Each sample was sieved (2 mm mesh size) and large elements (rocks, branches, etc.) were removed. The sieve was rinsed with porewater from each sample and collected in the same plastic bottle. The sample was homogenized with manual mixing (shaking and swirling during 30–50 s) and centrifuged during 10 min at 3000 RPM. The supernatant was collected as porewater. It was filtered (0.45 μm Ø filters) and stored in 50 ml Falcon tubes at −20 °C. The sediment was collected in plastic containers, weighed and stored at −20 °C until the toxicity tests were performed to kill infaunal species and preserve samples.