Denitrification in Soil and Sediment

The formation of atmospheric nitrogen gas by denitrifying bacteria may represent a significant nutrient sink in natural ecosystems. The rate of denitrification has often been difficult to measure in situ, however, and new methodologies should stimulate research on distribution of activity in space and time. The load of fertilizer nitrogen in modem agriculture has led to increasing nutrient reservoirs in recipient subsoils, aquifers, inland waters and coastal seas. By its conversion of nitrate to atmospheric nitrogen, bacterial denitrification is the only biological process to potentially reduce the impact of increasing nutrient loadings by fertilizer nitrogen in the environment. As part of a scientific program set up by the Danish Ministry of Environment to study environment cycling of nitrogen, phosphorous and organic matter (NPO program) in the light of agricultural, domestic and industrial activities, a symposium on DENITRIFICATION IN SOIL AND SEDIMENT was held at the University of Aarhus, Denmark from 6-9 June 19i9. On the basis of lectures given at the symposium, this book contains a number of invited contributions on the regulation of denitrification activity (control of enzyme synthesis and activity) and measurement of in situ rates of denitrification in terrestrial and aquatic environments (control factors, diel and seasonal variations, etc). Emphasis has been placed on including the recent improvements in methodologies and current understanding of process regulation, however the book also contains examples of integrated research on the significance of denitrification in environmental nutrient cycling.

Proceedings of a symposium held under the auspices of the Federation of European Microbiological Societies and the Danish Ministry of Environment, held in Aarhus, Denmark, June 6-9, 1990.

I. Biochemistry and Genetics of Denitrification.- 1. Bio-inorganic Aspects of Denitrification: Structures and Reactions of NxOy Compounds and their Interaction with Iron and Copper Proteins.- 2. Distribution and Diversity of Dissimilatory NO2- Reductases in Denitrifying Bacteria.- 3. Metabolism of Nitrous Oxide.- 4. Physiology, Biochemistry and Genetics of Nitrate Dissimilation to Ammonia.- II. Ecophysiology of Denitrification.- 5. Role of Environmental Factors in Regulating Nitrate Respiration in Intertidal Sediments.- 6. Physiological and Ecological Aspects of Aerobic Denitrification, a Link with Heterotrophic Nitrification?.- III. Emission of NxOy Compounds.- 7. Flux of NOx between Soil and Atmosphere: Importance and Soil Microbial Metabolism.- 8. Emissions of N2O from Various Environments - the Use of Stable Isotope Composition of N2O as a Tracer for the Studies of N2O Biogeochemical Cycling.- IV. Denitrification in Soil.- 9. Acetylene Inhibition Technique: Development, Advantages and Potential Problems.- 10. The Use of Acetylene for the Quantification of N2 and N2O Production from Biological Processes in Soil.- 11. Measuring Denitrification in Soils Using 15N Techniques.- 12. Rhizosphere Denitrification; a Minor Process but Indicator of Decomposition Activity.- 13. Characterizing the Variability of Soil Denitrification.- 14. Anaerobic Zones and Denitrification in Soil: Modeling and Measurement.- 15. Diffusion-Reaction Models of Denitrification in Soil Microsites.- V. Denitrification in Biofilm and Sediment.- 16. Combined Use of the Acetylene Inhibition Technique and Microsensors for Quantification of Denitrification in Sediments and Biofilms.- 17. Denitrification in Stream Biofilm and Sediment: In Situ Variation and Control Factors.- 18. Measurement of SedimentDenitrification Using 15N Tracer Method.- 19. Denitrification in Aquatic Sediments.- 20. Denitrification Model for Marine Sediment.- Contributors.