Director: Prof. Dr. Meinrat O. Andreae

Secretary: Karin Oliveira dos Santos

Phone: +49-6131-305421
Fax: +49-6131-305487
E-mail: biogeompic.de

Biogeochemistry is a new scientific discipline, which addresses the interactions of the biosphere with the Earth's chemical environment. Professor Andreae and his research groups are investigating a number of key aspects of global biogeochemistry: the role of the marine biota as a source of climatically important trace gases, the exchange of chemically and radiatively important trace gases between the soil/vegetation system and the atmosphere, and the effect of vegetation fires on ecology and atmospheric pollution. The research in Professor Andreae's groups is closely tied to the International Biosphere/Geosphere Program, and involves a high amount of international collaboration. Click here for a review paper on Feedbacks and Interactions between Global Change, Atmospheric Chemistry, and the Biosphere.

Plants may act both as sources and sinks of atmospheric trace gases. Previous studies have shown that carbonyl sulfide (COS) is taken up by plants together with CO₂ and processed in the plants by the enzymes responsible for CO₂ assimilation. This uptake represents a major sink for this compound, which on the other hand plays an important role as a source of sulfur-containing (sulfate) aerosols to the stratosphere. Current projects include a study of the emission of non-methane hydrocarbons by plants in Mediterranean ecosystems, the investigation of organic acid production and consumption by plants, and research on the emission of sulfur compounds by plants, algae, and lichens.

Vegetation fires are an important determinant in the ecology of many terrestrial systems, e.g. the North American boreal forest, the California chaparral, and the African savanna. Professor Andreae's groups are conducting studies on the role of fire in ecology, climate and atmospheric chemistry. Much of this work is being done in the course of field campaigns in Amazonia, Africa, the boreal region (e.g., Siberia), and southeast Asia. It includes the determination of the gaseous and particulate emissions from vegetation fires, and measurements of the products of the photochemical processing of these emissions in the atmosphere, particularly pollutant species like ozone and nitrogen oxides. Land use change in the tropics, e.g., the conversion of rain forest and savanna into grazing and agricultural lands, has a strong influence on the emission of several trace gases from soils, e.g., N₂O, NO, and CO. Professor Andreae's groups are studying these effects by conducting flux measurements at selected sites in the tropics and in temperate regions. Click here for a review paper on Emission of trace gases and aerosols from biomass burning.

Our group is investigating the impact of anthropogenic aerosols on the atmosphere over the tropics, with emphasis on the Amazon region. Under unpolluted conditions, biogenic processes dominate the aerosol population over the Amazon Basin. A large fraction of coarse and fine particles are of primary biogenic origin, and consist of spores, pollen-related material, microbes, plant debris, etc. Secondary biogenic materials, including organic condensates from VOC oxidation and biogenic sulfate account for much of the rest. Superimposed on this background are inputs of dust and marine particles from long-range transport. Aerosol number concentrations and CCN concentrations are low, in the range usually considered typical of remote marine locations. Under these low-CCN conditions, cloud droplets can grow rapidly to the size where precipitation occurs and rain production by warm clouds is an important process.

During the dry season, large-scale burning due to deforestation and clearing fires in the Amazon Basin and the surrounding regions leads to a dramatic increase of aerosol and CCN number concentrations. These smoke aerosols consist mostly of organic matter, and include light-absorbing organic and near-elemental carbon species. The presence of water-soluble organic substances and inorganic salts makes these smoke aerosols efficient CCN. The result of the increased CCN abundance is a major shift towards clouds with high droplet number concentration, and thus increased colloidal stability of the cloud and a lower probability of rainfall from warm clouds. This favors rainfall mechanisms involving ice particles, which has substantial effects for the redistribution of energy and chemical species in the tropical atmosphere. These effects are likely to reach far beyond the Amazon Basin and the tropics.