FELD 02/2017

DUST EMISSIONS DUST

DUST EMISSIONS DUST EMISSIONS Dust particles are so tiny that our eye can hardly distinguish the single particles. Although smaller in diameter than a hair, dust particles unveil a stunning diversity under the microscope. The dust phenomenon has fascinated Dr. Roger Funk from the Institute of Soil Landscape Research of the Leibniz Centre for Agricultural Landscape Research (ZALF) for more than 25 years. Because tiny as the particles may be, their importance for humans and the environment is tremendous: They transport nutrients around the world and are a prerequisite for clouds to form. Dr. Funk is particularly interested in the causes and effects of dust emissions in agricultural landscapes. His most important tool: a dust monitor, which he sets up for research in various fields. The measuring device draws in air and guides it past a laser beam that determines the number and size of the dust particles in the air stream. »It sounds trivial, but it‘s not,« says Funk. »We record the origin and exact composition of the individual particles and thus create a specific ›fingerprint‹ for each dust sample.« The scientist has since built up a considerable soil dust archive from many parts of the world. — 10 µm DUST IS A WORLD IN ITSELF — 10 µm The dust samples reflect the patterns in the landscape. DR. ROGER FUNK Church father Isidor of Seville (560 to 636) once described the phenomenon of dust as follows: »Everything that is so light that it is carried up by air« – a definition that is still valid today. It was not until the microscope was invented in the 17 th century that it became possible to have a closer look at the small particles. Gottfried Wilhelm Leibniz wrote enthusiastically in 1698: »So it is possible, or even necessary, that in the smallest dusts and even in the atoms, there are worlds which do not give in to our own world’s beauty and diversity.« Larger dust particles of approx. 0.1 millimetres, i. e. 100 micrometers in diameter, can be clearly seen under the light microscope. Fine dust particles, however, which are smaller than a millionth of a millimetre, can only be detected in the scanning electron microscope. »Small as the particles may be, each of them is unique«, says Funk. »We examine dust from a variety of sources, including samples from bogs, the nutrient-poor sandy soils in Brandenburg, the loess regions of China and Argentina, and the Arizona desert.« The microscope reveals the exciting variety of particle structures. Desert sand is composed of many small crystals. Soil dust from Brandenburg’s sandy soils, on the other hand, is a collection of fine mineral particles and coarser, organic particles arranged loosely next to each other. Dust from fertile loess regions contains small, solid lumps of organic and mineral components. »As diverse as landscapes are, so are their dusts.« Agricultural dusts contain a mix of mineral and organic particles of different shapes and sizes. 04 05