Technical Report

Guidelines for the use of lichens as bioaccumulators

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Abstract

These guidelines are based on the review of best practices and results of recent methodological and applicative studies. The guidelines address the use of epiphytic lichens (bioaccumulation by native lichens and lichen transplants) to monitor spatial and temporal trends of element concentrations (macro-elements and trace elements) related to atmospheric pollutant depositions. In this document, all the phases of a biomonitoring survey are separately addressed. Moreover, a guidance framework and practical details concerning the equipment and protocols for the collection, preparation, exposure and retrieving of lichen samples are made available, along with good practices for the elaboration, expression, and interpretation of results

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... These remote areas are situated about 20 and 16 km away from the survey area, respectively; and they have similar environmental conditions: oak-pine forests, mean annual temperature is 16 °C, annual precipitation is > 1000 mm, and the rainy season occurs from May to October (data from the Servicio Meteorológico Nacional CONAGUA, 2011). According to standard protocols (Giordani et al., 2020;Mikhailova, 2002), the quality of the background areas is related to the occurrence and abundance of poleosensitive lichen taxa which provide evidence that the area is not affected by major contamination phenomena. In our case, the two remote areas are characterized by the presence of nearby oak-pine forest where we found a high abundance and diversity of sensitive and tolerant lichen species. ...
... Thalli of both species were collected from oak trees (Quercus sp.) at about 2 m from the ground, together with their substrate, i.e., twig or bark (Giordani et al., 2020). We only collect lichens from oak trees because they are the most abundant trees species in both remote areas. ...
... Three samples of each species were processed per station, including the two control sites. Each sample was a mixture of several lichen thalli (n = 5) retrieved from each host tree (Giordani et al., 2020). The peripheral parts of thalli of Flavopunctelia praesignis (up 5 mm from lobes tips) were chosen for the analysis according to the protocols generally applied in the field of biomonitoring with foliose lichens (Paoli et al., 2018). ...
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The deposition of trace elements around a pulp and paper industry in Morelia, Mexico, was evaluated using two lichen species as biomonitors. Samples of the foliose lichen Flavopunctelia praesignis and the fruticose lichen Usnea ceratina were collected in two remote areas and transplanted at different distances and directions from the pollution source. Lichen samples were exposed for 4 months (1) around the industrial area and (2) in their native habitats (control sites). We investigated the bioaccumulation of 11 trace elements in lichen thalli, and we compared the response of the two lichen species. To identify possible common sources, we evaluated the relationships between trace elements by correlations and cluster analyses. Our results showed that Cd was a good tracer for air pollution from the pulp and paper mills. In samples of Usnea ceratina exposed around the industrial area, Cd was significantly higher than in the remote area. Within the study area, trace element contents increase with the distance from the source, and they showed high depositions in the direction of prevailing winds. Moreover, we were able to detect groups of elements with similar behavior and common origins. Our results indicated that Flavopunctelia praesignis showed a higher capacity to accumulate trace elements than Usnea ceratina.
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In bioaccumulation studies, the interpretation of pollutant contents in the target biomonitor has to be performed by assessing a deviation from an unaltered reference condition. A common strategy consists in the comparison with background element content (BEC) values, often built up by uncritically merging methodologically heterogeneous data. In this respect, the acid digestion of samples was identified as a major step affecting BEC data. Here, the analytical outcomes of two acid mixtures were compared on a set of matched paired samples of the lichen Pseudevernia furfuracea, a widely used biomonitor for which BEC values based on partial digestion were previously provided. The standard reference material BCR 482 (P. furfuracea) was used to validate analytical procedures consisting of either a HF total mineralization or an aqua regia partial one, both associated to ICP-MS multi-element analysis. In particular, the performance of the procedures was evaluated by comparing analytical results of field samples with the accuracy obtained on BCR aliquots (measured-to-expected percentage ratio). The total digestion showed a better performance for Al, As, Ba, Ca, Cd, Cu, Fe, Mn, Ni, Se, Sn, and Zn, whereas the opposite was found for Cr, Co, P, and S. Moreover, new BEC values were provided for P. furfuracea using a consolidated statistical approach, after a total sample digestion with hydrofluoric acid. The multivariate investigation of the background variability of 43 elements in 57 remote Italian sites led to the identification of geographically homogeneous areas for which BEC values are provided for use as reference in biomonitoring applications.
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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.
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The epiphytic lichen Pseudevernia furfuracea is widely used as biomonitor of airborne trace elements and other contaminants and consists of two taxonomic varieties (var. furfuracea and var. ceratea). Here, we assessed the occurrence of inter-varietal differences in the elemental composition of paired samples of var. furfuracea and var. ceratea collected in 20 remote sites of Italian mountains. The concentration of 40 elements was measured by inductively coupled plasma mass spectroscopy, after digestion with HNO3 and aqua regia. The magnitude of inter-varietal differences compared to the effect of large-scale site-dependent environmental factors (i.e., lithological substrate, host tree species, and altitude) on overall element content was explored by multivariate analysis techniques and tested by generalized linear mixed modeling (GLMM). Further GLMMs were separately fitted for each element testing taxonomic-related variability against uncertainty associated to the analytical procedure. Inter-varietal differences were statistically significant only for Hg and P, with higher content in var. ceratea at most sites, and for Mg and Zn, showing the opposite pattern. Since the elemental composition of P. furfuracea in remote sites was mostly affected by local lithology and climatic conditions, our results confirm that lichen material for active biomonitoring should be collected in a single ecologically homogeneous remote area. We also indicate sites in the Eastern Alps where P. furfuracea showed the minimum content of most elements, which are suggested as locations to collect lichen material for transplants. Besides the context-dependency at large spatial scale, variations of elemental composition apparently related to taxonomy, could possibly be due to unequal incidence of morphological traits of the collected material. Further research is needed to clarify this issue, and how it affects bioaccumulation phenomena.
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Repeated ecological assessments based on permanent plot data require sufficient data quality to detect a signal of change against a background of noise (sampling error of various kinds). We analyzed several components of error in the time-constrained method for sampling lichen communities used by the Forest Health Monitoring program: between-crew (Technicians), crew-to-expert, between-expert, and seasonal variation. Data were from the southeastern United States and Oregon. Two types of dependent variables were used: species richness and scores on lichen community gradients (responses to climatic and air quality gradients). Gradient scores were repeatable to within 2-10% for experts and technicians alike and did not differ between those groups. Species richness is much more difficult to estimate reliably. Despite relatively low species capture by technicians, the high repeatability in gradient scores demonstrates the statistical redundancy in information provided by various lichen species. These results simply that repeated assessments of species richness will contain considerable observer error, but that shifts in community composition may nevertheless be detected reliably.
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The results of a transplant experiment with the fruticose lichen Evernia prunastri aimed at monitoring the trends of trace elements deposition in a repeated biomonitoring study are reported. Data comparability between the two surveys and interpretation of the results were addressed in this study. The ratio between the concentration of each element after the exposure and in control samples prior to exposure (exposed-to-control ratio, EC ratio), as well as an appropriate interpretative scale, were adopted as a means of determining the temporal trends of element accumulation by lichen transplants. The results showed that the method adopted is indeed a reliable tool, pinpointing a Zn smelting plant and an oil refinery as principal pollution sources in the area, which indicate that elements associated with the former were similarly accumulated in both 2002 and 2003, while elements associated with the latter tended to decrease in 2003.
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Traditional peat sample preparation methods such as drying at high temperatures and milling may be unsuitable for Hg concentration determination in peats due to the possible presence of volatile Hg species, which could be lost during drying. Here, the effects of sample preparation and natural variation on measured Hg concentrations are investigated. Slight increases in mercury concentrations were observed in samples dried at room temperature and at 30 degrees C (6.7 and 2.48 ng kg(-1) h(-1), respectively), and slight decreases were observed in samples dried at 60, 90 and 105 degrees C (2.36, 3.12 and 8.52 ng kg(-1) h(-1), respectively). Fertilising the peat slightly increased Hg loss (3.08 ng kg(-1) h(-1) in NPK-fertilised peat compared to 0.28 ng kg(-1) h(-1) in unfertilised peat, when averaged over all temperatures used). Homogenising samples by grinding in a machine also caused a loss of Hg. A comparison of two Hg profiles from an Arctic peat core, measured in frozen samples and in air-dried samples, revealed that no Hg losses occurred upon air-drying. A comparison of Hg concentrations in several plant species that make up peat, showed that some species (Pinus mugo, Sphagnum recurvum and Pseudevernia furfuracea) are particularly efficient Hg retainers. The disproportionally high Hg concentrations in these species can cause considerable variation in Hg concentrations within a peat slice. The variation of water content (1.6% throughout 17-cm core, 0.97% in a 10 x 10 cm slice), bulk density (40% throughout 17-cm core, 15.6% in a 10 x 10 cm slice) and Hg concentration (20% in a 10 x 10 cm slice) in ombrotrophic peat were quantified in order to determine their relative importance as sources of analytical error. Experiments were carried out to determine a suitable peat analysis program using the Leco AMA 254, capable of determining mercury concentrations in solid samples. Finally, an analytical protocol for the determination of Hg concentrations in solid peat samples is proposed. This method allows correction for variation in factors such as vegetation type, bulk density, water content and Hg concentration in individual peat slices. Several subsamples from each peat slice are air dried, combined and measured for Hg using the AMA254, using a program of 30 s (drying), 125 s (decomposition) and 45 s (waiting). Bulk density and water content measurements are performed on every slice using separate subsamples.
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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.
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In the assessment of atmospheric deposition using lichen transplants, coping with uncertainty is mandatory in cases of environmental forensics, when understanding whether an area is polluted or not, or tracing a given pollution source is of paramount importance. In this article, we have suggested a method based on the calculation of exposed-to-control ratios of element concentrations and on the quantification of the overall uncertainty associated with such calculation, which proved to be very robust and can be applied in most cases using a minimum of three replicates. The method allowed the selection of significantly accumulated elements i.e. those polluting the site under study, as well as the evaluation of whether a site is significantly polluted or not. We recommend the use of this evaluation method in biomonitoring studies based on transplanted samples.
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In biomonitoring, the knowledge of background element content (BEC) values is an essential pre-requisite for the correct assessment of pollution levels. Here, we estimated the BEC values of a highly performing biomonitor, the epiphytic lichen Pseudevernia furfuracea, by means of a careful review of literature data, integrated by an extensive field survey. Methodologically homogeneous element content datasets, reflecting different exposure conditions across European and extra-European countries, were compiled and comparatively analysed. Element content in samples collected in remote areas was compared to that of potentially enriched samples, testing differences between medians for 25 elements. This analysis confirmed that the former samples were substantially unaffected by anthropogenic contributions, and their metrics were therefore proposed as a first overview at supra-national background level. We also showed that bioaccumulation studies suffer a huge methodological variability. Limited to original field data, we investigated the background variability of 43 elements in 62 remote Italian sites, characterized in GIS environment for anthropization, land use, climate and lithology at different scale resolution. The relationships between selected environmental descriptors and BEC were tested using Principal Component Regression (PCR) modelling. Elemental composition resulted significantly dependent on land use, climate and lithology. In the case of lithogenic elements, regression models correctly reproduced the lichen content throughout the country at randomly selected sites. Further descriptors should be identified only for As, Co, and V. Through a multivariate approach we also identified three geographically homogeneous macro-regions for which specific BECs were provided for use as reference in biomonitoring applications.
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Multi-matrix environmental monitoring was used to evaluate the influence of a municipal solid waste landfill (Ginestreto, Emilia Romagna, Italy) on the level and distribution of heavy elements in the surrounding environment (air, soil and soil biota). Concentrations of As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, Tl and Zn were measured by inductively coupled plasma-mass spectrometry in transplanted lichens, topsoils and isopods. The highest accumulation levels found for Cd, Cr, Pb, Sb and Zn in lichens transplanted within the Ginestreto landfill. However, similar concentrations of these heavy elements were also found in lichens exposed in monitoring sites influenced by other man-made sources, such as vehicle traffic and truck movements. The fallout of heavy elements emitted by the landfill had low impact on their levels in topsoil: Cd, Cr, Pb, Sb and Zn showed higher contents in topsoil collected close to the landfill and a slight decrease in concentrations with increasing distance from the landfill. There was no variation in heavy element accumulation in isopods in relation to distance from the landfill. The results of this study indicate that the Ginestreto municipal solid waste landfill had limited impact on the environmental distribution of heavy elements, since accumulation and enrichment in lichens and topsoils were only detected close to the landfill, up to about 100 m from its border.
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Trace elements in epiphytic lichens are determined by ICP-MS after solubilization of the material in a microwave oven. Three different acid mixtures were tested, but only HF acid ensures complete recovery of many elements present at very low concentrations. The accuracy and precision of the method were evaluated by analyzing BCR CRM 482, "Trace Elements in Lichen," and by comparing the results with those obtained for real samples using different analytical techniques. The use of a pneumatic and ultrasonic nebulizer with ICP-MS was evaluated and the results are discussed. The method detection limits for the standard configuration using ICP-MS with the pneumatic nebulizer were generally better than 0.2 μ/g, making the method suitable for analytical requirements.
Chapter
Human activities release large amounts of exchangeable elements into the environment and have become a major factor in altering biogeochemical cycles. This alteration is progressively affecting the long-established steady equilibrium between the Earth’s processes and biological evolution [50]. Increasing body burdens of potentially toxic elements in organisms, even from remote regions of the Northern Hemisphere far from significant sources of local pollution, have underlined the importance of establishing reliable monitoring systems at different scales. A reliable appraisal of pollutant concentrations in such an extremely variable compartment as the atmosphere needs a statistical approach based on a large number of samples in both time and space (see chapter 9, this volume). The high costs of establishing and managing automatic monitoring networks often limit the number of sampling stations and/or the number of pollutants considered. Thus, although very reliable, data from instrumental recording may be statistically weak and their integration with diffusion models cannot give reliable information about the deposition and impact of atmospheric pollutants on terrestrial ecosystems.
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The development of soredia strongly affects both the CO2 exchange and water balance of Parmeiia caperata. Sorediate thallus portions have a lower content of total chlorophyll, a lower net assimilation rate and a lower respiration rate than fastgrowing, non-sorediate lobes. Our results suggest that the net assimilation rates should be expressed on a chlorophyll basis rather than on a dry weight basis. The chlorophyll content of the samples used in experiments should be always reported.
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There are three general characteristics of the data to be collected in a monitoring program that should be met in order to maximize the use and value of the data: the data quality should be known, the data type and quality should be consistent and comparable, and the data should be available and accessible. Potential problems with each of these characteristics are addressed effectively by quality assurance and quality control. One of the most important aspects of quality assurance in a monitoring program is the development of a quality assurance plan, which should identify clearly the quality of the data needed and describe in detail the planned actions to provide confidence that the program will meet its stated objectives. Quality control data, which allow for the quality and suitability of the environmental data to be evaluated and ascertained, should be collected and utilized as an integral part of the QA effort associated with a monitoring program.
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: Lichen-forming ascomycetes and their green algal photobionts completely die off within approximately 3 years of storage at room temperature. Macroscopically this is recognizable as a colour change, the green shades of the chlorophylls being lost. In fluorescent light microscopy preparations an increase in fungal autofluorescence and a significant decrease in chlorophyll autofluorescence in the Trebouxia cells was observed. In transmission electron microscopy preparations of Xanthoria parietina and its green algal photobiont, Trebouxia arboricola, the fungal membrane systems were found to be largely broken down whereas the shrivelled algal protoplast failed to rehydrate after storage at room temperature. When stored in the desiccated state at - 20 °C, both partners of the symbiosis stayed fully viable for up to 13 years, their colouration and chlorophyll fluorescence being unchanged. Viability was measured as ascospore ejection and germination rates in Xanthoria parietina, soredium germination rates in Xanthoria fallax, Hypogymnia physodes and Parmelia sulcata, and autospore formation rate in Trebouxia cells (green algal photobiont), which had been isolated from the thalli after rehydration. Thallus fragments of Xanthoria parietina were shown to grow normally after one week of storage in LN2 without any cryoprotectant. In the desiccated state deep-frozen samples can be repeatedly brought to room temperature and back to - 20 °C without any loss of viability. Cryopreservation is therefore a suitable mode of long-term storage of viable lichen thalli for experimental studies or transplant experiments.
Article
A lichen research material, prepared from the species Evernia prunastri, was produced by a co-operation between the International Atomic Energy Agency (IAEA) and the Instituto de Ciencias e Engenharia Nucleares (INETI) in Sacavém, Portugal. An international intercomparison study was carried out, with 42 independent sets of results being reported from participants in 26 countries. The statistical evaluation of the collected data resulted in recommended values for 17 elements and information values for 15 elements. The criteria for assigning the values are provided, including the use of information obtained through the parallel analysis of a second material, IAEA-359, Cabbage.
Article
The saxicolous foliose lichen Pseudoparmelia baltimorensis (Gyelnik) Hale from a site in Maryland heavily polluted by atmospheric lead accumulates about half of its lead burden in newly formed thallus tissues in the first growing season. Two- and three-year-old tissues contain the highest lead concentrations, suggesting that an equilibrium with the atmospheric lead input is reached very rapidly.
Chapter
Chlorophyll fluorescence (CF) is the absorption of blue or red photons (= excitation) by chlorophyll molecules and the emission of far red photons (the energy difference is lost as heat). In contrast to chloroform solutions of chlorophyll or to fluorescent dyes, the emission from active photosynthetic systems does not remain constant, but changes in a complicated way after a constant excitation light is switched on. These changes (= variable fluorescence) are due to the onset of photosynthetic reactions that consume absorbed quanta. Accordingly, several derived fluorescence parameters (see below) provide diagnostic information about the state of the photosynthetic apparatus.
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Two-dimensional ordinary block kriging as an optimal interpolation technique was applied to produce regular grids of predicted estimates of copper, lead, and mercury contents in surface soil in the Shenzhen area for mapping purposes. The kriging analysis was based on theoretical variograms calculated from measured data of eighty three top soil samples. The appropriateness of the whole procedure of kriging analysis was evaluated by both cross-validation and kriging standard deviation mapping. The similarity in area variation between the distribution of soil parent material and the mapped results of copper and lead is demonstrated. The possible influence of agricultural contamination on the spatial distribution pattern of mercurcy is also discussed.
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Aspects of sampling and sample handling in the context of large-scale plant biomonitoring surveys of trace element air pollution are addressed. Topics such as survey goals and planning, choice of elements, biomonitor species (lichens, mosses, bark), interspecies calibration, SO2 effects, local variation, comparability of results, sample homogeneity, the problem of soil-derived elements, and elemental analysis are discussed. The paper stresses the need for stringent accuracy control, indicates the importance of local variation in the concept of the survey, and underlines the relevance of multi-elemental analysis. Furthermore, factor analysis is indicated as a powerful mathematical tool in dealing with the presence of both soil particle contamination and soil-derived absorbed elements.
Article
In the process of instrumental element analysis of plant samples, cleaning, drying and homogenization of the collected material are steps that constitute a very great potential source of error. One of the reasons for this is the difficulty of standardizing the procedure. A major obstacle to consistent quality control is the multitude of different plant species and their division into leaves, shoots and roots. The resulting morphological and physiological heterogeneity of the samples makes it necessary to plan and carry out each of these analytical steps in a highly specific manner according to the individual plant species. The extraordinary diversity of the sample material makes it impossible to establish a generally valid method. This paper describes and discusses various approaches to cleaning, drying and grinding such samples.
Article
In the absence of a standard wet preparation method for the determination of inorganic elements in peat, four acid digestion methods (nitric acid (HNO3), HNO3/hydrochloric acid (HCl), aqua regia and HNO3/hydrofluoric acid (HF)) were compared using a Canadian fen peat (OGS 1878 P-6), previously proposed as a reference material, and inductively coupled plasma-optical emission spectrometry (ICP-OES) as the instrumental analytical technique. Two microwave-assisted methods, HNO3 and HNO3/HF, representing ‘acid-extractable’ and total digestion, respectively, were then selected for optimisation and application to a newly developed ombrotrophic peat reference material (NIMT/UOE/FM/001) and to the individual sections of a 43 cm peat core, also from Flanders Moss, Scotland, for a range of elements, including Al, Co, Cr, Cu, Fe, Mn, P, Pb, S, Ti, V and Zn. While the results suggested the general efficacy of HNO3 in investigations of the greatly elevated levels of trace elements, such as Cu, Pb and Zn, resulting from the severe anthropogenic contamination of the environment during the industrial era, the need for addition of HF for the determination of major lithogenic elements, such as Al and Ti, present in aluminosilicates and other resistant minerals, and some trace elements (Co, Cr and V) was clearly demonstrated. The inclusion of HF in a total digestion method, such as HNO3/HF, is, therefore, necessary when normalisation of trace element concentrations to those of a conservative lithogenic reference element, such as Ti, is performed for the purpose of determining elemental enrichment factors. For elements other than Hg, the dry ashing of peat samples at 450 °C prior to acid digestion is recommended for the destruction of the predominantly organic matrix, especially relevant where inductively coupled plasma-mass spectrometry (e.g. quadrupole inductively coupled plasma-mass spectrometry (ICP-MS)) is to be used in the determination of the much lower concentrations of trace elements prevalent in pre-industrial and ancient times.
Article
Lichens are currently used as bioindicators to monitor air pollution and to follow changes in pollution patterns. In order to perform reliable biomonitoring, these analyses should give accurate results, which implies that a good quality control system should be applied. One way to achieve accuracy is to use certified reference materials (CRMs). In order to produce a lichen CRM, the BCR-programme (now renamed Standards, Measurements and Testing programme) of the European Commission has conducted a certification campaign involving expert laboratories. A lichen material has been collected on pine trees, oven-dried, homogenised and bottled, and its homogeneity and long-term stability verified. The material (CRM 482) was analysed by a group of 11 selected laboratories using different analytical methods. This paper describes the certification work performed to certify the elements Al, As, Cd, Cr, Cu, Hg, Ni, Pb and Zn. Indicative values are given for Ba, Br, Ca, Co, Fe, K, Mn, Mo, P, S, Sb, Se, Sn and V.
Article
This paper describes an assessment of environmental exposure to fluorine in the surroundings of an aluminium smelter, carried out by measuring fluorine concentrations in the tissues of mosses growing in the area. Forty-two samples were collected from within a 3300 m of radius of the smelter on two different occasions. Samples of either Hypnum cupressiforme Hedw. or Scleropodium purum (Hedw.) Limpr. were collected at each point, depending on which was the most abundant. The fluorine contents in the samples varied from <10 μg g−1 F (the limit of quantification of the analytical technique used) to 154 μg g−1 F. To analyse the spatial pattern of fluorine accumulation in the mosses, response surfaces were adjusted to the data using the geographic coordinates of the sampling points as independent variables. Details are given of the process used to select the best surface from among the many candidates available. The graphical and mathematical analyses of the surfaces allowed description of the effect of the distance from the smelter on fluorine concentration and of the spatial anisotropy, i.e. the existence of directions along which fluorine deposition is enhanced. Fluorine concentration decreased exponentially over all the study area, therefore the impact of the smelter decreased greatly within a short distance. The surfaces also allowed detection of differences between sampling times, in terms of the prevailing direction of pollutant movement, as well as differences in the rates of decrease in concentration with distance from the plant. Finally, it is discussed how the particular characteristics of the source of the pollutant affect its dispersal, and how some sampling difficulties encountered affected the results obtained.
Article
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.
Article
Rapid Biodiversity Assessments (RBAs) of lichen communities, obtained by means of simplified sampling lists based on morphospecies, showed good correlations with Lichen Diversity Values (LDVs), based on the complete identification of lichen species only when performed by operators with high levels of taxonomic knowledge. Furthermore, the use of highly simplified sampling lists did not lead to significant advantages in terms of time needed for field operations. This approach proved to be especially unreliable in high diversity ecological contexts where variation of morpho-structural composition within lichen communities is frequent (i.e. co-occurring crustose- and foliose-dominated communities); it may also lead to weak results if applied for conservation purposes. Hence, the use of simplified RBA sampling lists in lichen monitoring has to be carefully evaluated and, in any case, should be based on sound taxonomic knowledge on the part of those in charge of data collection. The proper assessment of descriptors of lichen abundance and/or frequency, however, strictly depends on the skill, taxonomic knowledge, and willingness to learn of the lichenologist-in-training.
Article
The concentrations of 16 metals were measured in peripheral and central parts of the foliose epiphytic lichens Parmelia caperata and Xanthoria parietina collected in north-east Italy. Relevant intra- and interspecific variability was shown by multivariate analysis (classification and ordination) of the matrix of metals and samples. The central, older parts of the thalli contained significantly higher amounts of most metals in both species. Significative differences were also found between peripheral parts of the two species, with higher concentrations of Fe and Al in Xanthoria, and Cd and Zn in Parmelia. An inter-species comparison of several hundred Italian measurements confirmed the higher affinity of Parmelia for Cd and Zn, but not that of Xanthoria for Fe and Al. In order to enhance data quality in biomonitoring studies, it is suggested to analyse only peripheral parts of the lichens, and to avoid the joint use of Parmelia and Xanthoria when monitoring Cd and Zn.
Article
A total of 65 operators involved in lichen mapping studies in central and northwestern Italy underwent quality control tests during five lichen biomonitoring workshops organized between 1999 and 2000. The results showed that 75% quantitative accuracy and 90% quantitative precision can be regarded as satisfactory levels for lichen biodiversity data; 65% proved to be sufficient for accuracy of taxonomic identification in the field. Average correct assignment of the interpretative naturality/alteration class was only 48.7%. The results indicated the need for taxonomic training.
Article
This paper presents the results of a bioaccumulation study of trace elements in the Naples urban area based on the use of the moss Sphagnum capillifolium (Ehrh.) Hedw. and the lichen Pseudevernia furfuracea (L.) Zopf exposed in bags in 23 sites. Moss and lichen bags were exposed for 4 months starting from the beginning of July 1999. Bags gathering was carried out after 10 weeks of exposure, at the end of the dry season, and after 17 weeks, during the wet season. The elements Al, As, Ca, Cd, Cr, Co, Cu, Fe, K, Mg, Mn, Mo, Ni, Pb, Ti, V and Zn were analysed by inductively coupled plasma-mass spectrometry ICP-MS in both biomonitors. For the majority of the elements the total amounts found in S. capillifolium were higher than in P. furfuracea whether considering the whole period of exposure or the weekly uptake. It was observed that there was a much greater difference in metal accumulation by P. furfuracea between the dry and wet seasons compared with S. capillifolium. In the wet period, the lichen seems to accumulate a larger quantity of metals. With the exception of Mn, trace element concentrations did not appear to be significantly affected by the washing away of rainfall. K loss during exposure suggested cell membrane damage in both organisms. For P. furfuracea the K leakage was limited to the dry period of exposure. A clear distinction between "lithophilic" and "anthropogenic" elements was achieved by cluster analysis. Significant correlations were found among Fe-Cu-Cr-Ni, Pb-Cd-Co, V-Cr-Ni, Zn-Ni-Pb, suggesting a common source for each group of elements.
Article
In this paper we discuss some difficulties associated with the process of constructing maps of pollution from data obtained in surveys covering extensive areas. As we show here, these problems may be wide-ranging but are seldom recognized by investigators. The origin of the problems is the existence of multiple sources of pollution in the study area, each of different intensity and affecting areas of different extent. The particular spatial structure of the pollution sources interacts with the spatial layout of the samples, resulting in data sets with distributions that are very different from the usually assumed normal distribution, and characterized by heavy tails and gross outliers. These distributions arise because of incomplete sampling of small-scale pollution processes (i.e. those occurring on a spatial scale smaller than the spatial scale of the sampling grid). After discussion of the potential problems and appropriate techniques for analyzing this kind of data, we applied the proposed techniques to a real data set of heavy metal contents in terrestrial mosses. From the exercise we concluded that a) the first step in analysis of this kind of data must be to check for the presence of spatial structure on scales larger than the sampling grid, to avoid mapping noise, and b) the map generated must not contain information about pollution sources with a spatial scale smaller than the spatial scale of the sampling grid. We present and discuss the performance of robust statistical methods of testing for spatial structure (based on robust variograms and randomization testing) and of filtering the small-scale spatial processes (using median-polishing) prior to mapping.
Article
The results of long-term biomonitoring of nine elements (Cd, Cr, Ni, Pb, V, Cu, Zn, Fe and Al) with the epiphytic lichen Xanthoria parietina over a seven year time span are reported. A total of 51 sampling stations were monitored in two surveys, obtaining information about heavy metal concentrations in a large area characterized by a high impact of industrial and urban sources of air pollution. The results showed that the approach adopted is indeed a reliable tool to assess environmental alteration, pinpointing not only the trends of the nine elements analysed but also their reciprocal correlations. As a consequence it was possible to characterize changes in air pollution composition and the common origin and behavior of several groups of elements.
Discriminating between the good and the bad: quality assurance is central in biomonitoring studies
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The Lichens of Italy. A Second Annotated Catalogue. EUT, Trieste, 739 pp. Nimis PL, Martellos S (2017) ITALIC -The Information System on Italian Lichens. Version 5.0
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Microwave assisted acid digestion of siliceous and organically based matrices
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Guidance for Quality Assurance Project Plans. EPA QA/G-5, Environmental Protection Agency
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