White mustard (Sinapis alba) is a sensitive test plant. Its growth is inhibited in contact with toxic substances. The toxic effect can be estimated by measuring its root and shoot length. The test method is based on HS  22902-4:1990 and HS 21976-17:1993 standards.

Test procedure:

5 ml liquid sample is pipetted on filter paper in a 9 mm diameter Petri dish. 25 white mustard seeds are uniformly arranged on top of the filter paper. The germination ability of white mustard seed should be minimum 95%. Germination ability and suitable growth is checked with distilled water. The sensitivity of the seeds is checked with Cu dilution series. The test is run in triplicate. Alternatively dilution series are prepared with distilled water. The samples are kept in thermostate for 72 hours at 20/25 °C, in the dark.

The root and shoot lengths are measured with a ruler. The results of the triplicates are averaged. Root and shoot growth inhibition is expressed in % compared to the root or/and shoot length of the test plants grown in the untreated control dish:

X=(K-M)/K*100, where: X: root or shoot growth inhibition %, K: root or shoot length of plants grown in the control, M: root or shoot length of plants grown in the tested sample.

In case of dilution series the inhibition is plotted versus the weighed amount and the ED20 and ED50 values (the amount causing 20 and 50% inhibition) are estimated.

For sediment samples the test procedure is according to the test method applied to soil. https://www.enfo.hu/en/node/175