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211.
Dinuke Munasinghe Sagy Cohen Yu‐Fen Huang Yin‐Phan Tsang Jiaqi Zhang Zheng Fang 《Journal of the American Water Resources Association》2018,54(4):834-846
The objective of this study was to determine the accuracy of five different digital image processing techniques to map flood inundation extent with Landsat 8–Operational Land Imager satellite imagery. The May 2016 flooding event in the Hempstead region of the Brazos River, Texas is used as a case study for this first comprehensive comparison of classification techniques of its kind. Five flood water classification techniques (i.e., supervised classification, unsupervised classification, delta‐cue change detection, Normalized Difference Water Index [NDWI], modified NDWI [MNDWI]) were implemented to characterize flooded regions. To identify flood water obscured by cloud cover, a digital elevation model (DEM)–based approach was employed. Classified floods were compared using an Advanced Fitness Index to a “reference flood map” created based on manual digitization, as well as other data sources, using the same satellite image. Supervised classification yielded the highest accuracy of 86.4%, while unsupervised, MNDWI, and NDWI closely followed at 79.6%, 77.3%, and 77.1%, respectively. Delta‐cue change detection yielded the lowest accuracy with 70.1%. Thus, supervised classification is recommended for flood water classification and inundation map generation under these settings. The DEM‐based approach used to identify cloud‐obscured flood water pixels was found reliable and easy to apply. It is therefore recommended for regions with relatively flat topography. 相似文献
212.
Yechiel Soffer Avishay Goldberg Bruria Adini Robert Cohen Menachem Ben‐Ezra Yuval Palgi Nir Essar Yaron Bar‐Dayan 《Disasters》2011,35(1):36-44
Perceptions, knowledge and mitigation are factors that might play a role in preventing injury and loss of life during a major earthquake.2 Little is known about the relationships between different demographic and educational parameters and these factors. A national representative sample of 495 adults was investigated in order to determine the relationship between demographic and educational parameters in terms of the perceived threat, perceived coping, knowledge and mitigation of earthquakes in Israel. Compared to females, males perceived the threat of earthquakes to be lower (t=3.183, p=0.002), manifested higher levels of perceived coping (t=2.55, p=0.011), and had higher levels of earthquake related knowledge (t=2.047, p=0.041). We conclude that there are gender differences in perceptions and knowledge regarding earthquakes. 相似文献
213.
M. Radhi M.A. Box G.P. Box R.M. Mitchell D.D. Cohen E. Stelcer M.D. Keywood 《Atmospheric environment (Oxford, England : 1994)》2010,44(29):3519-3528
Australia is the dominant mineral dust source in the southern hemisphere, yet the physical, chemical and optical properties of Australian dust aerosol are presently poorly understood. We have investigated the properties of Australian aerosol at a site near Lake Eyre in central Australia, which is strongly influenced by mineral dust. During a field campaign in November 2007 we collected eight sets of size-resolved aerosol samples for laboratory analysis: six during quiescent conditions, and two during dust storms. Ion Beam Analysis was used to determine the elemental composition of all filter samples. Scatter plots showed that Fe, Al and Ti were well correlated with Si, and hence soil-derived. The Fe/Si ratio was consistently higher than the global crustal average, confirming that Australian dusts are comparatively rich in Fe. Scatter plots for Na and Cl against Si showed clear evidence of a second aerosol population, associated with maritime advection. Profiles of water soluble ions for two sample sets, showed the importance of marine influences on both the fine and coarse modes, as well as the presence of organic acids. Estimates of the mass fraction of NaCl in our samples suggest that, for quiescent days, roughly 0.5% of the sample mass was NaCl. 相似文献
214.
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216.
The European fanworm Sabella spallanzanii (Gmelin, 1791) was recently introduced to Port Phillip Bay and is now a conspicuous component of most benthic communities.
Reproduction of the worm was investigated in a population at Queenscliff over a 2 yr period (October 1995 to October 1997)
using gonadal histology. The worms are dioecious (sex ratio 1:1, n=250), and attained sexual maturity at ∼50 mm body length. Reproductive periodicity followed a distinct annual cycle, and
spawning proceeded through an extended autumn/winter period. Spawning was broadly synchronous between sexes, and coincided
with falling seawater temperatures and shorter day-lengths. The females were highly fecund, and >50 000 eggs were probably
shed from large females (>300 mm body length) during the annual spawning period. Breeding cycles of S. spallanzanii in Port Phillip Bay are ∼6 mo out of phase with endemic populations located at similar latitudes in the northern hemisphere.
The spread of S. spallanzanii within Port Phillip Bay has been monitored by divers on an annual basis since 1994. The most recent dive survey (1998) indicates
that S. spallanzanii has extended its range through out the entire 2000 km2 embayment, and has invaded most subtidal habitats. Quantitative estimates of S. spallanzanii abundances were highest on pier pylons (12.5 individuals m−2, 0.5 to 7 m depths). On sediments, estimates were highest at shallow sites (0.3 m−2, 7 m depth), but numbers declined significantly with depth (0.1 m−2, 17 to 22 m depth). Mean worm lengths and biomass were, by contrast, significantly higher at intermediate depths (12 to 17 m)
than in shallower (7 m) or deeper (22 m) locations. S. spallanzanii demonstrates a clear preference for growth in sheltered, nutrient-enriched waters, so it may not spread from Port Phillip
Bay into the adjacent oceanic waters of Bass Strait; however, in view of S. spallanzanii's current high abundance, fecundity and extended spawning periodicity, there is a high risk of future range expansions, mediated
by shipping, into other temperate-water ports.
Received: 17 November 1998 / Accepted: 6 January 2000 相似文献
217.
David D. Cohen Jagoda Crawford Eduard Stelcer Vuong Thu Bac 《Atmospheric environment (Oxford, England : 1994)》2010,44(3):320-328
PM2.5 particulate matter has been collected on Teflon filters every Sunday and Wednesday at Hanoi, Vietnam for nearly eight years from April 2001 to December 2008. These filters have been analysed for over 21 different chemical species from hydrogen to lead by ion beam analysis techniques. This is the first long term PM2.5 dataset for this region. The average PM2.5 mass for the study period was (54 ± 33) μg m?3, well above the current US EPA health goal of 15 μg m?3. The average PM2.5 composition was found to be (29 ± 8)% ammonium sulfate, (8.9 ± 3.3)% soil, (28 ± 11)% organic matter, (0.6 ± 1.4)% salt and (9.2 ± 2.8)% black carbon. The remaining missing mass (25%) was mainly nitrates and absorbed water. Positive matrix factorisation techniques identified the major source contributions to the fine mass as automobiles and transport (40 ± 10)%, windblown soil (3.4 ± 2)%, secondary sulfates (7.8 ± 10)%, smoke from biomass burning (13 ± 6)%, ferrous and cement industries (19 ± 8)%, and coal combustion (17 ± 7)% during the 8 year study period. 相似文献
218.
An extremely acidic, heavy metal-rich sludge (pH=-1.2) was scrubbed with a Class-F fly ash in order to simultaneously neutralize the acidity and stabilize the heavy metals contained in both wastes. This paper outlines the leaching behavior of the aggregate material generated by scrubbing. For proper fly ash/sludge ratios, the fly ash acted as an outstanding neutralizer for the acidic waste. Leaching of heavy metals from the aggregate samples was below the environmental limits within a pH range between 3 and 9. Subsequent washing of the leached aggregate with acidic CALWET solutions did not result in an additional release of heavy metals. It is proposed that coordinative bonding of the metal cations onto neutral surface sites and electrostatic adsorption led to stabilization of the heavy metals within the aggregate structure below hydrolysis pHs. 相似文献
219.
Weekly variation of atmospheric particle micromorphology and chemistry in Brussels urban environment
Eli Zaady D. Carati L. Brenig P. Vanderstraeten Y. Lénelle A. Meurrens Z. Y. Offer 《Environmental monitoring and assessment》2010,169(1-4):45-54
The purpose of this study was to measure the impact of urban activities on airborne particle dynamics during weekend periods in Brussels urban area. Differences in the granulometry and micromorphology between particles sampled on working days and weekends were studied. We quantified the area, size, number, and the chemistry parameters of the airborne particles and compared between Saturday, Sunday, and Monday. We report and analyze data on airborne particles up to PM10, measured in the Brussels region from October 2002 to September 2003. Our investigation reveals detailed information regarding chemical composition of the airborne particles over the weekend period in the Brussels urban area. Furthermore, the majority of the airborne particles in the Brussels region may belong to sources geographically outside the (in situ) Brussels area. 相似文献
220.
Rachael Martin Kim Dowling Dora C. Pearce Singarayer Florentine Stafford McKnight Eduard Stelcer David D. Cohen Attila Stopic John W. Bennett 《Environmental geochemistry and health》2017,39(3):549-563
Mine wastes and tailings are considered hazardous to human health because of their potential to generate large quantities of highly toxic emissions of particulate matter (PM). Human exposure to As and other trace metals in PM may occur via inhalation of airborne particulates or through ingestion of contaminated dust. This study describes a laboratory-based method for extracting PM2.5–10 (coarse) and PM2.5 (fine) particles from As-rich mine waste samples collected from an historical gold mining region in regional, Victoria, Australia. We also report on the trace metal and metalloid content of the coarse and fine fraction, with an emphasis on As as an element of potential concern. Laser diffraction analysis showed that the proportions of coarse and fine particles in the bulk samples ranged between 3.4–26.6 and 0.6–7.6 %, respectively. Arsenic concentrations were greater in the fine fraction (1680–26,100 mg kg?1) compared with the coarse fraction (1210–22,000 mg kg?1), and Co, Fe, Mn, Ni, Sb and Zn were found to be present in the fine fraction at levels around twice those occurring in the coarse. These results are of particular concern given that fine particles can accumulate in the human respiratory system. Our study demonstrates that mine wastes may be an important source of metal-enriched PM for mining communities. 相似文献