Fig nbsp xA Location of sampling site in the

All reagents were of analytical grade, obtained from Merck (Darmstadt, Germany) Sigma-Aldrich (St. Louis, MO, USA), and were used without further purification unless otherwise stated. The sample-containing filters and unexposed blanks were stored in Petri dishes placed inside an unlit refrigerator below − 18 °C to prevent loss of semi-volatile species. To analyze carboxylates, anhydrosugars, sugar alcohols, cations and anions, the filter paper (L3) was placed in Astemizole PE bottle, 10.0 mL of deionized water (resistivity > 18.2 MΩ-cm at 25 °C, Milli-Q Direct 8/16 System) was added and the contents were shaken (Yihder TS-500 Shaker), in an genetic maps unlit refrigerator at 4 °C to prevent the decomposition of the extracted carboxylates, anhydrosugars and sugar alcohols, for 90 min. OC had been removed from the deionized water and the detection limits corresponded to 10–50 ng for the carboxylates, anhydrosugars and sugar alcohols investigated.