| dc.description.abstract | The overall objective of this thesis was to investigate responses of epiphytic lichens to traffic related pollutants and to get new insight into accumulation and despersal of airborne pollutants. This was done in short term factorial studies under laboratory conditions and in long term studies of lichens transplants in the field.
For the laboratory experiment we selected three common foliose lichens, one sensitive to air pollution (L. pulmonaria) and two more resistant species with different salt tolerance (P. sulcata and the sea shore species X. aureola). Lichen thalli during lab conditions were soaked in 0.01, 0.2 and 0.6 M of de-icing salt (NaCl) and/or in 10, 100 and 500 μM of metal salts solutions (CuSO4·5H2O, ZnSO4·7H2O) for 24 hrs. To induce photoinhibition lichen thalli were exposed to high light – 600-700 μmol photons m-2 s-1 for 4 hrs.
In the field, lichen thalli (L. pulmonaria, P. sulcata, U. filipendula, R. farinacea) were placed on stands at 10, 15, 30, 50 and 100 m from both sides of the highway E6 in Ås and Vestby road at six separate gradients for 6 months. In order to understand how external factors influence internal responses of the lichens, chlorophyll fluorescence, conductivity, growth (dry weight), pigment content, visible damage and element content were quantified.
Paper I dealt with effect of external stress (salt, irradiance, heavy metals) on lichens in the lab on biont and species levels.
Lichen mycobionts responded on the exerted toxic effect of stress agents in the order: “Salt x Metal”>“Metal”>“Salt x Light”>“Salt”; the photobionts: “Metal”>“Salt x Metal”>“Salt x Light”>“Salt”. The results showed that photobiont viability (Fv/Fm) varied during the experiment from 30.3 to 66.3% of start levels, while the mycobiont exhibited conductivity levels 3.4 to 77.1 times higher than control values.
Studied lichen species showed tolerance to the lowest agent concentrations applied separately. Osmotic and metal stresses applied together significantly increased the sensitivity among lichen bionts, while combination of osmotic stress and irradiance only effected lichen photobionts.
Copper (Cu) showed higher impact on lichen viability than Zn (94.5% of cases against 5.5%), while the interactions between NaCl and Zn were stronger than with NaCl and Cu (41.6% of cases against 8.3%). Copper (Cu) negatively affected viability of L. pulmonaria and X. aureola, whereas P. sulcata was more damaged by Zn.
Studied species can be placed in the order of sensitivity to external stresses:
L. pulmonaria >P. sulcata >X. aureola.
In Paper II, the changes in lichen viability and elemental composition of lichen thalli transplanted along E6 highway were assessed.
Paper II Part I, showed that Ca and Na represented up to 44-54%, while P and K – up to 11-26% of the total accumulated elemental pool of harvested lichens, whereas Ba and Cu together constituted up to 59-74% of the total trace elemental deposition. The EC class “severe accumulation” was evident for Na, Fe, Al, Ni, Cr, V, Co, Mo, As, Sn, Sb, from “normal” to “severe accumulation” for Cu and Zn, while up to “severe loss” for K compared to background values.
There were high correlations within groups of elements related to road dust (Ca, Al, Fe), exhaust emissions (Ni, V, As, Cr, Cu, Zn, Pb). Sodium (Na) correlated positively with heavy metals (r= 0.41 to 0.85) and negatively with K (r= -0.51 to -0.86).
Exceeded concentrations of Al, Fe, Na, Co, Mo, Sb, Ba, V, Pb were found even at 100 m from the road, while 30 m was sufficient to reduce by 60-70% of the majority of elemental content of lichens compared with background values.
External factors influenced the elemental accumulation in lichens in the order: “Species”>“Distance”>“Side”.
The accumulation capacity of lichen species increased in the order: R. farinacea <
L. pulmonaria | no_NO |
