Scientists' Contributions

Biological Monitoring of Environmental Contaminants - Established Systems and Potential Newcomers

M. C. Freitas¹, M. A. Reis¹, A. M. G. Pacheco², L. I. C. Barros²

    Biological monitoring has had quite an impressive development since the early observations of environmentally-induced stress on what would be now called biodiversity (lichen patterns), still made well into the 19th century by L.H. Grindon in Manchester (1859) and W. Nylander in Paris (1866). Since then, a mere bunch of incipient, scattered observations has turned into a serious alternative - or, at the very least, an useful complement - to traditional (instrumental) methods of assessing contamination from natural or anthropogenic sources. In what concerns vegetable organisms and airborne pollution only, the heyday really began after World War II. There is currently an amount of biomonitoring work that spans a whole lot of pollution inputs to about every ecosystem on Earth, and applications have grown to an extent barely envisaged just a few decades ago. This expansive growth has been gaining momentum mainly from lower organisms - lichens, bryophytes and, to a lesser degree, non-lichenised fungi - whereas the contribution from higher, vascular plants appears much more discreet. And yet, despite an arguably superior ability to accumulate and track down contaminants without an interference from soil elements- which is actually true only for epiphytic species - lichen communities are known for their slow regeneration, so an intensive sampling may put them in short supply or in the very threshold of extinction, while mosses seem hardly an option in dry areas. On the other hand, several genera of those underrated higher plants share an ubiquity, availability and ease of sampling that is unmatched by lower epiphytes.

    This work illustrates the value of epiphytic lichens in large-scale surveys of airborne pollution and the interesting, useful information that can be obtained therefrom. The study is based on a nation-wide campaign that was held in mainland Portugal, using a 10x10 km sampling grid up to 30-80 km inland and a 50x50 km grid in the innermost regions of the country. Replicate samples of Parmelia spp. - mostly, Parmelia sulcata Taylor - were collected from olive trees at each site and analysed for their elemental contents through instrumental neutron activation analysis (INAA) and proton-induced X-ray emission (PIXE), following suitable procedures. The presentation will be focused on an illustrative selection of elements from major sources, on their assignment and also on the advantage of multi-elemental techniques in environmental research at large. As a complement, and with the aim of start bridging the gap between the use of lower and higher plants, concentrations in bark of olive trees (Olea europaea Linn.) from a subset of the former grid are discussed as well. As far as the comparison goes, there appears to be no reason for discarding bark as an alternative to epiphytes, inasmuch as Olea europaea is an ubiquitous species in mainland Portugal, let alone southern Europe in its almost entirety and other significant areas of the globe.