杏吧原创

EVEN Europe鈥檚 remotest mountain lakes are chronically polluted, say
researchers in Spain and Britain. 鈥淥ur results show that there鈥檚 no pristine
ecosystem left in the northern hemisphere,鈥� says Pilar Fern谩ndez of the
Institute of Chemical and Environmental Research in Barcelona.

When the researchers looked at sediments that had been laid down after 1830
in 10 remote lakes around Europe, they found significant concentrations of
polycyclic aromatic hydrocarbons (PAHs). These chemicals are formed by burning
wood and fossil fuels and some of them are carcinogenic.

The findings echo studies of sediment in northern American lakes.
Fern谩ndez says that the pollutants could only have arrived at these
remote altitudes in rain and snow. 鈥淭he discovery shows that the northern
atmosphere is completely contaminated by this pollution from combustion,鈥�
she says. By establishing the age of each layer in the samples of sediment,
Fern谩ndez and her colleagues have shown that the heaviest pollution was
laid down as Europe鈥檚 Industrial Revolution gathered pace, with concentrations
peaking at up to 20 times the natural background level.

The most polluted lakes were in eastern and central Europe, while the least
polluted were on the fringes of the Continent, in the mountains of Spain and
Scandinavia. Analysis of individual PAHs shows that most pollution in these
fringe regions came from wood burning. Elsewhere, it reflects heavy urban and
industrial pollution.

Some PAHs are carcinogens鈥攖he best known being benzopyrene, which
causes lung cancer. Although the levels of PAHs are higher near cities and
industry, they turn up in the most unexpected places, with unpredictable
long-term effects on health and the environment. She has recently found PAHs in
trout, showing that these chemicals are finding their way into the food chain.