S

 ZCH

 ICG

 ZEL

In charge: Prof. A. Wahner, ICG, a.wahner@fz-juelich.de

Aims and Objectives

The aim of the research program "Chemistry and dynamics of the Geo-Biosphere" is to create the basis for the quantitative understanding of changes of state in the atmosphere, in vegetation, soil/groundwater and sediment systems on different space and time scales. For this purpose, the distribution, conversion and effects of selected substances in the atmosphere, biosphere, soil and sediment systems as well as the mass transport between these environmental compartments are investigated in interdisciplinary cooperation. Such processes are particularly important for areas with high industrial activity, great density of traffic and simultaneous intensive agricultural use, as are to be found in Germany and Europe, but they are also of special interest for issues of global development. The findings obtained will serve environmental precautions and contribute to a resource-conserving use of soils, plants, air and water. The programme of work contributes to the Helmholtz programmes "Geosystem: The changing Earth", "Atmosphere and Climate", and "Biogeosystems: Dynamics, Adaption and Adjustment" in the research field "Earth and Environment"

To realize this work programme, special scientific and technical infrastructure facilities, such as the atmosphere simulation chamber (SAPHIR), the plant emission chambers, facilities for investigating the transport of positron tracers (e.g. PlanTIS), green houses, lysimeter stations with handling licences for radioactive substances and field sites with different hydrogeological conditions are available to the ICG institute. Within the competence centre NIM non-invasive methodologies will be developed to characterise matter fluxes in biogeosystems at various space and time scales. Moreover, research balloons and various aircrafts are used as measuring platform and the ICG is a member of a European Economic Interest Group (EEIG) of the Geophysica high-altitude research aircraft. Furthermore, the ICG can build on the contributions made by the Department for Safety and Radiation Protection (S) on atmospheric trace substance dispersion near ground level and on the analytical expertise of the Central Department of Analytical Chemistry (ZCH).

Significant Results of the Year 2003

Climate Variability and Human Habitat
Microclimatological and tree-physiological studies were performed at a forest lysimeter site to describe the seasonal development of oxygen and carbon isotopes in tree-rings. A recently developed new instrument with the correspondingly new method for oxygen isotope analysis of silica was applied to establish the seasonal development of oxygen isotopes in lacustrine diatoms.
The environmental history of the transition between two important climate zones was reconstructed using lake sediments from Patagonia. The impact of abrupt climate changes on ecosystems of Central Europe was described for Lake Meerfelder Maar using high resolution isotope analyses. For the Karakorum region, Northern Pakistan, summer temperatures and winter precipitation could be reconstructed for the last 1200 years. A warm phase between 800 and 1200 AD shows temperature levels comparable to the present ones.
The importance of changes of the solar energy flux and the Earth's orbital elements was detected in various archives.
The results further the understanding of important processes of the climate system and its impact on geobiosystems.

• Atmosphere and Climate

Trace Substances in the Troposphere
Vertical radical profiles measured during the AFO2000 project ECHO for the first time in a forest followed the solar ultraviolet actinic radiation and reached their highest values above the canopy. Photolysis frequencies dropped to about 10% of above canopy values within the first 4-5 m below the canopy top and then gradually decreased to about 2% at ground level. The observed radical concentrations point towards a significant daytime source of gaseous HONO, the photolysis of which contributes a major fraction to the primary OH production in the forest.
The hydrolysis of nitric acid anhydride is an important removal step in the atmospheric nitrogen oxide cycle. Within the CASOMIO project it was shown, that condensation of oxidation products of biogenic hydrocarbons onto aqueous aerosol surfaces reduces the hydrolysis reaction of nitric acid anhydride by factors of 2 to 10. Our findings are the first direct experimental evidence for a significant modification of an important atmospheric process by organic coatings.

Changes in the Tropopause Region - The Stratosphere in a Changing Environment
(1) During the Arctic campaign EUPLEX (coordinated by ICG-I) chlorine activation and partitioning and the effects on chemical ozone loss were investigated. Precise chlorine observations made by the newly-developed HALOX instrument onboard the high-flying Russian research aircraft Geophysica suggest that an important rate constant has to be revised, with significant consequences for calculated ozone loss rates. (2) A Lagrangian method has been developed to link local and short-period validation measurements to global satellite data in order to increase its statistical significance. This method is intended to be applied on our airborne and balloon-borne measurements of water vapour and halogen radicals for validation of the Environmental Satellite ENVISAT. (3) The structure of the extra-tropical tropopause region was investigated during dedicated aircraft campaigns, with emphasis on transport and mixing processes. The results highlight the importance of meso-scale structures for stratosphere-troposphere-exchange (STE). (4) Long-term observations of water vapour, ozone, and nitrogen species were continued on commercial airlines as part of the European project MOZAIC. They have now delivered the first climatology for total odd-nitrogen (NOy) for the upper troposphere and lower stratosphere (> 1000 flights). The seasonal cycle of NOy is approximately in phase with that of ozone.

Functioning of Soils, Sediments and Groundwater
With financial support from industry, EU, DFG and government lab and field experiments were carried out to study the environmental fate of xenobiotics in agroecosystems. They focussed on the characterisation and modelling of the filter and buffer functions of soils for xenobiotics and their transport behaviour in soils and aquifers. The advancement of non-invasive measurement techniques for the investigation of porous media included the development of a novel magneto-electrical scanner and enabled the characterisation of solute transport in a heterogeneous aquifer in the course of tracer experiments. A research project about interactions of pollutants in the system water/suspended matter/sediment was established with the Chongqing Institute of the Three Gorges in China.

Stress and Adaption: Plants in Varying Environment
The analysis of dynamic responses of plants to a fluctuating environment by non invasive methods was further intensified. Digital imaging procedures for growth analysis in 3 dimensions and tomographic methods for determination of the carbon and element (nutrient) transport were developed. The distribution of nutrients in soils and the water uptake capacity of plant roots were analysed for their dynamics by micro suction cups and stable isotope tracers. Mapping of root growth and of concentrations of substances in the growing root tip showed strong differences between nutrients in the relative importance of uptake form the rhizosphere and the import into growing root tips via the phloem. Phloem transport was shown to be very sensitive to a decline of oxygen concentrations. Emissions of oxygenated volative organic compounds could be linked to lipoxygenase activity. Patterns of emitted substances and dynamics of the release during stress supported these finding.