Dendrochemical Analysis Research Articles

Dendrochemical Analysis as a Method to Identify Mineralized Zones: Insights from the Marathon Cu-PGE Deposit

The Marathon Cu-platinum-group element (PGE) deposit is located within the Eastern Gabbro Series of the Proterozoic Coldwell Alkalic Complex, 10 km north of Marathon, Ontario. The Cu-PGE mineralization occurs within the Two Duck Lake Gabbro, an olivine gabbro intrusion. This geochemical orientation study tested the trace element analysis of tree cores as a method of identifying mineralized versus background areas in the Marathon deposit, focusing on copper (Cu), sulfur (S), palladium (Pd), and silver (Ag). Tree core samples (n=25) were collected with an increment borer from black spruce (Picea mariana) trees and dated by counting growth rings. Fifteen cores, 12 near/overtop the deposit and three distal control samples, were analysed with Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) over a 10-year interval (1992-2002). Data normalization to 88Sr like in other dendrochemical studies corrected for tree health and growth effects. 32S, 63Cu, and 105Pd were found to have the highest concentrations at 94.198, 2.224, and 0.055 ppm, respectively, in control sample 23KPA2-3004. This tree is located beside the Pic River and receives large amounts of run-off from the entire Eastern Gabbro Series, possibly enhancing the chemical composition of the tree core. Excluding this anomalous sample, significant concentrations of Cu and Ag were found moving SSW along the deposit, aligning with the direction of movement of the Pleistocene Laurentide Ice Sheet. While this study did not clearly identify mineralized zones in the Marathon deposit, it has identified the possibility of mineralized run-off in the Pic River affecting nearshore tree chemical composition. The influence of local terrain and glacial till must be also considered when using this method. Future research will continue to study the factors influencing the uptake of elements in trees and refine methods for detecting mineralization through tree core analysis.

Tree-rings analysis to reconstruct atmospheric mercury contamination at a historical mining site.

Mercury (Hg) is a global environmental concern due to its toxicity (especially high in methylated form) and the long-range distribution of its gaseous elemental form (GEM). Hg-contaminated areas, such as abandoned mining sites, pose intrinsic difficulties for their management and heavy monitoring costs. In these environments, plant-based solutions may play a key role in the ecosystem quality assessment and support remediation strategies, combining reliability and cost-effectiveness. In this study, we adopted a biomonitoring approach by using tree rings of four different species collected in the proximity of the mining-metallurgical area of Abbadia San Salvatore, central Italy, a major former Hg mining district whose reclamation is currently in progress. Our dendrochemical analysis was aimed at identifying the historical changes of local atmospheric Hg contamination and at singling out, for the first time in the study area, other potentially toxic elements (PTEs) associated with the past mining activity. Collected cores dated back to early as 1940 and provided the temporal patterns of atmospheric Hg emission vs the produced liquid quantities, so reconstructing the historical impact of the mining site on nearby terrestrial ecosystems and resident human population. Current GEM contamination was found about twenty times lower than that of the fully operational mine periods. From a first survey on other PTEs, thallium (Tl) and lead (Pb) appeared to be potentially associated with the mining activity, thus suggesting new working assumptions for further dendrochemical analyses and for the inclusion of Pb in human biomonitoring surveys of the Mt. Amiata area, actually not present in the control list. The results prompt a more thorough assessment by tracking for a longer time span a critical site that is an ideal open-field lab to study the ecophysiology of different tree species in relation to environmental behavior of PTEs for better-assessing wildlife and human exposures.

Challenges in the Application of Dendrochemistry in Research on Historical Environmental Pollution in an Old Copper Mining Area

This research investigates the long-term environmental impact and historical temporal pollution patterns caused by a former copper mine in Iwiny (south-western Poland) using a dendrochemical approach. An additional aspect of this research was considering the possibility of using the inductively coupled plasma-optical emission spectrometry (ICP-OES) measurement technique as a cheaper alternative to inductively coupled plasma mass spectrometry (ICP-MS) in dendrochemical analyses conducted in copper mining areas. In the study area, a tailings storage facility (TSF) dam failure (1967) took place and the alkaline flotation waste containing high concentration of Cu and Pb are stored. Tree cores from pedunculate oak (Quercus robur L.) were analysed for the content of 11 trace elements (TEs) (Cd, Mn, Ni, Zn, Cr, Co, Pb, Cu, Fe, Al, Ag) using the ICP-OES technique, while tree rings’ widths (TRWs) were also measured. Samples that were most significant in the context of the research goals were verified with the ICP-MS method. The results revealed the strong long-term impact of the copper industry as reflected in a substantial increase in the mean contents of: (1) Mn, Ni, Zn, Cr, Pb, Cu and Fe in industrial vs. control trees, (2) TRWs for control vs. industrial trees. However, the observed patterns of TEs and TRWs did not correspond to the known timing of pollution inputs (mining activity, tailings spill). Peak levels were observed for Zn and Fe after the mine was closed. The lack of new sources of pollution and the temporal relationship strongly suggests that the tree rings recorded the chemical signal of the TSF reclamation (the use of fertilizers and agrotechnical interventions). Patterns of 7 elements were detected in most of the samples by ICP-OES (Co and Cd were not detected, Al and Ag were partly detected), while ICP-MS detected all of the elements. Significant differences were obtained for Ag, Cd, and Co. Despite challenges with the application of dendrochemistry in research on old mining areas (e.g., lack of old trees), it has proved to be a useful tool for investigating the aggregate environmental impact.

Chemical Signals in Tree Rings from Northern Patagonia as Indicators of Calbuco Volcano Eruptions since the 16th Century

The Calbuco volcano ranks third in the specific risk classification of volcanoes in Chile and has a detailed eruption record since 1853. During 2015, Calbuco had a sub-Plinian eruption with negative impacts in Chile and Argentina, highlighting the need to determine the long-term history of its activity at a high-resolution time scale to obtain a better understanding of its eruptive frequency. We developed a continuous eruptive record of Calbuco for the 1514–2016 period by dendrochemical analysis of Fitzroya cupressoides tree rings at a biennium resolution using inductively coupled plasma–mass spectrometry. After comparing the chemical record of 20 elements contained in tree rings with historical eruptions, one group exhibited positive anomalies during (Pb/Sn) and immediately after (Mo/P/Zn/Cu) eruptions, with a Volcanic Explosivity Index (VEI) ≥ 3, and so were classified as chemical tracers of past eruptions (TPE). The tree-ring width chronology also exhibited significant decreases in tree growth associated with eruptions of VEI ≥ 3. According to these records, we identified 11 new eruptive events of Calbuco, extending its eruptive chronology back to the 16th century and determining a mean eruptive frequency of ~23 years. Our results show the potential to use dendrochemical analysis to infer past volcanic eruptions in Northern Patagonia. This information provides a long-term perspective for assessing eruptive history in Northern Patagonia, with implications for territorial planning.

Spatial-temporal variability of metal pollution across an industrial district, evidencing the environmental inequality in São Paulo

Although air pollution decreased in some cities that shifted from an industrial to a service-based economy, and vehicular emission regulation became more restrictive, it is still a major risk factor for mortality worldwide. In central São Paulo, Brazil, air quality monitoring stations and tree-ring analyses revealed a decreasing trend in the concentrations of particulate matter and metals. Such trends, however, may not be observed in industrial districts located in the urban periphery, where the usual mobile sources may be combined with local stationary sources. To evaluate environmental pollution in an industrial district in southeastern São Paulo, we assessed its spatial variability, by measuring magnetic properties and concentrations of Al, Ba, Ca, Cl, Cu, Fe, K, Mg, Mn, P, S, Sr, Zn in the bark of 62 trees, and its temporal trends, by measuring Cd, Cu, Ni, Pb, V, Zn in tree rings of three trees. Source apportionment analysis based on tree barks revealed two clusters with high concentrations of metals, one related to vehicular and industrial emissions (Al, Ba, Cu, Fe, Zn) in the east side of the industrial cluster, and the other related to soil resuspension (Cu, Zn, Mn) in its west side. These patterns are also supported by the magnetic properties of bark associated with iron oxides and titanium-iron alloy concentrations. Dendrochemical analyses revealed that only the concentrations of Pb consistently decreased over the last four decades. The concentrations of Cd, Cu, Ni, V, and Zn did not significantly decrease over time, in contrast with their negative trends previously reported in central São Paulo. This combined biomonitoring approach revealed spatial clusters of metal concentration in the vicinity of this industrial cluster and showed that the local population has not benefited from the decreasing polluting metal concentrations in the last decades.

Testing the applicability of dendrochemistry using X-ray fluorescence to trace environmental contamination at a glassworks site

The potential of dendrochemistry as a tool for tracing anthropogenic contamination at a glassworks site in southeastern Sweden was investigated through a multidisciplinary approach combining continuous high-resolution time series of tree rings and sediment profiles. Tree cores from Scots pine (Pinus sylvestris), Norway spruce (Picea abies) and European aspen (Populus tremula) were analysed for their elemental composition using an energy dispersive X-ray fluorescence (ED-XRF) technique. Sediment cores were sampled along a transect extending from the pollution point source to unpolluted areas and analysed using core-scanning-XRF (CS-XRF). High contaminant concentrations in the soil were found for As (≈2000 ppm), Pb (>5000 ppm), Ba (≈1000 ppm) and Cd (≈150 ppm). The concentrations decreased with depth and distance from the pollution source. The dendrochemical analyses revealed alterations in the Barium, Chlorine and Manganese profiles, allowing the identification of seven potential asynchronous releases from the glassworks. Our results suggest that differences in the response of tree species to elemental uptake together with soil chemical properties dictate the success of dendrochemistry as an environmental monitoring tool.

Dendrochronology in mineral exploration: developing tools to see through anthropogenic impacts

The Sudbury Igneous Complex (SIC) and its associated mining camp is one of the largest Cu, Ni, PGE ore systems in the world. Due to a long history of mining (>100 years), the SIC has been extensively explored making the discovery of new surface deposits difficult. This study explored the use of dendrochemical analysis as an economic means to locate deposits concealed by overburden. Tree cores combined with soil samples were collected and analyzed from two sites to provide a comparison between a known deposit (Broken Hammer) and a known contamination location (downwind site). Samples were collected from both White Pine (Pinus Strobus) and Scots Pine (Pinus Sylvestris) species, however White Pine proved to have a stronger affinity for the uptake of ore-associated metals (i.e., Cu, Ni, Fe, Co, Hg, Cd, Pb, Sb, S). Analyses of tree-core intervals revealed clear anthropogenic effects in the samples from both sites; however, due to the age of the trees the magnitude of these effects compared to pre-mining conditions could not be determined. The concentrations of S, Cu, Ni, Fe, Al, Pb and As in the downwind samples increased over time. On average, S increased from 6.37 to 8.98 ppm, Cu from 0.503 to 0.908 ppm, Ni from 0.605 to 1.18 ppm, Fe from 124 to 273 ppm, Al from 4.38 to 6.60 ppm and As from 0.008 to 0.012 ppm. Conversely, the concentrations of Cu, Fe, Ni, Al, S and As in the samples from Broken Hammer decreased over time. Copper decreased from 0.84 to 0.55 ppm, Fe from 2.45 to 1.19 ppm, Ni from 1.02 to 1.18 ppm, Al from 6.81 to 4.96 ppm, S from 7.62 to 7.57 ppm and As from 0.014 to 0.002 ppm. The total Pb concentration decreased over time in all samples from both sites. There were no trends in the Pb isotopic ratios with the exception of the 207 Pb/ 206 Pb. A comparison of the samples from each location revealed unique trends in the distribution of the data, which could suggest two sources. Soil (Ah and B horizon) collected proximal to the sampled trees near Broken Hammer showed the metal concentration increasing with depth. Copper averaged 33.6 – 187.9 ppm, whereas Ni had an even steeper trend, increasing from an average of 22.4 ppm–234.5. Sulphur and Hg also displayed a similar trend, however the difference was not as substantial. The highs and lows in concentration levels in the tree cores correspond to various historical events. During WWII (1939 – 1945), the Korean War (1950 – 1953) and the Vietnam war (1964 – 1973), the demand for Ni increased resulting in increased smelting activities and a spike in contamination levels. Conversely, the recession in the late 1970s early 1980s and the INCO strike in the late 1990s resulted in a decrease in Ni production and a drop in contamination levels. The distribution of metal concentrations at Broken Hammer indicates a lack of surface contamination and therefore a non-contaminated B-horizon. The higher concentrations in the B-horizon are anomalous to other studies in the Sudbury area suggesting a possible subsurface source. This is encouraging and the potential remains to develop a method for mineral exploration applications utilizing tree core samples, even in heavily mining impacted areas like the Sudbury.

Dendrochemical evidence for soil recovery from acidic deposition in forests of the northeastern U.S. with comparisons to the southeastern U.S. and Russia

A soil resampling approach has detected an early stage of recovery in the cation chemistry of spruce forest soil due to reductions in acid deposition. That approach is limited by the lack of soil data and archived soil samples prior to major increases in acid deposition during the latter half of the 20th century. An alternative approach is the dendrochemical analysis of dated wood to detect temporal changes in base cations back into the 19th century. To infer environmental change from dendrochemical patterns of essential base cations, internal factors that affect cation chemistry such as the maturation of sapwood and the spread of wood infection need to be recognized. Potassium concentration was a useful marker of these internal maturation and infection that could affect the concentration of essential base cations in wood. Dendrochemical patterns in samples of red spruce in the eastern United States and Norway spruce in northwestern Russia were used to determine how internal changes in base cations can be separated from external changes in root-zone soil to date major changes in the availability of essential base cations associated with a changing environment.

CHEMICAL ELEMENTS AND HEAVY METALS IN EUROPEAN LARCH TREE RINGS FROM REMOTE AND POLLUTED SITES IN THE EUROPEAN ALPS

LEONELLI G., BATTIPAGLIA G., CHERUBINI P., MORRA DI CELLA U. & PELFINI M., Chemical elements and heavy metals in European larch tree rings from remote and polluted sites in the European Alps. (IT ISSN 0391-9838, 2011). Air pollution dispersal in the European Alps has been studied both for glacial and forest environments. In this study, chemical elements and heavy metals in the tree rings were analyzed for seven sites of European larch (Larix decidua Mill.) in the Italian European Alps. At three sites in the proximities of the Mont Blanc Tunnel (MBT) entrance the analyses were performed at the yearly scale on the periods 1950-1970 (comprising the MBT opening in 1965) and 1985-2008 (comprising the 3-yr MBT clo- sure after the 1999 car accident) with the aim to check if trees recorded at the yearly scale variations in chemical elements and changes in heavy metals concentrations over time. At the regional scale, the analyses on heavy metals were conducted without annual resolution for most sites on the common periods 1950-1970 / 1985-1998 with the aim to detect possi- ble ongoing trends and differences between some Alpine sites. Chemical elements concentrations at Entreves (EN) sites varied significantly be- tween heartwood and sapwood with generally higher concentrations in sapwood. At EN sites no clear patterns were found for heavy metals be- fore and after the MBT opening and during its 3-yr closure. We found that the high site (ENH) was generally less polluted than the (ENC) and the far (ENF) sites. At site ENC we found higher values of Cr, Ni and Cu, whereas at site ENF we found higher values for all the other elements analyzed. The analysis of heavy metals at the regional scale revealed generally no significant temporal changes in concentrations except for Cr and Cu, showing higher values in the recent period. On comparing the heavy metals concentration between the seven sites, the Palud site showed almost always the highest concentrations, except for Ni and Cu that were higher in two remote sites close to glacial environ- ments in the Gressoney and Valtellina valleys. Dendrochemical analysis revealed that the temporal information in the tree rings is covered by too many signals and no environmental changes are recorded at the yearly scale by European larch. However tree rings may provide useful informa- tion on ongoing long-term trends and on the spatial definition of pollu- tant dispersal in the Alpine environment.

Reconstructing contamination events on riverbanks in southern Québec using dendrochronology and dendrochemical methods

The riverbanks of the Saint-François and Massawippi Rivers are affected by hydrocarbons and heavy metals to varying degrees. The events associated with this riverbank contamination are not documented in the government reports or archives, which is why dendrochemical methods are useful for dating such pollution events. Samples of alluvial soils and trees were taken from the banks of the Saint-François River in Windsor and Richmond as well as the Massawippi River, where the level of hydrocarbon (C 10–C 50) contamination in the banks is low to moderate (300–700 mg/kg of dry soil). Core samples were taken from seven red ash ( Fraxinus pennsylvanica Marsh.) and dendrochemical analyses were done on the tree rings. Dendrochemistry was successfully used to determine that there were heavy metals in the rings, and also to estimate the date of the contamination events by using tree-ring wood. Several contamination events were identified through the presence of lead and other contaminants in the xylem of the trees analyzed at the selected sites. This suggests that various contaminants were transported by the river on several occasions and deposited on floodplains during successive floods. Also, a marked increase of some heavy metals like aluminum and nickel in the tree specimens can be attributed to recent atmospheric pollution. The emissions of metal-bearing particles may have varied widely over the century due to the different types of industrial activities, technological changes and atmospheric emission regulations. All of these anthropogenic changes reflected in the rings of the trees that showed variations in the geochemical profiles. Though several major contamination events can be determined, it is still difficult to identify all of the potential sources of pollution, of which there are many in this vast catchment.

Dating volcanic eruptions with tree-ring chemistry

Dendrochemical analyses of absolutely dated, overlapping sequences of tree rings allow identification of temporally conscribed, volcanically influenced periods of environmental change. Dendrochemistry, or the study of tree-ring elemental composition, is a promising new technique for reconstructing climate/environmental history at annual resolution. In particular, dendrochemistry may be useful for identifying periods of climatically and/or environmentally effective volcanic activity. Airborne pollution from major volcanic eruptions in the form of increased environmental acidity from sulfur dioxide can cause changes in availability and concentration of certain elements and can increase the availability of those elements in the soil, resulting in increased uptake by trees from the substrate or direct from the atmosphere. In particular, spikes, dips, or major changes in trace element concentration may be an indication of changes in soil or atmospheric chemistry (e.g., Padilla and Anderson 2002). Although there are other records of past volcanism (especially from ice-cores - e.g. Vinther et al. 2005), tree-ring based work (e.g. Salzer and Hughes 2007) offers several important advantages: first, tree-ring series are available with wide spatial coverage from most of the globe, and second, they are datable with annual and even subannual resolution on a fixed (absolute) calendar timescale (whereas even the best ice-core work has errors of several years or more beyond the last few hundred years).

Application of Dendrochronological and Dendrochemical Methods for Dating Contamination Events of the Saint-François and Massawippi Riverbanks (Québec, Canada)

Soils contaminated with hydrocarbons and others contaminants (heavy metals, PCBs, PAHs) were recently discovered in the banks of the Saint-François and Massawippi rivers. The aim of this study is to attempt to date the contamination events using dendrochronological and dendrochemical methods. For this study, dendrochronology is used to indicate the age of trees, identify the morphological growth anomalies, and provide the geochemical profile timeframe, with dendrochemistry used specifically to identify metal element concentrations in the growth rings of the selected specimens. Sampling for the two types of analysis was done on the banks of the Saint-François River in Windsor and Richmond, where the level of hydrocarbon contamination in the soil profiles is among the highest. Core samples were taken from three red ash (Fraxinus pennsylvanica Marsh.) and dendrochemical analyses were done on the tree rings (191 samples). Dendrochemistry was successfully used to determine that there were heavy metals in the rings, and also to estimate the date of the contamination events by using tree-ring wood. Several contamination events were identified through the presence of lead and other metal trace elements (As, Cd, Cu, Ni, and Zn) in the xylem of the trees analyzed at the selected sites. This suggests that various contaminants were transported by the river on several occasions and deposited on floodplains during successive floods. The atmospheric fallout must also be considered as the other source of pollutants recorded in the trees.

Dendrochemical analysis of a tree-ring growth anomaly associated with the Late Bronze Age eruption of Thera

The most marked tree-ring growth anomaly in the Aegean dendrochronological record over the last 9000 years occurs in the mid 17th century BC, and has been speculatively correlated with the impact of the Late Bronze Age eruption of Thera (Santorini). If such a connection could be proved it would be of major interdisciplinary significance. It would open up the possibility of a precise date for a key archaeological, geological and environmental marker horizon, and offer a direct tie between tree-ring and ice-core records some 3600 years ago. A volcanic explanation for the anomaly is highly plausible, yet, in the absence of a scientifically proven causal connection, the value of the proposed correlation is limited. In order to test the hypothesis, dendrochemical analysis via Synchrotron Radiation Scanning X-ray Fluorescence Microscopy (SXFM), Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES) and Inductively Coupled Plasma Mass Spectroscopy (ICP-MS) was carried out on growth-ring series from four trees displaying the anomaly. Increases of sulfur, calcium, and rare earth elements following the onset of altered growth, plus concentration spikes of zinc and hafnium in the first affected growth-ring provide promising new evidence in support of a volcanic causal factor. Although a volcanic association is implied, the new data are not sufficient to prove a link to the exact eruption source.

Essai de la dendrochimie sur le Frêne de Pennsylvanie pour la datation d’événements de contamination en zone riveraine (Sud du Québec, Canada)

Les méthodes dendrochimiques sont de plus en plus utilisées pour reconstituer les événements de contamination qui se sont produits dans le passé, notamment des déversements accidentels de polluants dans les cours d’eau ou le long d’emprise ferroviaire, sur des terrains vagues et des friches ou encore des boisés riverains. La contamination peut être locale ou s’étendre sur plusieurs sites. On peut détecter parfois des quantités appréciables de polluants qui contaminent tout autant les sols, les nappes ou l’environnement immédiat. À cet égard, les arbres peuvent constituer des “archives environnementales” permettant de retracer les événements associés à la contamination des sites. Dans le cadre de cette étude, l’analyse dendrochimique est utilisée pour tenter de reconstituer les événements de contamination le long de deux rivières affectées par une pollution industrielle et minière. L’échantillonnage a été réalisé sur des frênes de Pennsylvanie (Fraxinus pennsylvanica Marsh.) localisés sur des rives boisées, contaminées par des hydrocarbures et des métaux lourds (Al, As, Cd, Cu, Ni, Pb et Zn). Les analyses dendrochimiques ont permis de retracer plusieurs pics avec des concentrations élevées de métaux détectés à travers les cernes de croissance des arbres. Sur les courbes dendrochimiques, on note que certains métaux sont en décroissance, dont le cuivre, alors que d’autres présentent des courbes ascendantes, dont l’aluminium et le zinc. Certains pics pourraient être associés à la contamination des sols alluviaux par le transport fluvial des eaux polluées et d’autres à des rejets atmosphériques polluants.

Elemental line scanning of an increment core using EDXRF: From fundamental research to environmental forensics applications

Environmental forensics seeks to determine the responsible parties for contamination from leaks or spills of petroleum or other toxic products. Dendrochemistry contributes to environmental forensics at the intersection of analytical chemistry, tree biology, and environmental responsibility. To be useful, dendrochemistry requires the rigorous application of analytical techniques as well as an understanding of tree biology. The choice of analytical technique is usually driven by tradeoffs among the selection of chemical elements or molecules of interest, sensitivity and discrimination, spatial resolution, ease of sample preparation, availability, sample destructiveness, and cost. One useful solid-state spectroscopic technique for dendrochemical analysis is energy dispersive X-ray fluorescence (EDXRF). This method provides essentially non-destructive, simultaneous detection of a number of elements with an adjustable spatial resolution, typically from 0.1 to 0.3 mm. The most commonly targeted elements are S and Cl as markers for fossil fuels, Cl for solvents, and Pb for leaded gasoline. Other metal elements may also be used as indicators of mining and smelting. For elements that are not normally present in appreciable amounts in wood, the mere presence of the element anywhere in the tree-ring record indicates exposure of the tree to an unusual chemical event or process. Dating the environmental exposure from dendrochemical analysis can be complicated by internal changes in tree chemistry due to wood infection, tree maturation, and wood maturation.

The role of calcium uptake from deep soils for spruce ( Picea abies) and beech ( Fagus sylvatica)

Chemical analyses of the soil from up to 28 neighboring stands of pure spruce and mixed spruce–beech stands on two different bedrock materials for soil formation (Flysch: nutrient rich; Molasse: acidic) in Austria showed a marked enrichment of Ca in the O-horizon of the mixed stands as well as much wider Ca/Mg and Ca/K ratios. Because in mixed stands the Ca/Mg and Ca/K ratios in the O-horizon reflected the Ca content of the subsoil, we hypothesized that this relative Ca enrichment results both from higher transpiration of beech and uptake of water from deeper soil horizons, where the soil solution is expected to contain more Ca (Ca-pump of beech hypothesis). However, dendrochemical analyses justify the conclusion that acidification caused by pure spruce mobilizes base cations, increasing Ca stem wood concentrations. According to these studies, we suggested that top soil mobilization of Ca by acidifying effects of spruce is the main Ca source. Higher Ca soil solution concentrations in deep soil horizons under pure spruce than under mixed stands agreed with this revised hypothesis. Acidifying effects of spruce were much more pronounced on Flysch than on Molasse and preferential leaching of Ca from the top soil might explain the observed differences of Ca/Mg and Ca/K ratios in the O-horizon of mixed stands on these two bedrocks, which were reflected in the foliage as well. Comparisons of 87Sr/ 86Sr ratios of tree leaves and roots at different depths indicated that beech is indeed a real Ca-pump. This method confirmed that Ca of the current foliage is mainly of atmospheric source, due to similar 87Sr/ 86Sr ratios as measured in precipitation, and is hardly supplied by bedrock weathering. We conclude that even in mixed spruce–beech stands Ca is leached in high amounts together with NO 3, SO 4 and organic anions through the shallow top soil, which is rooted by spruce. Uptake of Ca in deep soil layers by beech minimizes substantial loss of Ca and other base cations, which would be inevitable under pure spruce stands.

High-Resolution Dendrochemical Analysis of Flood-Affected Oaks using Laser Ablation Icp-Mass Spectrometry

Dendrochemical analysis was conducted on Quercus macrocarpa Michx. (bur oak) growing within the floodplain of the Red River, Canada, to determine if xylem formed during severe floods contained significantly perturbed chemistry. Wood samples were taken from five living trees in the same stand and from three timbers from a 19th-century building. Laser ablation ICP-mass spectrometry was used to determine the trace element chemistry in the earlywood and latewood of rings formed before, during and after major floods. Between-tree correlations were significant (p < 0.05) for Hg, Mg, Mn, Sr and Zn, suggesting that changes in the abundance of these elements over time might reflect common physiological processes or environmental signals. Mg, Mn and Sr concentrations were higher in the earlywood than in the latewood for both living and historical samples. These intra-annual shifts may reflect varying rates of uptake driven by seasonal changes in anatomical development, as well as stability of these elements after their initial deposition. Although no chemical anomalies are associated with 20th-century floods, earlywood coinciding with an extreme flood in 1826 contained low levels of Mg, Mn and Sr. These elemental anomalies might represent an independent biochemical flood signature but it is also possible they are a secondary expression of wood formation disrupted by flooding. In either case, elemental analysis does not provide any information beyond that obtained from studying anatomical features, and does not appear to be a viable tool to identify the occurrence of past floods.

Laser ablation-combustion-GC-IRMS--a new method for online analysis of intra-annual variation of delta13C in tree rings.

We present a new, rapid method for high-resolution online determination of delta13C in tree rings, combining laser ablation (LA), combustion (C), gas chromatography (GC) and isotope ratio mass spectrometry (IRMS) (LA-C-GC-IRMS). Sample material was extracted every 6 min with a UV-laser from a tree core, leaving 40-microm-wide holes. Ablated wood dust was combusted to CO2 at 700 degrees C, separated from other gases on a GC column and injected into an isotope ratio mass spectrometer after removal of water vapor. The measurements were calibrated against an internal and an external standard. The tree core remained intact and could be used for subsequent dendrochronological and dendrochemical analyses. Cores from two Scots pine trees (Pinus sylvestris spp. sibirica Lebed.) from central Siberia were sampled. Inter- and intra-annual patterns of delta13C in whole-wood and lignin-extracted cores were indistinguishable apart from a constant offset, suggesting that lignin extraction is unnecessary for our method. Comparison with the conventional method (microtome slicing, elemental analysis and IRMS) indicated high accuracy of the LA-C-GC-IRMS measurements. Patterns of delta13C along three parallel ablation lines on the same core showed high congruence. A conservative estimate of the precision was +/- 0.24 per thousand. Isotopic patterns of the two Scots pine trees were broadly similar, indicating a signal related to the forest stand's climate history. The maximum variation in delta13C over 22 years was about 5 per thousand, ranging from -27 to -22.3 per thousand. The most obvious pattern was a sharp decline in delta13C during latewood formation and a rapid increase with spring early growth. We conclude that the LA-C-GC-IRMS method will be useful in elucidating short-term climate effects on the delta13C signal in tree rings.

Dendrochemical analysis of lead and calcium in southern Appalachian American beech.

The health of the northern hardwood forest in the southern Appalachian Mountains of Tennessee, North Carolina, and Virginia has gained attention from the media and environmental stakeholders due to a purported decline in forest health at higher elevations. This project examined lead (Pb) and calcium (Ca) concentrations in growth rings of an important northern hardwood species, American beech (Fagus grandifolia Ehrh.) at Mount Rogers and Whitetop Mountain, Virginia and attempted to examine concentration relationships with stem growth patterns. Dominant and codominant trees were sampled from 16 research plots at two elevations. Tree cores were crossdated, divided into sections of 10-yr periods, and analyzed using atomic absorption spectroscopy. Lead concentrations correlated negatively with ring width. Elevation and aspect were significantly associated with the Pb concentration, while Ca concentrations were only associated with aspect. Tree core samples taken from higher elevation plots contained higher Pb concentrations than samples collected from lower elevation plots, while the northwest and southwest aspects contained significantly higher amounts of Pb and Ca. Both Pb and Ca concentrations increased during the 1860s and again during the mid-1900s.

Monitoring historical changes in soil and atmospheric trace metal levels by dendrochemical analysis

The use of dendrochemistry for monitoring historical changes in trace metal deposition and mobilisation of metals in soils is evaluated. In experimental studies, mobilisation of trace metals in surface soil following deliberate acidification was recorded in sugar maple (Acer saccharum) tree-rings with minimal lateral movement between rings. Furthermore, positive correlations between wood (3 year section 1993–95) and foliar chemistry (mean concentration 1993–95) were found for Cd and Zn, but not for Cu and Ni, showing that mobility up the tree bole differs between metals. Even so, substantial lateral movement of elements between rings occurs in some species. Stable Pb isotope ratios in tree-rings were used to show that sacred fir (Abies religeosa) is not a useful monitor of Pb deposition because Pb accumulates in the heartwood. Numerous sophisticated analytical techniques are now used in dendrochemical studies, including laser ablation sampling in conjunction with inductively coupled plasma mass spectrometry that enable the multi-element analysis of extremely small tree-rings with low detection limits. Clearly, not all tree species are suitable for dendrochemical studies, but if careful sampling strategies are used and suitable tree species are chosen, the chemical analysis of tree-rings can provide information concerning historical changes in soil and atmospheric trace metal levels unavailable from any other source.