MAE-AR was performed with a StarT-1500 microwave (MLS GmbH, Leutkirch, Germany), which holds up to ten polytetrafluorethylene (PTFE) digestion vessels with a volume of 100 mL each. A modified US EPA Method (3051A (SW-846)) as described by was applied. In brief, 0.3 g of sediment sample were weighed directly into the PTFE vessels, 6 mL HCl (35 %) and 2 mL HNO3 (69 %) were added and the microwave program as described in the Online Resource 1 (Table ) was run. Following extraction and cooling, extracts were transferred to 50 mL calibrated polypropylene flasks, pretreated with HNO3. Extracts were made up to volume with deionized water, filtered (185 mm; Macherey-Nagel MN 280 1/4) and stored in polyethylene bottles at 4 °C until analysis. Blanks were treated like samples. To avoid cross contamination of PTFE vessels with TEs from previous extractions, vessels were cleansed using 10 mL HNO3 (69 %) and the same MAE-AR program as used for samples in between each sample extraction.