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191.
Increasing polybrominated diphenyl ether (PBDE) contamination in sediment cores from the inner Clyde Estuary,UK 总被引:1,自引:0,他引:1
Christopher H. Vane Yun-Juan Ma She-Jun Chen Bi-Xian Mai 《Environmental geochemistry and health》2010,32(1):13-21
The concentrations of 16 polybrominated diphenyl ether (PBDE) congeners in six short sediment cores from the Clyde Estuary
were determined by gas-chromatography mass-spectrometry. Total PBDE concentrations ranged from 1 to 2,645 μg/kg and the average
concentration was 287 μg/kg. BDE-209 was the main congener and varied from 1 to 2,337 μg/kg. Elevated total PBDE concentrations
were observed close to the sediment surface in the uppermost 10 cm of four of the six sediment cores. Comparison of the down
core PBDE profiles revealed that the increase was driven by the accumulation of deca-BDE. Although the deca-BDE mix was dominant,
the presence of lower molecular weight congeners BDE-47, BDE-99, BDE-183 and BDE-153 at most sediment intervals suggested
additional sources of penta-BDE and octa-BDE pollution. Changing PBDE source input was the major factor in influencing the
proportion of nona-brominated congeners, although other explanations such as post burial photo-debromination of BDE-209 cannot
be entirely discounted. A clear cascading to lower hepta-, hexa-, and penta-homologues was not found. The increase in total
PBDE concentrations and particularly the deca-BDE may possibly be ascribed to the use and subsequent disposal of electrical
appliances such as televisions and computers. In the Clyde sediments, the proportion of nona-brominated congeners was higher
than that reported for commercial mixtures. This might be due to changing sources of PBDEs or post burial photo-debromination
of BDE-209. 相似文献
192.
Christopher Brandl Alexander Mertens Christopher M. Schlick 《International journal of occupational safety and ergonomics》2013,19(1):110-117
In semi-trailer assembly, workers are exposed to several physical risk factors. Awkward working postures have not yet been investigated in semi-trailer assembly, although they are known to be a major risk factor for musculoskeletal disorders. We therefore conducted a comprehensive ergonomic analysis of working postures using the Ovako working posture analysing system (OWAS), with an individual sampling strategy. The postural load in semi-trailer assembly was assessed on the basis of 20,601 observations of 63 workers executing a representative set of nine work tasks. According to the OWAS, the postural load of various working postures and body part positions may have a harmful effect on the musculoskeletal system. We therefore give examples of corrective measures that could improve awkward working postures. Applying an individual sampling strategy was revealed to have advantages over a collective strategy, so this is recommended for future ergonomic analyses. 相似文献
193.
Eric D. Stein Matthew R. Cover A. Elizabeth Fetscher Clare O'Reilly Roxana Guardado Christopher W. Solek 《Journal of the American Water Resources Association》2013,49(4):780-792
Armoring of streambanks is a common management response to perceived threats to adjacent infrastructure from flooding or erosion. Despite their pervasiveness, effects of reach‐scale bank armoring have received less attention than those of channelization or watershed‐scale hydromodification. In this study, we explored mechanistic ecosystem responses to armoring by comparing conditions upstream, within, and downstream of six stream reaches with bank armoring in Southern California. Assessments were based on four common stream‐channel assessment methods: (1) traditional geomorphic measures, (2) the California Rapid Assessment Method for wetlands, (3) bioassessment with benthic macroinvertebrates, and (4) bioassessment with stream algae. Although physical responses varied among stream types (mountain, transitional, and lowland), armored segments generally had lower slopes, more and deeper pools and fewer riffles, and increased sediment deposition. Several armored segments exhibited channel incision and bank toe failure. All classes of biological indicators showed subtle, mechanistic responses to physical changes. However, extreme heterogeneity among sites, the presence of catchment‐scale disturbances, and low sample size made it difficult to ascribe observed patterns solely to channel armoring. The data suggest that species‐level or functional group‐level metrics may be more sensitive tools than integrative indices of biotic integrity to local‐scale effects. 相似文献
194.
Using Paleo Reconstructions to Improve Streamflow Forecast Lead Time in the Western United States 总被引:2,自引:0,他引:2
Christopher Carrier Ajay Kalra Sajjad Ahmad 《Journal of the American Water Resources Association》2013,49(6):1351-1366
In water stressed regions, water managers are exploring new horizons that would help in long‐range streamflow forecasts. Oceanic‐atmospheric oscillations have been shown to influence streamflow variability. In this study, long‐lead time streamflow forecasts are made using a multiclass kernel‐based data‐driven support vector machine (SVM) model. The extended streamflow records based on tree ring reconstructions were used to provide a longer time series data. Reconstructed data were used from 1658 to 1952 and the instrumental record was used from 1953 to 2007. Reconstructions for oceanic‐atmospheric oscillations included the El Niño‐Southern Oscillation, Pacific Decadal Oscillation, Atlantic Multidecadal Oscillation, and North Atlantic Oscillation. Streamflow forecasts using all four oscillations were made with one‐year to five‐year lead times for 21 gages in the western United States. This is the first study that uses both instrumental and reconstructed data of oscillations in SVM model to improve streamflow forecast lead time. SVM model was able to provide “satisfactory” to “very good” forecasts with one‐ to five‐year lead time for the selected gages. The use of all the oscillation indices helped in achieving better predictability compared to using individual oscillations. The SVM modeling results are better when compared with multiple linear regression model forecasts. The findings are statistical in nature and are expected to be useful for long‐term water resources planning and management. 相似文献
195.
Hummingbird with modern feathering: an exceptionally well-preserved Oligocene fossil from southern France 总被引:1,自引:0,他引:1
Louchart A Tourment N Carrier J Roux T Mourer-Chauviré C 《Die Naturwissenschaften》2008,95(2):171-175
Hummingbirds (Trochilidae) today have an exclusively New World distribution, but their pre-Pleistocene fossil record comes from Europe only. In this study, we describe an exceptionally preserved fossil hummingbird from the early Oligocene of southeastern France. The specimen is articulated, with a completely preserved beak and feathering. Osteological characters allow to identify it as Eurotrochilus sp. This genus is a stem group representative of Trochilidae and was recently described from the early Oligocene of southern Germany. The new fossil reveals that these European Trochilidae were remarkably modern in size, skeletal proportions and the shape of the wing, tail and beak and hyoid bones. These features confirm the early acquisition of the abilities of hovering and nectarivory in hummingbirds, probably before the Oligocene. In several morphological characteristics, they resemble members of the 'true hummingbirds' (subfamily Trochilinae) and differ from hermits (Phaethornithinae). These features, which include a short and square tail and a moderately long, almost straight beak, appear to be primitive within the family Trochilidae. 相似文献
196.
A new assemblage of basal dichobunoid artiodactyls from the middle-Eocene Shanghuang fissure fillings includes the diacodexeid
Jiangsudon shanghuangensis gen. and sp. nov., a new species of the lantianine dichobunoid Elaschitotherium, Elaschitotherium crepaturus sp. nov., and an indeterminate suoid which is presently the earliest record of this clade. Diacodexeids are also represented
by two forms provisionally referred to cf. Diacodexis sp. and to an indeterminate Diacodexeidae, respectively. The occurrence of diacodexeids in Shanghuang contrasts with the
early and earliest middle-Eocene chronological range of the family in Europe and North America and suggests that the stratigraphic
range of the family in Asia extends up to the middle Eocene. This may reflect particular habitats in coastal China that may
have been relatively stable during the early and middle Eocene, thus preserving forest-dwelling artiodactyls that became extinct
in the other Holarctic regions. Compared to other supposedly coeval North American, European, and Asian faunas, the Shanghuang
mammalian assemblage is most similar to early Uintan faunas of North America but is also remarkable in recording forms close
to taxa that are characteristic of the Wasatchian and Bridgerian North American Land Mammal Ages. The Irdinmanhan age of the
Shanghuang fauna is supported by the mammalian assemblage recovered from the fissure D, but an Arshantan age cannot be completely
ruled out at this point. Although the Shanghuang assemblage is biased towards preservation of small components of the mammalian
fauna, the Shanghuang fauna provide an important and unique window into the Eocene diversity and early evolution of cetartiodactyls
in eastern Asia. 相似文献
197.
This study presents a method for assessing conservation opportunity on private land based on landholders' socio-economic, behavioral, and farm characteristics. These characteristics include age, gender, education, level of off-farm income, farm size, proportion of remnant native vegetation on-farm, and ecological value of native vegetation on-farm. A sample of landholders who own greater than 2 ha of land in the South Australian Murray-Darling Basin region were sent a mail-based survey about their values and preferences for environmental management (N = 659, 52% response). Cross-tabulations and ANOVA statistical analysis techniques were used to compare the socio-economic attributes across three landholder classes: disengaged, moderately engaged, and highly engaged in native vegetation planting. Results indicate that highly engaged landholders were more likely to be female, formally educated, hobby farmers who managed small parcels of land and have high off-farm incomes, whereas disengaged landholders held significantly stronger farming connections (more farming experience, family have lived on the farm for more generations). Spatial analysis revealed area-specific differences in conservation opportunity and conservation priority. In some areas, properties of high ecological value were managed by highly engaged landholders, but nearby properties of high value were managed by moderately engaged or disengaged landholders. Environmental managers therefore cannot assume areas of high conservation priority will be areas of high conservation opportunity. At the regional scale, the potential for revegetation seems most promising within the moderately engaged landholder group considering the vast amount of land managed by this group in areas of high ecological value, particularly within the less represented Mallee and Coorong and Rangelands sub-regions. We suggest that incentive schemes which purchase conservation need to be targeted at disengaged landholders; mentoring schemes led by commercial farmers highly engaged in native vegetation planting should be directed at moderately engaged landholders, and; awards programs which acknowledge conservation successes should be targeted at highly engaged landholders. 相似文献
198.
Many alpine ski areas have recently adopted voluntary environmental programs (VEPs) such as using recycling, renewable energy,
and biofuels to help reduce their environmental impacts. Studies have addressed the performance of these VEPs in mitigating
environmental impacts of this industry, but little is known about visitor awareness and perceptions of these programs. This
article addresses this knowledge gap by exploring skier and snowboarder knowledge of VEPs at a ski area and the influence
of these programs on their motivations to visit this area currently and behavioral intentions to visit again in the future.
Data were obtained from an onsite survey at the Mt. Bachelor ski area in Oregon, USA (n = 429, 89.7% response rate). Few skiers and snowboarders were knowledgeable of VEPs at this area and fewer than 20% were
motivated to visit on their current trip because of these programs. Other attributes such as scenery, snow conditions, and
access were more important for influencing visitation. Up to 38% of skiers and snowboarders, however, intend to visit this
ski area more often if it adopts and promotes more VEPs. Managers can use these results to inform communication and marketing
of their environmental programs and performance to visitors. Additional implications for management and future research are
discussed. 相似文献
199.
The even-aged northern hardwood forests of the Upper Great Lakes Region are undergoing an ecological transition during which structural and biotic complexity is increasing. Early-successional aspen (Populus spp.) and birch (Betula papyrifera) are senescing at an accelerating rate and are being replaced by middle-successional species including northern red oak (Quercus rubra), red maple (Acer rubrum), and white pine (Pinus strobus). Canopy structural complexity may increase due to forest age, canopy disturbances, and changing species diversity. More structurally complex canopies may enhance carbon (C) sequestration in old forests. We hypothesize that these biotic and structural alterations will result in increased structural complexity of the maturing canopy with implications for forest C uptake. At the University of Michigan Biological Station (UMBS), we combined a decade of observations of net primary productivity (NPP), leaf area index (LAI), site index, canopy tree-species diversity, and stand age with canopy structure measurements made with portable canopy lidar (PCL) in 30 forested plots. We then evaluated the relative impact of stand characteristics on productivity through succession using data collected over a nine-year period. We found that effects of canopy structural complexity on wood NPP (NPPw) were similar in magnitude to the effects of total leaf area and site quality. Furthermore, our results suggest that the effect of stand age on NPPw is mediated primarily through its effect on canopy structural complexity. Stand-level diversity of canopy-tree species was not significantly related to either canopy structure or NPPw. We conclude that increasing canopy structural complexity provides a mechanism for the potential maintenance of productivity in aging forests. 相似文献
200.
Species interactions can induce morphological changes in organisms that affect their subsequent growth and survival. In Moorea,
French Polynesia, epibiotic gammaridean amphipods induce the formation of long, branch-like coral “fingers” on otherwise flat,
encrusting, or plating Montipora coral colonies. The fingers form as corals encrust tubes built by the amphipods and lead to significant changes in colony
morphology. This study examines the costs and benefits of this association to the amphipods and corals and demonstrates that
the interaction is a mutualism. Amphipods gain protection from predators by living within corals, and corals benefit by enhanced
growth and survival. Benefits to the coral arise through direct effects due to the amphipods’ presence as well as through
benefits derived from the altered colony morphology. This study demonstrates that induced morphological plasticity can be
a mechanism for facilitation, adding to our knowledge of the roles mutualism, and phenotypic plasticity play in ecology. 相似文献