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11.
A study of arsenic,iron and other dissolved ion variations in the groundwater of Bishnupur District,Manipur, India 总被引：1，自引：1，他引：0
Jayalakshmi Devi Oinam AL. Ramanathan Anurag Linda Gurmeet Singh 《Environmental Earth Sciences》2011,62(6):1183-1195
The presence of arsenic (As) in groundwater and its effect on human health has become an issue of serious concern in recent
years. The present study assessed the groundwater quality of the Bishnupur District, Manipur, with respect to drinking water
standards. Higher concentrations of pH, iron and phosphate were observed at several locations. Phosphate and iron levels were
highest in the pre-monsoon, followed by monsoon and post-monsoon seasons. The arsenic concentrations were highest during post-monsoon
(1–200 μg L−1) as compared to pre-monsoon (1–108 μg L−1) and monsoon (2–99 μg L−1). Kwakta and Ngakhalawai show higher levels of arsenic concentration as compared to the prescribed World Health Organization
(WHO) and Bureau of Indian Standards (BIS) norms. Arsenic showed a strong positive correlation with phosphate and negative
correlation with sulphate, suggesting a partial influence of anthropogenic sources. The study suggests that the Bishnupur
area has an arsenic contamination problem, which is expected to increase in the near future. 相似文献
12.
13.
Present study shows suspended sediment dynamics in the meltwater of Chhota Shigri glacier, Himachal Pradesh, India for different melt seasons during the period 2011-2014. Maximum suspended sediment concentration in the meltwater was found during the month of July 2011, 2012 and 2014 constituting to 55.2%, 48.3% and 46.9%, respectively. Whereas in 2013, maximum suspended sediment concentration was observed in August accounting for 46.1% of the total. On the other hand, maximum suspended sediment load was monitored in the month of July 2011, 2012 and 2014 constituting 59.5%, 63% and 55.7% of the total, respectively. Whereas in 2013, maximum suspended sediment load was observed in the month of August accounting for 49.8% of the total suspended sediment load. Annual distribution of suspended sediment concentration (SSC) and suspended sediment load (SSL) in the Chhota Shigri glacier shows higher value of SSC and SSL during the study period 2012 and 2013, which may be due to the presence of high glacial runoff and negative mass balance of the studied area during these time periods. Marked diurnal variation has been observed in the SSC of meltwater. Strong correlation was observed between SSC and SSL with discharge. On the other hand, SSC and SSL also showed strong exponential correlation with air temperature of the studied area. Sediment yield from the catchment of Chhota Shigri glacier is high during the peak melt season (July and August) and low during the late melt season (September and October). The average value of erosion rate for Chhota Shigri glacier basin during the study period 2011-2014 was calculated to be 1.1 mm/yr, which is lower than the average erosion rate of other Himalayan glaciers such as Rakiot, Chorabari and Gangotri glaciers, which may be caused by its geological setting containing high erosion resistant rocks such as granite, granite gneiss and porphyritic granite. 相似文献
14.
J. M. PAQUE J. R. BECKETT H. A. ISHII A. ALÉON‐TOPPANI D. S. BURNETT N. TESLICH Z. R. DAI J. P. BRADLEY 《Meteoritics & planetary science》2009,44(5):665-687
Abstract— We used focused ion beam thin section preparation and scanning transmission electron microscopy (FIB/STEM) to examine the interfacial region between spinel and host melilite for spinel grains in type B1 inclusions from the Allende and Leoville carbonaceous chondrites. Boundary clinopyroxenes decorating spinel surfaces have compositions similar to those of coarser clinopyroxenes from the same region of the inclusion, suggesting little movement after formation. Host melilite displays no anomalous compositions near the interface and late‐stage minerals are not observed, suggesting that boundary pyroxenes did not form by crystallization of residual liquid. Allende spinels display either direct spinel‐melilite contact or an intervening boundary clinopyroxene between the two phases. Spinel‐melilite interfacial regions in a Leoville B1 are more complex, with boundary clinopyroxene, as observed in Allende, but also variable amounts of glass, secondary calcite, perovskite, and an Mg‐, Al‐, OH‐rich and Ca‐, Si‐poor crystalline phase that may be a layered double hydrate. One possible scenario of formation for the glass veins is that open system alteration of melilite produced a porous, hydrated aggregate of Mg‐carpholite or sudoite + aluminous diopside that was shock melted and quenched to a glass. The hydrated crystalline phase we observed may have been a shocked remnant of the precursor phase assemblage, but is more likely to have formed later by alteration of the glass. In the mantle, boundary clinopyroxenes may have been crystallized from Ti‐rich liquids formed by the direct dissolution of perovskite and an associated Sc‐Zr‐rich phase or as a reaction product between dissolving perovskite and liquid. In the core, any perovskite and associated Ti‐enriched liquids that may have originally been present disappeared before the growth of boundary clinopyroxene, and the observed boundary clinopyroxene may have nucleated and grown from the liquid, along with the larger core clinopyroxene. 相似文献
15.
DIAGNOSIS OF WAVE ACTIVITY OVER RAINBAND OF LANDFALL TYPHOON 总被引：1，自引：0，他引：1
A generalized wave-activity density, which is defined as an absolute value of production of
three-dimensional vorticity vector perturbation and gradient of general potential temperature perturbation,
is introduced and its wave-activity law is derived in Cartesian coordinates. Constructed in an agoestrophic
and nonhydrostatic dynamical framework, the generalized wave-activity law may be applicable to diagnose
mesoscale weather systems leading to heavy rainfall. The generalized wave-activity density and
wave-activity flux divergence were calculated with the objective analysis data to investigate the character
of wave activity over heavy-rainfall regions. The primary dynamical processes responsible for disturbance
associated with heavy rainfall were also analyzed. It was shown that the generalized wave-activity density
was closely correlated to the observed 6-h accumulative rainfall. This indicated that the wave activity or
disturbance was evident over the frontal and landfall-typhoon heavy-rainfall regions in middle and lower
troposphere. For the landfall-typhoon rainband, the portion of generalized wave-activity flux divergence,
denoting the interaction between the basic-state cyclonic circulation of landfall typhoon and mesoscale
waves, was the primary dynamic process responsible for the evolution of generalized wave-activity density. 相似文献
16.
Weathering features are described from an arid coastal area in northern Morocco which are indicative of invasive chasmolithic and endolithic microbial communities. Active weathering of marine terraces and karst development is associated with endolithic and epilithic algae responsible for boring, disintegration of matrix and mineral fabrics, solution and biomineralization that undermines the marine carbonate platform. Evidence of a range of biological weathering agents remains preserved, speci?cally calci?ed ?laments and sporangial material. An abundance of ?laments and spores representative of a consortium of algae, fungi, cyanobacteria and lichens is associated with the most denuded outcrops. The array of microbes contributes to the formation of the stromatolites to depths of 0·5 m within the limestone substrate. The preservation of stromatolites is supported by calci?cation of spores and ?laments, with trapping and binding of carbonate held in suspension by vadose waters. The pervasive weathering on this sector of coastline has important practical implications for coastal planning and development authorities in Morocco. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
17.
Manish Kumar Kalpana Kumari AL. Ramanathan Rajinder Saxena 《Environmental Geology》2007,53(3):553-574
Punjab is the most cultivated state in India with the highest consumption of fertilizers. Patiala and Muktsar districts are
two agricultural dominated districts of Punjab located in extreme south-east and south-west of the state. This paper highlights
temporal variations of the groundwater quality and compares its suitability for irrigation and drinking purpose in these two
districts. Water samples were collected in March and September 2003, representing the pre-monsoon and post-monsoon seasons,
respectively. Water samples were analysed for almost all major cations, anions, dissolved heavy metals and turbidity. Parameters
like sodium adsorption ratio, % sodium, residual sodium carbonate, total hardness, potential salinity, Kelley’s ratio, magnesium
ratio, index of base exchange and permeability index were calculated on the basis of chemical data. A questionnaire was also
used to investigate perception of villagers on taste and odour. Comparison of the concentration of the chemical constituents
with WHO (world health organization) drinking water standards of 2004 and various classifications show that present status
of groundwater in Patiala is better for irrigation and drinking purposes except for a few locations with a caution that it
may deteriorate in near future. In Muktsar, groundwater is not suitable for drinking. Higher total hardness (TH) and total
dissolved solids at numerous places indicate the unsuitability of groundwater for drinking and irrigation. Results obtained
in this forms baseline data for the utility of groundwater. In terms of monsoon impact, Patiala groundwater shows dilution
and flushing but Muktsar samples show excessive leaching of different chemical components into the groundwater leading to
the enrichment of different anions and cations indicating pollution from extraneous sources. No clear correlation between
the quality parameters studied here and perceived quality in terms of satisfactory taste response were obtained at electrical
conductivity values higher than the threshold minimum acceptable value. 相似文献
18.
Safia AL MENOUFY 《《地质学报》英文版》2021,95(2):342-347
Nummulites multiplicutiospiralis n.sp.is described and illustrated for both generations from a claystone of Lutetian age in the Middle Eocene Qarara Formation, Maghagha,Nile valley,Egypt.Previously considered to be Nummulites gizehensis,we describe this form as a new species based on diameter of the test and protoconch sizes,septal shape and granulations.The primary feature of this species is spiral multiplication,seen in spiral section.The species is also characterized morphologically by lenticular to flat tests with rounded periphery,wrinkled to broadly meandering septal filaments and few granules on the periphery in microspheric forms.The granules are spirally arranged on the septal filaments in megalospheric forms.Chambers are longer than high and the spire is irregular.The new taxon belongs to the Nummulites partschi Group,Subgroup N.gizehensis.Reflexive coiling in the spiral may develop through ontogeny as in N.rollandi,the species which was considered to be an index species in the southern Tethys (Boukhary et al.,1982 and Boukhary et al.2010).The characters of the new species,as well as its retrogenesis and reflexive coiling,should be further studied in general in Nummulites spp.,to understand the importance of such characters phylogenetically. 相似文献
19.
Pablo Iribarren Anacona Kevin Norton Andrew Mackintosh Fernando Escobar Simon Allen Bruno Mazzorana Marius Schaefer 《Natural Hazards》2018,92(1):93-112
The rise of total water levels at the coast is caused primarily by three factors that encompass storm surges, tides and wind waves. The accuracy of total water elevation (TWE) forecast depends not only on the cyclonic track and its intensity, but also on the spatial distribution of winds which include its speed and direction. In the present study, the cyclonic winds are validated using buoy winds for the recent cyclones formed in the Bay of Bengal since 2010 using Jelesnianski wind scheme. It is found that the cyclonic winds computed from the scheme show an underestimate in the magnitude and also a mismatch in its direction. Hence, the wind scheme is suitably modified based on the buoy observations available at different locations using a power law which reduces the exponential decay of winds by about 30%. Moreover, the cyclonic wind direction is also corrected by suitably modifying its inflow angle. The significance of modified exponential factor and inflow angle in the computation cyclonic winds is highlighted using statistical analysis. A hydrodynamic finite element-based Advanced Circulation 2D depth integrated (ADCIRC-2DDI) model is used here to compute TWE as a response to combined effect of cyclonic winds and astronomical tides. As contribution of wave setup plays an important role near the coast, a coupled ADCIRC + SWAN is used to perceive the contribution of wind waves on the TWE. The experiments are performed to validate computed surge residuals with available tide gauge data. On comparison of observed surge residuals with the simulations using modified winds from the uncoupled and coupled models, it is found that the simulated surge residuals are better compared, especially with the inclusion of wave effect through the coupled model. 相似文献
20.
The Begnas Lake in the Pokhara Valley is one of the threatened habitats in Nepal. The major ion chemistry explains the status of most of the inorganic nutrients and their possible sources. However, the earlier studies mostly cover limnological investigations, and phytoplankton and zooplankton diversity. Thus, the present study has been conducted to investigate the geochemical processes and to examine the seasonal variation of chemical composition within Begnas Lake. The results showed that SO 4 2- , PO 4 3- , and NO 3 - increased compared with the previous values. The domination of Ca2+, Mg2+, and HCO 3 - explains the influence of carbonate weathering on the major ion concentration. In general, pH and dissolved oxygen decreased with the depth of water-column, while electric conductivity, total dissolved solids, HCO 3 - , Cl-, H4SiO4, K+, Mg2+, Ca2+, Mn2+, and Fe increased. Among the cations, the predominance of Ca2+ and Mg2+ as characterized by high (>0.6) (Ca2+ + Mg2+)/(Tz+) and (>0.8) (Ca2+ + Mg2+)/(Na+ + K+) equivalent ratios, also suggests prevalence of carbonate weathering. The low value of (Na+ + K+)/Tz+ ratio shows deficiency of Na+ and K+, suggesting low contribution of cations via aluminosilicate weathering. The C-ratio suggests a proton source derived both from oxidation of sulfide and dissolution and dissociation of atmospheric CO2 during different seasons. Though the major hydro-chemical parameters are within permissible limit, the increase in trophic state of the lake suggests that inherent biogeochemical processes make the limiting nutrients available, rendering eutrophic effect. Therefore, further comprehensive studies incorporating sediment–water interaction ought to be carried out to explain the ongoing phenomena and curb the eutrophication process in the lake. 相似文献