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351.
Timothy M. Barzyk Barbara Jane George Alan F. Vette Ronald W. Williams Carry W. Croghan Carvin D. Stevens 《Atmospheric environment (Oxford, England : 1994)》2009,43(4):787-797
The primary objective of the Detroit Exposure and Aerosol Research Study (DEARS) was to compare air pollutant concentrations measured at various neighborhoods, or exposure monitoring areas (EMAs), throughout a major metropolitan area to levels measured at a central site or community monitor. One of the EMAs was located near a busy freeway (annual average daily traffic (AADT) of ~130,000) so that impacts of mobile sources could be examined. Air pollution concentrations from the roadway-proximate sites were compared to the central site monitor. The volatile organic compounds (VOCs) selected (benzene, toluene, ethylbenzene, m,p- and o-xylene, 1,3 butadiene, 1,3,5-trimethylbenzene and 4-ethyltoluene) are typically associated with mobile sources. Gradients were also evident that demonstrated the amplification of pollutant levels near the roadway compared to the community monitor. A novel distance-to-roadway proximity metric was developed to plot the measurements and model these gradients. Effective distance represents the actual distance an air parcel travels from the middle of a roadway to a site and varies as a function of wind direction, whereas perpendicular distance is a fixed distance oriented normal to the roadway. Perpendicular distance is often used as a proxy for exposures to traffic emissions in epidemiological studies.Elevated concentrations of all the compounds were found for both a summer and winter season. Effective distance was found to be a statistically significant (p < 0.05) univariate predictor for concentrations of toluene, ethylbenzene, m,p-xylene and o-xylene for summer 2005. For each of these pollutants, effective distance yielded lower p-values than the corresponding perpendicular distance models, and model fit improved. Results demonstrate that this near-road EMA had elevated levels of traffic-related VOCs compared to the community monitor, and that effective distance was a more accurate predictor of the degree to which they were elevated as a function of distance. Effective distance produced a range of distance-to-roadway values for a single site based on wind direction, thus increasing the number and range of values that could be used to plot and predict relative differences in pollutant concentrations between two sites. 相似文献
352.
Travis B. Paveglio Pamela J. Jakes Matthew S. Carroll Daniel R. Williams 《Environmental management》2009,43(6):1085-1095
The lack of knowledge regarding social diversity in the Wildland Urban Interface (WUI) or an in-depth understanding of the
ways people living there interact to address common problems is concerning, perhaps even dangerous, given that community action
is necessary for successful wildland fire preparedness and natural resource management activities. In this article, we lay
out the knowledge and preliminary case study evidence needed to begin systematically documenting the differing levels and
types of adaptive capacity WUI communities have for addressing collective problems such as wildland fire hazard. In order
to achieve this end, we draw from two theoretical perspectives encompassing humans' interactions with their environment, including
(1) Kenneth Wilkinson's interactional approach to community, (2) and certain elements of place literature. We also present
case study research on wildfire protection planning in two drastically different California communities to illustrate how
social diversity influences adaptive capacity to deal with hazards such as wildland fire. These perspectives promote an image
of the WUI not as a monolithic entity but a complex mosaic of communities with different needs and existing capacities for
wildland fire and natural resource management. 相似文献
353.
Mehrey G. Vaghti Marcel Holyoak Amy Williams Theresa S. Talley Alexander K. Fremier Steven E. Greco 《Environmental management》2009,43(1):28-37
Societal constraints often limit full process restoration in large river systems, making local rehabilitation activities valuable
for regeneration of riparian vegetation. A target of much mitigation and restoration is the federally threatened Valley elderberry
longhorn beetle and its sole host plant, blue elderberry, in upper riparian floodplain environments. However, blue elderberry
ecology is not well understood and restoration attempts typically have low success rates. We determined broad-scale habitat
characteristics of elderberry in altered systems and examined associated plant species composition in remnant habitat. We
quantified vegetation community composition in 139 remnant riparian forest patches along the Sacramento River and elderberry
stem diameters along this and four adjacent rivers. The greatest proportion of plots containing elderberry was located on
higher and older floodplain surfaces and in riparian woodlands dominated by black walnut. Blue elderberry saplings and shrubs
with stems <5.0 cm in diameter were rare, suggesting a lack of recruitment. A complex suite of vegetation was associated with
blue elderberry, including several invasive species which are potentially outcompeting seedlings for light, water, or other
resources. Such lack of recruitment places increased importance on horticultural restoration for the survival of an imperiled
species. These findings further indicate a need to ascertain whether intervention is necessary to maintain functional and
diverse riparian woodlands, and a need to monitor vegetative species composition over time, especially in relation to flow
regulation. 相似文献
354.
H. T. Schreuder M. S. Williams R. M. Reich 《Environmental monitoring and assessment》1999,56(3):293-303
Using some large samples as actual populations we study a series of promising estimators for number of species in a population. We recommend a nonparametric estimator, CM2f = cs + fc1/(2c2) where cs is the number of species observed, c1 and c2 are the numbers of species occurring once and twice respectively on the sample plots, and f is the finite population correction for sampling, from such data as collected by Forest Inventory and Analysis (FIA) of the US Forest Service. For FIA samples, there are estimated to be 0, 4, 3, 1 and 6 rare tree species not sampled in Minnesota, Missouri, Pennsylvania, New, York, and Ohio respectively. 相似文献
355.
Phylogenetic relationships among giant clam species (Mollusca: Tridacnidae) determined by protein electrophoresis 总被引:1,自引:0,他引:1
Analyses of allozyme variation at 26 loci in eight species of giant clams, collected from the Western Pacific between 1989
and 1991, have confirmed the major groupings currently recognised within the family Tridacnidae on the basis of morphological
characters: the two genera Hippopus and Tridacna, and the subgenera within Tridacna; i.e. Chametrachea (comprising T.squamosa, T.crocea and T.maxima), Tridacna sensu stricto (containing only T. gigas), and Persikima (comprising T. derasa and T. tevoroa). All these groupings were each supported by several shared characters. In contrast to previous views, Persikima was found to be intermediate between Chametrachea and T. gigas. Although statistical support for branch lengths linking Chametrachea and T. gigas was limited in maximum-likelihood analyses, the occurrence of several shared alleles between these groups, and none shared
between only Chametrachea and Persikima, suggests a closer relationship between Chametrachea and T. gigas or, at least, an unresolved trichotomy. Morphological data traditionally assumed to support a closer association of Chametrachea and Persikima demonstrated that only one shared character linked subgenera, and this character supported an evolutionary association between
Chametrachea and T. gigas. These findings, together with the number of shared characters supporting the subgenus Persikima, suggest that Persikima is the most basal offshoot of the Tridacna line, and that the group may deserve generic status.
Received: 21 November 1997 / Accepted: 24 March 1998 相似文献
356.
R. Morgan E. Gatell R. Junyent A. Micallef E. Özhan A. T. Williams 《Journal of Coastal Conservation》2000,6(1):41-50
In many coastal resort areas of the world, it is likely that optimal climatic conditions for beach use might occur outside
the peak of the tourist season. Investigation of this issue together with associated publicity might help to spread the tourism
load and hence reduce undesirable social and environmental effects of extreme seasonality in tourist demand. For this to take
place, better knowledge of beach user preferences in terms of climate and bathing water temperature is required. Questionnaire
surveys were carried out in Wales, Malta and Turkey to establish the preferences of north European beach users for thermal
sensation and bathing water temperature, plus priority levels for other climatic attributes. A user-based beach climate index
based on these preferences and priorities was formulated. Linkage was made between the user-generated ratings for various
climatic conditions and published climate data to evaluate most major Euro-Mediterranean/Black Sea and a range of other beach
tourism areas on a month-by-month basis. Results showed excessively hot thermal sensation in many southern and eastern Mediterranean
coastal destinations during July and August, the present peak of the beach tourism season. Highest preference was given to
water temperatures rather lower than those found in these areas during late summer. Many long haul coastal destinations popular
with north European visitors had similar unpleasant thermal sensations over several months. Uncertainties and deficiencies
still exist with the system, but from the point of view of north European beach users the final scores generated in this study
may be regarded as good approximations of the quality of resort area climates for sedentary beach use. 相似文献
357.
R. H. F. Curr A. Koh E. Edwards A. T. Williams P. Davies 《Journal of Coastal Conservation》2000,6(1):15-22
The Mediterranean region plays host to ca. 33% of the world’s tourism industry. This population of visitors (ca. 147 million
in 1990) inevitably exerts an enormous impact on the natural resources of this coastal zone. In May 1997, a new generation
Aerial Digital Photographic System [ADPS] configured with a Kodak Digital Science 460 CIR digital camera was used to acquire
colour infrared digital photographs of the sand dune systems along the Mediterranean coast of France, from Le Barcares to
St-Cyprien-Plage. These have been used to assess the condition of the dunes along this coast. A series of simple analytical
techniques to identify and measure features indicative of public pressure using image processing software has been devised.
The dune manager with basic computer skills can analyse such indicators as path length, vegetation cover (and conversely the
extent of bare sand) to enable monitoring of the performance of their dune systems under particular management regimes. These
photographs have been compared with similar digital photographs of dune sites in SW France to allow a comparison of dune degradation
in a region with a different population pressure and climate regime. Dune systems sampled from the Mediterranean coastal zone
showed more evidence of anthropogenically induced change than those sampled in SW France. 相似文献
358.
Colomb A Yassaa N Williams J Peeken I Lochte K 《Journal of environmental monitoring : JEM》2008,10(3):325-330
Five marine cosmopolitan phytoplankton species namely; Calcidiscus leptoporus, Emiliania huxleyi, Phaeodactylum tricornutum, Chaetoceros neogracilis and Dunaliella tertiolecta were screened for emissions of selected VOCs using head space gas chromatography/mass spectrometry (HS-GC/MS) in single ion mode. The VOCs investigated included isoprene and various halogenated compounds. Among the different algae groups, the two diatoms Ch. neogracilis and P. tricornutum were the strongest emitters of methyl bromide (CH3Br), and Ch. neogracilis was the strongest emitter of isoprene. Furthermore, we present evidence that several chlorinated organic compounds, normally considered as anthropogenic, can be produced from marine phytoplankton (namely chloroform, dichloromethane, trichloroethylene, tetrachloroethylene, chlorobenzene and dichlorobenzene). 相似文献
359.
Profiling the ionome of rice and its use in discriminating geographical origins at the regional scale, China 总被引:6,自引:0,他引:6
Gang Li Luis Nunes Yijie Wang Paul N. Williams Maozhong Zheng Qiufang Zhang Yongguan Zhu 《环境科学学报(英文版)》2013,24(1):144-154
Element profile was investigated for their use to trace the geographical origin of rice (Oryza sativa L.) samples. The concentrations of 13 elements (calcium (Ca), potassium (K), magnesium (Mg), phosphorus (P), boron (B), manganese (Mn), iron (Fe), nickel (Ni), copper (Cu), arsenic (As), selenium (Se), molybdenum (Mo), and cadmium (Cd)) were determined in the rice samples by inductively coupled plasma optical emission and mass spectrometry. Most of the essential elements for human health in rice were within normal ranges except for Mo and Se. Mo concentrations were twice as high as those in rice from Vietnam and Spain. Meanwhile, Se concentrations were three times lower in the whole province compared to the Chinese average level of 0.088 mg/kg. About 12% of the rice samples failed the Chinese national food safety standard of 0.2 mg/kg for Cd. Combined with the multi-elemental profile in rice, the principal component analysis (PCA), discriminant function analysis (DFA) and Fibonacci index analysis (FIA) were applied to discriminate geographical origins of the samples. Results indicated that the FIA method could achieve a more effective geographical origin classification compared with PCA and DFA, due to its efficiency in making the grouping even when the elemental variability was so high that PCA and DFA showed little discriminatory power. Furthermore, some elements were identified as the most powerful indicators of geographical origin: Ca, Ni, Fe and Cd. This suggests that the newly established methodology of FIA based on the ionome profile can be applied to determine the geographical origin of rice. 相似文献
360.