Elsevier

Chemosphere

Volume 76, Issue 11, September 2009, Pages 1525-1532
Chemosphere

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

https://doi.org/10.1016/j.chemosphere.2009.05.044Get rights and content

Abstract

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.

Introduction

Since the Second World War, a massive production and a widely varying and extended industrial use of volatile chlorinated hydrocarbons (VCHCs) has taken place, due to their versatility in several processes. Taking into account the entity of the emissions (estimated in hundreds of thousands of tons per year (McCulloch et al., 1999)) and their physico-chemical properties (in particular volatility and persistence) (Campbell et al., 1985), VCHCs can spread from industrialized and inhabited regions and reach remote zones of the Earth, such as Antarctica. This large-scale diffusion takes place by means of long range transport via atmospheric and ocean currents, in particular by means of a process known as global distillation and fractionation (Wania and Mackay, 1993). According to the latter process, volatile and semi-volatile compounds evaporate into the atmosphere in temperate and tropical regions, where they are used and discharged, and are then carried by atmospheric currents until they reach colder climates, where they condense and are deposited (Wania and Mackay, 1995, Fernandez and Grimalt, 2003). As VCHCs have the peculiar capability of being diffused at planetary level, and being distributed between air and water, they were selected as indicators of global contamination (Zoccolillo and Rellori, 1994, Zoccolillo et al., 1996, Zoccolillo et al., 2004, Zoccolillo et al., 2007, Zoccolillo et al., 2009).

In the present work, the atmosphere/aquatic environment concentration ratio of VCHCs was evaluated in order to understand their transport and deposition mechanisms and the distribution between air and water (or snow). In addition, the VCHC concentration ratio in Antarctic matrices was compared with the concentration ratio in Italian matrices, in order to compare VCHC behaviour in polar and temperate climate. The VCHCs investigated were: chloroform (CHCl3), 1,1,1-trichloroethane (C2H3Cl3), tetrachloromethane (CCl4), 1,1,2-trichloroethylene (C2HCl3) and tetrachloroethylene (CCl4).

A preliminary and essential part of the present research consisted in modifying and improving air sampling equipment, in order to solve the problems associated with air collection operations in Antarctica, taking into account the operating difficulties facing air sampling in remote and cold zones.

Section snippets

Air sampling equipment

The air samplings were performed using a suitably modified diaphragm pump (model 8000-1) and canisters (model 6-L G.O. Stabilizer™) purchased from General Oceanics Environmental, Miami, Florida.

The air contact surfaces of the diaphragm pump were all made of stainless steel in order to avoid any release of organic compounds. The pump was battery operated and oil-free; therefore, in situ samplings can be performed even in absence of electric current and any contamination of the air sample during

Apparatus

For VCHC analysis in air, an ad hoc analytical system was used, based on a cryofocusing-trap-injector coupled to a gas chromatograph with mass spectrometric detection operating in selected ion monitoring mode (SIM) (CTI-GC–MS). For VCHC analysis in aqueous matrices (i.e. water and snow), a highly sensitive and selective technique was used based on a purge and trap injector coupled to a gas chromatograph with mass spectrometric detection operating in SIM (PTI-GC–MS) (Zoccolillo et al., 2005).

Results and discussion

In order to evaluate any drawbacks due to the relatively lengthy storage of the air and aqueous samples collected in Antarctica, some advance tests were made. Air samples with low VCHC concentrations (e.g. those from rural areas) were analysed immediately after collection and after a variable storage time (from 2 weeks to 2 months). In some cases, the canisters were maintained at −20 °C, for a period of time comparable to the duration of the Antarctic expedition, and brought back to room

Conclusions

The environmental monitoring of VCHCs, in particular the determination of concentration values and distribution among compartments, is fundamental for the purpose of determining the extent of the problem on a scientific basis in consideration of the toxicity of VCHCs above all for Antarctic ecosystems. Thus, several sampling campaigns were carried out to collect air, water and snow in both Italy, a typical temperate zone of the Northern Hemisphere, and Antarctica, a cold zone of the Earth. In

Acknowledgements

The authors wish to acknowledge financial support from the Italian National Research Programme in Antarctica (PNRA).

The authors gratefully thank Dr. Carlo Abete for his helpfulness during sampling operations during the Italian Antarctic expeditions.

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