# Chemical Speciation of Antarctic Atmospheric Depositions
## 2 Materials and Methods
### Apparatus and Procedures  
Sample treatments, analyses and decontamination procedures were carried out in clean room laboratories with areas in Class 5 (ISO 14644-1) under laminar flow, both in the Antarctica and in Italy [15]. The used filtration system was the Sulfoflo from Nalgene (Rochester, NY, USA), equipped with 0.45 \(\upmu\)m-pore size membrane filters (cellulose mixed esters \(\mathcal{O}\) 47 mm, Schleicher & Schuell, Dassel, Germany). Sampling bulks and plastic containers used for storage of sample solutions were of low-density polyethylene material (Kartell, Italy). For the determination of anions, the atmospheric depositions were analyzed with a Dionex DX 500 Ion Chromatograph, equipped with Rheodyne injector (20 \(\upmu\)L sample loop), LC 30 chromatography oven, GP 40 gradient pump, Dionex Ion Pac AG9-HC 4-mm (10-32) guard column, Dionex Ion Pac AS9-HC 4-mm (10-32) anion exchange column, ASRS-ULTRA 4-mm conductivity suppression unit, and ED 40 electrochemical detector, operated in conductivity mode at 30 \({}^{\circ}\)C. The eluent was a 1.1 \(\times\) 10\({}^{-2}\) mol L\({}^{-1}\) K\({}_{2}\)CO\({}_{3}\)/ 4.5 \(\times\) 10\({}^{-3}\) mol L\({}^{-1}\) NaHCO\({}_{3}\) mixture, with flow rate of 1.0 mL min\({}^{-1}\). Sodium, potassium, calcium, magnesium, and ammonium cations were analyzed with the same instrument, except that it was equipped with Ion Pac CG12A (4 \(\times\) 50 mm) (10-32) guard column, Ion Pac CS12A (4 \(\times\) 250 mm) (10-32) cation exchange column, and CSRS-ULTRA 4-mm conductivity suppression unit. The eluent was a 2.0 \(\times\) 10\({}^{-2}\) mol L\({}^{-1}\) methanesulfonic acid solution, at a flow rate of 1.0 mL min\({}^{-1}\). Copper, zinc, manganese, and iron cations were quantified according to the concentration levels, by either ICP-OES (Inductively Coupled Plasma--Optical Emission Spectrometer) or HR-ICP-MS (High Resolution--Inductively Coupled Plasma--Mass Spectrometer). In particular, ICP-OES was a Perkin Elmer (Waltham, MA, USA) Optima 7000 DV instrument, equipped with a Mira Mist nebulizer, a cyclonic spray chamber, a dual Echelle monochromator and a dual CCD detector. HR-ICP-MS was a Thermo Fisher Scientific (Waltam, MA, USA) Element 2 instrument, equipped with a conical nebulizer, a Scott spray chamber, a magnetic and electric sector, and a SEM detector. Wavelength, mass resolution, and isotope selection were optimized for each element, to avoid or minimize spectral interferences and to maximize sensitivity. The detection limits (DL) were experimentally determined. The samples were handled in a clean environment under a Class-100 laminar flow bench-hood, to avoid any possible contamination. The reagent blanks were composed of ultra-pure water, acidified with sub-boiling nitric acid (1:1000). The NIST 1640a Certified Reference Material (CRM) was used to validate the measurement procedures by both ICP-OES and HR-ICP-MS. The CRM was an acidified (2% HNO\({}_{3}\)) spring water, and it was analyzed either without treatment or diluted, in order to best simulate the concentration levels of real samples. All measurements were performed in triplicate.