Lichen and moss bags as monitoring devices in urban areas. Part II: trace element content in living and dead biomonitors and comparison with synthetic materials

Lobes of the lichen Pseudevernia furfuracea (L.) Zopf and shoots of the moss Hypnum cupressiforme Hedw. were subjected to different treatments (water washing, oven drying, HNO3 washing, NH4-oxalate extraction) to assess the influence of vitality on accumulation efficiency, during a 6-week exposure in bags in two Italian cities, Trieste and Naples. No trend emerged between treatments, in terms of accumulation ability, for major and trace elements. Only water-washed lichens showed an increased C and N content after exposure in both cities. Element concentrations generally reached higher values in mosses than in lichens, especially for Al, Fe, and Zn (both cities), and for Cu, Mg and Na (Naples). Surface development strongly influenced accumulation capacity of the biomonitors. Quartzose and cation exchange filters revealed, on a weight basis, a poor performance. In urban environments, surface interception of atmospheric particulate seems to play a major role in accumulation, irrespective of organism vitality.     

Effects of site-specific climatic conditions on the radial growth of the lichen biomonitor <Emphasis Type="Italic">Xanthoria parietina</Emphasis>

The protocols commonly applied in surveys with lichens as biomonitors of airborne trace elements require analyses of samples derived from thalli or parts of thalli grown in the last year before sampling, under the postulation that samples of the same size are of the same age. Unfortunately, the influence of ecological site-specific factors on lichen growth is still largely ignored, so that samples of the same size collected in environmentally and climatically diverse sites might actually differ in age. This work aims at quantifying the influence of climatic conditions on the radial growth rates (RaGRs) of Xanthoria parietina, one of the most popular lichen biomonitors. RaGR was monitored in seven populations distributed along an altitudinal transect of 30 km in the Classical Karst (NE Italy), from 20 to 500 m above sea level. For c. 17 months, lobe growth was measured seasonally with a digital calliper, and site-specific climatic variables were monitored by means of thermo-hygrometric sensors and implemented by meteorological data. Finally, the lobe growth of X. parietina was modelled as a function of 18 environmental variables. Results revealed that thalli of relatively dry sites had significantly lower seasonal RaGR with respect to moister ones. Considering that cumulative precipitations were equally distributed along the transect, it was concluded that RaGR of X. parietina is affected negatively by high air temperatures and positively by high relative humidity. The importance of RaGR variation in lichen bioaccumulation studies is critically discussed.     

Natural and pre-treatments induced variability in the chemical composition and morphology of lichens and mosses selected for active monitoring of airborne elements

To enhance the reliability of the moss and lichen transplant technique for active biomonitoring of trace metals in urban environments, we evaluated the natural variability in the chemical composition of the (epilithic and epiphytic) moss Hypnum cupressiforme and the epiphytic lichen Pseudevernia furfuracea from two reference areas in NE Italy. Green shoots of epilithic mosses and lobes of epiphytic lichens from larch branches showed rather homogenous composition and were selected for the exposure in nylon bags. As different physico-chemical pre-treatments are usually applied to selected cryptogamic material before its exposure, we also evaluated the effects of oven-drying at 120 degrees C for 24h, washing in 1N HNO3 solution, and in 0.5% NH4 oxalate solution at 85 degrees C for 15 h on the chemical composition and morphology of water-washed moss shoots and lichen lobes. Pre-treatments remarkably changed the chemical composition of selected materials but not their surface morphology.     

Lichen transplants as a suitable tool to identify mercury pollution from waste incinerators: a case study from NE Italy

A lichen transplant study aimed at investigating a strong increase in mercury concentrations in lichens was run in a territory of NE Italy where background values were very low only 8 years before. Thalli of the lichen Pseudevernia furfuracea collected in a pristine area were exposed for 1.5, 3 and 6 months at 31 sites selected according to the observed pattern of Hg concentrations, location of the suspected source (a new waste incinerator) and prevailing wind direction. Hg strongly increased at eight sites after 1.5 months, at 12 after 3 months and at 20 after 6 months. The highest values were always located SW and S of the incinerator, in good agreement with the prevailing night wind direction. It was concluded that, although the immediate risk for the population living close to the incinerator is low, long-term hazard due to Hg accumulation in the surrounding environment should be seriously taken into account.     

Element accumulation performance of living and dead lichens in a large-scale transplant application

Environmental Science and Pollution Research - In bioaccumulation studies, sample devitalization through acid washing or oven drying is commonly applied to enhance the element accumulation...     

Lichen and moss bags as monitoring devices in urban areas. Part I: influence of exposure on sample vitality

Samples of the lichen Pseudevernia furfuracea (L.) Zopf and the moss Hypnum cupressiforme Hedw. were exposed for 6 weeks in nylon bags in two air pollution monitoring stations in Trieste and Naples (Italy) with different climates and pollution loads to evaluate influence of environmental conditions on sample vitality. This was assessed before and after exposure by transmission electron microscopy observations, K cellular location, and measurements of C, N, S and photosynthetic pigments content, CO2 gas exchange, and chlorophyll fluorescence. Almost all data sets indicate that exposures caused some damage to the species, considerably heavier in the moss, especially in Naples. The two cryptogams differed significantly in accumulation and retention of C, N, and S, the lichen clearly reflecting NO2 availability. The difference in vitality loss was related to the different ecophysiology of the species, because concentrations of phytotoxic pollutants were low during exposure. Critical notes on the analytical techniques are also given.