Expansion of Canopy-Forming Willows Over the Twentieth Century on Herschel Island,Yukon Territory,Canada

Canopy-forming shrubs are reported to be increasing at sites around the circumpolar Arctic. Our results indicate expansion in canopy cover and height of willows on Herschel Island located at 70° north on the western Arctic coast of the Yukon Territory. We examined historic photographs, repeated vegetation surveys, and conducted monitoring of long-term plots and found evidence of increases of each of the dominant canopy-forming willow species (Salix richardsonii, Salix glauca and Salix pulchra), during the twentieth century. A simple model of patch initiation indicates that the majority of willow patches for each of these species became established between 1910 and 1960, with stem ages and maximum growth rates indicating that some patches could have established as late as the 1980s. Collectively, these results suggest that willow species are increasing in canopy cover and height on Herschel Island. We did not find evidence that expansion of willow patches is currently limited by herbivory, disease, or growing conditions.     

Documenting lemming population change in the Arctic: Can we detect trends?

Lemmings are a key component of tundra food webs and changes in their dynamics can affect the whole ecosystem. We present a comprehensive overview of lemming monitoring and research activities, and assess recent trends in lemming abundance across the circumpolar Arctic. Since 2000, lemmings have been monitored at 49 sites of which 38 are still active. The sites were not evenly distributed with notably Russia and high Arctic Canada underrepresented. Abundance was monitored at all sites, but methods and levels of precision varied greatly. Other important attributes such as health, genetic diversity and potential drivers of population change, were often not monitored. There was no evidence that lemming populations were decreasing in general, although a negative trend was detected for low arctic populations sympatric with voles. To keep the pace of arctic change, we recommend maintaining long-term programmes while harmonizing methods, improving spatial coverage and integrating an ecosystem perspective.     

Cadmium concentrations in tissues of willow ptarmigan (Lagopus lagopus) and rock ptarmigan (Lagopus muta) in Nunavik, Northern Québec

Willow and rock ptarmigan were obtained from Northern Québec. Willow ptarmigan were found to have mean cadmium concentrations of 179.7 microg/g (dw) in the kidneys and 25.8 microg/g (dw) in the liver; these levels were three times higher than those found in the rock ptarmigan. The cadmium levels in the ptarmigan were below the threshold above which adverse effects can be observed in birds. The difference between the two ptarmigan species in cadmium content is explained by the diet. A comparison of their diet showed that willow, which stores cadmium, is an important food resource for willow ptarmigan but not for rock ptarmigan. Because there is limited information available on the consumption of ptarmigan kidneys and liver by the Inuit, and the fact that this is a traditional way of life and provides nutritional benefits to the Inuit population, no consumption guidelines are proposed.     

Monitoring of raptors and their contamination levels in Norway

This article summarizes results from raptor monitoring and contamination studies in Norway of the golden eagle, gyrfalcon, white-tailed sea eagle, osprey, peregrine, and merlin. Golden eagle and gyrfalcon populations have been monitored since 1990 as part of the "Monitoring Programme for Terrestrial Ecosystems" (TOV). No long-term trend in the population size or productivity of golden eagle has been shown in any of the 5 study areas. The reproductive output of gyrfalcon is monitored in 3 areas. It is positively correlated with the populations of its main prey species, the rock ptarmigan and the willow ptarmigan. The white-tailed sea eagle population has been monitored since 1974 by the Norwegian Ornithological Society, and the population is increasing. The levels of pesticides and polychlorinated biphenyls are low in the eggs of both the golden eagle and the gyrfalcon, but elevated levels and effects on reproduction have been indicated for a coastal subpopulation of golden eagle. The pollutant levels in white-tailed sea eagle are lower than in the Baltic population of sea eagles, and shell thinning was never severe overall, but individual eggs have contained pollutant concentrations above critical levels. The levels of pollutants in the bird-eating falcons, peregrine, and merlin were higher than in other species. New emerging pollutants, like brominated diphenylethers and perfluorinated organic compounds, could be detected in all species. By incorporating available published and unpublished data, we were able to produce time trends for pollutants and shell thickness over 4 decades.     

Trends in large-scale VOC concentrations in the Southern Netherlands between 1991 and 1997

Results of C₆–C₁₂ hydrocarbon measurements at three sites in the southern part of The Netherlands, a polluted region in Western Europe, are presented. The measurements were carried out over the period March 1991–February 1997. The concentrations at the sites, with 100–150 km distance between them, are quite similar and they are predominantly determined by large-scale transport. The concentrations in this part of the country are substantially higher than those observed at a coastal site in the north of The Netherlands, but much lower compared to the concentrations in cities and near streets. A distinct difference between the trends of aromatics and aliphatics was observed. The concentrations of the aromatic components display trends that are systematically 4–5% yr^-1 lower than the trends of the aliphatics, which is possibly related to the increased use of catalysts in cars and, partly, to an enhanced atmospheric chemical activity. For the chlorinated species the trends are highly significant. The trend of 1,1,1-trichloroethane is in the order of 8–12% yr^-1 downward while for tetrachloromethane an annual downward trend of 4–6% is found. These downward trends suggest that measures have been taken to fulfil the requirements of the Montreal Protocol to ban the production of these species in a few years time from now.     

Status and trends of tundra birds across the circumpolar Arctic

Tundra-breeding birds face diverse conservation challenges, from accelerated rates of Arctic climate change to threats associated with highly migratory life histories. Here we summarise the status and trends of Arctic terrestrial birds (88 species, 228 subspecies or distinct flyway populations) across guilds/regions, derived from published sources, raw data or, in rare cases, expert opinion. We report long-term trends in vital rates (survival, reproduction) for the handful of species and regions for which these are available. Over half of all circumpolar Arctic wader taxa are declining (51% of 91 taxa with known trends) and almost half of all waterfowl are increasing (49% of 61 taxa); these opposing trends have fostered a shift in community composition in some locations. Declines were least prevalent in the African-Eurasian Flyway (29%), but similarly prevalent in the remaining three global flyways (44–54%). Widespread, and in some cases accelerating, declines underscore the urgent conservation needs faced by many Arctic terrestrial bird species.     

Vegetative buffers for fan emissions from poultry farms: 2. ammonia,dust and foliar nitrogen

This study evaluated the potential of trees planted around commercial poultry farms to trap ammonia (NH₃) and dust or particulate matter (PM). Norway spruce, Spike hybrid poplar, hybrid willow, and Streamco purpleosier willow were planted on five commercial farms from 2003 to 2004. Plant foliage was sampled in front of the exhaust fans and at a control distance away from the fans on one turkey, two laying hen, and two broiler chicken farms between June and July 2006. Samples were analyzed for dry matter (DM), nitrogen (N), and PM content. In addition, NH₃ concentrations were measured downwind of the exhaust fans among the trees and at a control distance using NH₃ passive dosi–tubes. Foliage samples were taken and analyzed separately based on plant species. The two layer farms had both spruce and poplar plantings whereas the two broiler farms had hybrid willow and Streamco willow plantings which allowed sampling and species comparisons with the effect of plant location (control vs. fan). The results showed that NH₃ concentration h^{? 1} was reduced by distance from housing fans (P ≤ 0.0001), especially between 0 m (12.01 ppm), 11.4 m (2.59 ppm), 15 m (2.03 ppm), and 30 m (0.31 ppm). Foliar N of plants near the fans was greater than those sampled away from the fans for poplar (3.87 vs. 2.56%; P ≤ 0.0005) and hybrid willow (3.41 vs. 3.02%; P ≤ 0.05). The trends for foliar N in spruce (1.91 vs. 1.77%; P = 0.26) and Streamco willow (3.85 vs. 3.33; P = 0.07) were not significant. Pooling results of the four plant species indicated greater N concentration from foliage sampled near the fans than of that away from the fans (3.27 vs. 2.67%; P ≤ 0.0001). Foliar DM concentration was not affected by plant location, and when pooled the foliar DM of the four plant species near the fans was 51.3% in comparison with 48.5% at a control distance. There was a significant effect of plant location on foliar N and DM on the two layer farms with greater N and DM adjacent to fans than at a control distance (2.95 vs. 2.15% N and 45.4 vs. 38.2% DM, respectively). There were also significant plant species effects on foliar N and DM with poplar retaining greater N (3.22 vs. 1.88%) and DM (43.7 vs. 39.9%) than spruce. The interaction of location by species (P ≤ 0.005) indicated that poplar was more responsive in terms of foliar N, but less responsive for DM than spruce. The effect of location and species on foliar N and DM were not clear among the two willow species on the broiler farms. Plant location had no effect on plant foliar PM weight, but plant species significantly influenced the ability of the plant foliage to trap PM with spruce and hybrid willow showing greater potential than poplar and Streamco willow for PM_2.5(0.0054, 0.0054, 0.0005, and 0.0016 mg cm^{? 2}; P ≤ 0.05) and total PM (0.0309, 0.0102, 0.0038, and 0.0046 mg cm^{? 2}, respectively; P ≤ 0.001). Spruce trapped more dust compared to the other three species (hybrid willow, poplar, and Streamco willow) for PM₁₀ (0.0248 vs. 0.0036 mg cm^{? 2}; P ≤ 0.0001) and PM_{> 10} (0.0033 vs. 0.0003 mg cm^{? 2}; P = 0.052). This study indicates that poplar, hybrid willow, and Streamco willow are appropriate species to absorb poultry house aerial NH₃–N, whereas spruce and hybrid willow are effective traps for dust and its associated odors.     

Characterizing changes in surface ozone levels in metropolitan and rural areas in the United States for 1980–2008 and 1994–2008

In this analysis, we characterize urban and rural ozone (O₃) trends across the US for the periods 1980–2008 (29 years) and 1994–2008 (15 years) using three exposure metrics, which summarize daily O₃ concentrations to reflect different ways O₃ may affect human health and vegetation. We observe that a statistically significant trend at a specific monitoring site, using one exposure metric, does not necessarily result in a similar trend using the other two metrics. The two most common trends among the monitoring sites are either a continuation of negative trending over the 29-year period or a shift from negative to no trend status, indicating a leveling off of the trending. Very few sites exhibit statistically significant increases in the exposure indices. In characterizing the statistically significant changes in the distribution of hourly average O₃, we observe subtle statistically significant changes in the lower part of the distribution (i.e., below 50 ppb) that are not necessarily captured by the trending patterns associated with the three exposure metrics. Using multisite data from 12 metropolitan cities, we find that as the frequency of higher hourly average concentrations is reduced, the lower hourly average concentrations also move upward toward the mid-level values. The change in the number of the hourly average concentrations in the lower range is consistent with decreased NO scavenging. We recommend assessing possible subtle shifts in O₃ concentrations by characterizing changes in the distribution of hourly average concentrations by month. Identifying statistically significant monthly changes in the mid- and low-level hourly average concentrations may provide important information for assessing changes in physical processes associated with global climate change, long-range transport, and the efficacy of models used for emission and risk reductions. Our results indicate that it is important to investigate the change in the trending pattern with time (e.g., moving 15-year trending) in order to assess how year-to-year variability may influence the trend calculation.     

Increase in surface ozone at rural sites in the western US

We evaluated O₃ data for the period 1987–2004 from 11 rural and remote sites in the north and western US, including two sites in Alaska. All sites show a seasonal cycle with a spring or spring-summer maximum. By deseasonalizing the data, we are better able to identify seasonal and spatial patterns and long-term trends. For most of the locations in the western US that we considered, there are significant inter-site correlations in the deseasonalized monthly means. This indicates that there are large scale factors that influence the monthly mean O₃ concentrations across the western US. At seven out of nine sites in the western US, there is a statistically significant increase in O₃ with a mean trend of 0.26 ppbv year⁻¹ (range at the seven sites is 0.19–0.51 ppbv year⁻¹). At three of the sites, we examined the data in more detail to find that the trends are present in all seasons. At the two sites in Alaska, no clear pattern was found. At the one ozonesonde site in the western US with long-term observations (Boulder, Colorado), no significant trend was identified. However, the statistical power in the ozonesonde analysis is limited due to the low frequency of ozonesonde launches. Temperature changes can explain only a fraction of the surface O₃ trend. We consider several possible explanations for these trends, including: increasing regional emissions, changes in the distribution of emissions, increasing biomass burning or increasing global background O₃. With the available data, we are not able to unambiguously identify the cause for increasing O₃ in the western US     

Circumpolar terrestrial arthropod monitoring: A review of ongoing activities,opportunities and challenges,with a focus on spiders

The terrestrial chapter of the Circumpolar Biodiversity Monitoring Programme (CBMP) has the potential to bring international multi-taxon, long-term monitoring together, but detailed fundamental species information for Arctic arthropods lags far behind that for vertebrates and plants. In this paper, we demonstrate this major challenge to the CBMP by focussing on spiders (Order: Araneae) as an example group. We collate available circumpolar data on the distribution of spiders and highlight the current monitoring opportunities and identify the key knowledge gaps to address before monitoring can become efficient. We found spider data to be more complete than data for other taxa, but still variable in quality and availability between Arctic regions, highlighting the need for greater international co-operation for baseline studies and data sharing. There is also a dearth of long-term datasets for spiders and other arthropod groups from which to assess status and trends of biodiversity. Therefore, baseline studies should be conducted at all monitoring stations and we make recommendations for the development of the CBMP in relation to terrestrial arthropods more generally.     

Ozone Air Quality over North America: Part I—A Review of Reported Trends

ABSTRACT

Ozone and precursor trends can be used to measure the effectiveness of regulatory programs that have been implemented. In this paper, we review trends in the concentrations of O₃, NO_x, and HCs over North America that have been reported in the literature. Although most existing trend studies are confounded by meteorological variability, both the raw data trends and the trends adjusted for meteorology collectively indicate a general decreasing trend in O concentrations in most areas of the United States during 1985-1996. In Canada, mean daily maximum 1-hr O₃ concentrations at urban sites show mixed trends with a majority of sites showing an increase from 1980 to 1993. Mean daily maximum 1-hr O₃ at most regionally representative Canadian sites appears to decrease from 1985 to 1993 or shows no significant change. There are far fewer data and analyses of NO_x and HC trends. Available studies covering various ranges of years indicate decreases in ambient NO_x and HC concentrations in Los Angeles, CA, decreases in HC concentrations in northeastern U.S. cities, and decreases in NO concentrations in Canadian cities. Two key needs are long-term HC and NO_x measurements, particularly at rural sites, and a systematic comparison of trend detection techniques on a reference data set.     

The impact of climate change on three indicator Galliformes species in the northern highlands of Pakistan

The rise in global temperature is one of the main threats of extinction to many vulnerable species by the twenty-first century. The negative impacts of climate change on the northern highlands of Pakistan (NHP) could change the species composition. Range shifts and range reduction in the forested landscapes will dramatically affect the distribution of forest-dwelling species, including the Galliformes (ground birds). Three Galliformes (e.g., Lophophorus impejanus, Pucrasia macrolopha, and Tragopan melanocephalus) are indicator species of the environment and currently distributed in NHP. For this study, we used Maximum Entropy Model (MaxEnt) to simulate the current (average for 1960–1990) and future (in 2050 and 2070) distributions of the species using three General Circulation Models (GCMs) and two climate change scenarios, i.e., RCP4.5 (moderate carbon emission scenario) and RCP8.5 (peak carbon emission scenario). Our results indicated that (i) under all three climate scenarios, species distribution was predicted to both reduce and shift towards higher altitudes. (ii) Across the provinces in the NHP, the species were predicted to average lose around one-third (35%) in 2050 and one-half (47%) by 2070 of the current suitable habitat. (iii) The maximum area of climate refugia was projected between the altitudinal range of 2000 to 4000 m and predicted to shift towards higher altitudes primarily?>?3000 m in the future. Our results help inform management plans and conservation strategies for mitigating the impacts of climate change on three indicator Galliforms species in the NHP.

     

Spatio-temporal assessment and trend analysis of surface water salinity in the coastal region of Bangladesh

The study was designed to collect water samples over two seasons—wet-monsoon season (n = 96) (March–April) and dry-monsoon season (n = 44) (September–October)—to understand the seasonal variation in anion and cation hydrochemistry of the coastal rivers and estuaries contributing in the spatial trend in salinity. Hydrochemical examination of wet-monsoon season primarily revealed Ca–Mg–HCO₃ type (66%) and followed by Na–Cl type (17.70%) water. In the dry-monsoon season, the scenario reversed with primary water being Na–Cl type (52.27%) followed by Ca–Mg–HCO₃ type (31.81%). Analysis of Cl/Br molar ratio vs. Cl (mg/L) depicted sampling area affected by seawater intrusion (SWI). Spatial analysis by ordinary kriging method confirmed approximately 77% sample in the dry-monsoon, and 34% of the wet-monsoon season had shown SWI. The most saline-intruded areas in the wet-monsoon seasons were extreme south-west coastal zone of Bangladesh, lower Meghna River floodplain and Meghna estuarine floodplain and south-eastern part of Chittagong coastal plains containing the districts of Chittagong and Cox’s Bazar adjacent to Bay of Bengal. In addition, mid-south zone is also affected slightly in the dry-monsoon season. From the analyses of data, this study could further help to comprehend seasonal trends in the hydrochemistry and water quality of the coastal and estuarine rivers. In addition, it can help policy makers to obligate some important implications for the future initiatives taken for the management of land, water, fishery, agriculture and environment of coastal rivers and estuaries of Bangladesh.

     

Atmospheric polycyclic aromatic hydrocarbons observed over the North Pacific Ocean and the Arctic area: Spatial distribution and source identification

During the 2003 Chinese Arctic Research Expedition from the Bohai Sea to the high Arctic (37–80°N) aboard the icebreaker Xuelong (Snow Dragon), air samples were collected using a modified high-volume sampler that pulls air through a quartz filter and a polyurethane foam plug (PUF). These filters and PUFs were analyzed for particulate phase and gas phase polycyclic aromatic hydrocarbons (PAHs), respectively, in the North Pacific Ocean and adjacent Arctic region. The ∑PAHs (where ∑=15 compounds) ranged from undetectable level to 4380 pg m⁻³ in the particulate phase and 928–92 600 pg m⁻³ in the gas phase, respectively. A decreasing latitudinal trend was observed for gas-phase PAHs, probably resulting from temperature effects, dilution and decomposition processes; particulate-phase PAHs, however, showed poor latitudinal trends, because the effects of temperature, dilution and photochemistry played different roles in different regions from middle-latitude source areas to the high latitudes. The ratios of PAH isomer pairs, either conservative or sensitive to degradation during long-range transport, were employed to interpret sources and chemical aging of PAHs in ocean air. In this present study the fluoranthene/pyrene and indeno[123-cd]pyrene/benzo[ghi]pyrene isomer pairs, whose ratios are conservative to photo-degradation, implies that biomass or coal burning might be the major sources of PAHs observed over the North Pacific Ocean and the Arctic region in the summer. The isomer ratios of 1,7/(1,7+2,6)-DMP (dimethylphenanthrene) and anthracene/phenanthrene, which are sensitive to aging of air masses, not only imply chemical evolving of PAHs over the North Pacific Ocean were different from those over the Arctic, but reveal that PAHs over the Arctic were mainly related to coal burning, and biomass burning might have a larger contribution to the PAHs over the North pacific ocean.     

Combined effect of polystyrene plastics and triphenyltin chloride on the green algae Chlorella pyrenoidosa

The combined effect of polystyrene (PS) particles and triphenyltin chloride (TPTCl) to the green algae Chlorella pyrenoidosa was studied. The 96 h IC₅₀ of TPTCl to the green algae C. pyrenoidosa was 30.64 μg/L. The toxicity of PS particles to C. pyrenoidosa was size-dependent, with the 96 h IC₅₀ at 9.10 mg/L for 0.55 μm PS but no toxicity observed for 5.0 μm PS. The exposure to 0.55 μm PS led to damage on structure of algal cells, which could in turn cause inhibition on photosynthesis and population growth of the green algae. TPTCl concentrations in test medium were lowered by 15–19% at presence of 0.55 μm PS particles, indicating a reduced bioavailability of TPTCl. In spite of this reduced bioavailability, the presence of PS increased the toxicity of TPTCl, which might be attributed to facilitated uptake of TPTCl by the green algae after the damage of cell structure. The overall results of the present study provided important information on the effect of PS on the bioavailability and toxicity of TPTCl to phytoplankton species.

     

Sources,distribution, and acidity of sulfate–ammonium aerosol in the Arctic in winter–spring

We use GEOS-Chem chemical transport model simulations of sulfate–ammonium aerosol data from the NASA ARCTAS and NOAA ARCPAC aircraft campaigns in the North American Arctic in April 2008, together with longer-term data from surface sites, to better understand aerosol sources in the Arctic in winter–spring and the implications for aerosol acidity. Arctic pollution is dominated by transport from mid-latitudes, and we test the relevant ammonia and sulfur dioxide emission inventories in the model by comparison with wet deposition flux data over the source continents. We find that a complicated mix of natural and anthropogenic sources with different vertical signatures is responsible for sulfate concentrations in the Arctic. East Asian pollution influence is weak in winter but becomes important in spring through transport in the free troposphere. European influence is important at all altitudes but never dominant. West Asia (non-Arctic Russia and Kazakhstan) is the largest contributor to Arctic sulfate in surface air in winter, reflecting a southward extension of the Arctic front over that region. Ammonium in Arctic spring mostly originates from anthropogenic sources in East Asia and Europe, with added contribution from boreal fires, resulting in a more neutralized aerosol in the free troposphere than at the surface. The ARCTAS and ARCPAC data indicate a median aerosol neutralization fraction [NH₄⁺]/(2[SO₄^2?] + [NO₃^?]) of 0.5 mol mol^?1 below 2 km and 0.7 mol mol^?1 above. We find that East Asian and European aerosol transported to the Arctic is mostly neutralized, whereas West Asian and North American aerosol is highly acidic. Growth of sulfur emissions in West Asia may be responsible for the observed increase in aerosol acidity at Barrow over the past decade. As global sulfur emissions decline over the next decades, increasing aerosol neutralization in the Arctic is expected, potentially accelerating Arctic warming through indirect radiative forcing and feedbacks.     

Atmospheric mercury in the Great Smoky Mountains compared to regional and global levels

Improvements in measurement technology are permitting development of a more detailed scientific understanding of the cycling of mercury in the global atmospheric environment. Critical to advancing the state of knowledge is the acquisition of accurate measurement of speciated mercury (gaseous and particulate) at ground research stations in a variety of settings located around the globe. This paper describes one such research effort conducted at TVA's Look Rock air quality monitoring site in Tennessee—a mountain top site (813 m elevation) just west of the Great Smoky Mountains National Park. The Great Smoky Mountains National Park is the largest National Park in the eastern US and it receives environmental protection under a variety of US statutes. Gaseous and particle mercury species along with some additional trace gases were measured at Look Rock during two field studies totaling 84 days in the spring and summer of 2004. Average results for the entire sampling period are: gaseous elemental mercury Hg(0): 1.65 ng m⁻³, reactive gaseous mercury RGM: 0.005 ng m⁻³, particulate mercury Hg(p): 0.007 ng m⁻³. Literature review indicates that these levels are within the range found for other rural/remote sites in North America and worldwide. Reactive and particulate mercury comprised together less than 1%, on average, of total airborne mercury at Look Rock. When compared to the global background mercury literature, the Look Rock measurements demonstrate that the atmospheric mercury levels in the vicinity of the Great Smoky Mountains National Park are clearly dominated by the global atmospheric pool, not by local or regional sources.     

Multi-year measurements of polybrominated diphenyl ethers (PBDEs) in the Arctic atmosphere

Weekly high-volume air samples have been collected in the Canadian High Arctic (Alert, Nunavut) since 1992. Fifteen polybrominated diphenyl ethers (PBDEs) are quantified in 104 samples over the time period of 2002–2004. To our knowledge, this study reports the first continuous multi-year measurements of PBDEs in Arctic air. Average air concentrations (in pg m⁻³) were 7.7 (0.40–47) and 1.6 (0.091–9.8) for 14 PBDEs (excluding BDE-209) and BDE-209, respectively, over the entire sampling period. BDE-28/33, 47, 99, 100, 153, 154, and 209 accounted for 90% (72–97%, n=104) of the 15 PBDEs. Occurrence of BDE-47, 99, and 209 suggests that PBDEs in Alert air were likely associated with the usage of “penta-BDE” and “deca-BDE” technical mixtures worldwide. Natural logarithm of concentrations for less brominated PBDEs correlated significantly with ambient temperatures in the summertime, suggesting importance of volatilization emissions in a local and/or regional scale. On the other hand, episodically elevated concentrations of the less brominated PBDEs in the wintertime and lack of seasonality for the non-volatile BDE-209 indicate potential inputs of particle-bound PBDEs through long-range transport (LRT), especially during the Arctic haze season. Inter-annual trend data further show that concentrations of the eight PBDEs increased inter-annually in 2002–2004 with doubling times of 2–6 years, which were similar to growth rates found in Arctic biotic samples. The results of this study and previous measurements suggest that potential sources of PBDEs in Arctic air include both volatilization emissions and LRT inputs.     

Air concentrations of polybrominated diphenyl ethers (PBDEs) in 2002–2004 at a rural site in the Great Lakes

Atmospheric PBDEs were measured on a monthly basis in 2002–2004 at Point Petre, a rural site in the Great Lakes. Average air concentrations were 7.0 ± 13 pg m^?3 for Σ₁₄BDE (excluding BDE-209), and 1.8 ± 1.5 pg m^?3 for BDE-209. Concentrations of 3 dominant congeners (i.e., BDE-47, 99, and 209) were comparable to previous measurements at remote/rural sites around the Great Lakes, but much lower than those at urban areas. Weak temperature dependence and strong linear correlations between relatively volatile congeners suggest importance of advective inputs of gaseous species. The significant correlation between BDE-209 and 183 implies their transport inputs associated with particles. Particle-bound percentages were found greater for highly brominated congeners than less brominated ones. These percentages increase with decreasing ambient temperatures. The observed gas/particle partitioning is consistent with laboratory measurements and fits well to the Junge–Pankow model. Using air mass back-trajectories, atmospheric transport to Point Petre was estimated as 76% for BDE-47, 67% for BDE-99, and 70% for BDE-209 from west–northwest and southwest directions. During the same time period, similar congener profiles and concentration levels were found at Alert in the Canadian High Arctic. Different inter-annual variations between Point Petre and Alert indicate that emissions from other regions than North America could also contribute PBDEs in the Arctic. In contrast to weak temperature effect at Point Petre, significant temperature dependence in the summertime implies volatilization emissions of PBDEs at Alert. Meanwhile, episodic observations in the wintertime were likely associated with enhanced inputs through long-range transport during the Arctic Haze period.     

Trends in near-surface ozone concentrations in Switzerland: the 1990s

A time series analysis of ozone monitoring data from several locations in Switzerland from 1991 to 1999 is presented. Different methods are used to address changes in the ozone level during these years and to account for the influence of changing meteorological conditions. The results show a slight decrease of the peaks but a highly significant increase of the mean value of around 0.5–0.9 ppb yr⁻¹. The frequency distribution has changed in the sense that very low values have become less frequent and that there is a strong increase in frequency of occurrence of half-hourly mean values between about 45 and 55 ppb. A selection procedure reveals slight tendencies towards different trends of afternoon ozone peaks in summer depending on weather and pollution situations. Ozone peaks tend to decrease on fair weather days at rural sites (but increase at urban sites) and show a small increase on cloudy and windy days. A non-linear regression model is used to estimate trends of summertime afternoon ozone peaks in the presence of meteorological variability. In the model, the long-term signal is additively split into a linear part and a part which is modulated by global radiation. The coefficients for both terms are statistically significant at many sites, with an increasing linear trend at the sites north of the Alps of around 1 ppb yr⁻¹ and a decrease of ozone peaks under fair weather conditions relative to cloudy conditions. When additionally considering the effect of precursor concentrations in the regression models, both trends are weakened, which means that they can partly be explained by changes in local to regional emissions. However, at the sites north of the Alps remains a tendency towards a positive linear “base trend” of around 0.4 ppb yr⁻¹. This could possibly be due to increasing background ozone concentrations.