Comparison of atmosphere/aquatic environment concentration ratio of volatile chlorinated hydrocarbons between temperate regions and Antarctica

For the purpose of understanding the transport and deposition mechanisms and the air–water distribution of some volatile chlorinated hydrocarbons (VCHCs), their atmosphere/aquatic environment concentration ratio was evaluated. In addition, for the purpose of differentiating VCHC behaviour in a temperate climate from its behaviour in a polar climate, the atmosphere/aquatic environment concentration ratio evaluated in matrices from temperate zones was compared with the concentration ratio evaluated in Antarctic matrices.In order to perform air samplings also at rigid Antarctic temperatures, the sampling apparatus, consisting of a diaphragm pump and canisters, was suitably modified.Chloroform, 1,1,1-trichloroethane, tetrachloromethane, 1,1,2-trichloroethylene and tetrachloroethylene were measured in air, water and snow using specific techniques composed of a purpose-made cryofocusing-trap-injector (for air samples) and a modified purge-and-trap injector (for aqueous samples) coupled to a gas chromatograph with mass spectrometric detection operating in selected ion monitoring mode. The VCHCs were retrieved in all the investigated matrices, both Italian and Antarctic, with concentrations varying from tens to thousands of ng m⁻³ in air and from digits to hundreds of ng kg⁻¹ in water and snow.The atmosphere/aquatic environment concentration ratios were always found to be lower than 1. In particular, the Italian air/water concentration ratios were smaller than the Antarctic ones, by reason of the higher atmospheric photochemical activity in temperate zones. On the other hand, the Antarctic air/snow concentration ratios proved to be largely in favour of snow with respect to the Italian ratios, thus corroborating the hypothesis of a more efficient VCHC deposition mechanism and accumulation on Antarctic snow.     

Volatile chlorinated hydrocarbons in Antarctic superficial snow sampled during Italian ITASE expeditions

In order to detect the presence of some volatile chlorinated hydrocarbons (VCHCs) and to understand their transport and deposition mechanism, superficial snow was sampled during two Italian ITASE (International Trans Antarctic Scientific Expedition) expeditions: the first traverse was carried out in 1998/1999 from Terra Nova Bay to Dome Concordia; the second traverse was carried out in 2001/2002 through Adélie, George V, Oates and Northern Victoria Lands. Some VCHCs (chloroform; 1,1,1-trichloroethane; tetrachloromethane; 1,1,2-trichloroethylene; tetrachloroethylene) were analysed using a highly sensitive and selective hyphenated technique composed of a purge-and-trap injector coupled to a gas chromatograph with a mass spectrometric detector (PTI-GC-MS) operating in SIM mode. Investigated VCHCs were present in all analysed snow samples with concentration levels of several units, tens, or sometimes hundreds of ng kg(-1). VCHC snow concentration levels remained approximately constant with changing distance from the coast and the comparison between fresh and aged snow did not show any substantial differences; on the basis of this evidence marine aerosol and dry deposition may be rejected as principal VCHC transport and deposition mechanism hypotheses. VCHC concentration levels in Antarctic snow samples were comparable to or greater than those found in snow from temperate zones.