4.6.2. Testing different sampling strategies

From the 3 min composite samples, we tested time proportional sampling strategies with intervals of 6, 9, 15, 30 and 60 min for all substances. First, the measured EMC was calculated from the 3 min composite sample according to Eq. 2.

From the 3 min composite samples, we took hypothetical samples for the chosen intervals and calculated the EMC of the selection by using the measured concentration and cumulated discharge volume during this interval (Fig. 5a). Next, we calculated the relative difference from the measured and the estimated EMC via Eq. 3. The outer boundaries of the possible outcomes are reported (Fig. 5b). This was done for all substances.

An alternative approach to determining the necessary sampling interval could be to analyse the frequency spectrum of the micropollutant concentrations. Such an approach would be interesting for determining the optimal sampling interval for evaluating the detailed concentration pattern over time for future work. However, in this study, we are focusing on the EMC assessment rather than the detailed concentration pattern over time.