Influence of temporal variations in water chemistry on the Pb isotopic composition of rainbow trout (Oncorhynchus mykiss)

Field and laboratory investigations were undertaken to determine (1) the relations between discharge, Pb concentration, and the Pb isotopic composition of the dissolved load in Richland Creek, western North Carolina, and (2) the potential influence of varying Pb water chemistry on the Pb isotopic abundances in liver and bone tissues of rainbow trout (Oncorhynchus mykiss). Stream waters were characterized by relatively low Pb concentrations during periods of base flow exceeding 10 days in length. Moreover, greater than 65% of the Pb was derived from orchard soils located upstream of the monitoring site which are contaminated by lead arsenate. During small to moderate floods, the dissolved load exhibited Pb concentrations more than twice as high as those measured during base flow, but the contribution of Pb from lead arsenate was relatively low and varied directly with discharge. In contrast to smaller events, Pb from lead arsenate in an 8- to 10-year (overbank) event in May 2003 was minimal during peak flow conditions, suggesting that discharge-source relations are dependent on flood magnitude. The hydrologic and geochemical data demonstrate that aquatic biota in Richland Creek are subjected to short-term variations in Pb concentrations and Pb isotopic abundances within the dissolved load ranging from a few hours to few a weeks. Laboratory studies demonstrated that when rainbow trout were exposed to elevated Pb concentrations with a distinct isotopic fingerprint, the bone and liver rapidly acquire isotopic ratios similar to that of the water. Following exposure, bone retains Pb from the contaminant source for a period of months, while the liver excreted approximately 50% of the accumulated Pb within a few days and nearly all of the Pb within a few weeks. Differences in the rates of excretion resulted in contrasting isotopic ratios between the tissues. It seems plausible, then, that previously observed differences between the isotopic composition of bone and liver in rainbow trout from Richland Creek are related to their short-term exposure to Pb from soils contaminated with Pb arsenate that result from fluctuating hydrologic conditions. If these trends prove to be common in other contaminated aquatic environments, it may be possible to use the Pb isotopic composition of bone as an indicator of the long-term exposure to Pb and the liver as a biomarker for short-term Pb exposures.     

REE characteristics and Pb, Sr and Nd isotopic compositions of steel plant emissions

A comprehensive Pb-Sr-Nd isotope and REE tracer study of atmospheric trace metal pollution by a steel plant situated to the north of the urban communities of Strasbourg (France) and Kehl (Germany) has been performed using tree barks as biomonitors. The 206Pb/207Pb and 208Pb/207Pb isotopic ratios of the steel plant's filter dust are similar to values found in dust of waste incinerators. The 87Sr/86Sr ratio is similar to present-day ratios of Phanerozoic or Precambrian granitic rocks. The 143Nd/144Nd isotopic composition is very low and corresponds to an (Nd) value of -17.5. Such a low value is characteristic of old Precambrian granitic rocks and banded iron formations. Thus, this low (Nd) value might point to the origin of the iron necessary for the steel production. The fact, that this isotopic composition does not occur in crustal rocks of Western Central Europe makes the Nd isotope ratio a powerful tool to trace steel plants atmospheric emissions. The rare earth element (REE) distribution pattern of the steel plant's filter dust shows very specific fractionations like La and Nd enrichments which are traceable in tree barks over a distance of 4 km. The Pb, Sr and Nd isotope ratios not only enable the steel plant's emissions to be traced in a north-easterly direction, along the principal wind pathway but also enables the interference of this emission at 4 km NE from the steel plant with another atmospheric component originating from the Strasbourg Rhine harbour to be identified.     

The isotopic record of atmospheric lead fall-out on an Icelandic salt marsh since AD 50

We report a record of atmospheric Pb deposition at a coastal site in western Iceland that spans the last two millennia. The elemental concentrations of Pb, Al, Li and Ti are determined using ICP-MS from a sediment monolith collected from a salt marsh. Multicollector (MC) ICP-MS analysis is used to obtain isotopic ratios of stable Pb. The Pb/Ti and Pb/Li ratios are used to separate natural Pb background concentrations from Pb derived from remote anthropogenic sources. The pollution record in western Iceland is subdued in comparison with Pb records from the European mainland, but the isotopic character, profile and timing of Pb deposition show good agreement with the atmospheric Pb fall-out reported from sites in Scandinavia and northwestern Europe. At the bottom of the sequence we isolate a low-level (0.1-0.4 mg kg^− 1) Pb enrichment signal dated to AD 50-150. The isotopic signature and timing of this signal suggest Roman metal working industries as the source. In the subsequent millennium there was no significant or very low (i.e. elemental concentrations < 0.01 mg kg^− 1) anthropogenic Pb deposition at the site up to, and including, the early Medieval period. Above a pumice layer, dated to AD 1226-1227, a small increase in Pb deposition is found. This trend is maintained until a more substantive and progressive increase is signalled during the late 1700s and early 1800s. This is followed by a substantial enrichment signal in the sediments (> 3.0 mg kg^− 1) that is interpreted as derived from industrial coal burning and metal working during the 19th and 20th centuries in northern Europe. During the late 20th century, significant fall-out from European fuel additives reached Iceland.     

Pb and stable lead content in fungi: Its transfer from soil

The uptake and transfer of natural radionuclides, other than ⁴⁰K, from soil to mushrooms has been somewhat overlooked in the literature. Their contribution to the dose due to the consumption of mushrooms was considered negligible. But the contribution of ²¹⁰Pb in areas unaffected by any recent radioactive fallout has been found to be significant, up to 35% of the annual dose commitment in Spain. More than 30 species of mushrooms were analyzed, and the ²¹⁰Pb detected was in the range of 0.75-202 Bq/kg d.w. A slight difference was observed between species with different nutritional mechanisms (saprophytes ≥ mycorrhizae). The ²¹⁰Pb content was correlated with the stable lead content, but not with its predecessor in the uranium radioactive series, ²²⁶Ra. This suggested that ²¹⁰Pb was taken up from the soil by the same pathway as stable lead. The bioavailability of ²¹⁰Pb in soil was determined by means of a sequential extraction procedure (NH₄OAc, 1M HCl, 6M HCl, and residue). About 30% of the ²¹⁰Pb present in the soil was available for transfer to mushrooms, more than other natural radionuclides in the same ecosystem. Lycoperdon perlatum, Hebeloma cylindrosporum, and Amanita curtipes presented the highest values of the available transfer factor, ATF. As reflected in their ATF values, the transfer from soil to mushroom of some natural and anthropogenic radionuclides was in the following order:

^228,230,232Th ≈ ⁴⁰K ≥ ¹³⁷Cs ≥ ^234,238U ≈ ²²⁶Ra ≥ ⁹⁰Sr ≥ ²¹⁰Pb ≈ ^239 + 240Pu ≈ ²⁴¹Am.     

Intrinsic biodegradation potential of aromatic hydrocarbons in an alluvial aquifer--potentials and limits of signature metabolite analysis and two stable isotope-based techniques

Three independent techniques were used to assess the biodegradation of monoaromatic hydrocarbons and low-molecular weight polyaromatic hydrocarbons in the alluvial aquifer at the site of a former cokery (Flémalle, Belgium).Firstly, a stable carbon isotope-based field method allowed quantifying biodegradation of monoaromatic compounds in situ and confirmed the degradation of naphthalene. No evidence could be deduced from stable isotope shifts for the intrinsic biodegradation of larger molecules such as methylnaphthalenes or acenaphthene. Secondly, using signature metabolite analysis, various intermediates of the anaerobic degradation of (poly-) aromatic and heterocyclic compounds were identified. The discovery of a novel metabolite of acenaphthene in groundwater samples permitted deeper insights into the anaerobic biodegradation of almost persistent environmental contaminants. A third method, microcosm incubations with ¹³C-labeled compounds under in situ-like conditions, complemented techniques one and two by providing quantitative information on contaminant biodegradation independent of molecule size and sorption properties. Thanks to stable isotope labels, the sensitivity of this method was much higher compared to classical microcosm studies. The ¹³C-microcosm approach allowed the determination of first-order rate constants for ¹³C-labeled benzene, naphthalene, or acenaphthene even in cases when degradation activities were only small. The plausibility of the third method was checked by comparing ¹³C-microcosm-derived rates to field-derived rates of the first approach. Further advantage of the use of ¹³C-labels in microcosms is that novel metabolites can be linked more easily to specific mother compounds even in complex systems. This was achieved using alluvial sediments where ¹³C-acenaphthyl methylsuccinate was identified as transformation product of the anaerobic degradation of acenaphthene.     

A lead isotopic study of the human bioaccessibility of lead in urban soils from Glasgow, Scotland

The human bioaccessibility of lead (Pb) in Pb-contaminated soils from the Glasgow area was determined by the Unified Bioaccessibility Research Group of Europe (BARGE) Method (UBM), an in vitro physiologically based extraction scheme that mimics the chemical environment of the human gastrointestinal system and contains both stomach and intestine compartments. For 27 soils ranging in total Pb concentration from 126 to 2160 mg kg^− 1 (median 539 mg kg^− 1), bioaccessibility as determined by the ‘stomach’ simulation (pH ~ 1.5) was 46-1580 mg kg^− 1, equivalent to 23-77% (mean 52%) of soil total Pb concentration. The corresponding bioaccessibility data for the ‘stomach + intestine’ simulation (pH ~ 6.3) were 6-623 mg kg^− 1 and 2-42% (mean 22%) of soil Pb concentration. The soil ²⁰⁶Pb/²⁰⁷Pb ratios ranged from 1.057 to 1.175. Three-isotope plots of ²⁰⁸Pb/²⁰⁶Pb against ²⁰⁶Pb/²⁰⁷Pb demonstrated that ²⁰⁶Pb/²⁰⁷Pb ratios were intermediate between values for source end-member extremes of imported Australian Pb ore (1.04) - used in the manufacture of alkyl Pb compounds (1.06-1.10) formerly added to petrol - and indigenous Pb ores/coal (1.17-1.19). The ²⁰⁶Pb/²⁰⁷Pb ratios of the UBM ‘stomach’ extracts were similar (< 0.01 difference) to those of the soil for 26 of the 27 samples (r = 0.993, p < 0.001) and lower in 24 of them. A slight preference for lower ²⁰⁶Pb/²⁰⁷Pb ratio was discernible in the UBM. However, the source of Pb appeared to be less important in determining the extent of UBM-bioaccessible Pb than the overall soil total Pb concentration and the soil phases with which the Pb was associated. The significant phases identified in a subset of samples were carbonates, manganese oxides, iron-aluminium oxyhydroxides and clays.     

A comparison of the isotopic composition of lead in rainwater, surface vegetation and tree bark at the long-term monitoring site, Glensaugh, Scotland, in 2007

The lead concentrations and isotopic ratios (²⁰⁶Pb/²⁰⁷Pb, ²⁰⁸Pb/²⁰⁶Pb, ²⁰⁸Pb/²⁰⁷Pb) of 31 rainwater (September 2006-December 2007) and 11 surface vegetation (moss, lichen, heather) samples (October 2007) from the rural upland catchment of Glensaugh in northeast Scotland and of nine bark samples (October 2007) from trees, predominantly Scots pine, in or near Glensaugh were determined. The mean ²⁰⁶Pb/²⁰⁷Pb ratios for rainwater in 2006 and 2007 were similar to those previously determined for 2000 to 2003 at Glensaugh, yielding an average mean annual value of 1.151 ± 0.005 (± 1 SD) for the period from 2000, when an outright ban on leaded petrol came into force in the UK, to 2007. The mean ²⁰⁶Pb/²⁰⁷Pb ratio (1.146 ± 0.004; n = 7) for surface vegetation near the top (430-450 m) of the catchment was not significantly different (Student's t test) from that of rainwater (1.148 ± 0.017; n = 24) collected over the 12-month period prior to vegetation sampling, but both were significantly different, at the 0.1% (i.e. p < 0.001) and 1% (p < 0.01) level, respectively, from the corresponding mean value (1.134 ± 0.006; n = 9) for the outermost layer of tree bark. When considered in conjunction with similar direct evidence for 2002 and indirect evidence (e.g. grass, atmospheric particulates, dated peat) for recent decades in the Glensaugh area, these findings confirm that the lead isotopic composition of surface vegetation, including that of suitably located moss, reflects that of the atmosphere while that of the outermost layer of Scots pine bark is affected by non-contemporaneous lead. The nature and relative extent of the different contributory sources of lead to the current UK atmosphere in the era of unleaded petrol, however, are presently not well characterised on the basis of lead isotopic measurements.     

Childhood lead exposure and uptake in teeth in the Cleveland area during the era of leaded gasoline

Childhood uptake of lead from exposure to atmospheric leaded gasoline in the United States has been studied using mainly blood lead levels. Since reliable blood lead techniques were used only after the peak use of leaded gasoline, the prior exposure history is unclear. The well-documented decline in blood lead levels after the mid-1970s could represent the continuation of a historic steady decline in exposure from many sources. Alternatively, the post-1970s decline might represent the declining phase of a unimodal rise and fall corresponding closely to usage of leaded gasoline. To assess these possibilities, lead concentration and 207Pb/206Pb isotope ratios were measured in the enamel of permanent molar teeth formed between 1936 and 1993 in mainly African-American donors who grew up in the Cleveland area. Tooth enamel preserves the lead concentration and isotope ratio that prevails during tooth formation. Historical trends in enamel lead concentration were significantly correlated with surrogates of atmospheric lead exposure: lead in sediments of two dated Lake Erie cores, and lead consumed in gasoline. About two-thirds of the total lead uptake into enamel in this period was attributable to leaded gasoline, and the remainder to other sources (e.g. paint). Enamel 207Pb/206Pb isotope ratios were similar to those of one lake sediment. Multivariate analysis revealed significant correlation in neighborhoods with higher levels of traffic, and including lake sediment data, accounted for 53% of the variation in enamel lead levels. Enamel lead concentration was highly correlated with reported African-American childhood blood levels. The extrapolated peak level of 48 μg/dL (range 40 to 63) is associated with clinical and behavioral impairments, which may have implications for adults who were children during the peak gasoline lead exposure. In sum, leaded gasoline emission was the predominant source of lead exposure of African-American Cleveland children during the latter two-thirds of the 20th century.     

Decomposition of belowground litter and metal dynamics in salt marshes (Tagus Estuary, Portugal)

The concentrations of C, Fe, Mn, Zn, Cu, Pb and Cd were determined monthly in decomposing roots of Halimione portulacoides, using litterbag experiments, in two salt marshes of the Tagus estuary with different levels of contamination. Although carbon concentrations varied within a narrow interval during the experiment, litter decomposed rapidly in the first month (weight loss between 0.051 and 0.065 g d(-1)). The time variation of metals was examined in terms of Me/C ratios and metal stocks. Ratios of Fe/C and Mn/C and their metal stocks increased in spring, presumably due to the precipitation of oxides in the surface of decomposing roots. Subsequent decrease of Fe/C and Mn/C ratios suggests the use of Fe and Mn oxides, as electron acceptors, in the organic matter oxidation. Zinc, Cu, Pb and Cd ratios to C were, in general, higher than at initial conditions implying that metal that leached out was slower than carbon. However, metal stocks decreased during the experiment indicating that incorporation or sorption of metals in Fe and Mn oxides did not counterbalance the amount of Zn, Pb and Cd released from decomposing litter. An exception was observed for Cu, since stock in the less contaminated marsh (Pancas) increased during the decomposition, indicating that litter was efficient on Cu binding under more oxidising conditions. These results emphasize the importance of litter decomposition and sediment characteristics on metal cycling in salt marshes.     

Lead isotopes reveal different sources of lead in balsamic and other vinegars

Fifty-eight brands of balsamic vinegars were analyzed for lead concentrations and isotopic compositions (²⁰⁴Pb, ²⁰⁶Pb, ²⁰⁷Pb, and ²⁰⁸Pb) to test the findings of a previous study indicating relatively high levels of lead contamination in some of those vinegars — more than two thirds (70%) of them exceeded California's State Maximum Level (34 μg/L) based on consumption rates ≥ 0.5 μg Pb per day. The Lead isotopic fingerprints of all those vinegars with high lead concentrations were then found to be primarily anthropogenic. This isotopic analysis unquestionably reveals multiple contamination sources including atmospheric pollutant Pb and an unidentified contamination source, likely occurring after grape harvest. Organically grown grape vinegars display the same Pb content and isotopic signatures as other vinegars. This implies that pesticides might not be a significant source of pollutant Pb in vinegars. A significant post-harvest contamination would be inherited from chemicals added during production and/or material used during transport, processing or storage of these vinegars. This is consistent with the highest Pb levels being found in aged vinegars (112 ± 112 μg/L) in contrast to other vinegars (41.6 ± 28.9 μg/L) suggesting contamination during storage. It is, therefore, projected that lead levels in most vinegars, especially aged balsamic and wine vinegars, will decrease with improvements in their manufacture and storage processes consequential to recent concerns of elevated levels of lead in some vinegars.     

Present limitations and future prospects of stable isotope methods for nitrate source identification in surface- and groundwater

Nitrate (NO₃⁻) contamination of surface- and groundwater is an environmental problem in many regions of the world with intensive agriculture and high population densities. Knowledge of the sources of NO₃⁻ contamination in water is important for better management of water quality. Stable nitrogen (δ¹⁵N) and oxygen (δ¹⁸O) isotope data of NO₃⁻ have been frequently used to identify NO₃⁻ sources in water. This review summarizes typical δ¹⁵N- and δ¹⁸O-NO₃⁻ ranges of known NO₃⁻ sources, interprets constraints and future outlooks to quantify NO₃⁻ sources, and describes three analytical techniques (“ion-exchange method”, “bacterial denitrification method”, and “cadmium reduction method”) for δ¹⁵N- and δ¹⁸O-NO₃⁻ determination. Isotopic data can provide evidence for the presence of dominant NO₃⁻ sources. However, quantification, including uncertainty assessment, is lacking when multiple NO₃⁻ sources are present. Moreover, fractionation processes are often ignored, but may largely constrain the accuracy of NO₃⁻ source identification. These problems can be overcome if (1) NO₃⁻ isotopic data are combined with co-migrating discriminators of NO₃⁻ sources (e.g. ¹¹B), which are not affected by transformation processes, (2) contributions of different NO₃⁻ sources can be quantified via linear mixing models (e.g. SIAR), and (3) precise, accurate and high throughput isotope analytical techniques become available.     

Carbon and nitrogen stable isotopes and metal concentration in food webs from a mining-impacted coastal lagoon

Two food webs from the Mar Menor coastal lagoon, differing in the distance from the desert-stream through which mining wastes were discharged, were examined by reference to essential (Zn and Cu) and non-essential (Pb and Cd) metal concentrations and stable isotopes content (C and N). The partial extraction technique applied, which reflects the availability of metals to organisms after sediment ingestion, showed higher bioavailable metal concentrations in sediments from the station influenced by the mining discharges, in agreement with the higher metal concentrations observed in organisms, which in many cases exceeded the regulatory limits established in Spanish legislation concerning seafood. Spatial differences in essential metal concentrations in the fauna suggest that several organisms are exposed to metal levels above their regulation capacity. Differences in isotopic composition were found between both food webs, the wadi-influenced station showing higher delta(15)N values and lower delta(13)C levels, due to the discharge of urban waste waters and by the entrance of freshwater and allochthonous marsh plants. The linear-regressions between trophic levels (as indicated by delta(15)N) and the metal content indicated that biomagnification does not occur. In the case of invertebrates, since the "handle strategy" of the species and the physiological requirements of the organisms, among other factors, determine the final concentration of a specific element, no clear relationships between trophic level and the metal content are to be expected. For their part, fish communities did not show clear patterns in the case of any of the analyzed metals, probably because most fish species have similar metal requirements, and because biological factors also intervened. Finally, since the study deals with metals, assumptions concerning trophic transfer factors calculation may not be suitable since the metal burden originates not only from the prey but also from adsorption over the body surfaces and seawater ingestion.     

Distribution of trace elements in organs of six species of cetaceans from the Ligurian Sea (Mediterranean), and the relationship with stable carbon and nitrogen ratios

Mercury (total and organic), cadmium, lead, copper, iron, manganese, selenium and zinc concentrations were measured in different organs of 6 different cetacean species stranded in an area of extraordinary ecological interest (Cetaceans' Sanctuary of the Mediterranean Sea) along the coast of the Ligurian Sea (North-West Mediterranean). Stable-isotopes ratios of carbon ((13)C/(12)C) and nitrogen ((15)N/(14)N) were also measured in the muscle. A significant relationship exists between (15)N/(14)N, mercury concentration and the trophic level. The distribution of essential and non-essential trace elements was studied on several organs, and a significant relationship between selenium and mercury, with a molar ratio close to 1, was found in the cetaceans' kidney, liver and spleen, regardless of their species. High selenium concentrations are generally associated with a low organic to total mercury ratio. While narrow ranges of concentrations were observed for essential elements in most organs, mercury and selenium concentrations are characterised by a wide range of variation. Bio-accumulation and bio-amplification processes in cetaceans can be better understood by comparing trace element concentrations with the stable-isotopes data.     

Assessing the effects of the Prestige oil spill on the European shag (Phalacrocorax aristotelis): trace elements and stable isotopes

The Prestige oil spill resulted in the mortality of several seabird species on the Atlantic NW coast of Spain. Shag casualties were particularly relevant, since populations are resident in the area the whole year round and because of several features which make them highly vulnerable to environmental hazards. Ecological catastrophes give us the opportunity of collecting samples which, otherwise, would be difficult to obtain. We examine the potential of shag corpses as bioindicators of inorganic pollution and the possible factors of variability, such as biological traits (sex, age) or nutrition status. We determined trace elements (Hg, Se, Cr, Pb, Zn and Cu) and isotopic signatures (¹⁵N, ¹³C) in soft tissues (muscle, liver) and in primary feathers formed at different times (before and after the Prestige) in individuals of known sex and age, collected at the time of the Prestige disaster. These were compared with data from another group of shags trapped accidentally in fishing gear in 2005.Our results did not seem to be affected by sex or age on any of the analysed variables. The higher nitrogen isotopic signatures in the soft tissues of the Prestige shags may be related to the nutrition stress caused by a poorer body condition, which is also reflected in increasing levels of some metals in the liver. This isotopic enrichment was also observed in newly forming feathers when compared to the old ones. On the other hand, the lower δ¹⁵N and Hg values in shag feathers from 2005 point to a shift in feeding resources to prey of lower trophic levels. We found that feather features (being an inert tissue and having a conservative composition), if combined with careful dating and chemical analysis, offer a very useful tool to evaluate temporal and spatial changes in seabird ecology in relation to pollution events.     

Temporal trends of pollution Pb and other metals in east-central Baffin Island inferred from lake sediment geochemistry

Concentrations and stable isotope ratios of lead (Pb) from lake sediments were used to quantify temporal patterns of anthropogenic Pb pollution in the Clyde River region of Baffin Island, Arctic Canada. Surface sediments from eight lakes on eastern Baffin Island and one from northern-most Greenland, spanning a gradient of 20° latitude, showed great variability with respect to Pb concentration and stable isotopic Pb ratios, with little apparent latitudinal trend. To constrain the temporal evolution of regional Pb pollution, a well-dated core from one of the sites, Lake CF8 on east-central Baffin Island, was analyzed geochemically at high stratigraphic resolution. A pronounced decrease in the ²⁰⁶Pb/²⁰⁷Pb ratio occurs in sediments deposited between 1923 and the mid-1970s, likely reflecting alkyl-Pb additives derived from the combustion of fossil fuels at a global scale. A two-component mixing model indicates that 17-26% of the Pb in the labile fraction of sediments deposited in Lake CF8 between 2001 and 2005 is from anthropogenic input. A Pb-Pb co-isotopic plot (²⁰⁶Pb/²⁰⁷Pb vs.²⁰⁸Pb/²⁰⁶Pb ratios) of the Lake CF8 time series data indicates multiple possible sources of industrial Pb pollution. Despite widespread reductions in industrial Pb emissions since the 1970s, there is no evidence for attendant reductions of pollution Pb at Lake CF8. Enhanced scavenging from increased primary production as well as changing precipitation rates as climate warms may represent important factors that modulate Pb deposition to Lake CF8, and Arctic lakes elsewhere.     

Anthropogenic impacts in North Poland over the last 1300 years — A record of Pb, Zn, Cu, Ni and S in an ombrotrophic peat bog

Lead pollution history over Northern Poland was reconstructed for the last ca. 1300 years using the elemental and Pb isotope geochemistry of a dated Polish peat bog. The data show that Polish Pb-Zn ores and coal were the main sources of Pb, other heavy metals and S over Northern Poland up until the industrial revolution. After review of the potential mobility of each element, most of the historical interpretation was based on Pb and Pb isotopes, the other chemical elements (Zn, Cu, Ni, S) being considered secondary indicators of pollution. During the last century, leaded gasoline also contributed to anthropogenic Pb pollution over Poland. Coal and Pb-Zn ores, however, remained important sources of pollution in Eastern European countries during the last 50 years, as demonstrated by a high ²⁰⁶Pb/²⁰⁷Pb ratio (1.153) relative to that of Western Europe (ca. 1.10). The Pb data for the last century were also in good agreement with modelled Pb inventories over Poland and the Baltic region.     

An isotopic investigation of mercury accumulation in terrestrial food webs adjacent to an Arctic seabird colony

At Cape Vera (Devon Island, Nunavut, Canada), a seabird colony of northern fulmars (Fulmarus glacialis) congregates and releases nutrients through the deposition of guano to the coastal terrestrial environment, thus creating nutrient-fertilized habitats important to insects, birds, and mammals. Here we determined whether mercury was similarly enriched in various terrestrial food web components in this High Arctic coastal ecosystem due to seabird inputs. Stable isotopes (δ¹⁵N, δ¹³C) were used to identify trophic linkages and possible routes of contaminant transfer in the food web. Values of δ¹⁵N were significantly higher in lichens and certain plants collected closer to the bird colony, demonstrating a gradient of seabird influence, and were higher at Cape Vera than our reference site at Cape Herschel, on eastern Ellesmere Island, an area relatively unaffected by seabirds. In contrast, δ¹³C showed little variation among terrestrial species, suggesting minimal influence by seabirds. Concentrations of total mercury (THg) in primary producers and phyto/zooplankton were not significantly correlated with distance from the seabird colony or δ¹⁵N values, and were similar to other taxa from the High Arctic. Our results provide novel data on THg in several Arctic taxa where concentrations have not been reported previously. Moreover, the analyses indicate that δ¹⁵N is significantly enriched in the adjacent environment by guano fertilization, but our study was unable to show an enrichment of THg and δ¹³C in the terrestrial food web near the seabird colony.     

Uptake of Pb and Cu by novel biopolymers

A series of different functionalized biopolymers were prepared and their comparative efficiencies for removing lead (II) and copper (II) ions from water at part per million concentrations determined. The biopolymers evaluated included cellulose, alginic acid, chitin, chitosan and carrageenan. Besides the base biopolymers, the carboxymethyl and hydroxamic acid derivatives of these materials were prepared and tested as well. Terephthalic acid and its hydroxamic acid derivative and a state of the art ion exchange resin, Chelex 20™ (Bio-Rad), were also tested as controls. It was found that, generally, the hydroxamic acid derivatives were the most efficient at removing both metals at a number of different starting ion concentrations although no one material was found to be the best under all experimental circumstances.     

Traffic pollution affects tree-ring width and isotopic composition of Pinus pinea

This study presents new evidence that radiocarbon, combined with dendrochronological and stable isotopes analysis in tree rings and needles, can help to better understand the influence of pollution on trees. Pinus pinea individuals, adjacent to main roads in the urban area of Caserta (South Italy) and exposed to large amounts of traffic exhaust since 1980, were sampled and the time-related trend in the growth residuals was estimated. We found a consistent decrease in the ring width starting from 1980, with a slight increase in δ¹³C value, which was considered to be a consequence of environmental stress. No clear pattern was identified in δ¹⁵N, while an increasing effect of the fossil fuel dilution on the atmospheric bomb-enriched ¹⁴C background was detected in tree rings, possibly as a consequence of the increase in traffic exhausts. Our findings suggested that radiocarbon is a very sensitive tool to investigate small-scale (i.e. traffic exhaust at the level crossing) and large-scale (urban area pollution) induced disturbances.     

Changes in mercury and cadmium concentrations and the feeding behaviour of beluga (Delphinapterus leucas) near Somerset Island, Canada, during the 20th century

Beluga (Delphinapterus leucas) continues to be an important food species for Arctic communities, despite concerns about its high mercury (Hg) content. We investigated whether Hg and cadmium (Cd) concentrations had changed during the 20th century in beluga near Somerset Island in the central Canadian Arctic, using well-preserved teeth collected from historical sites (dating to the late 19th century and 1926-1947) and during subsistence hunts in the late 1990s. Mercury concentrations in both historical and modern teeth were correlated with animal age, but 1990s beluga exhibited a significantly more rapid accumulation with age than late 19th century animals, indicating that Hg concentrations or bioavailability in their food chain had increased during the last century. The geometric mean tooth Hg concentration in modern 30 year old animals was 7.7 times higher than in the late 19th century, which corresponds to threefold higher concentrations in muktuk and muscle. Teeth from 1926 to 1947 were similar in Hg content to the late 19th century, suggesting that the increase had occurred sometime after the 1940s. In contrast, tooth Cd was not correlated with animal age and decreased during the last 100 years, indicating that anthropogenic Cd was negligible in this population. Late 19th century beluga displayed a greater range of prey selection (tooth delta15N values: 15.6-20.5 per thousand) than modern animals (delta15N: 17.2-21.1 per thousand). To prevent this difference from confounding the temporal Hg comparison, the Hg-age relationships discussed above were based on historical animals, which overlapped isotopically with the modern group. Tooth delta13C also changed to isotopically more depleted values in modern animals, with the most likely explanation being a significant shift to more pelagic-based feeding. Industrial Hg pollution is a plausible explanation for the recent Hg increase. However, without further investigation of the relationship between the range exploitation of modern beluga and their possible exposure to regional marine food chains with (naturally) higher Hg contents than their historical counterparts, we cannot unequivocally conclude that the increase was anthropogenically driven.