The Antarctic Continent, thanks to its remarkable distance from thickly populated areas and its poor biological activity, is regarded as a privileged observatory for research on global changes recently caused by man in the environment: it can be considered as the largest environmental and climatological memory of the Earth.
Pollutants are generally present in Antarctica because of the atmospheric and oceanic circulation that carries them from the most anthropic areas to the remotest ones.
What is the present level of contamination and what kind of global modification processes are taking place in the environment?
We can answer these questions by using all the information concerning modifications, transport and distribution of certain chemicals (whether of anthropic origin or not) in the Antarctic ecosystem.
The environmental studies focus research on sea, atmosphere, snow, ices, lakes as well as on processes that makes all these components a "system". Therefore, for example, if micro components and micro pollutants are carried from the sea to the emerged surface through the sea aerosol and atmosphere, the process of formation and melting of sea ice influences the quantity contained in the sea water.
It is clear that we deal with interdisciplinary studies concerning Glaciology, Oceanography, Biology, Ecotoxicology and Atmospheric Physics.
The chemicals in question are organic substances of antrophic origin (e.g. chlorofluorocarbons, polychlorobyphenils, and pesticides) and of natural origin (e.g. humic and fulvic acids), chemical elements (e.g. heavy metals such as cadmium, chromium, copper, mercury, lead) and radionuclides.
Decontaminated atmosphere chemical laboratories have been fitted out both at the Italian base in Antarctica and on the oceanographic ship (mobile chemical laboratory installed in ISO-20 container) in order to carry out on-site analysis of substances present in traces.
It is extremely useful to measure the global distribution of chlorofluorocarbons, called CFCs, or other gases (such as methane, carbon monoxide, carbon dioxide, nitrous oxide) that can have a direct or indirect influence on the ozone stratospheric levels.
Antarctica is the ideal site to measure the troposheric concentration of these gases. The measurements carried out by the Italian expeditions in Antarctica in 1989/90 and 1990/91 have highlighted an increase of CFCs content in the low atmosphere.
Polychlorobyphenils, called PCBs, are compounds having a high stability and, under certain forms, toxic effects comparable with the dioxin ones. After being synthesized at the end of the last century and mass-produced since 1930, they were widely used for about 40 years and spread in the environment without taking any precaution causing a global contamination. In Antarctica PCBs have been found in sea water, sea sediments and soil samples.
Carbon tetrachloride and similar chloride compounds as well as PCBs are important indicators of environmental contamination with respect to their prolonged persistence in the environment. In Antarctica they have been found in sea water and lake water.
Toxic heavy metals, extremely harmful to health, are released into the atmosphere by natural or anthropic processes and are good indicators in order to assess the environmental contamination caused by man. Therefore, for example, the lead concentrations in the water surface layers are higher than in the deepest ones because man releases this metal into the atmosphere. No remarkable increase in the lead content in surface waters in relation to the base value measured in deep waters has been observed in Antarctica (Terra Nova Bay). That means the absence of a significant local lead pollution in Antarctic sea water (studies on snow samples have given information about remote origin lead pollution).
The study of the sea system has been completed by research on the bioaccumulation and transport of inorganic elements (for example mercury) and organometallic substances in sea organisms.
We can find useful information about the past earth's atmosphere composition inside high altitude glaciers and ice-caps. The snow layers settling during the years preserve many chemicals collected in the air and mixed in the blanket of snow while falling to the ground. The stratigraphic chemical analysis of these "ice archives" allow us to establish approximately when the snow layers settled, which substances are mixed in them, including the ones present in traces, and consequently to reconstruct the chemical composition of the atmosphere in recent years or in remote ages. Now we can study the climate and environmental modifications occurred in the past due to natural causes or related to the human activity and imagine how things might change in the future both on a local and a global level.
The alpine glaciers very close to thickly populated and highly industrialized areas enable us to study the effect of environmental contamination in Europe during the last millennia.
The ice-caps in Greenland and in Antarctica, highly influenced by air masses coming from the middle altitudes, are a sort of archive on a hemispheric level. They are over three kilometres thick and allow us to get information dating back to about 500,000 years ago. Heavy metals are present in the snow in such low concentrations that until some decades ago it was almost impossible to determine them owing to the low sensibility of analysis techniques and the contamination probabilities during the analytical process.
Lead is one of the oldest contaminants released into the atmosphere by man.
Recent studies carried out in Greenland have highlighted signs of contamination related to the flourishing mining activity during the Greek-Roman period.
However, data concerning the ice-cap analysis in Greenland clearly show that in the last two centuries the pollution has become more serious first because of the Industrial Revolution and then owing to the ever-growing use of high lead level petrol. The lead concentration, that reached its highest level by the end of the 1970s, is estimated to be one hundred times greater than the natural level of the pre-industrial period. The recent marketing of the low lead level petrol, the so-called "unleaded", and its extensive use have dramatically reeduced this problem.
In the 1940s in Antarctica the lead concentration in snow was already approximately ten times greater than the one present in ice some thousands years ago. Between 1940 and 1980 its concentration has further increased, showing that the man contribution to the lead emissions into the atmosphere has also been significant in the austral hemisphere, even if on a smaller scale than in the north hemisphere.
Our recent studies have proved that even in the Antarctic snow the lead concentration has quickly decreased during the 1980s, showing that the reduction of this toxic metal in petrol has dramatically improved the air quality on a global level.
For further information on these subjects you can contact:
Prof. Gabriele Capodaglio
Department of Environmental Sciences
University of Venice
Calle Larga S. Marta, 2137