Atmospheric deposition of persistent organic pollutants and chemicals of emerging concern at two sites in northern Sweden

Bimonthly bulk atmospheric deposition samples (precipitation + dry particle) were taken for one year at an arctic (Abisko, 68 degrees 20' N, 19 degrees 03' E) and a sub-arctic (Krycklan 64 degrees 14' N, 19 degrees 46' E) location in northern Sweden using Amberlite IRA-743 as an absorbent for hydrophobic pollutants. The samples were analyzed by gas chromatography-high resolution mass spectrometry (GC-HRMS) for polychlorinated biphenyls (PCBs), legacy organochlorine pesticides (OCPs = hexachlorocyclohexanes and chlordane-related compounds), polybrominated diphenyl ethers (PBDEs) and emerging chemicals. Higher deposition rates of most compounds were observed at the more northern site despite its receiving less precipitation and being more remote. HCHs and PCBs made up the bulk of the total deposition at both sites. Five emerging chemicals were detected: the current-use pesticides trifluralin and chlorothabnil; and non-BDE flame retardants 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), and Dechlorane Plus (DP). A decrease in the fraction of the anti isomer of DP was observed at the arctic site, indicating isomer-selective degradation or isomerization during long range transport. Air parcel back trajectories revealed a greater influence from air originating over the ocean at the more northern site. The differences in these air sources were reflected in higher Sigma HCH to Sigma PCB ratios compared to the more southern site, as HCHs are related to volatilization from the ocean and Abisko is located <100 km from the Norwegian coast, while PCBs are emitted from continental sources.