1,721,081 research outputs found
Comparison of the trace element content in transplants of the lichen Evernia prunastri and in bulk atmospheric deposition: A case study from a low polluted environment (C Italy)
No full textThis study investigated whether lichen samples transplanted and retrieved monthly for six months reflect bulk deposition under conditions of relatively low air pollution. The study investigated also whether samples exposed for six months provide data consistent with the one-month transplants. The lichen Evernia prunastri was collected from a remote site and exposed at a study site (the Botanical Garden of the University of Siena, Italy), along with an atmospheric bulk deposition collector. Lichens and bulk deposition were analysed by ICP-MS for the content of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Sb, Ti and Zn. The results showed significant correlations between lichen content and bulk deposition for Al, As, Cu, Fe, Hg, Sb and Ti, suggesting that in one month the equilibrium is reached for these elements between the lichen and the atmosphere. The above elements (but Sb) in lichen and bulk deposition are related to soil-particulates, while traffic is the source for Sb deposition. In addition, samples exposed for 6 months showed results consistent with the one-month transplants for As, Cu and Hg, suggesting that for these elements in the study site the equilibrium is maintained also for longer periods
May lichen biomonitoring of air pollution serve for the implementation of waste management policies?
No full textThere is a high public concern for the environmental and health impact connected with waste management, and the public acceptance of incinerators, waste disposal sites and other related facilities is generally low since these are often causing concern for the population living nearby. Biomonitoring of air pollution is a reliable tool for the implementation of environmental policy on air quality and atmospheric pollution control, and it can be successfully applied for the implementation of waste management strategies. This chapter summarizes evidences on the usefulness of lichen biomonitoring as a tool for the implementation of environmental friendly waste management policies. There is enough evidence that lichen biomonitoring can be profitably used to detect spatial and temporal biological effects caused by airborne pollutants released by solid waste incinerators, landfills and composting facilities. An integrated use of lichen based methods, i.e., methods with a stronger link to source attribution (e.g., bioaccumulation), methods reflecting ongoing processes (e.g., ecophysiological responses and bioaccumulation with transplants) and their environmental effects (e.g., biodiversity assessments), can provide useful biological outputs for decision-makers to establish correct science-based environmentally sustainable waste management policies
Is the length of the drying period critical for photosynthesis reactivation in lichen and moss components of biological soil crusts?
No full textLichens and mosses represent the macroscopic components of biological soil crusts (biocrusts). Their ability to exploit short periods of water availability and reversibly deactivate metabolism is crucial for their growth and survival. In this work we investigated photosynthesis reactivation, respectively after long (65–66 days) and short (15 days) dry periods, in lichen and moss species widespread in two Mediterranean environments (Portugal and Italy). Chlorophyll a fluorescence emission of the samples was investigated and the parameter Fv/Fm, an indicator of vitality of photosynthetic organisms, was used as a proxy for photosynthesis reactivation. The fruticose lichens Cladonia convoluta and C. rangiformis, and the moss Pleurochaete squarrosa, typical of Mediterranean environments, showed a significantly slower reactivation of photosynthetic activity when subjected to a longer period of drought. Conversely, the alien invasive moss Campylopus introflexus was not affected by prolonged dry conditions. The study showed that drought duration influences the reactivation of photosynthetic activity in terricolous lichens and mosses forming biocrusts in re-hydration cycles. These results indicate the likelihood of a reduction in biocrust productivity as a consequence of climate change in Mediterranean drylands
Reconstructing Air Pollution Trends in Remote Forests of Central Europe Using Lichen Herbarium Specimens
No full textLichen collections may contribute to a better understanding of past environmental conditions. By analysing herbarium specimens and recently collected material of the lichen Lobaria pulmonaria, this study reconstructs six decades (1960–2022) of air quality changes in remote forests of Central Europe (the Western Carpathians). Twenty specimens were selected for retrospective analysis of major and trace elements (Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, S, Sb, and Zn), focusing on both historical and current background concentrations. The results revealed peaks of potentially toxic elements (As, Fe, Hg, Mn, Ni, S, and Sb) up to 1989, with a progressive decline observed thereafter, particularly for Pb following the introduction of unleaded gasoline. Background element concentrations from 1960 to 1989 were at least four times higher than actual levels. The study highlights the value of herbarium collections for reconstructing air pollution history and tracking changes in background element concentrations in remote areas, particularly when alternative data sources are unavailable. It also addresses both the opportunities and limitations of this approach
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Differential elemental stoichiometry of two Mediterranean evergreen woody plants over a geochemically heterogeneous area
No full textLeaf nutrient composition and stoichiometry reflect complex interactions of the plant with its environment and are useful traits to explore ecological processes and relationships. In the present study, the foliar elemental compositions of two common Mediterranean woody species, the evergreen broad-leaved Quercus ilex and the coniferous Pinus pinaster growing in an area of Central Italy known for geochemical and geothermal anomalies, were investigated. To assess the site-specific and age-dependent pattern of foliar composition and stoichiometry, macronutrients (C, N, P, K, Mg, S) and trace elements (Al, As, Ba, Cd, Cr, Cu, Fe, Hg, Ni, Pb, Sb, V, Zn) were determined in leaves and needles of three different ages (6-, 12- and 24-month-old) collected from metalliferous (geothermal, mining) and rural areas. Leaves of Q. ilex showed comparatively high concentrations of micronutrients (i.e., Cu, Fe and Zn), while needles of P. pinaster accumulated significantly high concentrations of potentially toxic elements (i.e., As, Pb and S). No significant trend was found in elemental concentrations in relation to the age of leaves and needles. Multi-element stoichiometry of P. pinaster was driven by the geochemical heterogeneity of the sites, suggesting plastic adaptation at the sites with the most selective edaphoclimatic conditions (i.e., patches with nutrient poor and metalliferous soils). On the other hand, the content of both nutrients and potentially toxic elements in Q. ilex leaves varied little across the study area, reflecting stoichiometric stability; this is consistent with the ecophysiological features of Q. ilex as a late-successional species with a dominant role in the ecosystems of the Mediterranean area. Our findings demonstrate the value of foliar stoichiometric traits for understanding plant adaptation in a heterogeneous environment and also the consequences of biotic interactions during succession
May lichen biomonitoring of air pollution be used for environmental justice assessment? A case study from an area of N Italy with a municipal solid waste incinerator
No full textIn this work, we aimed to identify the contribution of a municipal solid waste incinerator (MSWI) to the air contamination of a complex urbanized area of N Italy using lichen transplants as biomonitors, and to compare the values of contamination with the data of socioeconomic deprivation of the population living in the area.
The method adopted allowed the identification of the elements of atmospheric origin that contaminate the study area. Although not distinguishable from the background, the contribution of the MSWI could be apportioned and mercury emerged as atmospheric tracer. Although not posing immediate risk, it is advisable to monitor in time the accumulation of Hg in biological systems.
Consistently with similar studies, in the surrounding of the MSWI, we observed also the highest socio-economic deprivation. Overall, we found a close correlation between socioeconomic deprivation and air pollution, clearly showing that the most disadvantaged population is clustered in the most polluted areas
Effects of acute NH3 air pollution on N-sensitive and N-tolerant lichen species
Full text linkLichens are sensitive to the presence of ammonia (NH3) in the environment. However, in order to use them as reliable indicators in biomonitoring studies, it is necessary to establish unequivocally the occurrence of certain symptoms following the exposure to NH3 in the environment. In this paper, we simulated an episode of acute air pollution due to the release of NH3. The biological effects of acute air pollution by atmospheric NH3 have been investigated using N-sensitive (Flavoparmelia caperata) and N-tolerant (Xanthoria parietina) species. Lichen samples were exposed to ecologically relevant NH3 concentrations for 8 weeks, simulating three areas of impact: a control area (2 μg/m3), an area of intermediate impact (2–35 μg/m3) and an area of high impact (10–315 μg/m3), with a peak of pollution reached between the fourth and fifth week. Ammonia affected both the photobiont and the mycobiont in F. caperata, while in X. parietina only the photosynthetic performance of the photobiont was altered after exposure to the highest concentration. In the photobiont of F. caperata we recorded chlorophyll degradation as indicated by OD435/415 ratio, decrease of the photosynthetic performance (as reflected by the maximum quantum yield of primary photochemistry FV/FM and the performance index PIABS); in the mycobiont, ergosterol reduction, membrane lipid peroxidation (as reflected by the increase of thiobarbituric acid reactive substances), alteration (decrease) of the secondary metabolite usnic acid. No effects were detected on caperatic acid and dehydrogenase activity. In X. parietina, the only signal determined by NH3 was the alteration of FV/FM and the performance index PIABS. The results suggest that physiological parameters in N-sensitive lichens well reflect the effects of NH3 exposure and can be applied as early indicators in monitoring studies
Lichen transplants as indicators of gaseous elemental mercury concentrations
Full text linkLichens play an important role in the biogeochemical cycling of mercury (Hg) and are commonly used as indicators of Hg enrichment in remote and anthropogenically impacted environments. To assess their capacity for Hg uptake and accumulation, we determined the concentration of gaseous elemental mercury (GEM) in air and the concentration of total Hg (THg) in transplanted thalli of two lichen species. Lichen transplants and passive air samplers (PASs) were concurrently deployed, side by side, at 10 sites within an abandoned mining area, characterized by large gradients in atmospheric Hg contamination. Highly variable time-weighted GEM concentrations determined by the PASs, ranging from 17 to 4,200 ng/m3, were mirrored by generally high Hg concentrations in transplanted thalli of both Xanthoria parietina (174–8,800 ng/g) and Evernia prunastri (143–5,500 ng/g). Hg concentrations in the two species co-varied linearly indicating about 60% greater Hg accumulation in X. parietina than in E. prunastri. Whereas Hg uptake in the fruticose E. prunastri increased linearly with GEM, a power law equation with a fractional exponent described the uptake in the foliose X. parietina. Extrapolating the relationships observed here to higher GEM levels yielded concentrations in lichen that agree very well with those measured in an earlier fumigation experiment performed under laboratory-controlled conditions. The uptake model of X. parietina was further verified by correctly estimating GEM concentrations from the THg measured in autochthonous thalli collected from the urban area adjacent to the mine site. Passive sampling can effectively provide time-weighted data of suitable spatial resolution to quantitatively describe GEM assimilation by lichens. Therefore, the combined use of passive sampling and lichen transplants can contribute to a more comprehensive understanding of the role of lichens, and potentially also of other cryptogams, in the deposition of atmospheric Hg to terrestrial ecosystems
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