Background element content in the lichen Pseudevernia furfuracea: a comparative analysis of digestion methods.

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.

Estimating atmospheric mercury concentrations with lichens.

The uptake kinetics of elemental gaseous Hg (Hg(0)) in three species of epiphytic lichens (Pseudevernia furfuracea, Evernia prunastri, and Xanthoria parietina) were investigated under four different Hg concentrations (10, 15, 30, and 45 µg/m(3)) and three different temperatures (10, 20, and 30 °C) with the aim of evaluating the lichen efficiency for Hg(0) accumulation and their potential use in the estimate of atmospheric concentrations of this metal in the field. The results showed that under our experimental conditions the lichens accumulated Hg according to exposure time and that the metal is not released back to the atmosphere after Hg(0) was removed from the air (clearance). Pseudevernia furfuracea showed the highest Hg accumulation capacity and Evernia prunastri showed the lowest, but in these species the metal uptake kinetics was affected by temperature. Xanthoria parietina showed an intermediate metal accumulation capacity and a Hg accumulation rate independent of temperature (in the range 10-30 °C). The use of first-order kinetics equations for Hg uptake in X. parietina and available field data on Hg bioaccumulation in this species allowed reliable estimates of atmospheric Hg concentrations in the environment.

Persistent pollutants and the patchiness of urban green areas as drivers of genetic richness in the epiphytic moss Leptodon smithii.

We determined genetic variation and metal and polycyclic aromatic hydrocarbon concentrations in Leptodon smithii moss collected in holm oak stands at cities, outskirts and remote areas of Campania and Tuscany (Italy) to investigate if anthropogenic pressure (pollutant emissions and land use change) affects moss genetic richness. In both regions, metal and polycyclic aromatic hydrocarbon concentrations reflected the trend urban>outskirts>remote areas, excepting Tuscany remote site. In both regions, the moss gene diversity increased from urban to remote areas. The findings suggest the extent and the fragmentation of urban green areas, as drivers of moss genetic richness.

Biotic interactions as a structuring force in soil communities: evidence from the micro-arthropods of an Antarctic moss model system.

Current meta-community theories postulate that the structure of local communities depends on dispersal, environmental filtering, and biotic interactions. However, disentangling the relative effects of these factors in the field and for diverse assemblages is a major challenge. A solution is to address natural but simple communities (i.e. with low numbers of species in few trophic levels), wherein one of these factors is predominant. Here, we analyse the micro-arthropod community of a moss-turf habitat typical of the Antarctic Peninsula region, and test the widely accepted hypothesis that this system is abiotically driven. In the austral summers 2006/7 and 2007/8, we sampled nearly 80 units of moss from four islands in the Argentine Islands. Using variance partitioning, we quantified the relative contribution of: (1) multiple scale spatio-temporal autocorrelation; (2) environmental effects; (3) the island effect. Little variance (1 %) was accounted for by sources 1 (1 %, significant) and 2 (<1 %, not significant). The island effect significantly accounted for the largest amount of variation (8 %). There was a relatively large effect of spatially structured environmental variation (7 %). Null models demonstrated that species co-occurred less frequently than expected by chance, suggesting the prevalence of negative interactions. Our data support the novel hypothesis that negative biotic interactions are the most important structuring force of this micro-arthropod community. The analysed system is a good proxy for more complex communities in terms of taxonomic composition and the functional groups present. Thus, biotic interaction might be a predominant factor in soil meta-community dynamics.

Baseline element composition of foliose and fruticose lichens along the steep climatic gradient of SW Patagonia (Aisén Region, Chile).

Samples of foliose (Nephroma antarcticum) and fruticose (Usnea sp.) lichens were collected across a steep climatic and vegetation gradient in a remote, almost pristine region of SW Chilean Patagonia. Concentrations of major and trace elements in lichens from the rainforest were among the lowest ever reported worldwide for foliose and fruticose lichens and can be considered background levels for the region. The two lichen growth forms showed different elemental compositions mainly due to the greater capacity of foliose thalli to intercept elements from windborne and canopy-leached particles. The patterns of spatial variation in the chemical composition of lichens were effectively explained by statistical methods and reflected the different availability of wet and dry deposition along the steep climatic gradient. Baseline values established for N. antarcticum samples growing in temperate Nothofagus forests were therefore distinct from those of samples growing in more open, drier habitats. The fruticose Usnea sp. showed a higher affinity for atmophile Hg, low concentrations of lithophilic elements, and the same baseline composition whether from temperate forests or from dry, barren environments. The provided background and baseline values against which variations can be measured will be useful in the early detection of local or regional climatic and environmental change, especially in view of the planned construction of hydropower dams under the recently approved HidroAysén Project.

Microplastic Interactions and Possible Combined Biological Effects in Antarctic Marine Ecosystems.

Antarctica and the Southern Ocean are the most remote regions on Earth, and their quite pristine environmental conditions are increasingly threatened by local scientific, tourism and fishing activities and long-range transport of persistent anthropogenic contaminants from lower latitudes. Plastic debris has become one of the most pervasive and ubiquitous synthetic wastes in the global environment, and even at some coastal Antarctic sites it is the most common and enduring evidence of past and recent human activities. Despite the growing scientific interest in the occurrence of microplastics (MPs) in the Antarctic environment, the lack of standardized methodologies for the collection, analysis and assessment of sample contamination in the field and in the lab does not allow us to establish their bioavailability and potential impact. Overall, most of the Southern Ocean appears to be little-affected by plastic contamination, with the exception of some coastal marine ecosystems impacted by wastewater from scientific stations and tourist vessels or by local fishing activities. Microplastics have been detected in sediments, benthic organisms, Antarctic krill and fish, but there is no clear evidence of their transfer to seabirds and marine mammals. Therefore, we suggest directing future research towards standardization of methodologies, focusing attention on nanoplastics (which probably represent the greatest biological risks) and considering the interactions of MPs with macro- and microalgae (especially sea-ice algae) and the formation of epiplastic communities. In coastal ecosystems directly impacted by human activities, the combined exposure to paint chips, metals, persistent organic pollutants (POPs), contaminants of emerging interest (CEI) and pathogenic microorganisms represents a potential danger for marine organisms. Moreover, the Southern Ocean is very sensitive to water acidification and has shown a remarkable decrease in sea-ice formation in recent years. These climate-related stresses could reduce the resilience of Antarctic marine organisms, increasing the impact of anthropogenic contaminants and pathogenic microorganisms.

Selective uptake of major and trace elements in Erica andevalensis, an endemic species to extreme habitats in the Iberian Pyrite Belt.

To assess the ecophysiological traits and the phytoremediation potential of the endemic heather Erica andevalensis, we determined the concentrations of major and trace elements in different plant parts and in rizosphere soils from Riotinto mining district (Huelva, Spain). The results showed that E. andevalensis may grow on substrates with very high As, Cu, Fe and Pb concentrations (up to 4114, 1050, 71900 and 15614 microg/g dry weight, respectively), very low availability of macro- and micronutrients and with pH values ranging from 3.3 to 4.9. In these harsh edaphic conditions E. andevalensis selectively absorbed and translocated essential nutrients and excludes potentially phytotoxic elements, which were accumulated in the root epidermis. The concentrations of major and trace elements in E. andevalensis aerial parts from the Riotinto mining district were in the normal range for plants; likewise other Erica species it accumulated Mn and only in a very polluted site we measured leaf concentrations of As and Pb within the excessive or toxic limits for plants. Differently from previous studies, which emphasized the soil pH and bioavailability of phytotoxic elements as the main stress factors, this study showed that in the Riotinto region, E. andevalensis can tolerate wide range of pH and toxic element concentrations; the harshest environments colonized by monospecific patches of this species were characterized above all by very low availability of nutrients. The extraordinary capability to adapt to these extreme habitats made E. andevalensis a priority species to promote the phytostabilization and the development of a self-sustaining vegetative cover on Riotinto mine tailings.

Organisms in wall ecosystems as biomonitors of metal deposition and bioavailability in urban environments.

Vegetated walls are common structures in urban environments, and aiming to test the hypothesis that the biogenic crusts and plant and animal communities inhabiting these vertical surfaces can be more reliable indicators of atmospheric metal deposition than plants or animals inhabiting urban soils, we analyzed the chemical composition of the wall crusts, moss cushions (Tortula muralis) and the shells, soft tissues and feces of the stonework snail Papillifera papillaris collected in three small towns in Tuscany (Central Italy). Crusts and mosses from the same stones or bricks indicated that Cd, Pb, and Zn are the main pollutants released by vehicular traffic, while Hg and Cu probably originate from other sources. The soft tissues of P. papillaris (purged of the gut contents) showed as well higher Cd, Pb, and Zn and lower Hg concentrations at more traffic-affected sites, while data from shells and feces suggested that this species probably ingests large amounts of Al, Cr, Fe, Mn, and Pb, and avoids eating mosses. Most lithophilic elements and Pb are scarcely absorbed in the snail digestive tract and soft tissues mainly accumulate Cd and essential elements such as Cu and Mn. This study definitively confirms the extraordinary Mn bioaccumulation in P. papillaris soft tissues and reports extraordinary Mn levels also in the shell. The shells also contain unusually high Cu, Fe, and Zn concentrations and this bioaccumulation likely remains after death, potentially providing a historical record of the snail exposure to metals over lifetime.

Background element content of the lichen Pseudevernia furfuracea: A supra-national state of art implemented by novel field data from Italy.

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.

Infraspecific variability in baseline element composition of the epiphytic lichen Pseudevernia furfuracea in remote areas: implications for biomonitoring of air pollution.

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.

Moss and lichen biomonitoring of atmospheric mercury: A review.

Long-range transport and residence time of elemental Hg (Hg°) in air promote global dispersion and deposition in remote ecosystems. Many biotic and abiotic factors contribute to the photoreduction and phytovolatilization of Hg from terrestrial ecosystems, and the assessment of deposition and volatilization fluxes is very challenging. Mosses and lichens are widespread in nature and constitute the dominant vegetation in alpine and polar ecosystems. This review surveys the results of Hg biomonitoring with cryptogams in areas with different Hg sources and deposition processes. Lichen and moss ecophysiology, and factors affecting Hg uptake and bioaccumulation are discussed. Although some laboratory experiments indicate a linear accumulation of Hg in cryptogams exposed to Hg°, without any significant release, in nature the Hg accumulated in cryptogams is in a dynamic equilibrium with Hg in air and decreases when organisms are transplanted to clean environments. Mercury concentrations in mosses and lichens have often been used to estimate concentrations and deposition fluxes of atmospheric Hg; however, Hg° exchanges between cryptogams and air, and the time necessary for mosses and lichens to equilibrate elemental composition with changing atmospheric chemistry, preclude reliable estimates. Biological processes of Hg uptake and exchange with air cannot be reproduced by mechanical collectors, and comparisons between Hg concentrations in biomonitors and those in atmospheric deposition are scarcely reliable. However, the Hg biomonitoring with mosses and lichens is easy and cheap and allows to locate "hot spots" of natural or anthropogenic emissions and to assess spatio-temporal changes in Hg deposition patterns. Climate change is affecting the global Hg cycle through the melting of sea-ice in coastal Polar Regions, and modifying Hg sequestration in mountain ecosystems. Despite limitations, large-scale monitoring of Hg with mosses and lichens may be used as a tool to evaluate the impact of global processes in remote ecosystems.

Organochlorine pollutants in soils and mosses from Victoria Land (Antarctica).

The major organochlorine (OC) pollutants, i.e. pentachlorobenzene (PCBz), hexachlorobenzene (HCB), hexachlorocyclohexanes (HCHs), polychlorobiphenyls (PCBs) and DDTs have been analyzed in soils and mosses from coastal areas of Victoria Land (70-80 degrees S, 160-170 degrees E). PCBs (23-34 ng g(-1) dry wt.) and PCBz (0.38-1.3 ng g(-1) dry wt.) were the dominant OCs in mosses and soils, respectively. In general, the concentrations of OC in soils, i.e. HCB (0.034-0.17 ng g(-1) dry wt.), PCBs (0.36-0.59 ng g(-1) dry wt.) and 4,4'-DDE (0.053-0.086 ng g(-1) dry wt.), range among the lowest reported in remote regions. These concentrations exhibited high correlation coefficients when represented vs. total organic carbon (TOC) which is consistent with the general correlation between OC and TOC in soils from remote areas recently observed (Meijer, S.N., Ockenden, W.A., Seetman, A., Breivik, K., Grimalt, J.O., Jones, K.C., 2003. Global distribution and budget of PCBs and HCB in background surface soils: implications for sources and environmental processes. Environ. Sci. Technol. 37, 667-672). Statistically significant dependences between reciprocal of temperature and log-transformed concentrations of HCB and 4,4'-DDE in mosses and alpha-HCH in soils have been found. These observations provide further data illustrating that temperature is a major factor determining the planetary scale distribution and accumulation of OCs giving additional ground to the general validity of the global distillation effect for description of planetary OC distribution.

Distribution of heavy metals and polycyclic aromatic hydrocarbons in holm oak plant-soil system evaluated along urbanization gradients.

Heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) were analysed in topsoil and in Quercus ilex L. leaves from holm oak woodlands located along urbanization gradients (urban, periurban and extraurban sites) in two Italian regions (Campania and Tuscany). In each sampling site, the metal bioavailability factors (MBFs) and the pollutant bioaccumulation factors (BAFs) were calculated to estimate the fraction of each total metal concentration in soil potentially available to root uptake and to know the fate of both HMs and PAHs in the plant-soil system. In general, the results indicated a low atmospheric deposition of pollutants and, in some cases, leaves and soils accumulated higher HM and PAH concentrations in the most urbanized areas. Correlation analyses showed that in each sampling site topsoil and leaves were exposed to the same atmospheric inputs of HMs and PAHs, although to a different extent. Notwithstanding the MBFs and BAFs differed between the two regions for the most HMs, they did not show a clear pattern in relation to the urbanization gradient. However, some information could be deduced by these ratios: the high BAF calculated for Mn shows that the foliar uptake plays an important role in accumulation of this metal. Moreover, for PAHs the different values of BAFs among low and high molecular weight compounds suggest their different fate, the first accumulated in leaves by stomata and the latter preferentially deposited on topsoil.

Element concentrations in Chianti Classico appellation wines.

The concentrations of 21 elements (Al, B, Ba, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Si, Sr, Ti, V and Zn) were determined in wine samples of the very popular Italian Chianti Classico appellation, vintage 1997. Concentrations of most elements in Chianti Classico wines fell in the range of European red wines. Data variability (expressed as a coefficient of variation, CV) was maximum for elements more prone to exogenous contamination such as Cu (a residue of vineyard treatments; CV = 165), Pb (from atmospheric contamination; CV = 99) or Ni (from wine-making contamination; CV = 78). With respect to the results of a previous survey on 1987 vintage wines (n = 24) from the same appellation, levels of Mn, Cr, Pb and Cd decreased by a factor of 1.65, 1.84, 2.67, and 3.00, respectively. The improved quality and standard of hygiene in wine-making, and the phasing out of leaded gasoline during the last decade are probably responsible for these results. No differences were found for Al, Mg, Fe and Zn. The principal component analysis successfully distinguished Chianti Classico wines from Chianti and Venetian Cabernet Sauvignon, which were analysed for comparison. Seven elements (Al, Mg, Ca, K, Sr, Mn and Si) described a distinctive pattern. The classification success rate was lower for the two Tuscan wines because of similarities in the growing environment and variety composition. However, several elements appear as important chemometric parameters for developing a specific system to protect the designation of origin of Chianti Classico wines.

Holm Oak (Quercus ilex L.) canopy as interceptor of airborne trace elements and their accumulation in the litter and topsoil.

We investigated the role of urban Holm Oak (Quercus ilex L.) trees as an airborne metal accumulators and metals' environmental fate. Analyses confirmed Pb, Cd, Cu and Zn as a main contaminants in Siena's urban environment; only Pb concentrations decreased significantly compared to earlier surveys. Additionally, we determined chemical composition of tree leaves, litter and topsoil (underneath/outside tree crown) in urban and extra-urban oak stands. Most notably, litter in urban samples collected outside the canopy had significantly lower concentrations of organic matter and higher concentrations of Pb, Cu, Cd and Zn than litter collected underneath the canopy. There was a greater metals' accumulation in topsoil, in samples collected under the tree canopy and especially near the trunk ('stemflow area'). Thus, in urban ecosystems the Holm Oak stands likely increase the soil capability to bind metals.

Effects of soil pollutants, biogeochemistry and microbiology on the distribution and composition of enchytraeid communities in urban and suburban holm oak stands.

Holm oaks form typical urban woodlands in the Mediterranean region. We aimed at characterizing the enchytraeid communities in these environments and searching for possible correlations with soil parameters, including the traffic contamination. Samples of litter and topsoil were collected at different spatial scales and seasons in Naples and Siena cities and in two suburban stands. Only the co-variation between pollution and other soil chemico-physical factors showed significant effects, whereas no direct effect of soil microbiology was detected. Some thermophilous Fridericia and Achaeta tolerate high concentrations of heavy metals and PAHs and their abundance was mainly determined by Ca bioavailability. Central-European mesophilous species increased significantly under more temperate environmental conditions. Different combinations of soil cohesiveness, grain size composition and moisture regime seem to select species of certain body sizes.

Spatial patterns and autocorrelation in the response of microarthropods to soil pollutants: the example of oribatid mites in an abandoned mining and smelting area.

Although exogenous factors such as pollutants can act on endogenous drivers (e.g. dispersion) of populations and create spatially autocorrelated distributions, most statistical techniques assume independence of error terms. As there are no studies on metal soil pollutants and microarthropods that explicitly analyse this key issue, we completed a field study of the correlation between Oribatida and metal concentrations in litter, organic matter and soil in an attempt to account for spatial patterns of both metals and mites. The 50-m wide study area had homogenous macroscopic features, steep Pb and Cu gradients and high levels of Zn and Cd. Spatial models failed to detect metal-oribatid relationships because the observed latitudinal and longitudinal gradients in oribatid assemblages were independent of the collinear gradients in the concentration of metals. It is therefore hypothesised that other spatially variable factors (e.g. fungi, reduced macrofauna) affect oribatid assemblages, which may be influenced by metals only indirectly.

Iron demand by thermophilic and mesophilic bacteria isolated from an antarctic geothermal soil.

The thermophilic bacterial strain MP 4 assigned to a new species, likely of the genus Alicyclobacillus, was isolated from geothermal soils on the NW slope of Mount Melbourne, Antarctica. These soils have high iron concentrations and the strain MP 4 requires iron additions for growth. Four mesophilic bacterial strains Paenibacillus validus MP 5, MP 8, and MP 10, and P. apiarius MP 7, isolated from the same site, need iron supply for growth depending on the medium. Growth temperature of thermophilic strain ranges from 42 to 70 degrees C, and that one of mesophiles from 25 to 44 degrees C. Thermophilic and mesophilic strains shared microenvironments with temperature of 42-44 degrees C and showed optima of pH values ranging from 5.5 to 6.0. The thermophilic strain MP 4 reached values of 10(6) CFU ml(-1) in aqueous soil extract from the NW slope of Mt. Melbourne, and 10(5) CFU ml(-1) in water extracts from other geothermal Antarctic areas (Mt. Rittmann and Cryptogam Ridge). Growth of thermophilic bacteria in aqueous extracts of the NW slope of Mount Melbourne soils caused a reduction of 50% of soluble iron content, which was recovered in bacterial biomass. These results suggest a possible involvement of the thermophilic strain MP 4 in iron bioavailability in these geothermal soils.

Enhanced deposition and bioaccumulation of mercury in Antarctic terrestrial ecosystems facing a coastal polynya.

Mercury emitted by anthropogenic and natural sources occurs in the atmosphere mostly in the gaseous elemental form, which has a long lifetime in tropical and temperate regions. Once deposited in terrestrial and aquatic ecosystems the metal is partly re-emitted into the air, thus assuming the characteristics of global pollutants such as persistent volatile chemicals. In polar regions, during and after the sunrise, the photochemically driven oxidation of gaseous Hg by reactive halogens may result in areas of greatly enhanced Hg deposition. Mercury concentrations in soils, lichens, and mosses collected in a stretch between 74 degrees 30' S and 76 degrees 00' S, in ice-free coastal areas of Victoria Land facing the Terra Nova Bay coastal polynya, were higher than typical Antarctic baselines. The finding of enhanced Hg bioaccumulation in Antarctic terrestrial ecosystems facing a coastal polynya strongly supports recent speculations on the role of ice crystals ("frost flowers") growing in polynyas as a dominant source of sea salt aerosols and bromine compounds, which are involved in springtime mercury depletion events (MDEs). These results raise concern aboutthe possible environmental effects of changes in regional climate and sea ice coverage, and on the possible role of Antarctica as a sink in the mercury cycle.