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Toxic chemical pollutants detected in lichens and mosses in Irati forest

A study by the IBeA research group of the University of the Basque Country (UPV/EHU) revealed relatively high concentrations of three groups of organic pollutants. The study concluded that some of these pollutants come from nearby urban areas; others originate from combustion processes currently taking place in agriculture; and finally the ones corresponding to pollution caused by pesticides and some electrical insulators before they were banned several years ago.

The work is in the journal Atmospheric Pollution Research.

"We measured significant concentrations of persistent organic compounds in each species of lichen and moss in the Irati forest, but they are no higher than the concentrations measured in other similar places," said Alberto de Diego, researcher in the UPV/EHU's IBeA research group.

In fact, in a joint study with members of the CNRS (French National Centre for Scientific Research) and the University of Navarre, members of the IBeA group used a species of lichen (Parmelia sulcata) and a species of moss (Hypnum cupressiforme) from Irati as sentinels or biomonitors to determine the organic pollution in the atmosphere.

Persistent organic compounds are toxic and three types were explored in this study: PAHs (polycyclic aromatic hydrocarbons) are by-products of combustion processes. In particular, PCBs (polychlorinated biphenyls) were used in electrical insulation and are currently banned; and OCPs (organochlorine pesticides) used to be routinely used in agriculture and are also currently banned.

"These organic compounds travel a long way through the atmosphere on the wind," explained Ainara Gredilla, an IBeA researcher, "and they build up in the environment: they are absorbed and accumulated by living beings. Areas at high altitudes are very sensitive to persistent organic pollutants, so we wanted to find out the extent to which they had accumulated in the lichens and mosses in Irati. In fact, the Irati forest is regarded as a clean environment, since, apart from tourism, there is no human activity other than sustainable livestock and agriculture."

Located in the western Pyrenees, the Irati Forest is one of the largest and best-preserved protected beech and fir forests in Europe.

From urban centers and activities dating back several decades

The results showed that, in general, PAH concentrations are significantly higher than those of the other two pollutants. The researchers say that pollution that is transported through the atmosphere over long distances should not be underestimated, but the study showed that urban and agricultural practices that have been around Irati for decades have exerted an impact on air quality.

"You may think that part of the pollution has come from and continues to come from urban areas, but to a great extent the impact of local agriculture is also significant," said the UPV/EHU researchers.

"Today, there are still controlled burning processes in some areas around the Pyrenees, and we believe that there are still many PAHs coming from there. To reduce the presence of PAHs in the atmosphere of the Irati forest, controlling the combustion processes that take place around the forest is mandatory. On the other hand, traces of pesticides that were used in the past have not been eliminated (OCPs)."

As for PCBs, "We suspect they come from electrical insulators used around the Irabia reservoir. It is likely that the PCBs used in the past have remained there and are still detectable today."

The researchers insist that such studies serve to "confirm, above all, that these pollutants have a great capacity to reach very distant places from where they have been produced and to accumulate in naturally clean places like Irati. So, even if the concentrations are not very high, due to their very high toxicity, it is something that needs to be monitored to prevent future problems."

They also consider it necessary to pursue the research "to analyze changes according to seasons and/or years, and to confirm the trends that have been explained in this study."