Comparison of particulate mass, chemical species for urban, suburban and rural areas in central Taiwan, Taichung

Aerosol samples for PM2.5, PM(2.5-10) and TSP were collected from June to September 1998 and from February to March 1999 in central Taiwan. Ion chromatography was used to analyze the acidic anions: sulfate, nitrate and chloride in the Universal samples. The ratios of fine particle concentrations to coarse particle concentrations displayed that the fine particle concentrations are almost greater than that of coarse particle concentrations in Taichung area. The average concentrations of PM2.5, PM(2.5-10) and TSP in urban sites are higher than in suburban and rural sites at both daytime and night-time. Chloride dominated in the coarse mode in daytime and in fine mode in night-time. Nitrate can be found in both the coarse and fine modes. Sulfate dominated in fine mode in both daytime and night-time.     

Suitability of process-based tree growth models for addressing tree response to climate change

Empirical models of tree growth have been used for many years to predict timber yields and other properties of trees. However, such models rely on measured relationships between tree growth and historic environmental conditions. As anthropogenic actions alter the environment, especially atmospheric composition, empirical models become less reliable and process-based models become more useful. Process-based models are challenged to simulate growth of structurally and physiologically complex organisms using explicit mathematical expressions to capture growth response to environmental conditions. In this review we summarize the physiological requirements of process-based models and examine the capabilities of six published models (CARBON, ECOPHYS, PGSM, TREE-BGC, TREGRO, W91) for simulating tree response to changes in environmental conditions (elevated temperature, increased CO(2) concentration, and enhanced concentrations of tropospheric ozone). These analyses indicate that current models are reliable integrators of environmental effects on individual processes (e.g. photosynthesis), but may be less reliable where physiological acclimation occurs or when extrapolated to growth of specific tree compartments.     

Dynamics of radionuclide concentrations in calcified tissues of reindeer in the western Russian Arctic

The specific activities of artificial and natural nuclides were determined in bone and teeth of reindeer that had lived before, during, and after nuclear tests on the Archipelago Novaya Zemlya and of reindeer from the nearby mainland region. In bone of reindeer from Novaya Zemlya, 90Sr and 210Pb are the main source of beta-activity, the 210Po is the main source of the alpha activity. In bone of reindeer that lived on Novaya Zemlya during underground tests, the 90Sr activity was relatively high (0.75 +/- 0.20 Bq/g dry weight). In animals that lived after the tests were banned, the level was significantly lower (0.44 +/- 0.17 Bq/g) and did not differ from the level of the 90Sr activity found in the mainland reindeer bone. On Novaya Zemlya, the concentrations of the natural 210Pb in bone of the recent reindeer (0.57 +/- 0.19 Bq/g) is similar to that which was in the teeth of reindeer a hundred years ago (0.65-0.75 Bq/g) and significantly higher than in the recent mainland reindeer from different regions (0.18-0.17 Bq/g).     

Heavy metal pollution in sediments of the Pasvik River drainage

The purpose of this paper is to study the regional impacts of heavy metals (Ni, Cu, Co, Zn, Cd, Pb, Hg) on the watershed of the Pasvik River. On the basis of sediment investigations at 27 stations of the watershed, background concentrations of the heavy metals, vertical distribution of heavy metals in sediments, heavy metal concentrations in surface sediments, contamination degree, and risk index were determined. The atmospheric emissions of Ni, Cu, Co, Zn, Cd and Hg from the smelters and waste waters from tailing dams and mines of the Pechenganickel Company are likely to be the main sources of increasing concentrations observed in recent sediments of the lower river reaches. Lead showed a different pattern from the other heavy metals--increasing Pb concentrations in the upper sediment layers towards the Norwegian side.     

Accumulation pattern and biotransformation enzyme induction in rainbow trout embryos exposed to sublethal aqueous concentrations of 3,3',4,4'-tetrachlorobiphenyl

Accumulation pattern of 3,3',4,4'-tetrachlorobiphenyl (PCB 77) and the exposure time needed to activate the monooxygenase (EROD) and conjugation (GST) enzyme systems of fish at the advanced embryonic stage were studied. Eyed stage embryos of rainbow trout (Oncorhynchus mykiss) were exposed to sublethal doses (0, 1, 10, and 100 micrograms/l) of PCB 77. Results indicated direct accumulation of the chemical into the eggs, but the exposure time was not long enough for PCB 77 to reach constant steady state. However, at the two lowest test concentrations (1 microgram/l and 10 micrograms/l) a temporary plateau at chemical accumulation was reached at the third exposure day (185 and 1221 ng PCB/g egg w.w). At the highest concentration (100 micrograms/l) the decrease in the accumulation rate was already evident after the first day (2182 ng PCB/g egg w.w). The chemical uptake increased again at day 7 in all the exposure groups. That event could have been caused by the increased metabolic rate of the embryos in preparation for the upcoming hatching event. The microsomal CYP1A monooxygenase system (EROD) was shown to be a sensitive indicator of embryonic exposure, being induced at the low (1 microgram/l, 182 ng/g egg) PCB concentration and after a short (3 day) exposure time. The conjugation enzyme system (GST) was shown to be functioning already at the advanced embryonic stage, although no response to the studied chemical stress was detected.     

Heavy metal pollution and forest health in the Ukrainian Carpathians

The Ukrainian Carpathians are characterized by high air pollution caused by emissions from numerous industries. We have been monitoring the state of forests in this region since 1989. The highest levels of tree defoliation (>30%) are found close to industrial emission sources and in the upper mountain forests of the Ivano-Frankivsk and Chernivtsi regions. This is caused by a combination of strong anthropogenic influences (pollution, illegal uses, recreation) as well as poor site and climatic conditions. In the Ivano-Frankivsk region, Cd and Mo accumulate in forest soils; Cr, Mo and Zn soil concentrations are higher than their limit levels; and Pb concentrations exceed toxic levels close to industrial areas (10% of the region territory). Local background levels of heavy metals are greatly exceeded in snow close to industrial regions. Analysis of correlation matrices shows that the chemical elements Ba, Cd, Co, Cr, Cu, Mo, Ni, Pb, V and Zn occur at pollution levels in natural ecosystems in the Ukrainian Carpathians. Maximum concentrations of toxic elements occur in the oak forest zone; the most industrially developed area of the region. Toxic heavy metals in the Ukrainian Carpathians forests enter with precipitation and dustfall, then become fixed in soil and accumulate in leaves, needles of vascular plants and mosses. Concentrations of these metals decrease with altitude: highest in the oak forests, less in beech, and lowest in the spruce forest zones. However, some chemical elements have the highest concentrations in spruce forests; V in needles, As in snow, and Ba and Al in soils.     

Atmospheric lead deposition to Okefenokee Swamp, Georgia, USA

Contamination of the environment from atmospheric deposition during the twentieth century is pervasive even in areas ostensibly considered pristine or remote from point sources. In this study, Pb concentrations in a 210Pb-dated peat core collected from the Okefenokee Swamp, GA were used to assess historical contaminant input via atmospheric deposition. Lead isotope ratios were determined by dynamic reaction cell ICP-MS (DRC-ICP-MS). Increases in Pb concentration occurred in the late nineteenth century and a marked rise in Pb concentrations pre-dated the widespread use of leaded gasoline within the US. The 206Pb/207Pb ratios of 1.19 during this period were consistent with coal combustion emissions. A later increase in Pb concentration, concurrent with a trend toward more radiogenic 206Pb/207Pb ratios in gasoline is consistent with an increased input of Pb from leaded gasoline emissions. However, it appears that coal combustion emissions remain a major source of Pb to the Okefenokee.     

Growth response to ozone of annual species from Mediterranean pastures

Ozone (O3) phytotoxicity has been reported on a wide range of plant species. However, scarce information has been provided regarding the sensitivity of semi-natural grassland species, especially those from dehesa Mediterranean grasslands, in spite of their great biological diversity and the high O3 levels recorded in the region. A screening study was carried out in open-top chambers (OTCs) to assess the O3-sensitivity of representative therophytes of these ecosystems based on the response of selected growth-related parameters. Three O3 treatments and 3 OTCs per treatment were used. Legume species were very sensitive to O3, because 78% of the tested species showed detrimental effects on their total biomass relative growth rate (RGR) following their exposure to O3. The Trifolium genus was particularly sensitive showing O3-induced adverse effects on most of the assessed parameters. Gramineae plants were less sensitive than Leguminosae species because detrimental effects on total biomass RGR were only observed in 14% of the assessed species. No relationship was found between relative growth rates when growing in clean air and O3 susceptibility. The implications of these effects on the performance of dehesa acidic grasslands and on the definition of ozone critical levels for the protection of semi-natural vegetation are discussed.     

Synthesis of effects in four Arctic subregions

An assessment of impacts on Arctic terrestrial ecosystems has emphasized geographical variability in responses of species and ecosystems to environmental change. This variability is usually associated with north-south gradients in climate, biodiversity, vegetation zones, and ecosystem structure and function. It is clear, however, that significant east-west variability in environment, ecosystem structure and function, environmental history, and recent climate variability is also important. Some areas have cooled while others have become warmer. Also, east-west differences between geographical barriers of oceans, archipelagos and mountains have contributed significantly in the past to the ability of species and vegetation zones to relocate in response to climate changes, and they have created the isolation necessary for genetic differentiation of populations and biodiversity hot-spots to occur. These barriers will also affect the ability of species to relocate during projected future warming. To include this east-west variability and also to strike a balance between overgeneralization and overspecialization, the ACIA identified four major sub regions based on large-scale differences in weather and climate-shaping factors. Drawing on information, mostly model output that can be related to the four ACIA subregions, it is evident that geographical barriers to species re-location, particularly the distribution of landmasses and separation by seas, will affect the northwards shift in vegetation zones. The geographical constraints--or facilitation--of northward movement of vegetation zones will affect the future storage and release of carbon, and the exchange of energy and water between biosphere and atmosphere. In addition, differences in the ability of vegetation zones to re-locate will affect the biodiversity associated with each zone while the number of species threatened by climate change varies greatly between subregions with a significant hot-spot in Beringia. Overall, the subregional synthesis demonstrates the difficulty of generalizing projections of responses of ecosystem structure and function, species loss, and biospheric feedbacks to the climate system for the whole Arctic region and implies a need for a far greater understanding of the spatial variability in the responses of terrestrial arctic ecosystems to climate change.     

Uncertainties and recommendations

An assessment of the impacts of changes in climate and UV-B radiation on Arctic terrestrial ecosystems, made within the Arctic Climate Impacts Assessment (ACIA), highlighted the profound implications of projected warming in particular for future ecosystem services, biodiversity and feedbacks to climate. However, although our current understanding of ecological processes and changes driven by climate and UV-B is strong in some geographical areas and in some disciplines, it is weak in others. Even though recently the strength of our predictions has increased dramatically with increased research effort in the Arctic and the introduction of new technologies, our current understanding is still constrained by various uncertainties. The assessment is based on a range of approaches that each have uncertainties, and on data sets that are often far from complete. Uncertainties arise from methodologies and conceptual frameworks, from unpredictable surprises, from lack of validation of models, and from the use of particular scenarios, rather than predictions, of future greenhouse gas emissions and climates. Recommendations to reduce the uncertainties are wide-ranging and relate to all disciplines within the assessment. However, a repeated theme is the critical importance of achieving an adequate spatial and long-term coverage of experiments, observations and monitoring of environmental changes and their impacts throughout the sparsely populated and remote region that is the Arctic.