|
(335) Measuring the potentially affected fraction of species in surface water as a monitoring tool. Struijs, Jaap1, De Zwart, Dick1, Van de Kamp, Rob1, 1 ABSTRACT- There are serious limitations on conventional chemical monitoring: 1) the number of chemicals is necessarily limited, 2) toxicity data of many chemicals is lacking, impeding the assessment of damage to the aquatic ecosystem and 3) it is not feasible to quantify the combined effects of complex mixtures of chemicals. High volume (100 L) of water samples are taken into the laboratory and aqueous concentrates of organic chemicals are prepared that are compatible to micro-biotests. The toxicity of the concentrates is evaluated by means of bioassays, without any qualitative or quantitative chemical analysis on organic micropollutants. The method, referred to as the toxic potency or pT method, is focused on the unknown cocktail of toxic organic micropollutants in surface water. The aim is to evaluate the toxic potency as the fraction of species, chronically exposed to a complex mixture above the no-observed effect level. In this context, toxic potency of a water sample has been named the measured Potentially Affected Fraction (PAF), indicating that bioassays are applied to investigate the toxicity of concentrated water samples. This technique enables separating toxic pressure from other environmental stressors. The pT monitoring system has been used for monitoring the toxic pressure on aquatic ecosystems in the Netherlands. The measured PAF varied between 0 % (blank and the River Rhine) and 4.4 % (River Scheldt), however, this may be an underestimation due to the loss of some substances during the extraction procedure. The performance of the method is illustrated with the results obtained from test samples with known mixtures of organic chemicals. Key words: toxic potency, toxic pressure, potentially affected fraction, monitoring surface water |
