| Popis: |
The detection of sudden contamination pulses in surface waters has gained increasing importance over the past few years with view to drinking water production and the protection of aquatic life communities. An efficient monitoring system for practical applications cannot be based alone on physico-chemical analyses because, on the one hand, suitable analytical methods are not always available and, on the other, continuous analyses of all relevant parameters are hardly practicable for reasons of time and economy (Juhnke and Besch, 1971; van Hoof, 1980; Nusch, 1993). Moreover, measured concentrations do not provide any information about the biological availability of the detected substance. Neither does one know which effects the compound has on aquatic organisms in combination with other substances to which they may be exposed simultaneously. Estimates about the unnatural compounds which occur in the River Rhine range in an order of magnitude between 30,000 to 50,000 (Botterweg, 1988), of which only about 150 to 200 substances are covered by routine analyses (Botterweg et al., 1989). Furthermore, the interpretation of the results of chemical routine analyses by reference to available toxicity data is problematic, since toxicity data that were measured under standardized laboratory conditions are hardly relevant for field conditions, because theyleave the influence of the matrix of the water body out of account. For instance, humic acids, which occur ubiquitously, may alter the biological effectivity of contaminants by some orders of magnitude (Mayr, 1992). |
