100 years of pheromone research

Dedicated to Prof. H. Autrum on the occasion of his 85th birthday.     

Emotional social support and job burnout among high‐school teachers: is it all due to dispositional affectivity?

The authors investigated whether the relationship between the contents of emotional social support and job burnout among high‐school teachers is spurious because of the role of dispositional positive and negative affectivity. A national sample of 339 teachers was surveyed via a web‐based procedure. Hierarchical regression analyses did not support spuriousness; emotional social support was uniquely predictive of three dimensions of burnout controlling for affectivity. As positive emotional social support increased, emotional exhaustion and cynicism decreased, and professional efficacy increased. As negative emotional social support increased, emotional exhaustion and cynicism also increased. Commonality analyses based on the present data and data reported by K. L. Zellars and P. L. Perrewé (2001; Journal of Applied Psychology, 86, 459–467) provided additional support for the unique role of emotional social support on burnout, but these analyses suggest a greater role of affectivity than emotional social support. These findings have implications for research on burnout as well as the prevention of burnout among teachers. Copyright © 2006 John Wiley & Sons, Ltd.     

Impact of temperature on the dynamics of organic matter and on the soil-to-plant transfer of Cd,Zn and Pb in a contaminated agricultural soil

Predicting the soil-to-plant transfer of metals in the context of global warming has become a major issue for food safety. It requires a better understanding of how the temperature alters the bioavailability of metals in cultivated soils. This study focuses on one agricultural soil contaminated by Cd, Zn and Pb. DGT measurements were performed at 10, 20 and 30 °C to assess how the bioavailability of metals was affected by a rise in soil temperature. A lettuce crop was cultivated in the same conditions to determine if the soil-to-plant transfer of metals increased with a rise in soil temperature. A gradual decline in Cd and Zn bioavailability was observed from 10 to 30 °C, which was attributed to more intense complexation of metals in the pore water at higher temperatures. Together with its aromaticity, the affinity of dissolved organic matter (DOM) for metals was indeed suspected to increase with soil temperature. One main output of the present work is a model which satisfactorily explains the thermal-induced changes in the characteristics of DOM reported in Cornu et al. (Geoderma 162:65–70, 2011) by assuming that the mineralization of initial aliphatic compounds followed a first-order reaction, increased with soil temperature according to the Arrhenius law, and due to a priming effect, led to the appearance of aromatic molecules. The soil-to-plant transfer of Cd and Zn was promoted at higher soil temperatures despite a parallel decrease in Cd and Zn bioavailability. This suggests that plant processes affect the soil-to-plant transfer of Cd and Zn the most when the soil temperature rises.     

Influence of operating conditions on nitrous oxide formation during nitritation and nitrification

Nitrous oxide (N₂O), a strong greenhouse gas, can be produced by ammonium-oxidizing bacteria (AOB) as a by-product of ammonium oxidation and can potentially be formed in all types of nitrification processes. However, partial nitritation has been reported to cause significantly higher N₂O emissions than complete nitrification. In the study presented here, the mechanisms and factors that drive N₂O formation by AOB were investigated with respect to different operational strategies to achieve nitrite accumulation base on combined evaluation of oxygen uptake rate (OUR) and N₂O formation rate. On the one hand, N₂O formation during partial nitritation and nitrification in a continuously stirred tank reactor (CSTR) with continuous aerobic conditions was observed. On the other hand, the effect of intermittent aeration on N₂O formation during nitrification was investigated. The presence of nitrite, the extend of sludge-specific ammonium loading, low oxygen concentration, and transition from aerobic to anoxic conditions significantly increased N₂O formation in this reactor independently from each other, indicating that different formation pathways, supposedly via nitrite or hydroxylamine, were active.