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Nowadays, in the air over cities and industrial regions, on average only half as much carbon dioxide is converted into oxygen as in the air over natural countryside. To an ever-increasing degree, the biosphere is being charged with elements which do not belong to its natural constituents and which, in some places and at some times, are already present in such a high concentration that they can be harmful to animal and plant life.
In the Federal Republic of Germany alone, exhaust pipes and chimneys pollute the air annually with 20 million tons of dirt: with sulphur, lead, carbon monoxide, soot and dust.
Electronic measuring instruments which have been in use for some months now to check the air in city centres frequently indicate alarming values.
In order to call a halt to this contamination of the atmosphere, we must first of all find out how the elements contained in the atmosphere influence plant and animal organisms.
The institute for forest botany in Munich is about to conclude a two-year series of experiment sin which for the first time the exchange of oxygen, carbon dioxide and water vapour in a forest on the outskirts of a city has been measured systematically and without interruption.
For their test tree the scientists chose a 35 meters high spruce and attached to it a number of special conditioning chambers developed jointly by the institute for forest botany and Siemens, in order to make a continuous study of the growth process of individual branches. An exact record is made of how much carbon dioxide and oxygen is absorbed or eliminated by the plants and how much water vapour they give off to the atmosphere. Temperature, humidity of the air, and light conditions are also measured.
The information coming in steadily from the various measuring probes passes via some hundred pneumatic and electrical leads to a small log-house where it is registered and stored for later computer evaluation.
Interrogation, recording and storage of the data are controlled centrally by a program control unit.
This apparatus is used to measure the air flow in the measuring chambers.
A gas multi-way switch automatically connects the various measuring positions to the analysing equipment in a fixed pattern.
All measured values are printed out.
From their thorough knowledge of the time-dependent radiation and climatic factors and from the continuous record of the exchange of gases, the scientists hope to obtain a precise under standing of the dependence of plant growth on the environment.
From these measurements it is possible to determine how and to what degree the foreign elements in the air affect growth. Only when we know this can we start to think about controlled environmental care.
Such environmental control will in any case require that healthy forests be planed wherever and in whatever magnitude needed to form a climate-regulating, water-preserving green belt around large cities....
and that cities be provided with adequate traffic-free zones, enabling the people living and working there to once again enjoy urban life without risk to health.
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