Analysis of the 2003 Varunawat Landslide,Uttarkashi, India using Earth Observation data     

K. Vinod kumar  R. C. Lakhera  Tapas R. Martha  R. S. Chatterjee  A. Bhattacharya 《Environmental Geology》2008,55(4):789-799

Mass movements such as landslides in mountainous terrains are natural degradation processes and one of the most important landscape-building factors. Varunawat Parbat overlooking Uttarkashi town witnessed a series of landslides on 23 September 2003 and the debris slides and rock falls continued for 2 weeks. This landslide complex was triggered due to the incessant rainfall prior to the event, and its occurrence led to the blockage of the pilgrim route to Gangotri (source of the Ganges river) and evacuation of thousands of people to safer places. Though there was no loss of lives due to timely evacuation, heavy losses to the property were reported. High-resolution stereoscopic earth observation data were acquired after the incidence to study the landslide in detail with emphasis on the cause of the landslide and mode of failure. Areas along the road and below the Varunawat foothill region are mapped for landslide risk. It was found that the foothill region of the Varunawat Parbat was highly disturbed by man-made activities and houses are dangerously located below steep slopes. The potential zones for landslides along with the existing active and old landslides are mapped. These areas are critical and their treatment with priority is required in order to minimise further landslide occurrences.  相似文献   

Genetic identification of hake and megrim eggs in formaldehyde-fixed plankton samples   总被引：4，自引：0，他引：4  

Perez  Juliana; Alvarez  Paula; Martinez  Jose L.; Garcia-Vazquez  Eva 《ICES Journal of Marine Science》2005,62(5):908-914

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Measurement of the redox speciation of iron in seawater by catalytic cathodic stripping voltammetry     

Martha Gledhill  Constant M. G. van den Berg 《Marine Chemistry》1995,50(1-4)

Catalytic cathodic stripping voltammetry (CSV) preceded by adsorptive collection of complexes of 1-nitroso-2-napthol (NN) can be used to determine iron in seawater. It is shown here that iron(II) is effectively masked in the presence of 2,2-dipyridyl (Dp) so that iron(III) is measured selectively. The concentration of iron(II) is then calculated as the difference between the concentrations of reactive iron (Fe_R) in the absence and presence of 2 μM Dp, Fe_R being defined as that which was complexed by 20 μM NN at pH 6.9 in the presence of 1.8 mM H₂O₂ and 5 ppm sodium dodecyl sulphate. A 30 min reaction time was allowed for Dp to react with iron(II) in seawater prior to the determination of reactive iron(III) using the same conditions as used for Fe_R. Detection limits of 0.08 nM, 0.077 nM and 0.12 nM were obtained for Fe_R, iron(III) and iron(II), respectively, using a 60 s deposition time.The method was utilised to determine the redox speciation of iron in the northern North Sea. Concentrations of Fe_R ranged between 0.8 and 3.5 nM with nutrient-like depth profiles. Iron(II) was found to be present at concentrations up to 1.2 nM, the highest concentrations occurring in the upper 20 m of the water column.  相似文献   

Factors affecting spatial and temporal variability in material exchange between the Southern Everglades wetlands and Florida Bay (USA)     

Martha A. Sutula  Brian C. Perez  Enrique Reyes  Daniel L. Childers  Steve Davis  John W. Day  Jr.  David Rudnick  Fred Sklar 《Estuarine, Coastal and Shelf Science》2003,57(5-6):757-781

Physical and biological processes controlling spatial and temporal variations in material concentration and exchange between the Southern Everglades wetlands and Florida Bay were studied for 2.5 years in three of the five major creek systems draining the watershed. Daily total nitrogen (TN), and total phosphorus (TP) fluxes were measured for 2 years in Taylor River, and ten 10-day intensive studies were conducted in this creek to estimate the seasonal flux of dissolved inorganic nitrogen (N), phosphorus (P), total organic carbon (TOC), and suspended matter. Four 10-day studies were conducted simultaneously in Taylor, McCormick, and Trout Creeks to study the spatial variation in concentration and flux. The annual fluxes of TOC, TN, and TP from the Southern Everglades were estimated from regression equations. The Southern Everglades watershed, a 460-km² area that includes Taylor Slough and the area south of the C-111 canal, exported 7.1 g C m⁻², 0.46 g N m⁻², and 0.007 g P m⁻², annually. Everglades P flux is three to four orders of magnitude lower than published flux estimates from wetlands influenced by terrigenous sedimentary inputs. These low P flux values reflect both the inherently low P content of Everglades surface water and the efficiency of Everglades carbonate sediments and biota in conserving and recycling this limiting nutrient. The seasonal variation of freshwater input to the watershed was responsible for major temporal variations in N, P, and C export to Florida Bay; approximately 99% of the export occurred during the rainy season. Wind-driven forcing was most important during the later stages of the dry season when low freshwater head coincided with southerly winds, resulting in a net import of water and materials into the wetlands. We also observed an east to west decrease in TN:TP ratio from 212:1 to 127:1. Major spatial gradients in N:P ratios and nutrient concentration and flux among the creek were consistent with the westward decrease in surface water runoff from the P-limited Everglades and increased advection of relatively P-rich Gulf of Mexico (GOM) waters into Florida Bay. Comparison of measured nutrient flux from Everglades surface water inputs from this study with published estimates of other sources of nutrients to Florida Bay (i.e. atmospheric deposition, anthropogenic inputs from the Florida Keys, advection from the GOM) show that Everglades runoff represents only 2% of N inputs and 0.5% of P input to Florida Bay.  相似文献   

On the albedo of the interplanetary dust     

Martha S. Hanner 《Icarus》1980,43(3):373-380

The zodiacal light brightness and measured spatial density of the interplanetary dust lead to a mean geometric albedo of 0.24 for the dust particles near 1 AU; whereas the composition of collected micrometeroids suggests a geometric albedo ?0.1. The data do not support the very low albedo (?0.01) proposed by A. F. Cook [Icarus33 (1978), 349–360]. The evidence is against a change in the mean particle albedo between 0.1 and 2 AU. Beyond 2 AU the data are unclear and a change in albedo is not ruled out.  相似文献   

A powder diffraction quantification method (ALJOR) for atmospheric particulate matter     

M. Jordán  C. Alvarez  T. Sanfeliu 《Environmental Geology》2002,42(7):810-816

The percentage calculation of crystalline phases in atmospheric particulate matter samples by means of an adiabatic approach of the matrix-flushing method with preferred preparations that avoids preferential orientations, should never be interpreted as absolute values. On the contrary, it should be seen as an indicator of the significant differences between each and every analyzed sample. Factors such as the application of constants, which are only useful for preparations of polycrystalline samples free of preferential orientation, and/or like the deficient resolution shown by the diffraction diagrams for certain phyllosilicate phases, bring a high degree of uncertainty to these percentage calculations. An alternative method of crystalline and amorphous phase quantification is presented below. Once the majority phases in the samples were identified, appropriate pure phases corresponding to each of them were selected. Then, the corresponding calibration curves were built using corundum (number 676 NIST) as a reference pattern phase. After validating the obtained calibration curves, the constants corresponding to each phase and selected spacing were calculated. The ALJOR method has been used for the quantification of five samples.  相似文献   

Relationship between crustal finite strain and seismic anisotropy in the mantle, Pacific–Australia plate boundary zone, South Island, New Zealand     

Timothy A. Little  Martha K. Savage  Basil Tikoff 《Geophysical Journal International》2002,151(1):106-116

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Morphological variation and reproductive biology of Polaskia chende (Cactaceae) under domestication in Central Mexico     

Martha Cruz  Alejandro Casas 《Journal of Arid Environments》2002,51(4):561

The columnar cactus Polaskia chende, endemic to Central Mexico, occurs in the wild and in silviculturally managed populations where artificial selection for better edible fruits operates by sparing and favouring desirable phenotypes during vegetation clearance. Wild and managed populations were compared in morphology and reproductive biology to analyse if human selection has influenced phenotypic divergence, if it has modified breeding systems and if reproductive isolation exists between them. Fruits from managed populations were larger (6·36±0·17 cm³), heavier (19·62±1·32), sweeter (9·07±0·25 °Brix), and with thinner peel (2·09±0·13 mm) than those from wild populations (5·77±0·18 cm³, 15·73±0·85 g, 8·23±0·31 °Brix, and 2·58±0·14 mm, respectively). Both population types bloom synchronically, show diurnal anthesis, with bees as the most likely pollinators, and have breeding system predominantly self-incompatible. Spatial and temporal barriers to pollen exchange between wild and managed populations are unlikely, and morphological differences would be related with an ongoing process of artificial selection.  相似文献   

A Comparison of Benzene and Toluene Plume Lengths for Sites Contaminated with Regular vs. Ethanol-Amended Gasoline   总被引：3，自引：0，他引：3  

G.M.L Ruiz-Aguilar  K. O'Reilly  P.J.J. Alvarez 《Ground Water Monitoring & Remediation》2003,23(1):48-53

This article describes various statistical analyses of plume-length data to evaluate the hypothesis that the presence of ethanol in gasoline may hinder the natural attenuation of hydrocarbon releases. Plume dimensions were determined for gasoline-contaminated sites to evaluate the effect of ethanol on benzene and toluene plume lengths. Data from 217 sites in Iowa (without ethanol; set 1) were compared to data from 29 sites in Kansas that were contaminated by ethanol-amended gasoline (10% ethanol by volume; set 2). The data were log-normally distributed, with mean benzene plume lengths (± standard deviation) of 193 ± 135 feet for set 1 and 263 ± 103 feet for set 2 (36% longer). The median lengths were 156 feet and 263 feet (69% longer), respectively. Mean toluene plume lengths were 185± 131 feet for set 1 and 211 ±99 feet for set 2 (14% longer), and the median lengths were 158 feet and 219 feet (39% longer), respectively. Thus, ethanol-containing BTEX plumes were significantly longer for benzene (p < 0.05), but not for toluene. A Wilcoxon signed rank test showed that toluene plumes were generally shorter than benzene plumes, which suggests that toluene was attenuated to a greater extent than benzene. This trend was more pronounced for set 2 (with ethanol), which may reflect that benzene attenuation is more sensitive to the depletion of electron acceptors caused by ethanol degradation. These results support the hypothesis that the presence of ethanol in gasoline can lead to longer benzene plumes. The importance of this effect, however, is probably site-specific, largely depending on the release scenario and the available electron acceptor pool.  相似文献   

Viruses as potential regulators of regional brown tide blooms caused by the alga,Aureococcus anophagefferens     

Mary Downes Gastrich  Justine A. Leigh-Bell  Christopher J. Gobler  O. Roger Anderson  Steven W. Wilhelm  Martha Bryan 《Estuaries and Coasts》2004,27(1):112-119

Blooms of the brown tide organismAureccoccus anophagefferens have recurred in the coastal bays in New Jersey since 1995 and in the coastal bays of Long Island since 1985. Intracellular viral-like particles (VLPs) were documented during 1999–2000 brown tide blooms in Little Egg Harbor, New Jersey, but it was not determined whether cells were infected during the termination of the bloom. The objective of this study was to determine if VLPs infected and lysed natural populations ofA. anophagefferens in coastal bays of New Jersey and New York in 2002 with the same frequency as in 1999–2000 and especially at the termination of the bloom. Our results confirmed that the highest percentage (37.5%) of VLP-infected cells occurred at the termination of the brown tide bloom in New Jersey in 2002. Intracellular VLPs were present throughout the bloom event. The percentage of visibly infected cells was higher at the beginning of the bloom than during the peak of the bloom. The intracellular VLPs in natural populations ofA. anophagefferens were consistent in size and shape (approximately 140 nm in diameter) and comparable to those in previous studies. Concentrated viral isolates, prepared from waters during brown tide blooms in New York and New Jersey in 2002, infected healthy laboratoryA. anophagefferens cultures in vitro. The viral isolates associated with the highest laboratory viral activity (lysis positive) were concentrated from water samples having the highest viral and bacteria concentrations. The intracellular viruses in these virally infected laboratory cultures ofA. anophagefferens were similar in size and shape to those found in natural populations. The successful isolation of a virus specific toA. anophagefferens from a brown tide bloom in the field, the similarity of ultrastructure of VLPs infecting both natural populations and laboratory infected cultures, and the pattern of VLP infection during bloom activity in combination with the observed high percentage of VLP-infected cells during bloom termination, supports, the hypothesis that viruses may be a major source of mortality for brown tide blooms in regional coastal bays of New Jersey and New York.  相似文献