AN ARTIFICIAL STREAM MESOCOSM TO SIMULATE FATE AND EFFECTS OF CHEMICALS - TECHNICAL DATA AND INITIAL EXPERIENCE WITH THE BIOCENOSIS

An artificial stream system is described which has been installed at t he Fraunhofer Institute to simulate fate and effects of environmental chemicals in relevant water compartments. The artificial stream is par t of the institute's outdoor field simulation facilities for studies w ith radio-labelled substances. The circular stream system has a length of about 35 m, a width of 0.6 m, a depth of 0.35 m and is made of sta inless steel to avoid contaminations. Two inlets and an extended segme nt diversify the current. Current is generated by electrically-driven steel paddles which allows a regulation of velocity. The artificial st ream is filled with sediment (about 2.5 m(3)) and water (approx. 3 m(3 )) from a small natural stream. Each of the inlets contains an aquatic lysimeter with an undisturbed sediment core of 0.6 m diameter and 0.6 m column height, which is flanged at the bottom of the water basin. T his design allows the study of fate of substances in the ecosystem com partments water, sediment and water leaching through the river bed. A preliminary study was performed comparing various physical-chemical wa ter parameters and the development of the biocenosis in the natural an d the artificial stream in order to determine whether the natural stre am can serve as reference stream in experiments. Following an adaptati on period of 4-8 weeks, macroinvertebrate species diversity and popula tion densities were similar in both streams. Therefore, it is conclude d that the natural stream can be used as control in future investigati ons. Exposure studies are planned including investigations of adverse effects of contaminants on organisms transferred to the artificial str eam from a natural water. (C) 1996 Elsevier Science Ltd