Analysis of tree rings using inductively coupled plasma mass spectrometry to record fluctuations in a metal pollution episode

Analysis of Acer pseudoplatanus L. (sycamore) tree rings using ICP-MS was used to assess the impact of metal deposition on trees growing in the vicinity of a metal refinery at Prescot, north-west England compared to a reference site at Croxteth 6 km distant receiving minimal deposition. No difference in tree growth between sites was recorded. Large reductions in Cu and Cd deposition since the late 1970s was accompanied by a steep decline in Cd concentrations in the outer rings in trees close to the refinery. A similar reduction in Cu concentrations was less apparent due to a tendency for Cu to increase in the outer rings. Zinc and Ni were higher in xylem at Prescot compared to Croxteth. There was no trend in Zn concentrations at either site although Ni concentrations increased in trees close to the refinery after 1982. Manganese concentrations in xylem were much higher at Prescot; Mn levels declined until the late 1970s and then increased slightly in later years interspersed by large concentration peaks within individual years during the 1980s. There was little change in Mn concentrations in trees at Croxteth during this period. Calcium, Mg and Sr concentrations remained steady or declined slightly in rings formed since 1965 in trees at Croxteth. Concentrations of Ca, Mg and Sr were higher in rings formed prior to the mid 1970s in trees at Prescot, but declined steadily after this period, although peaks in concentrations of each element were recorded in individual years during the 1980s. Phosphorous concentrations in rings increased towards the cambium at Croxteth, although P levels decreased in rings formed after 1982 at Prescot. No difference in K concentrations between sites was recorded. Lead concentrations in xylem at both sites declined steadily in rings formed after 1970, although concentrations were higher at the reference site. Analysis of individual sycamore tree rings appears to record short-term changes in pollution episodes, with little lateral movement of elements occurring. It is suggested that changes in element concentrations in trees close to the refinery are a result of reduced metal deposition combined with increased soil acidity due to reduced buffering capacity of metal ions in rainfall.     

Depositional history of sedimentary linear alkylbenzenes (LABs) in a large South American industrial coastal area (Santos Estuary, Southeastern Brazil)

This paper reports the reconstruction of the contamination history of a large South American industrial coastal area (Santos Estuary, Brazil) using linear alkylbenzenes (LABs). Three sediment cores were dated by ¹³⁷Cs. Concentrations in surficial layers were comparable to the midrange concentrations reported for coastal sediments worldwide. LAB concentrations increased towards the surface, indicating increased waste discharges into the estuary in recent decades. The highest concentration values occurred in the early 1970s, a time of intense industrial activity and marked population growth. The decreased LAB concentration, in the late 1970s was assumed to be the result of the world oil crisis. Treatment of industrial effluents, which began in 1984, was represented by decreased LAB levels. Microbial degradation of LABs may be more intense in the industrial area sediments. The results show that industrial and domestic waste discharges are a historical problem in the area.     

Reproductive success and chlorinated hydrocarbon contamination of resident great blue herons (Ardea herodias) from coastal British Columbia,Canada, 1977 to 2000

Over the period 1977-2000, eggs of Pacific great blue heron (Ardea herodias fannini) were collected from 23 colonies along the southern coast of British Columbia, Canada, and analyzed for persistent organochlorine (OC) pesticides and polychlorinated biphenyls (PCBs). Concentrations of OC pesticides in eggs declined sharply in the late 1970s, after which there were minimal changes. The sums of PCB congeners were not reduced appreciably during the 1980s and 1990s, but Aroclor 1260 concentrations suggested a sharp decline in PCB contamination of eggs in the late 1970s, similar to that shown for OC pesticides. Eggs collected along or near the Fraser River delta showed higher levels of most pesticides compared to other monitored colonies. Although the delta lands support a long-standing agricultural economy, the primary factors influencing OC levels in the delta colonies were thought to be driven by estuarine processes. We suggest two possible influencing factors were: 1) a greater rate of bioaccumulation in the estuary due to the deposition of particulates collected over a vast area encompassed by the Fraser River watershed; or 2) a higher rate of biomagnification in the estuary due to species differences at lower trophic levels of the heron food chain. Eggs from urban colonies contained higher levels of PCBs. The congener pattern was not clearly different from that observed in less contaminated eggs from rural and pulp mill-influenced colonies, except that colonies in Vancouver had greater proportions of PCB-66, suggesting a local source of Aroclor 1242. Productivity in the coastal heron colonies was highly variable over the period of study, with 71% of recorded colony-wide reproductive failures occurring in colonies near pulp mills. However, the predominant factors influencing reproductive success were probably disturbance by humans and bald eagles, combined with loss and degradation of nesting habitat, and not sublethal toxicity.     

Ozone distribution and phytotoxic potential in mixed conifer forests of the San Bernardino Mountains, southern California

In the San Bernardino Mountains of southern California, ozone (O(3)) concentrations have been elevated since the 1950s with peaks reaching 600ppb and summer seasonal averages >100ppb in the 1970s. During that period increased mortality of ponderosa and Jeffrey pines occurred. Between the late 1970s and late1990s, O(3) concentrations decreased with peaks approximately 180ppb and approximately 60ppb seasonal averages. However, since the late 1990s concentrations have not changed. Monitoring during summers of 2002-2006 showed that O(3) concentrations (2-week averages) for individual years were much higher in western sites (58-69ppb) than eastern sites (44-50ppb). Potential O(3) phytotoxicity measured as various exposure indices was very high, reaching SUM00 - 173.5ppmh, SUM60 - 112.7ppmh, W126 - 98.3ppmh, and AOT40 - 75ppmh, representing the highest values reported for mountain areas in North America and Europe.     

Chlorophenols in lake bottom sediments: A retrospective study of drinking water contamination

Lake and brook bottom sediments were analyzed for chlorophenols to provide historical data of exposure assessment, after the water intake plant of a Finnish village had been found to be contaminated in 1987, and subsequently elevated non-Hodgkin lymphoma risk was detected. Highly elevated 2,3,4,6-tetrachlorophenol and pentachlorophenol levels were found in all four lake sediment cores investigated. The distribution was uneven with much higher concentrations in the estuary, in contrast to PCB compounds which were more evenly distributed within the basin. The inlet origin of the chlorophenols in the sediments was further supported by the regional distribution pattern of these compounds in the sediment and water along transects of the inlet and its tributaries. The composition of chlorophenol congeners in the sediments was similar to that in a commercial fungicide used by a local sawmill, but different from other sediment analyses reported in Finland, also implying a local source. Dating of three cores by Pb-210 and soot ball chronology indicated that the contamination of the watercourse started in the early 1970s at the latest but possibly earlier. This would provide the latency time required for tumour appearance in the 1970s and 1980s.     

Pollution Control by Locational Change and Technological Abatement

In recent years, there has been a downward trend in sulfur dioxide concentrations in downtown St. Louis. This paper examines the contribution to this trend from locational changes of polluting sources and from technological abatement. A simple diffusion model is used to relate annual average concentrations to annual emission data. The results suggest that, had there been no abatement activity, the changes in location of sources that occurred between 1963 and 1970 have more or less offset a 40% increase in annual emissions over that period. However, the abatement activity, essentially the consequence of air pollution regulations, may possibly be credited with a decline of 35% in the annual average concentration.     

Trends of organochlorine residues in eggs of birds from Italy, 1977 to 1985

All the eggs, collected in Italy in 1982 and 1983, of two species of passerine birds, three gulls, four terns and the night heron, contained DDE and, with lower frequencies, other organochlorine contaminants. Organochlorines were more concentrated in the species of higher trophic level. DDE contamination showed a decreasing trend from 1978 to 1985 in one passerine, two terns and in the heron. After 1980-1982, the level of contamination was below the critical threshold beyond which reproduction is affected, eggshell thickness was only slightly or not reduced; therefore, the current impact of organochlorines on these birds is probably negligible. Detrimental effects may have occurred during the 1970s, when some of the eggs were contaminated beyond the critical threshold.     

Sediment analysis to support the recent glacial origin of DDT pollution in Lake Iseo (Northern Italy)

In the present study, a depth-related distribution of Persistent Organic Pollutants (POPs) in sediments of Lake Iseo, one of the major southern Alpine Italian lakes, is reported in order to further test the hypothesis of melting Alpine glaciers as a secondary source of contamination. In a previous paper, a “glacier contamination hypothesis” was suggested to explain the unexpected contamination of the biota of Lake Iseo, mainly fed by the Alpine melting ice.The sediment core analyses covered around the last 50 years. The organic matter profile evaluated as a Loss-On-Ignition percentage indicated transition of the basin from an oligotrophic to a mesotrophic status at around the early 1970s, but there was no evidence of the shift to eutrophy in the 1980s. Among DDTs, pp’DDE was the predominant metabolite, accounting on average for 79.4% of the total DDT concentrations and ranging from 6.4 to 447.5 ng g⁻¹ d.w. PCBs ranged from 5.0 to 163.7 ng g⁻¹ d.w. The maximum PCB concentrations were found in sediment layers corresponding to the 1970s when the highest production and use of these compounds occurred in Italy. In contrast, concentrations of DDTs showed a sharp increase from the early 1990s, long after their agricultural use was banned in Italy. This delayed pollution provides support for the hypothesis that the recent retreat of glaciers represents a secondary pollution source for old pesticides that were stored in the ice at the time of their use in agriculture.     

Sources of variation in concentrations of nickel and copper in mountain birch foliage near a nickel-copper smelter at Monchegorsk, north-western Russia: results of long-term monitoring

Concentrations of nickel and copper, two principal metal pollutants of the 'Severonikel' smelter at Monchegorsk, NW Russia, were measured in unwashed leaves of mountain birch, Betula pubescens subsp. czerepanovii, collected in eight study sites along the pollution gradient during 1991-2003. In spite of significant decline in metal emissions, concentrations of foliar metals in most of the study sites did not decrease, indicating that soil contamination remains extremely high. Multiyear mean values peaked at 6.6 km S of the smelter, where they were 20-25 times higher than in the most distant study site. Concentrations of both metals demonstrated pronounced annual variation, which was explained by the meteorological conditions of early summer: higher precipitation in May increased foliar concentrations of both metals, whereas higher precipitation in June resulted in lower foliar concentrations of nickel. These data suggest that ecotoxicological situation in metal-contaminated areas can be modified by the expected climate change. In heavily polluted sites individual birch trees generally retained their ranks in terms of metal contamination during 1995-2003, demonstrating that the use of the same set of trees can significantly increase the accuracy of the monitoring data.     

Air pollution, precipitation chemistry and forest health in the Retezat Mountains, Southern Carpathians, Romania

In the Retezat Mountains concentrations of O3, NO2 and SO2 in summer season 2000-2002 were low and below toxicity levels for forest trees. While NH3 concentrations were low in 2000, the 2001 and 2002 concentrations were elevated indicating possibility for increased N deposition to forest stands. More than 90% of the rain events were acidic with pH values <5.5, contributing to increased acidity of soils. Crown condition of Norway spruce (Picea abies) and European beech (Fagus sylvatica) was good, however, defoliation described as >25% of foliage injured increased from 9.1% in 2000 to 16.1% in 2002. Drought that occurred in the southern Carpathians between fall 2000 and summer 2002 and frequent acidic rainfalls could cause the observed decline of forest condition. Both Norway spruce and European beech with higher defoliation had lower annual radial increments compared to the trees with low defoliation. Ambient O3 levels found in the Retezat did not affect crown condition of Norway spruce or European beech.     

Persistent organochlorine contaminants in eggs of northern goshawk and Eurasian buzzard from northeastern Spain: temporal trends related to changes in the diet

Persistent organochlorine compounds (pesticides and polychlorinated biphenyls) were determined in 24 northern goshawk (Accipiter gentilis) and eight Eurasian buzzard (Buteo buteo) samples of eggs collected between 1988 and 1999 in La Segarra (northeast Spain), in order to evaluate the changes in exposure and detrimental effects during this period. In the study area, both species exhibited similar levels of contamination, which may be related to their similar diet, mainly based on European rabbits (Oryctolagus cuniculus) in terms of biomass. The buzzard showed contamination levels similar to those found in other Spanish areas, but the levels found in the goshawk were much lower. The shell index in goshawk eggs was inversely correlated to concentration of p,p'-DDE. In late eighties, the concentrations of p,p'-DDE and heptachlor-epoxide in goshawk eggs were positively correlated to the biomass percentage of passeriforms in the diet. In goshawk samples, a decline in HCB concentration in the 1990s as compared to the 1980s was detected. Surprisingly, p,p'-DDE concentrations did not decline, as could be expected from the ban on DDT use. On the contrary, the highest p,p'-DDE concentrations were detected in some samples from the nineties, which also showed the lowest shell indices. This may be related to a severe reduction of rabbit population after 1989 that produced an increase in the consumption of passeriformes, which are known to accumulate higher levels of organochlorine compounds. Our study suggests that monitoring programs aiming to detect temporal trends in chemical contamination should take into account changes in diet composition before any conclusion can be drawn.     

Uptake and mobility of uranium in black oaks: implications for biomonitoring depleted uranium-contaminated groundwater

In a preliminary study, the uptake and the mobility of uranium (U) by black oak trees (Quercus velutina) were assessed by measuring the isotopic composition of tree rings in two mature oak trees in a heavy metal contaminated bog in Concord, MA. The bog is adjacent to a nuclear industrial facility that has been processing depleted uranium (DU) since 1959. Over the past 40 years, DU has been leaking from an onsite holding basin and cooling pond down gradient to the bog where the oaks are located. Because DU has no source outside the nuclear industry, contamination from the industrial facility is readily discernable from uptake of natural U by measuring isotopic compositions. Isotope ratio analysis confirms the occurrence of DU in bark, sapwood and heartwood tree rings dating back to 1937, pre-dating the introduction of DU at the site by at least 20 years. Isotope dilution analysis indicates high concentrations of U (>3 ppb) in sapwood that drop rapidly to relatively constant concentrations (0.3-0.4 ppb) in heartwood. These data indicate that once incorporated into tree cells, U is mobile, possibly by diffusion through the tree wood. Concentrations of U in sapwood are approximately equal to average U concentrations in groundwater onsite over the past 10 years, suggesting that oak trees can be used as present-day bioindicators of U-contaminated groundwater. We suggest that regional sampling of oak bark and sapwood is a reasonable, inexpensive alternative to drilling wells to monitor shallow groundwater U contamination.     

Nitrogen species in drinking water indicate potential exposure pathway for Balkan Endemic Nephropathy

This study explored two hypotheses relating elevated concentrations of nitrogen species in drinking water and the disease Balkan Endemic Nephropathy (BEN). Drinking water samples were collected from a variety of water supplies in both endemic and non-endemic villages in the Vratza and Montana districts of Bulgaria. The majority of well water samples exceeded US drinking water standards for nitrate + nitrite. No statistically significant difference was observed for any of the nitrogen species between villages classified as endemic and non-endemic. Other constituents (sodium, potassium and chloride) known to be indicators of anthropogenic pollution were also found at elevated concentrations and all followed the order wells > springs > taps. This ordering coincides with the proximity of human influences to the water sources. Our results clearly establish an exposure pathway between anthropogenic activity and drinking water supplies, suggesting that the causative agent for BEN could result from surface contamination.     

Organochlorine and mercury contamination of little terns (Sterna albifrons) breeding at the western Baltic Sea, 1978-96

Between 1978 and 1996, egg and chick samples of little terns (Sterna albifrons) breeding at different colony sites along the eastern coast of Schleswig-Holstein, Germany, were annually gathered by chance in the framework of a long-term ringing programme. Analyses of polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT), hexachlorobenzene (HCB), hexachlorocyclohexane (HCHs), and mercury were carried out on eggs, chicks, and down (only mercury). In all matrices, pollutant concentrations decreased over the 19-year period. The mixture compositions of Sigma PCB, Sigma DDT, and Sigma HCH changed during the previous decades indicating decreasing releases of PCB mixtures, DDT, and technical HCH mixtures. The pollutant concentrations currently found in the tern eggs are compared with those of other bird species from other Baltic Sea subregions, suggesting a relatively low pollution of the Belt Sea. The temporal trends in contamination are related to international measurements and conventions on bans of pollutants. Since individually known females were recaptured up to three times, inter-individual variation in pollutant burdens could be studied. Remarkable variation among individuals as well as between breeding seasons were found that were not explainable by general temporal trends. Influences of individually and seasonally varying feeding habits on this phenomenon are discussed. Compositions of individual PCB mixtures varied in relation to total PCB concentrations found in eggs suggesting a concentration-dependent metabolization of PCBs as with other species. Amounts of particular organochlorines varied between matrices possibly indicating metabolization of low chlorinated PCBs, beta-HCH, and HCB during embryogenesis. In mercury, body detoxification via down is assumed. As indicated by eggshell parameters (thickness and index) being not related to organochlorine concentrations and being similar to that found in historical studies, respectively, effects of recent organochlorine contamination on eggshell thickness seem to be improbable. In conclusion, influences of contamination on declining little tern stocks observed in Germany are discussed. Negative influences of contamination in the 1960s and 1970s are assumed to be probable.     

Spatial patterns concentrations in upland Wales in relation to catchment forest cover and forest age

Data on nitrate nitrogen were collected weekly during 1984 from 136 sites on streams in upland Wales. Mean nitrate concentrations in summer (0.02 to 1.5 mg litre(-1)) were significantly lower (P<0.001) than in winter (0.02 to 1.26 mg litre(-1)), particularly at sites with mature conifers (>30 years old). Mean concentrations increased significantly with the average age of conifers on each catchment (P<0.001), and with increasing areal cover by trees over 30 years old (P<0.001). Nitrate concentrations increased significantly with stream total hardness (P<0.001), possibly reflecting nitrogen mineralisation in soils of higher base status. Concentrations also increased with stream chloride (P<0.001), which is predominantly atmospherically derived, implying that increased nitrate occurred where general atmospheric inputs of solutes were increased. After accounting for variation in hardness, residual nitrate concentrations still increased with the average age of the conifers (P<0.001), and with catchment cover by mature trees (P<0.001). We infer that some additional nitrate under older conifers is thus independent of catchment sources associated with increasing hardness. Two possibilities are increased inputs and decreased retention of nitrogen within the ecosystem of maturing conifer forest. Residual nitrate after accounting for variations in chloride also increased significantly with conifer age (P<0.01) and cover (P<0.01), a pattern implying that some sources of nitrate may also be independent of increased sea-salt deposition. We allude to the possibility that additional nitrogen deposition adds to nitrogen throughputs from maturing forests, and we discuss the potential ecological role of additional nitrogen in runoff.     

Long-term interactions between migratory caribou, wildfires and Nunavik hunters inferred from tree rings

Barren-ground caribou (Rangifer tarandus) herds in North America may reach considerable size and undertake large-scale seasonal migrations from the Arctic tundra to the boreal forest. To test the caribou decline hypothesis associated with native harvesting and fire, we have documented the long-term trends of caribou activity based on a novel approach which uses tree-ring dated trampling scars produced by caribou hooves in the extensive trails distributed over the summer and winter ranges of the Rivièreaux-Feuilles herd (RAF herd, east of Hudson Bay in northern Quebec). The age structure data of trampling scars from lichen woodlands distributed over the entire RAF range confirmed the overall trends of caribou activity from the late 1700s to present time. Over the last 200 years, the RAF herd has undergone two highs in the late 1700s and 1900s separated by a moderate activity pattern in the late 1800s. Native harvesting was possibly involved in the early 1900s decline, although at a moderate level. The reduced magnitude of caribou activity during this period has not modified the natural cycle of highs and lows, which suggests that other demographic factors were controlling the changing caribou abundance. Our data also show that only exceptionally large fires may have a minor, short-lived impact on caribou migrations but not on caribou numbers.     

Levels and trends of brominated flame retardants in the European environment

In this paper, we review those data which have recently become available for brominated flame retardants (particularly the brominated diphenyl ethers (BDEs) and hexabromocyclododecane (HBCD)) in samples from the European environment. Environmental compartments studied comprise the atmosphere, sediments and soils, sewage sludges, and a variety of biological samples and food chains. This is currently a very active research area, and we cite over 70 studies reported in the literature during 2003-04. Findings include that the input of BDEs (especially BDE209) to the Baltic Sea by atmospheric deposition now exceeds that of PCBs by a factor of almost 40 times. Sewage sludge samples from both industrial and background locations show concentrations of BDEs, HBCD and tetrabromobisphenol-A (TBBP-A) that are of a similar order, indicating that the major source is from diffuse leaching from products into wastewater streams from users, households and industries generally. Point-sources from industries using BFRs (e.g. the textile industry) also generate local hot-spots. Sediment core studies identified the presence of two of the three PBDE formulations. The penta-mix formulation was clearly present from the beginning of the 1970s, but the deca-mix only appeared in the late 1970s. BDE183, BDE209 and HBCD were detected in peregrine falcons from Sweden and other birds feeding on terrestrial food chains. BDEs are found widely distributed in fish, including those from high mountain lakes in Europe, as a consequence of long-range atmospheric transport and deposition. A temporal trend study in archived freeze-dried mussels from the Seine estuary, France, indicated an exponential increase in BDE concentrations during the period 1982-1993, which levelled off in 1999 and 2001 and then began to decline after 2002. HBCD was detected in liver and blubber samples from harbour seals and harbour porpoises from the Wadden and North Seas, though very few animals yielded positive values for TBBP-A. There are difficulties in comparing data on summation operatorBDE from studies in which different suites of BDE congeners have been determined, and we suggest a common suite which will allow the study of all three commercial PBDE formulations.     

Herbicide levels in rivers draining two prairie agricultural watersheds (1984)

A monitoring survey was conducted during 1984 on the Ochre and Turtle Rivers, which flow into Dauphin Lake in western Manitoba, Canada, to determine levels of the herbicides MCPA, diclofop-methyl, dicamba, bromoxynil, 2,4-D, triallate and trifluralin which were widely used in each watershed. Triallate concentrations exceeded 4 ng/L in 50% and 10% of the 21 samples taken from each of the Turtle and Ochre River, respectively, during the period March to October 1984. Trifluralin concentrations exceeded 3 ng/L in 14% and 10% of the samples from the respective rivers. Maximum concentrations did not exceed 25 ng/L and were unrelated to changes in river flow. Bromoxynil and diclofop were detected in the Turtle River, at concentrations of 113 and 476 ng/L, respectively, following a major high water event in late June, but were undetectable (less than 2 and 12 ng/L, respectively) at other sampling times. Dicamba and 2,4-D were detectable throughout most of the sampling period in both rivers at low levels (less than 100 ng/L). High levels of dicamba and 2,4-D (5476 and 2568 ng/L respectively) were found in water from the Turtle River prior to the high water event event possibly caused by spraying of ditches or rights-of-way near the river. Discharges (grams/year) of all seven herbicides monitored in the study represented less than 0.1% of the amounts estimated to be used in each watershed. Unit loadings (mg/ha/year) of 2,4-D and dicamba were similar to those reported for Southern Ontario streams in the mid-1970's. The results indicate that herbicide contamination of Manitoba streams draining agricultural areas is generally low except when major runoff occurs during the application period in May and June.     

Long-term development of inorganic nutrients and chlorophyll alpha in the open northern Baltic Sea

Eutrophication is an ongoing process in most parts of the Baltic Sea. This article reports on the changes during recent decades of several eutrophication-related variables in the open sea areas surrounding Finland (wintertime nutrient concentrations, wintertime nutrient ratios, and summer time chlorophyll alpha concentrations at the surface). The sum of nitrate- and nitrite-nitrogen ([NO3+NO2]-N) was observed to increase nearly fourfold in the Northern Baltic Proper and the Gulf of Finland and almost double in the Bothnian Sea from the 1960s until the 1980s or 1990s. The increase was followed by a decrease, which was modest in the two former subregions. Phosphate-phosphorus (PO4-P) concentrations followed a similar pattern in the Northern Baltic Proper (threefold increase and subsequent slight decrease) and Bothnian Sea (30% increase and subsequent decrease), but increased throughout the study in the Gulf of Finland, with the present concentration being threefold to the measurements made in the early 1970s. The PO4-P concentration decreased throughout the study in the Bothnian Bay. Silicate-silicon (SiO4-Si) concentrations decreased 30-50% from the early 1970s to the late 1990s and increased 20-40% thereafter in the Northern Baltic Proper, the Gulf of Finland, and the Bothnian Sea. Chlorophyll alpha showed an increase of over 150% in the Northern Baltic Proper and the Gulf of Finland from the 1970s until the early 2000s. In the Bothnian Sea the chlorophyll alpha concentration increased more than 180% from the late 1970s until the late 1990s, and decreased thereafter. According to these long-term observations, the Gulf of Finland and Northern Baltic Proper show clear signs of eutrophication, which may be emphasized by hydrographical changes affecting the phytoplankton communities and thus the algal biomass.     

Growth reduction of the Japanese black pine corresponding to an air pollution episode

Changes of tree-ring widths of Japanese black pine (Pinus thunbergii Parl.) trees growing in air-polluted and unpolluted areas were analyzed. In the stand close to an industrial complex, a large reduction in the series of tree-ring index (TRI), which were computed by removing endogenous effects from the measured series, appeared from the 1960s to 1970s. This reduction in radial tree growth was not explained by the climatic response model calibrated for a pre-pollution period. TRI changes corresponding with changes in concentrations of sulfur dioxide (SO(2)), and a significant negative correlation between the TRI and SO(2) concentration were found in the polluted area. Reduction in tree-ring growth was not seen in the unpolluted area. These results indicate that the past reduction in the growth of Japanese black pine trees growing in an industrial area was mainly caused by SO(2).