Bulk deposition samples were filtered through from sodium sulphate (Na2SO4) after extraction in order to remove any residual water in the samples. The BDS surface was NSC 125973 then rinsed with ACE/HEX mixture. This process was repeated a few times and the solvents were stored in a jar. Finally, the BDS surface was wiped with a paper napkin to remove contaminants from the surface and the used paper napkins were put into sample bottle so as to analyze them.The volume of the extracted samples was reduced to 2mL with the use of rotary evaporator and gentle stream of nitrogen (N2), and these samples were passed through a cleanup column including 1cm sodium sulphate (Na2SO4), 2g of aluminium oxide (120��L pure water to 2g of aluminium oxide), and 3g of silica (100��L pure water to 3g of silica).

The column was cleaned with 20mL DCM and then with 25mL PE. The volume of the PCB samples in PE was reduced to 5mL, and the solvent exchange was performed by adding 15mL HEX. This was repeated twice. Finally, samples with reduced volume of 2mL were rinsed with acid and taken to the vials. An internal standard solution consisting of PCB 30 and PCB 204 was added to concentrated samples for volume correction and internal standard was added just before the quantification of the PCB compounds.Quantification of PCB congeners was conducted using an Agilent 7890A model gas chromatograph equipped with a ��ECD (Micro-Electron Capture Detector) (Hewlett-Packard, USA). GC-ECDs have been employed for PCB analysis in many studies because of their sensitivity [6, 20�C22].

The oven temperature program used in the PCB analyses was 70��C (2min), increasing with 25��C/min to 150��C, then 3��C/min to 200��C, then Entinostat 8��C/min to 280��C, followed by 8 minutes of holding under 280��C, increasing with 10��C/min to 300��C and holding for 2 minutes. The final program time was 41.87 minutes. The inlet temperature was kept at 250��C and the detector temperature was 320��C. The carrying gas was helium (He) (1.9mL/min) and the make up gas was N2 (25mL/min). HP5-MS (30m �� 0.32mm �� 0.25��m, Agilent, 19091 Je413) was used as a capillary column. For the calibration of the instrument, five levels of standard solutions ranging between 0.05 and 25ng/mL were used for calibration. After each 25 samples injection, the medium standard was injected to check instrument stability. The instrument detection limit, IDL, was determined as 0.1pg for 1��L injection. The linear r2 values determined with these standards varied between 0.99457 and 0.99996 for each PCB congener.2.4.