Biosensors for On-Line Monitoring of the Waterways and for Sample Taking Aimed at Relieving Disturbances

Abstract

Organismic and suborganismic testing methods are well suited as biological warning systems (biosensors) which build a sensitive system used in screening for hazardous substances. Although chemo-physical testing methods can never detect and identify all polluting chemicals in the environment to the fullest extent, biological early warning systems make it possible to monitor dangerous substances or groups of substances in waterways. Electrodes made up of cyanobacteria, i.e. Synechococcus, for immediate detection of acute toxic effects, are used as a biological early warning system for recognizing damage to the waterways. The so-called “cyanobacterial electrodes” are graphite electrodes (see Figure 1) which have cyanobacteria, i.e. Synechococcus, affixed to them. The measurements of the photosynthetic electron transport system, PET, under alternating light - dark conditions, are conducted in a flow-through cell against reference electrodes (Ag/AgCl).. A mediator (Fe II / Fe III) makes the flow of current possible by becoming reduced by these bacteria and then reoxidized at the working electrode. The time which the electrode takes to react is about two minutes, and a multiple confirmed result is available after ten minutes. The detection limits for the individual substances have been set according to the results obtained up to present at less than 10 Ug per litre for atrazine and at 100 ug per litre for linuron (see Table 1).