands, however, changes in alpha and thetamax due to decreasing ionic strength were minimal. These findings demonstrate the importance of geochemical controls on the maximum bacterial retention capacity of sands.     

Patient demands,lack of reciprocity,and burnout: a five‐year longitudinal study among general practitioners

This study among a sample of 207 general practitioners (GPs) uses a five‐year longitudinal design to test a process model of burnout. On the basis of social exchange and equity theory, it is hypothesized and found that demanding patient contacts produce a lack of reciprocity in the GP–patient relationship, which, in turn, depletes GPs' emotional resources and initiates the burnout syndrome. More specifically, structural equation analyses confirmed that—both at T1 and T2—lack of reciprocity mediates the impact of patient demands on emotional exhaustion. Emotional exhaustion, in turn, evokes negative attitudes toward patients (depersonalization), and toward oneself in relation to the job (reduced personal accomplishment). Moreover, this process model of burnout was confirmed at T2, even after controlling for T1‐scores on each of the model components. Finally, T1 depersonalization predicted the intensity and frequency of T2 patient demands, after controlling for T1 patient demands. This major finding suggests that GPs who attempt to gain emotional distance from their patients as a way of coping with their exhaustion, evoke demanding and threatening patient behaviors themselves. The theoretical and practical implications of these findings are discussed. Copyright © 2000 John Wiley & Sons, Ltd.